Help my new plane flies like a big peice of .......

I took my new Gieseke Bear out last night and it sucks.

Weight, 58 oz
Area, 680
Stab/Elev, 22%
Power, Strong PA 61
Prop, Eather 4 blade

Motor Run Excellent. So that part of the equation is covered.

Flight Characteristics. CRAP!!

I know form the get go it is tail heavy so I am ready for that. What I was not ready for was what I call the dreaded "DOUBLE TURN" You give it input and half way through the turn it stalls and falls then completes the turn. I was not happy seeing as how I have been working on this since January 27 2001. I added nose weight and tip weight. It was more flyable with the nose weight but the "Double Turn" was still there. I have always been under the impression that this occurs when the plane is too heavy. There is another flier here who built the exact same plane(kit) and it weighs 60oz and flys great. I am sure the leadouts are way to far forward and the tip weight issue is way off. Can this cause the double turn?

If anyone out there has ever trimmed this out of a plane please help me. I am really dissappointed I hope I can straighten it out.

If you all need more info let me know.

HELP!!!

DMoon

My first inclination there Doug, is that you probably have a loose nut on the handle...

I had the same problem with my Cirrus and had done all that you described several times over. I was a Brodak's and was so frustrated that I was about to put a foot through it. Someone said "Well here's your problem you got too big of flaps!" I was on my way to John's shop to butcher 1/4 in all the way across the flaps when Tom Dixon asked what I was doing. After my story was over he suggested that I simply had too much throw in the control surfaces. The airplane was stalling especially in the hard corners and all I needed was to move the spacing in on my handle.

It worked like a charm and I have an airplane that flies really well.

I hope yours can be fixed as easily. - Ed

I am sure the leadouts are way to far forward and the tip weight issue is way off. Can this cause the double turn?

Doug...Had some of the same with my "Succubus" Handle spacing for a tail heavy plane becomes a nightmare. I had to adjust so many times to get it right. I'm now flying at 23% of CG
Dose your plane HUNT in level flight if yes your lead out are to far forward.
Do you have Engine at Zero-Zero on the axis pole to pole and east to west.
Wheel pants? Vertical CG
How much behind CG are you now?
ARE YOUR LINES CLEAN!!
I know that you know all of this.....Your a good flyer!!!

ALSO is your Stab Sheeted? Is there flex anywhere? Took care of My Problem of comming out of the hard corner.

Remember Fix one problem at a time. You'll have good responces on this one Doug.
Scott(worked for me)Riese

>I took my new Gieseke Bear
>out last night and it
>sucks.
>
>Weight, 58 oz
>Area, 680
>Stab/Elev, 22%
>Power, Strong PA 61
>Prop, Eather 4 blade
>
>Motor Run Excellent. So that
>part of the equation is
>covered.
>
>Flight Characteristics. CRAP!!
>
>I know form the get go
>it is tail heavy so
>I am ready for that.
> What I was not
>ready for was what I
>call the dreaded "DOUBLE TURN"
> You give it input
>and half way through the
>turn it stalls and falls
>then completes the turn.
>I was not happy seeing
>as how I have been
>working on this since January
>27 2001. I added
>nose weight and tip weight.
>It was more flyable with
>the nose weight but the
>"Double Turn" was still there.
> I have always been
>under the impression that this
>occurs when the plane is
>too heavy. There is
>another flier here who built
>the exact same plane(kit) and
>it weighs 60oz and flys
>great. I am sure
>the leadouts are way to
>far forward and the tip
>weight issue is way off.
> Can this cause the
>double turn?
>
>If anyone out there has ever
>trimmed this out of a
>plane please help me.
>I am really dissappointed I
>hope I can straighten it
>out.
>
>If you all need more info
>let me know.
>
>HELP!!!
>
>DMoon

Whoa, Doug!

None of this makes a lot of sense. At 58oz and 680 Squares a stall should never enter into the equation. Something else is amiss.

Stalls are a pretty simply evaluated phenomenom. The angle of attack is increased until the flow separates over the top of the surface. When the angle of attack exceeds "critical" the airfoil stalls and no longer produces lift. The nose drops as a result until the A of A reduces to less than critical ,lift is regenerated and the corner continues.

The question than becomes: why is the wing stalling before it generates the lift necessary to complete the corner. The "conventional" wisdom is that the wing loading is too high and that the wing simply isn't capable of generating the lift required for the corner. At 52oz and 680 squares this simply shoudn't be a problem. Ergo, something else is happening.

Two things immediately come to mind. First, the flap hinge line isn't sealed and the high pressure on the bottom of the airfoil is bleeding through to the upper surface and the necessary difference in pressure over and under the wing isn't developed. The cure for this problem is to seal the hinge line with a material which eliminates the transfer of high pressure air below the surface to the (desired) low presssure area on top of the surface. As I've said repeatedly, this sealing is especially important on a ship using the "modern" RC style hinges which leave large lengths of the hinge-line unsealed and thus susceptible to pressure bleed-through.

The second area of concern is the leading edge radius. Review my article in STUNT NEWS on the DOCTOR for an in depth discussion of this aspect of lift development. Sharp leading edges are predictably at risk for stalls at an early angle of attack because the stagnation point is so clearly defined. The sharper the leading edge the shallower the angle of attack at which the airfoil will stall.

Lastly, you stated the airplane is "tail heavy". At 58 ounces with a piped .61 in the nose this seems unlikely to me. The engine/tank/spinner/header etc. of such a power train would seem to be a huge percentage of the overall weight of a 58 oz package. To suggest that such a combination is tail heavy seems illogical from a thousand miles away.

In addition, if a ship is stalling "as is" adding nose weight will predictably make it stall more drastically. As the CG moves forward "more" control deflection will be required to make a given corner and, as a result, a greater angle of attack required to support the load which results. Predictably, the stall will occur sooner rather than later. I don't think this is a likely solution to your problem.

Give us a little more info on the ship. Where, in percentage of the average chord, is the CG located? Are the flap hingelines sealed? Is there a nice radius to the leading edge?...or is it simply a meeting of the upper and lower sheeting? What are the line length and lap times?

Adequate (more likely, blistering) corners on a 58 oz 680 square inch airplane should be a given. Something else is amiss here. Let's figure out what?

Happy holidays to the Moons

Ted Fancher

I was thinking that something funky is happening with a pushrod or control horn, but you use all that heavy duty stuff, right? If you did something different, it may be worth a think. Steve

>
>Line length is 66' foot eyelet
>to eyelet inboard wing is
>28" inches long with about
>3 inches of leadouts.
>Lap time 5.5 sec.
>The average cord with no flap
>it is 9.75" with the
>flap it is 11.75"
>The CG is now placed
>at 3.25 inches from the
>leading edge of the plane
>at the fuse wing joint.

Where is the CG relative to the MGC?

Tail-heavy might mean that it's unstable in pitch, and the turn is tightening up on it's own causing it to stall. Nose-heavy, in contrast, might mean the tail is stalling trying to force the nose around. This is particularly problematic if you have a thick, flat stab airfoil.

Brett

>LAST EDITED ON Nov-10-01
>AT 00:17 AM (CST)
>
>Here are some more facts about
>the plane in question.
>
>Line length is 66' foot eyelet
>to eyelet inboard wing is
>28" inches long with about
>3 inches of leadouts.
>Lap time 5.5 sec.
>The average cord with no flap
>it is 9.75" with the
>flap it is 11.75"
>The CG is now placed
>at 3.25 inches from the
>leading edge of the plane
>at the fuse wing joint.
> It is tail heavy
>becuase yours truly got a
>little carried away with the
>Urethane clear and now it
>has a major amount of
>clear on the tail area.
> Also the nose moment
>is only 9" Tail moment
>is 16 7/8"
>
>The hingelines were not sealed the
>day I flew but they
>are now.
>
>Leading edge radius is almost identicle
>to my last bear.
>That would be sharp compared
>to the TP. It
>is just slightly sharper than
>a Saturn leading edge.
>The sheeting comes together then
>I smooth and round it
>off. Once the edge
>is gone I get the
>rasius as even as possible
>along the entire length of
>the wing and stop.
>It is a small radius.
> I still think it
>should fly. My other
>one does. It is
>5 or 6 ounces lighter.
>
>
>I will be flying it tomorow
>morning I will check back
>and let you all know
>how it is coming along.
> If you have any
>ideas or need more info
>please let me know.
>
>DMoon


Hi Doug,

I'm anxious to hear how it flies with the hingelines sealed. I can't stress strongly enough how important sealing them can be. Always remember that the lift of the wing is dependent on a difference in air pressure above and below the surface. And it really doesn't matter a lot how tight the gap may appear...as Brett has often said, "I don't care how narrow the gap is it's still larger than an air molecule"...which is a great line and one to keep in mind.

Remember, in the early days of stunt we all used cloth hinges and painted the flaps and elevators along with the rest of the ship. The use of full span cloth hinges would effectively seal the hingelines for us.

The modern approach is to use R/C style pinned hinges every four to six inches or so of span and we usually paint the ship before installing the hinges to keep them from getting sticky. The result is a gap of whatever dimension "right at the front of what we call a high lift device...the flap"! When deflected there is a natural occuring increase in pressure on the "bottom" of the surface right at the hingeline and an accompanying decrease "above" it. This is more or less the manner in which the flap increases the lift to support the ship in high G corners.

If we have any gap at that point the high pressure air bleeds through reducing any lift increase...perhaps even making things worse as a result of the drag increase not being accompanied by the desired lift increase. Thus you could be doing something as damaging as increasing your form drag (from the shape of a device...the deflected flap surface) at the same time you are decreasing lift (from the ineffective flap disrupting laminar flow over the wing's surface).

When the hingeline is sealed the airflow remains laminar and the increase in lift desired is developed. There is still, of course, an increase in drag but in this case it is "induced" drag (drag resulting from the production of lift). Induced drag is a natural given from any increase in lift (it can be diagramatically illustrated by 1.drawing an airfoil at, say, 10 degrees angle of attack, 2. draw a lift arrow (for good procedure, draw it from a point 25% aft of the leading edge of your airfoils chordline, the approximate "center of lift") at right angles to the wing chord of "X" dimension to illustrate the total lift generated by the section; 3. from the same point draw another line at right angles to the "ground" going as high as the tip of the total lift arrow (this represents the proportion of lift working vertically to support the wing section); 4. connect the two points of the lift lines; 5. the resulting line between the two lift arrows represents the amount of lift which actually produces drag...retarding the forward motion of the section...which must, of course, be overcome with thrust. That lift produced drag is called induced drag.

By the way. I did some quick math based on the numbers you gave us. Like Brett I would like to know the position of the CG halfway out the span. If the ship were mine I would have started out with the CG located at 22% aft of the leading edge at that "halfspan" location. That would be roughly 2 5/8" on your ship. Depending on the amount of taper in the wing planform this could result in pretty much any number measured at the fuselage. Frankly, 3.25" at the fuse doesn't sound like it would be particularly far aft.

Ted

I flew the plane this morning. The sealed hinge lines seemed to make all the difference.

It is still stalling when it is told to enter the triangle. It wont exit the manuver or enter it. Same with the hourglass. When I fly it into the square it stalls just before reaching the 90 degree point. It seems now to be stalling due to weight. It is different stall than the other day. If that is possible. It seems to be more of a give up. Before it would not turn at all. Before if the flaps were activated it would just fall. Now it flys and can do decent rounds but in hard corners it jsut gives up. I have been told at the field by some of the other flyers that the flaps maybe too small. I am going to add some balsa strips the length of the flaps and head back the field. I only live 2 miles away.(cool huh?)

What is the troubles when the flaps are too small what should I encounter? What happens when the flaps are to big?

The CG is now really in the ballpark. The tip weight and LO guides are close also. Once i get rid of this hitch in the turn I should have a decent plane.

I added one of those Prather spinner weights that bolts on in place of the washer. It weighs 2 OZ!!!!!!!!!! It was the answer for stability and control. Will this large weight damage the motor??????

I will be back in little while. Thanks for all your help.

DMoon

Hi Doug,

You've confused me. You said the seals make "all the difference" and then went on to document a lot of stalls regardless. Is the ship better? or not?

I'm still reluctant to believe at 58 oz the ship is too heavy. For comparison, my Trivial Pursuit (the tan original) is all of 68 oz on about 660 Squares and turns just fine.

Two questions. first, have you figured out the CG location as Brett and I requested (at the average chord point, halfway out the wing)? This is really important info for us. Second, did you also seal the elevator hinge line?

Ted

Here is what I found today at the field. I added 3/8 inched of balsa to the flaps. It flew much better as far as the stall was concerned but it was still present. It was dropping the outboard wing big time. I removed tip weight. I am now down to 1/2 oz. Still dropping the wing.

One thing is for sure the control was alot slower with the added flap. It took alot more input to get the plane to turn. it sure was stable with all that flap. I slid the L/O back a quarter. After that it was making good tension.. I was trying to get rid of the yaw as well as the stall.

Adding to the flaps worked so I detached my trim tab device and tapped it to the flap. So now I have a full span flap on the outboard flap. The trim tab is setup just like the flap then I add a holding device to set it at the desired angle to keep the wing level. It turns out with peice added to the flap the wing was still perfectly level. It flew better yet. Now I am able to fly the pattern. Still a funny turn and some minor very minor yawing in the corners. But the 90 degree trun is excellent. The triangle is still lacking the ability to just slam the CRAP out of it.

Next I added another 1/2 inch to the flap on both sides. Overall we ended up adding 7/8 inches to the flaps full span and the outboard trim tab. I new this would make the plane's controls very sluggish. I removed 1/2 oz of nose weight. The plane was finally a Stunt Plane. I can now succesfully enter and exit the triangle without the thought of crashing.

Conclusion; I will need to make larger flaps. I am going to make them removable. Godzilla has convinced me that when it gets hot it might even need larger flaps. Wow I really made this one too heavy. Bob told me 56oz was the limit. It is now weighing in at very hefty 61oz. That 5oz is just killing the lift abilities of the wing and flaps. I guess I am cheating by enlarging the flaps.

I would still like to know what I should expect if I get the flaps too large? Also will the 1.5oz weight on the front of the motor damage it? The motor guy around here says that as long as it centered and not out of balance it wont hurt a thing. I have noticed that it runs really good with that flywheel weight on there.

I shall start on the new flaps tomorow. How much larger should I make the outboard flap. I was thinkin I would have it be 1/16 larger all the way down the span. Is this the right thinking???

DMoon

Doug,
With the added flap size, what % are the flaps as compared to the total wing area. I got a set a 97 Bear plans and I figured them out to be 16%. Does your wing have a larger inboard wing? When you're finished making new flaps, are both the same size in area? This year flying my Legacy 40 I "discovered" that it flew much better when my flaps ended up being the same size. The Legacy 40 wing has a 3/8 offset...inboard wing is 3/4 in longer. Thanks for the info...,

Crist Rigotti
"A Driver trying to be a Pilot"

Doug,

I'm flying a reasonably new Bear Ship too.

It weighs 58.5oz. Power is Jett 60, Eather #6 pipe.

As far as the wing goes it is all to plan, with the exception of the flaps. Inboard is to plan but goes full span. Outboard flap goes full span also, but is 1/4" wider at the tip.

The only other changes are increased tail span, 1/2" added to each side at the root end of things, giving 1" more span but also slightly increased chord. Control horns are more typical than Bob's setup.

The model turns as hard as I like, no signs of any stalling.

I think you'll find the area isn't 680" though. Closer to 657-660 squaers.

BRI

Maybe you guys do not understand the other aspect to the equation here, which is Doug.

Doug flies extremely hard and aggressive and turns extremely sharp corners. A lot of flyers would possibly not see the stalls and bangs that Doug sees, because they might nurse the corner more. Not Doug, he smacks the POOP out of them.

Overall, the Bear is a totally better airplane (in Doug’s case-at 61 OZ) with 7/8” of area added to the trailing edge, and even better at full span. Eh, no big deal, Doug will make bigger flaps. The airfoil seems to be weight intolerant, and the original flaps are designed for a max of 54-56 OZ.

The airplane was in quite good trim by the end of the day. I think it turns better (quality) with the bigger flaps. No sign of “wheelying” out of the corner, like the Blue Chevy Bear had some tendency to do. Just BOOM-flatness, like my airplane (snicker).

This will be good airplane, I have no doubt.

P.S. I want his PA 61.

Ted,

Yes the sealed hinges made all the difference at first. It did make the plane fly much better. However it was still unacceptable as I flew the pattern. It was able to exit squares and wingovers but not the triangle and hourglass. To answer your questions; Yes it helped.

I found the cg at half the span. It is 2 3/8". The average chord being 9 3/4" no flaps. With the originl flaps the average chord was 11 3/4" with the original flaps. With the added balsa the average chord is 12 3/4". Quite a difference huh?

I did not have the elev hinge lines sealed yesterday. I sealed them this morning but did not get to fly it because it started raining. I have a feeling that this will cure the sluggish turn.

The weight is now 61 oz. It is deffinently out of the weight range.

Bri,

There is a little more wing area on this Bear. I sweep the tips out instead of the way they are shown on the plans. This adds 2 inches to the span at the trailing edge. I just figured it up and the area wing and flaps is a 670 without the added balsa strips.

A few other changes on this plane from the plans is the stab/elev is 22% as opposed to the original 20%. With the swept tips on wing(extra area) the stab/elev is really only 18.9% That is how it worked out on my 97 Bear. The fuse is also 1" longer overall. The nose moment is 9". The Tail momoent is 16 7/8". The fuse also has 1/2" depth added to the entire length. These numbers are just a bit bigger than called for on the plans. Overall it is a larger plane than that on the plans but still uses the same wing. This is where I ran into trouble and didnt know it while I was building. You can bet I will know it next time.

As Crist said the original flaps are 16% and they are not full span. Bob G. is an expert builder one of the best for sure. He can get away with tiny flaps because his planes rarely weigh more than 52oz.(yet they last for thousads of flights) 1" at the tip and 3" at the root and 5" short of the wing tip. They are 5" short when the tips are swept out. My new flaps will be full span with less taper. I am going with less root and more at the tip. I am hoping this will help keep the lift more evenly distributed across the wing. The new flaps will be rigt at 21%. they will be removable so if it doesn't work out I can always change them. Is this way out of the norm??

Thanks for all the help.

DMoon

>
>I found the cg at half
>the span. It is
>2 3/8". The average
>chord being 9 3/4" no
>flaps. With the originl
>flaps the average chord was
>11 3/4" with the original
>flaps. With the added
>balsa the average chord is
>12 3/4". Quite a
>difference huh?
>
>I did not have the elev
>hinge lines sealed yesterday.
>I sealed them this morning
>but did not get to
>fly it because it started
>raining. I have a
>feeling that this will cure
>the sluggish turn.
>
>The weight is now 61 oz.
> It is deffinently out
>of the weight range.
>
My new flaps
>will be full span with
>less taper. I am
>going with less root and
>more at the tip.
>I am hoping this will
>help keep the lift more
>evenly distributed across the wing.
> The new flaps will
>be rigt at 21%.
>they will be removable so
>if it doesn't work out
>I can always change them.
> Is this way out
>of the norm??
>

I'm astonished that a 61 oz airplane with 680 square inches can be stalled! The various Trivial Pursuits are between 58 and 70 with ~650 square inches, and pretty much can't be stalled. Same with mine - 665 and 62 oz, and even the old oft-repaired Imitation XL was 610 squares at 64 oz, and couldn't be stalled even at Lubbock in the heat of the day.

The original flaps sound a little on the small side, but not way out of the ballpark. 21% is fine and at this light-moderate wing loading the airplane *should not stall* no matter how hard you hit it. There's something else wrong that's making the wing not carry the weight well. I would look at the LE radius - this is a classic problem area that can greatly inhibit the max Cl of an otherwise good airfoil. Another possibility is that the flap hinge line is somehow allowing separation, but the LE is where I would start.

Brett

> I'm astonished that
>a 61 oz airplane with
>680 square inches can be
>stalled! The various Trivial Pursuits
>are between 58 and 70
>with ~650 square inches, and
>pretty much can't be stalled.

A Bear airfiol is not a TP airfoil. TOTALLY DIFFERENT ANIMAL. Period.

Like comparing a 45ACP to a .223. Both effective and deliver similar force but through a completely seperate set of physics numbers.

Hi Doug,
I got to this thread a little late but I think you are on the right track. You are experiencing most ot the same problems I experienced with the Millennium, i.e. stalling corners. It has been my experience that using bigger flaps or deflecting the flaps farther both increase lift. There is no adverse effect to using truly large flaps except the drag caused in the process of making lift but you are going to have that no matter how you make the lift. I use flaps which are about 1/3 the length of the wing chord and wouldn't consider using less, but then I typically build airplanes with a high wing loading.
Back to your problem, I would have followed with your airplane, the same schedule of trials which fixed the Millennium's stall.
First, remove elevator hinge tape. Taped elevators make the elevator sensitivite so the airplane turns with small flap deflections. To avoid stalls you need lift. Restricting flap travel minimizes available lift.
Second, adding nose weight moves the C.G. forward makes the airplane more stable. It takes a larger control deflection to turn a stable airplane and this larger control deflection results in more lift, less stall (not a disasterous stall). I think you found this out yourself. It also makes for a verry groovy airplane. I never considered the possibility that weight in the spinner might be hard on the engine. I have many thousands of flights, nearly all having weight in the spinner and never had a problem though on occasions I carried as much as 3 oz. I used 2 oz to initally trim the Millennium, and would have left it there forever had I not lengthened the nose.
In sort, larger flap deflections or larger area create more lift. They also create more drag in the process. Drag is simply a retarding force opposite thrust. With a 61 in a 60 oz airplane, drag is not a limiting factor. You already have a comfortable excess of power.
Using a lot of control deflection requires a larger handle movement. This may be uncomfortable or awkward. Simply increase the line spacing on the handle. Because of the control deflections I normally use, I seldom fly with less than a 6" line spacing. I prefer nose heavy airplanes for groovy maneuvers as opposed to useing "tandem wing" airplanes (extremely large stab/elevator area which also limits control deflections.
In my Stunt News reprinted 1977 Mustang article, I suggested the use of small asymmetry (1/2") and equal area flaps obtained by using wider wider outboard flaps (1/8") flaps.
If improving lift hadn't fixed your problem, I would have also suggested that you try to sharpen the stab leading edge.
Based on my airfoil tests, I am of the opinion that smaller leading edge radius is seldom the cause of stalling in a stunt ship but it dose seem to improve handling characteristics especially in the wind. I usually use 7/8". I have corected stalling before but never found it necessary to blunt the leading edge.
Hope some of this helps.
Al

>First, remove elevator hinge tape.
>Taped elevators make the elevator
>sensitivite so the airplane turns
>with small flap deflections.
>To avoid stalls you need
>lift. Restricting flap travel
>minimizes available lift.
>Second, adding nose weight moves
>the C.G. forward makes the
>airplane more stable. It
>takes a larger control deflection
>to turn a stable airplane
>and this larger control deflection
>results in more lift, less
>stall (not a disasterous stall).
> I think you found
>this out yourself. It
>also makes for a verry
>groovy airplane. I never
>considered the possibility that weight
>in the spinner might be
>hard on the engine.
>I have many thousands of
>flights, nearly all having weight
>in the spinner and never
>had a problem though on
>occasions I carried as much
>as 3 oz. I
>used 2 oz to initally
>trim the Millennium, and
>would have left it there
>forever had I not lengthened
>the nose.
>In sort, larger flap deflections
>or larger area create more
>lift. They also create
>more drag in the process.
> Drag is simply a
>retarding force opposite thrust.
>With a 61 in a
>60 oz airplane, drag is
>not a limiting factor. You
>already have a comfortable excess
>of power.
>Using a lot of control deflection
>requires a larger handle movement.
> This may be uncomfortable
>or awkward. Simply increase
>the line spacing on the
>handle. Because of the
>control deflections I normally use,
>I seldom fly with less
>than a 6" line spacing.
> I prefer nose heavy
>airplanes for groovy maneuvers as
>opposed to useing "tandem wing"
>airplanes (extremely large stab/elevator area
>which also limits control deflections.
>

Don't you think that maybe simply reducing the elevator travel relative the flap might be a more direct solution than throwing in nose weight? This is easily accomplished with slider elevator horns. Removing the hinge seal also increases the possibility of different inside/outside performance, and also significant roll trim issues if everything isn't perfectly symmetrical with the hinge gap.


One nice thing about modern airplanes (as you refer to them, tandems, with the typical 25% tail) is that they groove just fine with the CG at 24-25%, without incurring the heavy drag penalties and heavy control forces that come with far-forward CGs. It's been my experience with these type of airplanes that lots of times, moving the CG forward causes them to hunt, or at least be very hard to settle down after a corner.


I agree that using shaft weights don't seem to cause any wear problems.

Brett

Just a thought, but some airfoils don't seem to like to fly at 5.5, have you thought about trying a 5.2 or 5.3 lap speed. Seems to work best for me on the SV type planes, especially if your engine has a really soft break or no break at all.
EJV

> Don't you think
>that maybe simply reducing the
>elevator travel relative the flap
>might be a more direct
>solution than throwing in nose
>weight? This is easily accomplished
>with slider elevator horns. Removing
>the hinge seal also increases
>the possibility of different inside/outside
>performance, and also significant roll
>trim issues if everything isn't
>perfectly symmetrical with the hinge
>gap.
>
> Brett

Brett, are you suggesting less than 1:1 ratio here? Matt has been using the adjustable horns on his last 4 or 5 planes and has had to increase elevator throw in relation to flap on all of them. But, then, he builds with large flaps, thick airfoils, and light loading.

In answer to one of Doug's questions, you need more flap with a heavy airplane, less flap with a lighter one. That is how Bob gets away with his small flaps. Instead of changing flaps, however, by using the above adjustable elevator horn with the slider, one can "dial in" the amount of flap needed after the plane is built. In Matt's case he was getting too much lift. So he dialed in more elevator (net effect, less flap for the same amount of elevator travel) and narrowed the spacing on his handle. It would be best to have too much flap and do it this way, I would think, than the other way around.

And, yes, the Bear has a thinner airfoil than the Trivial Pursuit, so the lift characteristics are going to be different. If it makes you feel better, it took us about 200 flights to get Matt's last plane "dialed in" and we were still trimming after 1000 flights.

Trimming is a never ending process.


Leonard Neumann

>Brett, are you suggesting less than
>1:1 ratio here?


Yes, more flap than elevator. This would appear to be a more direct solution to getting more flap travel than running the CG forward.

I am still incredulous that the airplane is running out of lift at this relatively light wing loading. There has to be some detail that's causing it. If it's this close to the edge in the winter, what's going to happen when it's 100 degrees out?

Brett

> I am still incredulous
>that the airplane is running
>out of lift at this
>relatively light wing loading. There
>has to be some detail
>that's causing it. If it's
>this close to the edge
>in the winter, what's going
>to happen when it's 100
>degrees out?
>

Doug said the weight was up to 61 ounces now, and someone else here estimated the actual area at 657 squares, down a bit from the published number.

This gets the loading up to 13.3 ounces/ft2. This would be the equivalent of a 50.8 ounces Nobler. Not exactly light, but not in stall territory. And his power to weight ratio is still quite comfortable.

As Godzilla stated, it may come down to the definition of a stall.


Currell

I just finished building the new flaps. They are 21%. They are also removable. I will not build another plane without removable surfaces. Two coats of butyrate and I will be flying it and we shall see. These new flaps are full span and there is alot less taper.

Brett,

I know it sounds crazy that 61 oz stunt ship with a 61 in it wont turn. What do think I am thinking???? Believe me I will be looking for anything that could be causing this problem. I really dont like the way the new flaps look. If I can get back to the original look I will.

The airfoil is so different than the TP. I believe you could ride around on the outbaord wing of Teds plane and it would still turn. I have found all the thicker foils tried down here in TX have an uncontrollable urge to bobble all around all the time. The thinner lower aspect ratio are more stable. EXCEPT for one, that green thing Godzilla flies is down right smooth and solid.(Time Machine basis)

The first time I built one of these in 1997 Bob said and I qoute "Keep it light, more than 56 and it wont fly" He wasn't kidding.

Al,

I gotta keep the tape on. Without it the plane just flops and farts around really makes me crazy. With the tape on it is smooth and I get a real reaction from the input. Without it there is no telling what will happen. I really wish I had a slider horn so I could dial in flap. Drag is not an issue. I dont have that horn so I had to go with bigger flaps.

Len,

I know it takes along time to bring a plane "in" There is huge difference between coming in and simply truning 120 degrees. Trimming is an ongoing process that is really pretty cool. I am keeping a log of every flight and have all the adjustments that I made along the way are written down.(but not all the cuss words I said)

I hope to fly it soon.

I check this all the time so keep it coming.

Thanks for the all the input. I am keeping it all in mind as I go through this horrible process of hacking the flaps off of my new plane.

DMoon

Doug
There is nothing wrong with fat airfoils here in texas or anywhere else. One observation dose not a fact make. I'll bet that that fat airfoil you didn't like had a very rounded leading edge. That leading edge profile is a lot more likely to be a cause of 'bobbling' than the airfoil. it gives the stagnation point plenty of room to wander around changing the lift as it moves. This is why I recommend a fairly sharp leading edge. Also I do not agree with Brett's comment that nose heavy airplanes tend to hunt. The farther forward the C.G. is the more stable any airplane is. End of story. Let anyone show me any text that would suggest otherwise. The more stable an airplane is the better it will groove. I strongly disagree that observations of model airplanes create new laws of aerodynamics. In any case, My fat airfoils with moderately sharp leading edges have flown well in Texas heat for many thousands of flights. They groove as well as any 24% stab. The laws of aerodynamics are for all practical purposes static. The application varies. I have no trouble with 24% stabs and aft C.G.. It is just another way to achieve stability. Why is it that people think that the way they do something is the only right way, or at least the best. Ain't necessairly so.
Al
Doug, If your airplane is flying well with noseweight, why change it? You obviously don't like the look of the larger flaps so why install them just to avoid harmless nose weight.
Doug

>Doug
>There is nothing wrong with fat
>airfoils here in texas or
>anywhere else. One observation
>dose not a fact make.
> I'll bet that that
>fat airfoil you didn't like
>had a very rounded leading
>edge. That leading edge
>profile is a lot more
>likely to be a cause
>of 'bobbling' than the airfoil.
> it gives the stagnation
>point plenty of room to
>wander around changing the lift
>as it moves. This
>is why I recommend a
>fairly sharp leading edge.


7/8" LE radius (as you suggested above) is *extremely blunt* even by West Coast standards. I assume you mean 7/8 diameter-7/16 radius, which is still what I would consider moderately blunt, and is about what my airplane is.


>Also I do not agree
>with Brett's comment that nose
>heavy airplanes tend to hunt.
> The farther forward the
>C.G. is the more stable
>any airplane is. End
>of story. Let anyone
>show me any text that
>would suggest otherwise. The
>more stable an airplane is
>the better it will groove.
> I strongly disagree that
>observations of model airplanes create
>new laws of aerodynamics.

But understanding does change. Running minimal stability margin reduces phugoid stability. Therefore you don't have too much tendency to nose up into the wind, and nose down downwind, therefore there's little need to input control effort, which tends not to trigger an latent hunting tendency. I would also point out that the same effect happens in the manevuers. A far-forward CG, leading to lots of phugoid stability, just requires a lot of compensation by the pilot as the airspeed changes while manevuering as well. As long as it just barely positively stable, you aim it in a particular direction, and airspeed change doesn't affect it's track. This is one of the things that makes these style airplanes, trimmed as most modern airplanes are, so easy to fly once you get them right.

Hunting rarely has anything to do with aerodynamics directly. It's almost always a result of slop or binding in the controls, excessive yaw angles, or aeroelasticity. Anything that can be done to minimize the control input required helps.


>In any case, My fat
>airfoils with moderately sharp leading
>edges have flown well in
>Texas heat for many thousands
>of flights.

I certainly agree that there's not anything that different about Texas that should require grossly different design. However, there is a compromise to be made. The thicker airfoil gets incrementally more lift (although not nearly as much as the thickenss difference suggests), but it also is a speed stabilizer. The mere fact that it's thick creates a lot of parasitic drag,and a high ratio of parasitic to induced drag makes the airspeed tend to be very very stable. In 4-2 break days, this was highly desirable, since the engine/prop didn't provide much stability, at least in the short term. With piped engines spinning low-pitch props at relatively high revs, you get a tremendous stabilizing from the engine. This is a double-edged sword - it keeps the speed up in the middle of the corner, keeping 650 square inch/70 oz airplanes from stalling (and allowing them to win the NATS) and generally keeping the control feel constant throughout the maneuvers. The down side is that it can be overdone, and cause a lack of "drive" into the wind, like at the tops of square 8s, and overheads. Add a hugely thick wing to stabilize it further, and the timing required to fly the manevuers gets pretty difficult. Note this isn't an indication of lack of power, but in fact an indication of a lot of power being overdone.

The wing thickness is a compromise - too thin, one runs out of lift and, more importanly, are too prone to slight engine power variations causing the model to "burst" in speed whenever the engine speed changes. Too thick, and you get too much speed stability and a lack of penetration back into the wind.

Bill Werewage's airplanes are closer to the former, and the West Coast airplanes are closer to the latter. I think that Ted and I have gone too far with ours, and that somewhere in between is probably ideal. This is also why we end up using different props - our Brian Eather's have quite a bit more effective pitch than an equivalent Bolly's. The net effect is for us to reduce the speed stability of our airplanes to get better penetration, and making it back up with the airplane. The thin-wing midwest/southeast models end up with less effective pitch to give better speed stability, making up for the reduced speed stability of the airplane. In comparison, they end up about the same.

The quest for more lift is (or had been until Doug's new airplane came along) pretty moot, as almost any airplane at any buildable wing loading has no trouble at all with stalling. There have been a few - Jim Aron's "Boogaloo 3" at 615 and 70 oz is marginal - but it's pretty hard to build a tuned-pipe airplane too heavy to get through corners.

As an illustration of the speed stability effect on the cornering ability, with a 40VF and a Bolly 11.5-3.4 2-blade, the Boogaloo 3 had very little issue stalling in the corners, and when it did, it was the last corner of the manevuers (third leg of second triangle, last few corners of the square 8, etc) as it slowed down during the maneuver. With a PA61/Brian Eather 12-3.6 u/c 3blade, it stalled in the first corner of every maneuver, and made it through the rest with no problem at all.

The interpretation I think applies is that the short-period speed stability provide by the low pitched Bolly spinning very fast keeps the speed up in the middle of the corner better than the Brian Eather prop, just by virtue of the lower effective pitch. Of course, the engine doesn't come on as much, so the speed slowly bleeds off during the maneuver, and ends up to slow by the end. Conversely, the Eather prop on the 61 doesn't have nearly as good short-term speed stability, allowing the speed to drop in the middle of the corner, leading to a stall. But the engine subsequently breaks and speeds the airplane back up, making the rest of the corners doable.

Of course, with any 4-2 break motor, this airplane would be a mega-dog that you'd have next to no chance of getting through a pattern, much less finish 4th in Advanced as it did.


The design driver for wing thickness with piped airplanes has very little to do with lift capability, and everything to do with complementing the engine/prop speed stability characteristics.

4-strokes seem to be a middle ground, but I don't think anyone claims to have come up with the optimum design yet.

They groove
>as well as any 24%
>stab. The laws of
>aerodynamics are for all practical
>purposes static. The application
>varies. I have no
>trouble with 24% stabs and
>aft C.G.. It is
>just another way to achieve
>stability. Why is it
>that people think that the
>way they do something is
>the only right way, or
>at least the best.
>Ain't necessairly so.

Indeed.

Brett

Brett,
What is this phugoid stability argument? Are you serious suggesting that all nose heavy airplanes are subject to pilot induced oscilation in maneuvers and hunting in the wind. And you have no farther justification for this rather esoteric line of thought than your own observations? First I have never been subject to any of the effects you describe and have won a few NATs myself with nose heavy airplanes. Second, since when do all modern airplanes use pipes? I have observed many piped airplanes and still prefer the old standby 4-2 engine runs. My airplanes are very draggy in corners because they are designed to use much more lift/wing area than modern airplanes. They slow noticably in hard corners and depend upon a great deal of thrust to recover flying speed while climbing vertically. Stop-Go corners are very pleasant to fly and allow, in my opinion, a superior presentation. It is not always ideal to be so locked into a speed that the wrong prop has the effects which you describe. With a 4-2 engine run, the engine runs slower in level flight and breaks very hard to accelerate vertically, pulling, perhaps, instantaneously more power than a "locked in" pipe would permit.
I agree that 4s may bring a whole new day with unknown possibilities in the development of usable power and torque. In anticipation of those new days, I have ready for paint a new Bearcat with Saito 72 power. Maybe then we can be in closer agreement about engine runs than aerodynamics.
Till then, I'm also building a new Millennium 2 with another 4-2 breaking Pa 65 which is such a pleasant combination to fly in my Millennium 1.
Too bad I don't compete anymore. It was easier so "sell" new, radical (but classical in the book sense) ideas by beating people with them.
" Modern airplanes" with aft C.G.s and pipes are not necessarily the best but they have become the fashion. If they were truly the best, they shouldn't require such vehement defense.
I may be out of touch competitionwise but 50 years of professional flying and instructing gives me a nose for opinion being passed as fact.
Al

>Brett,
>What is this phugoid stability argument?
> Are you serious suggesting
>that all nose heavy airplanes
>are subject to pilot induced
>oscilation in maneuvers and hunting
>in the wind. And
>you have no farther justification
>for this rather esoteric line
>of thought than your own
>observations? ...
>...I may be out of touch
>competitionwise but 50 years of
>professional flying and instructing gives
>me a nose for opinion
>being passed as fact.
>Al

For crying out loud, Al. That comment was out of line. Just because you don't understand the point doesn't mean it hasn't merit.

Brett may not build himself a pontifical podium based on his professional accomplishments...although he well could. His entire life's work is based on the minute control of very, very expensive objects in very, very rapid motion with a whole lot more at stake than a plaque on the wall. His opinions on such subjects are informed and worthy of consideration. He certainly has as much right to have them considerately reviewed as do you or I.

You mentioned championships? Paul Walker has seven, David Fitz three and I've got four. Brett's got none. When Brett talks, we listen. And by opening our ears rather than our mouths we learn a lot because his "opinions" on nuances of mass in motion are the result of more real world knowledge of the subject than pretty much the rest of us put together.

Brett has offered nothing other than his opinion on subject matter for which he has much to offer his fellow flyers. He has offered specic reasons why his approach diverges from yours with courtesy and respect for your opinions and accomplishments. He deserves nothing less than the same from you.

Ted Fancher

For crying out loud Ted. Do you always take comments out of context when you want to criticise someone. You picked the first and last sentences of my response and linked them. I really don't like the phugoid stability argument as I think it isn't demonstrable and very unlikely to be a problem in anyones stunt ship. The last sentence which you tied to the first was a general comment that there is much too much squirrley opinion being passed off as fact, and I'll point it out when I see it, even if its yours, particularly if its yours. I meant no insult to Brett whose opinion I also respect. And what makes you think that I don't understand Phugoid stability or the points Brett was making?

Brett,
I really do have a problem understand the practical effect of tape on flaps. You propose an excellent experiment. I will tape the outboard flap on the Millennium and give it a try. As for the rest of it, I like a Semi-scale airplane, macho in every possible way that draws every eye and occasionally pulls me off balance. I like Harleys, you like Lexus. I don't like anyone suggesting that Lexus thought is the only way to win. It may take more practice to win with Harley types but the practice itself is fun and invigorating. Maybe thats not so bad.
Al

>
>The last sentence which you
>tied to the first was
>a general comment that there
>is much too much squirrley
>opinion being passed off as
>fact, and I'll point it
>out when I see it,
>even if its yours, particularly
>if its yours. I
>meant no insult to Brett
>whose opinion I also respect.
> And what makes you
>think that I don't understand
>Phugoid stability or the points
>Brett was making?
>
>Al



If you respect his position why the comment about nothing other than his experience to back up his comments?

I see no problem with people airing their understanding of aerodynamics on boards such as this..even if they aren't trained in the science. By doing so a discussion (like this one) is generated in which various theories (yes, not all of which are supportable by the science) are addressed, experiments might take place (as Doug is doing) and knowledge is gained by all (or most all) who participate. Why do you find it necessary to disparage other points of view with such language rather than merely providing more precisely correct arguments. Why do you find it necessary to disparage the choice of successful stunt ship selected by others rather than to simply recognize that it is a different way than yours but obviously works just fine.


"Tandem" stunters (another pejorative choice of words apparently chosen to disparage the choices of others) are hardly a fad or "fashion". A number of very competent designers, builders and flyers have seen some degree of merit in the approach and have advocated it as a means of doing the stunt thing. Nobody on this thread remotely suggested that theirs was the ONLY way to fly stunt. Why you chose to say they did is illuminating of something...

What follows is a point of view informed by some practical and book knowldege but does not come as if from an oracle. Feel free to address it in an appropriate fashion if you find it to be in error factually.

The phugoid stability discussion is valid and can be demonstrated. Which is not the same as saying it can't be dealt with.

Very far forward CGs require greater "logitudinal dihedral" than do CGs located farther aft. In other words the download on the tail (or upload on the canard, in such a case) becomes greater the further forward the CG is from the neutral point or center of pressure. In our case this means the elevators are up and the flaps down an amount appropriate to achieve a balance of lift to gravity.

This results, in fact, in a higher angle of attack on the mainplane to support the additional load (to be more precise, on the forward plane to again address the issue of canards).

Lift is a function of the square of airspeed. Because we are tethered and because four pounds moving at 55 to 60 MPH has inertia our airspeed as well as our ground speed varies as we circulate around the circle in significant winds. As we travel upwind, lift increases proportionately and the airplane will attempt to climb and the AoA must be lowered to maintain altitude. As it progresses to the downwind side the reverse occurs as the ship is momentarily slower in airspeed and the angle of attack must be raised proportionately.

(To others, the above may sound counter-intuitive. In normal untethered flight an aircraft moves in the airstream much as a boat in a current. Thus, absent meteorlogical phenomena such as wind shears, the planes AIRspeed "within" the airmass is constant even though the apparent speed to an observor on the ground is quite different. When we tether or c/l ships additional consideration must be made for the existence of the "mass in motion" aspects as we fly into and out of the moving air mass. Since mass can't change speeds instantaneously the inertia into the wind will result in an increase of airspeed for a duration dependent on how much mass is moving how fast. The reverse is true going into a downwind condition...the mass can't accelerate instantaneously and, thus, AIRspeed will be slightly slower (and lift less) until inertia is depleted)

The farther forward the CG is the greater the load and thus the effect. Taken to an extreme it is fully conceivable to move the CG forward to a point that full up control is required simply to keep the nose from dropping...don't even need an aeronautical degree to visualize this.

Somewhere between our "tandem" stunters and this last example are a number of workable "in-betweens" which will variously appeal to a given flyer. The only thing anyone else on this thread has done is to advocate why one way appeals to them. Noone has suggested anything about the "only" way...except you.

By the way, have you ever built that canard stunter with the CG at 25% of the mainplane?

Ted

Ted,
I must admit that in this case your aerodynamics are impeccable. Both you and Brett certainly are correct that theoretically there is a requirement For down elevator for all stunt ships in flight at all times and this need increases when the stunt ship passes downwind and picks up airspeed from momentum and this effect is greater for nose heavy airplanes. OK, why are we discussing this? It is very theoretical. I'm not saying that it isn't there, I'm just saying that differences in C.G. location aren't that great so differences in the experience of the effect are small and lost in normal maneuvering, For the rest of us it has little, if any, practical effect. You choose to incorporate the possibility of experienceing this effect into the design of your airplanes. The effect is small enough that I see no harm in ignoring it. Dose this make your airplane better than mine? The answer to that would hang on more noticable criteria than this.

While thinking about the argument that airplanes with aft C.G.'s have greater phugoid stability, it occurred to me that nose heavy airplanes have greater inertia in pitch. They balance farther forward from the C.L. or neutral point. This greater moment arm must make the nose heavy airplane more resistant to momentary longitudinal upsets i.e., turbulence. This is a practical definition of a "groovy " airplane. There is seldom a win-win in aircraft design. We compromise. I have a very groovy airplane. If I've lost something in phugoid stability when the wind blows, I'll just have to live with it, surely made easier by not noticing it.
Al

Brett,
Of course I meant 7/8" diameter. I just read the number off my template without thinking about it. It isn't a radically sharp leading edge but then you and I aren't having problems with it either.
Al

Doug,
I am frankly baffled by the use of taped surfaces. I have certainly experienced the increased sensivity of elevators with tape but I am not sure the elevators are acting as airfoils when we deflect them to large angles when we maneuver. In fact many people are using fat flat stabs now which certainly aren't airfoils in any conventional sense. I do agree tape works here probably by stopping air from escaping from the high pressure area.
Flaps are a different matter though. They are definitely airfoils. I have been unable to make tape work (do anything) on the flaps of two airplanes I tried it on. Theoretically, I would think a gap at the hinge line would be benificial. I spent more than 9000 hours flying an airplane (B-727) with triple slotted trailing edge flaps to make more lift at slow speeds. Stalls are turbulent, seperating airflow over the trailing edge of a wing. Airflow through slots has the effect of smoothing and reattaching that turbulent aiflow or at least delaying its seperation. Maybe hinge bleed is more turbulent than "slotted" airflow. Excepting this, I can't see how sealing the flap slot would improve lift. Maybe it dose. Maybe it dosen't. It didn't on my two airplanes but it has wide acceptance. I don't think many stunt ships actually get anywhere near stalling as they maneuver. The wings are bigger than necessary and flaps don't do much on reduced stability aft C.G. airplanes which turn easily with small control deflections. If tape dose anything, it probably has to do more with airflow than lift.
As for flying squirrely without tape on the tail, again, I've found no problems flying untaped airfoiled stabs with sufficient tail volume coefficient. Flat stabs may be easy to build and install with precision but people who fly them seem to have more trouble with groove and bobbling. When I use a calculated value for tail volume tape gives me too much sensivity. I tried tape. With an open mind, I put it on my new Millennium before I flew it expecting great benefit. The airplane flies better with the tape off both the wing and tail (removed at different times).
Al

The bigger flaps made the airplane better overall. They were needed, no matter what. I question those tiny flaps now, even at 52 OZ.

What next? Is it possible that Doug is stalling the stab also. As Brett said, this is very extreme case for such a slightly overweight airplane. But, trust me, it was STALLING, but only in the 120 degree corner.

The new stab is flat and very thick (it appears to be 1/2" or more) with a very blunt leading edge.

The airplane tracks extremely well and does 90 degree manuevers VERY well.

About this tape stuff. I have yet to try it on the elev. due to the rain on Sunday. As far as the tape on the flaps. Some planes need it and some dont. I dont think it has to do with size of the gap as much as the amount of lift the wing is producing. If the wing is producing more than the required lift at the AoA then air escaping through the gap would not be detrimental to the lift of the entire surface structure. You talked about flying 727 with flaps with gaps. I am sure the AoA of a 727 on approach or take off is not anywhere near the AoA of a modern stunt ship trying to make 120 degree turn form level flight in a radius as small as humanly possible. The air escaping through the hinge lines at low AoA is not going to make a difference but at high AoA it very well does. You are correct laws of phyisics dont change. However the numbers that can be applied in real life full size airplanes cant always be applied in small models such as ours.(reason being there are no real airplanes in the world that fly like ours do end of story) When an airplane has exceeded its weight limits such as mine has you want to get all the airleaks sealed and keep as much pressure on one side of the wing. Once the flap becomes large enough to support the undersized(Thickness is small) airfoil then the tape can come off and the difference wont be noticeable. I have to increase the flap because I cannot change the ratio in flap deflection to the elev.(I wish I could) 7/8" radius is extremely blunt in my book. This might make a few cringe but take a piece of 1/4 inch bar stock balsa a round it off and that is my leading edge radius no larger for sure. Some will say that is way to sharp. Dont tell my second place nats plane that. It really flys will with sharp edge. It only weighs 53 oz on the heavy days. It was 52 at the nats I took out alot of tail weight when I got there. It also has a BIG FAT FLAT STAB. It works very good. I am sold on the flat stab. I am wondering about the thickness of it. What would be good and what would be bad? How thin or thick can it be?

Brett and Al are in a friendly debate about nose heavy. A plane can be to nose heavy. I would be very willing to bet that Al's plane is still very much in normal ballpark area of cg being forward. If it were to be out way in front it would hunt. No question about that. The Barbell effect comes into play sooner or later either way you go. I flew Al's blue and white Bearcat. Cool plane for sure. He told me it would be sensitive due to the large line spacing. It was not sensitive to me at all. It did seem however to react differently than other stunt planes I had flown. With all that spacing I still had to really pull on it to turn it. Like it didnt have enough leverage. It did not take alot of movement just alot of force to get that movement. Not really nose heavy. I know that sounds stupid but that is what it felt like. Spacing at 6" sometimes in a very hard corner it seemed to be on one line. Then I blew it on the landing I felt like a big idiot. Sorry about that Al. I just hate it that blew it like that. I would like to get another shot that sometime.

Every airfoil has a weight limit. I feel the limit in this particular design for my flying style will be at 56oz or lower.(the designer himself said so) Any heavier and you will have to make adjustments accordingly. I am having to do so.

After going back and reading articles and talking with Godzilla I have torn off the old very tapered flaps and added full span flaps with a slight taper. On the last few flights the other day it was turning relativly well. It seemed to tip stall or bang the tip as some say. The complete and drastic loss of lift was pretty much gone. I asked just the other day about howcome the outboard flap is larger. My new outboard flap is larger just slightly. I hoping the less taper flaps will help support the tip more. By the way I am way low on tip weight. It is not the weight in the box banging it. I think it is the wing itself.

Wish me luck.

DMoon

Doug,
I think you missed a point. In fact, I think you missed all of them. First, yes, obviously, I meant 7/8" diameter. Until my last airplane I built all of my airplanes the same as you with 1/4" diagonal leading edges. If you are still building the same then we probably have very nearly the same radius leading edges.
Second, why do you thing that a stunt ship and a 727 stall at vastly different angles of attack. From what text or airfoil tests did you arrive at the idea that a 727 with 30 degrees of flap stalls at a lesser angle of attack than a stunt ship with 30 degreees of flap in a triangle corner. A stall is a stall. It is the result of seperating airflow, usually starting at the trailing edge of the wing. Most airfoils stall at very nearly 15 degrees angle of attack. A landing stunt ship stalls with the nose up a bit and the airplane setteling a bit, probably around 15 degrees. A landing 727 gets stall warning at about the same attitude. When maneuvering, an airplane stalls at a higher speed but much the same angle of attack. It stalls at a faster speed because "G" loading makes the airplane seem heavier to the wing. It stalls at higher speed because it is carrying much more weight, maybe 15 times more weight for a stunt ship but the angle of attack remains much the same as a landing airplane. As for your supposition that a high speed stall forces more air through the hinge gap, there is no evidence of this and even if this were true, why isn' that slotted air helping to reattach the seperating airflow? Unless you hinge your flaps in a non- traditional way, then the hinge slot closes anyway as the flaps reach their limit of travel. The interesting this here is that aft C.G. airplanes probably don't use flaps to their limit to maneuver. Ah, such a mystery. Read some basic aerodynamics for pilots or run some tests. Relying on opinion to design airplanes is a suspect tactic.
Before you and Richard flew the Bearcat I added 1/2 oz more noseweight to make the airplane more comfortable for a pilot not familiar with the airplane. If I had known you wanted it to turn like a Bear, I'd have taken nose weight out. I don't think that one flight on a strange airplane would give more than a taste of what the airplane might be capable of if trimmed to suit.
Al

Reference the above:

"...the leading of the wing is made very BLUNT (caps in original) which helps to delay the stall to a higher angle of attack which in turn produces more lift"

from the aritlce "MUSTUNT", American Aircraft Modeler, February 1973. Author, Al Rabe.

Ah yes, That was a carelessly written comment twenty odd years ago in the middle of an article meant to help beginners. I'm flattered you read the article well enough to be able to quote from it. It was, of course a different conclusion from those expressed in the Sea Fury article which preceeded it where I chose the Sea Fury airfoil because of its sharper leading edge.
Thank you.
Al

Its hard to rember a train of thought from 28 years ago, but, on second thought, I'll stand by my original published comment. I think blunt airfoils probably contribute to greater lift. In the original context, I was designing a small stunt ship for beginners. It was small so that a worn out Fox 35 should be able to pull it adequately. It had a fat airfoil because I thought lots of lift would be beneficial to a beginner who might finish his airplane with a couple or three coats of house paint. The goal was give a poorly built airplane a chance to fly well enough to let a beginner learn to fly and build. I don't think I've said since that moderately sharp leading edges contribute to lift. I have said that moderately sharp leading edges fly better in indefinable ways, maybe a better groove, or better penetration, things a good flyer would recgonize and appreciate but would be of secondary importance to a beginner.
When I buile the Millennium I used Tom's Lincon log type jig. I designed in a 7/16" radius leading edge. When time came to sand the leading edge to shape, it seemed too blunt. I added a 1/16" strip to the entire leading edge and sanded it into the rib contour. When the airplane was flown and was found to be stall prone, I questioned whether I had made a mistake in sharpening the leading edge. When the airplane responded admirably to the usual remedys for stall I was relieved to find, once again, that, generally speaking, a moderately sharp leading edge dosen't aggravate a stalling tendency. Thisw is a far cry from suggesting that sharp leading edges delay stall or increase lift.
Al

A thought about Mr Rabe's comments about slotted flaps and stalls, etc. I tend to agree that having a gap in the hingeline would, I would think, aid in flow attachment over the flap and be a good thing. Empirical observation of stunt planes and taped surfaces shows it works on some planes, and does not(appear to) on others. My Fluids math is pretty much non-existent anymore, but I'm wondering if that at the Renyolds numbers for such small planes as we use if some of the normal aerodynamic theories don't work as well as they do on full size aircraft. Certainly with a small wind tunnel model you have to be aware of this issue when testing something that will be scaled up. I wonder if stunters are just on the edge in terms of size of being something that will not always behave in a way we expect. Even if that hinge gap looks pretty big to an air molecule, I would imagine the boundary layer over that Bear wing is as big as on Teds 747. That has to have an effect on how the wing flies, or what that hinge gap sees, that might not be reproduceable on a full scale airplane.

Steve

>Flaps are a different matter though.
> They are definitely airfoils.
> I have been unable
>to make tape work (do
>anything) on the flaps of
>two airplanes I tried it
>on. Theoretically, I would
>think a gap at the
>hinge line would be benificial.
> I spent more than
>9000 hours flying an airplane
>(B-727) with triple slotted trailing
>edge flaps to make more
>lift at slow speeds.
>Stalls are turbulent, seperating airflow
>over the trailing edge of
>a wing. Airflow through
>slots has the effect of
>smoothing and reattaching that turbulent
>aiflow or at least delaying
>its seperation.


The analogy of 727 triple-slotted flaps to what we build on stunt planes is pretty thin. If you did manage to come with a similarly articulated system that worked in both directions, you would no doubt get more lift than a sealed hinge. But just a plain gap doesn't remotely work that way.

>Maybe hinge
>bleed is more turbulent than
>"slotted" airflow. Excepting this,
>I can't see how sealing
>the flap slot would improve
>lift. Maybe it dose.
> Maybe it dosen't.

Sealing the flap hinge prevents the air bleeding through from messing up the flow over the flap. There's one quick and unequivocal way to find out -seal just the outboard flap hinge line. Should be pretty easy to see which way it rolls. I urge you to go pretty easy with it, I have done limited versions of this experiment, and it works a little too well. Same thing happens in the tail, which is in fact an airfoil, just a really crappy one. Frank Williams' wind tunnel test proved the point pretty conclusively.

But the best reason to seal the hinge lines, in my opinion, has nothing to do with enhancing the lift (which is largely moot anyway), but instead is to even out any possible differences in the gap. If one makes a ~.020 hinge gap, even being off .001 from side to side makes the gap 5% different, which is bad no matter which way it effects the lift. Even worse, if the hinges are not exactly centered, it can cause the gap to be different at different control deflections, which makes it very difficult to trim.

Ironically, the larger you make the gap, the smaller the likely difference in the airflow through the gap, and the less differential lift and hence rolling torque, you get. I haven;t looked at your hinge gaps closely, but if it's around 1/16-3/32, you probably won't have much side-to-side difference.



>It didn't on my two
>airplanes but it has wide
>acceptance. I don't think
>many stunt ships actually get
>anywhere near stalling as they
>maneuver. The wings are
>bigger than necessary and flaps
>don't do much on reduced
>stability aft C.G. airplanes which
>turn easily with small control
>deflections.

This is almost certainly true. I know my airplane will turn much tighter than I ever try. I beleive the real issue is that the technical capability of the airplane to turn is far in excess of what I (and I strongly suspect everyone else) can reliably control. Running out of lift simply isn't an issue.

If tape dose
>anything, it probably has
>to do more with airflow
>than lift.
>As for flying squirrely without tape
>on the tail, again, I've
>found no problems flying untaped
>airfoiled stabs with sufficient tail
>volume coefficient. Flat stabs
>may be easy to build
>and install with precision but
>people who fly them seem
>to have more trouble with
>groove and bobbling. When
>I use a calculated value
>for tail volume tape gives
>me too much sensivity.
>I tried tape. With
>an open mind, I put
>it on my new Millennium
>before I flew it expecting
>great benefit. The airplane
>flies better with the tape
>off both the wing and
>tail (removed at different times).


I think the reason for this is clear. The sorts of thing people like about aft-cg airplane with highly effective stabs and high l/d wings, like speed stability and consistency of control feel, are diametrically opposed to what you want. You say you want it to slow down a bunch in the corner, turn, and then accelerate out. For this, you need a 4-2 break motor with a lot of pitch, low l/d, a reasonably large amount of lift (to support the turn at reduced speed), reqasonably light wing loading. and a far-forward CG to give you a large control force so that you can get the control centered again on the exit.

Sealing the controls, running low-pitch props at high revs, and aft CG's with slow controls have the effect of making the airplane slide through corners with little drama, almost as if nothing happened. This is for sure what I'm shooting for, as are most others flying today. I seem to remember you using the word "deplorable" to describe this approach in our last phone conversation . That's perfectly valid opinion, even though I couldn't disagree more.

My net assesment of this hopefully friendly argument is that we seem to largely agree on the technicalities (i.e. why certain things have particular effects), but we are diametrically opposed on the ultimate goal.

I don't think there's any need to argue about the best approach; it is personal preference. My one defense is that I've flown a lot of flights both ways. There's no doubt that I personally fly a lot better with airplanes trimmed my way than I did when I trimmed them your way. It's also my observation that most other people do as well. But if you give both ways an fair try and don't like mine, that's fine by me.

Brett

Hi again, Doug.

Just occurred to me after re-reading all the posts on the thread that we've ignored one possible area of consideration.

None of your comments about stalls (particularly in the initial stages) seemed directed to outside corners. In retrospect you mentioned only triangle and bottom of the hourglass.

Did you "ever" experience stalls in outside corners?

Have you noticed any difference in the "character" of the inside turns versus outsides? Does the ship turn more readily one way than the other? Does the ship fly tail high (even a little) one direction and tail low (even a little) the other?

Can you adjust the length of the flap to elevator horn?

Have you considered taping a large piece of thin plastic around the leading edge from high point to high point to effectively blunt the leading edge and tried to stall the ship?

Ted

p.s. going to Shanghai tomorrow. Not back 'til Friday.

>Hi again, Doug.
>
>Just occurred to me after re-reading
>all the posts on the
>thread that we've ignored one
>possible area of consideration.
>
>None of your comments about stalls
>(particularly in the initial stages)
>seemed directed to outside corners.
> In retrospect you mentioned
>only triangle and bottom of
>the hourglass.
>
>Did you "ever" experience stalls in
>outside corners?
>
>Have you noticed any difference in
>the "character" of the inside
>turns versus outsides?

HEY, I GUESS I AM PRETTY SMART, Doug. That is what I told you on the phonne last night. Outside triangles, remember?

Your Pal with love and kisses,
The Big Green

>
>>>
> I agree that
>using shaft weights don't seem
>to cause any wear problems.
>
>
> Brett
>

I could see, however, how two or three ounces in addition to a large diameter prop and a very large spinner could combine to produce a lot more precession than other combinations.

Ted

>>
>>>>
>> I agree that
>>using shaft weights don't seem
>>to cause any wear problems.
>>
>>
>> Brett
>>
>
>I could see, however, how two
>or three ounces in addition
>to a large diameter prop
>and a very large spinner
>could combine to produce a
>lot more precession than other
>combinations.


For sure that's true. The shaft weight in and of itself is probably not a huge contributing factor since the radius of gyration is not too big. Even a little change in the prop mass makes a huge difference in the amount of precession. Whether you think a large change in the precession is a signficant trim factor is another thread...

I think the usual practice of getting the CG close with the shaft weights since they are easy to alter, then transfer it to lead in the fuse, is probably the way to go.

On a related note, the Eather U/C props are tremendously lighter than most others, even a lot of wood props of equivalent load. That's another thread as well.

Brett

I dont know where I am going to put 2oz of lead in the nose. It only has 9" moment.(ouch) It is really going to be large task to find some place to hide 2oz.

I have talked alot about scale models with some guys from the local hobby shop. They tell me that Real Scale numbers can only be taken down so far before things start to change drastically. You get to a point where there is not enough power on the flying surfaces to create the desired effect in flight. He then went on to say hook control lines on it and turn it 120 degrees and it is all out the window. He calls it "VooDoo Aerodynamics"

I will state it again there are no planes world wide that do what ours do. In RC they emmulate a pattern flown by real stunt planes.(except for prop hanging at 5 feet) In scale they fly scale like flights. Take Typhoon scale it down and build it exactly scale and it will not be competitive in our sport.

This is where I believe keeping the pressure on each side of the wing to be a key essintial point in some designs or trim for certain bad characteristics. Yes if the air bleeds through it may help it to stick to the flap. Also the pressure has changed and this can cause seperation also. It needs to be in wind tunnel to see for sure.

DMoon

I am not missing the point. I am not missing any of them.

It is simple. The plane stalled early on in its initial test flights. It stalled on all corners inside and out. It did not stall in simple climb and dive manuvers. Not straight up and down but gradual up and down. No matter what anyone says or proves or tests or reads or blurts out this plane had less of a tendancy to stall when the tape was added to the FLAP hinge lines. I dont know all about the aerodynamics and I am not an egineer but I do know that it flew better with tape on the plane.

Stall is loss of lift correct? Do I have that right? Well the tape helped keep this plane from stalling in simple 90 degree turns. Not blistering corners I am looking for but better than before. The tape helped the flaps produce more lift. It worked that is all there is to it.

Brad looked at me and said "It's not rocket science. If it is running out of lift add lift wherever you can to produce more." In this case we added flap area and Bingo back in the game. And yes the hinge lines stayed sealed. I am sure there are many ways to add lift. Several o them were touched on in this thread, but the simplest way to do it in this case was add flap area.

I find it difficult to compare 727 under power on landing stalling and a stunt ship gliding(no power) in and stalling with nose up. I know what you are saying though. A stall is a stall. Yes this is true. What I have found was we had to get lift for some reason or another it would not make the trianle corners. Maybe the elevator was overpowering the wing and turning it tighter than it could handle.(stall) Maybe a smaller stab/ele and this would not be an issue. My previous airplane. Same wing. Has an 18.9% tail area and this is not a problem no matter how hard you hit it. No matter where the control setup is, nose heavy, tail heavy, ultra huge handle spacing: NO STALLING.(even at 5.75 laptimes) New tail area is 22%. It is quite effective. If you hit hard it will turn and then the wing gives up and I cuss at it.(I yell at it but none can hear because the motor is quite loud and making lots of good power)

"mmmmmmmmm power"

If I can get out of work early I am going to fly it with the new flaps and see what happens. I will try it sealed and not sealed and see what I get.

Ted,

I was lying in bed last night trying to figure out what to do next. I am will try anything. I thought of the same thing. Put on some wood or milar of some sort to change the wing's leading edge and possibly is thickness at the highpoint and see what I get. Even it does fly better with new flaps I think will put smaller ones on and get it to stall again and then try this test. It will be really cool. If it quits stalling when I add to the wing thickness then we will know for sure if it is running out of lift or what??

Thanks for all the input.

Keep it coming.

DMoon

>>Ted,
>
>I was lying in bed last
>night trying to figure out
>what to do next.
>I am will try anything.
> I thought of the
>same thing. Put on
>some wood or milar of
>some sort to change the
>wing's leading edge and possibly
>is thickness at the highpoint
>and see what I get.
> Even it does fly
>better with new flaps I
>think will put smaller ones
>on and get it to
>stall again and then try
>this test. It will
>be really cool. If
>it quits stalling when I
>add to the wing thickness
>then we will know for
>sure if it is running
>out of lift or what??
>
>
>Thanks for all the input.
>
>Keep it coming.
>
>DMoon

Hi Doug,
Haven't left yet...just packing my bags and got on the computer for some company stuff on the trip and checked in here.


Glad you're willing to check the leading edge thing. As we're learning nothing is carved in stone on these things. always have to remember that each one of these critters is "carved" out of a soft wood and not machined to identical tolerances like one of Randy's engines.

Even though this wing and the earlier Bear are "the same", they really "aren't" inasmuch as each is a separate entity. The only constant is the air and if it thinks one wing is different than the other it will tell you so. Sounds like you're listening! (VBG)

Yeah, I think just stretching a piece of mylar/thin plastic from top spar to bottom spar will result in a slightly larger leading edge radius by virtue of it bending "around" the existing leading edge...causing a slight "bubbling" just above and below the current trailing edge...rather than simply "laying" on it will give a good inflight indication of whether it is worth reshaping the leading edge to a slightly larger radius.

Looking forward to all the results.

Ted

p.s. It is no surprise that enlarging the flaps helped as well. As Al suggests this is a perfectly legitimate way to increase lift...heck, it not only increases the size of the high lift device but the area of the entire wing as well.

As you've discovered, however, there is a slight dark outside to that silver lining. Increasing the flap size increases the negative pitching moment they cause and thus retards the rate of turn.

If a means can be found to delay the stall to a higher angle of attack (maybe by a blunter leading edge) the additional lift capbability may be achieved via that resource (higher AoA) rather than increasing the area. This might result in a control response more to your liking and still get the job done.

Good luck

> Put on
>some wood or milar of
>some sort to change the
>wing's leading edge and possibly
>is thickness at the highpoint
>and see what I get.


I think that everyone would agree that if the LE radius is in the range Al suggests (7/16" or so) the LE is not the problem. You could try measuring it - just push a peice of clay onto the leading edge to make an impression, and then find a peice of K&S tubing that corresponds to dent. Of course, the included angle of the radius is also important - if the airfoil meets the radius with an included angle of 45 degrees, that's a lot blunter than if it meets at an included angle of 120 degrees - but knowing it should help.


> Even it does fly
>better with new flaps I
>think will put smaller ones
>on and get it to
>stall again and then try
>this test. It will
>be really cool. If
>it quits stalling when I
>add to the wing thickness
>then we will know for
>sure if it is running
>out of lift or what??


I've done things like this before. The way I did it was to make foam "slippers" that had the outside cut to match the desired airfoil, and the inside cut to conform to the underlying airfoil. Then just use removable spray adhesive and tape to hold it down. That way you can test other shapes accurately.

I flew the Imitation XL with Infinity-wing shaped slippers to test the design before I built the first one.


Brett

Zow! Aren't things going a little quickly here?

It's seems like you've had the plane finished for less than a week and you've already built new flaps for it and are seriously considering reworking the leading edge and perhaps other more radical modifications.

I guess I'd go a lot slower, changing one small thing at a time and flying it a few times with your coach, then going to the next. I'd certainly finish experimenting with taping hinge lines (a small, reversible change) before starting to cut into the wing.

You've been working on this plane for months. Don't be too impatient now.

Preston

Preston,

I usually take this approach. Slow and make adjustments after several flights at each point of adjustment.

The difference here is the planes actuall inability to fly the entire pattern. When it is able to fly with some consistancy I will then make the small incrimental adjustments and trim it out.

Is it possible that the stab/ele is over powering the wing and turning it tighter than it can allow? I know someone earlier said to slow the control of the handle and the stall will go away. The only thing is when it is that slow by the time you have completed a turn you will be past the next one.

I am really not happy with all this happening to my new plane. At the same time I am learning alot about what it takes to get it right after you foul it all up.

DMoon

>I guess I'd go a lot
>slower, changing one small thing
>at a time and flying
>it a few times with
>your coach, then going to
>the next.

I guess I Am the closest thing to a coach that Doug has (really I just watch him fly and listen to him groan a lot) and I am really quite proud of Doug for his willingness to accept his fate and move on. Doug has a style, and this airplane was not going to fit that style without modification. That’s what I believe.

There is not enough 3m tape in the world to seal the hingeline well enough to keep that hog from stalling in a Doug Moon triangle, and it’s COLD right now. It will be much worse in the summer. Leadout sliders, tape, and lead will only go so far.

Doug held his chin up and started cutting.

Now is the time, not in June.

We in fact discussed this at the field, and I expressed that there is a willingness with some people to accept poor flying airplanes because there paint job so pretty, and they do not want to mess it up. Well, this Bear has a gorgeous paint job. Well done, I say.

Removable flaps are a viable option, especially in Texas.

Doug,
This has turned into quite a post and there is a lot to wade through. Help me understand a little bit about the Bear. First of all I have great admiration for Bob and I have follwed his carrer through the mags, dreaming I could do half as well as he has. I got to meet him this year at my 1st NATS. It seems that the Bear might be (and rightly so) very much designed for the way Bob flys and builds. The 16% flaps, the short nose (because he builds a very light airplane aft of the CG), The "quick" control system, etc. I think we could learn from your experience with your Bear. What I'm trying to say is that when we pick a design we should realize that maybe we can't build it as light or whatever. With that in mind we should make some "corrections" before we cut balsa. In your case, maybe lengthen the nose, increase the flap area, etc. I repeat, this is NOT a critizism of the design, BOB, or you in any way. I want to thank you for letting us know and posting the troubles you are having with your airplane. We can and should learn from this forum. I'm still amazed at the information that is so freely shared by all the posters and how we can all benefit by it. Doug, please keep us informed as to what worked for you. Perhaps in a condensed and outlined post. Take care and all the best with your new machine,


Crist Rigotti
"A Driver trying to be a Pilot"

>It seems that the Bear
>might be (and rightly so)
>very much designed for the
>way Bob flys and builds.

That's what I keep tellin' the boy, and he won't listen.

Boy's stubborn... and ugly too.

IN MY HUMBLE OPINION! Doug's style is more suiting a West Coast design.

I have told him this before, so it will come as no shock to him, but I thought I would let all 47 of the other guys responding to this thread know that I said it.

P.S. All this for some balsa sticks taped to the back of the flaps. You are a trouble maker.

Doug should try building an Impact. Howard's flies super at 3,500 feet on a hot day with only the .40VF...amazing squares and triangles. Paul didn't bring his Impact, but used the Skylark after deciding the Ukey 35 wouldn't be enough. There should be an Impact kit... Steve

>Doug should try building an Impact.
>Howard's flies super at 3,500
>feet on a hot day
>with only the .40VF...amazing squares
>and triangles.

I almost got punched in the nose for saying this at the Team Trials, but I like to live dangerously, so - Howard's Impact may be the best-flying airplane I have ever seen. Hard cornering even to the point of over-controlling seems to have *no* effect on roll and yaw. It goes around the corner as if absolutely nothing happened. The engine is perfectly adjusted, it just flies a constant speed up down, sideways, inside, outside. Everywhere on the sphere it's exactly the same. Just incredible.

For the record (correct me if I'm wrong Howard), the airplane has a box-stock 40VF spinning a 11.25-4.2 Bolly 2-blade, ~700 square inches, 65 oz, on max-length .015 lines.

Brett

Steve,

If you can find Dave Tribble, he may have some IMPACT kits left over from his Heartbeat Models days. He kitted the IMPACT, MUSIC and a couple of others that escape me right now. Of course, there are a number of people around the world that are trying to locate him and collect items or money paid to him for products not yet delievered.

Jim Pollock

>There
>should be an Impact kit...

Funny you shoyuld say that. Ultra Hobbies is developing that kit right now. Guess who is half of Ultra Hobbies?

Brother Steve...

This has been an interesting discussion, and since I am rather new to this hobby after a 20 year layoff, I do not know if I can contribute any worthwhile advice. But since Doug's problem is similar to what I have recently experienced, maybe there is a link here.

My latest ship is a bit overweight, and tail heavy, just like Doug's. It is 610 squares, and 54 ounces. However, in this condition, the wing loading is less than my Time Machine 60 (which flies beautifully), but maybe wing loading is not the big issue here. Even at 54 ounces, the Double Star 50 hauls it around well, and power does not seem to be lacking.

The problem I am having is in hard inside corners. It looks like it is stalling. On the last corner of the inside square, for example, the plane appears to stop, drop a bit, then continue on its way. This does not happen in outside corners, so I was at a complete loss to figure out what is going on. An ounce of nose weight has helped tracking and stability. The cornering problem is reduced, but it is still there.

This is the only thing that I can come up with: it is a matter of excessive control input. I fly with my arm stretched out and elbow locked. Also, I prefer slow controls, with rather narrow line spacing. In this position, my wrist is not able to move down as much as it is able to move up. In an attempt to minimize this assymetry of control input, I usually have the lines set up so that the top of the handle tilts back a bit. I am also thinking that when I apply up elevator, I am also pivoting the forearm up a bit at the elbow, thus adding to the control input. When I concentrated on minimizing the up elevator input, the plane zipped around the corner with no problem. It required finesse, but it could be done. What I need is another handle that will allow me to narrow the line spacing a bit more. With the current handle, I cannot narrow the line spacing any more. Is my analysis correct here? I do not know for sure, as I ran out of daylight my last time out, and I have not been flying since.

This plane simply does not need all the control travel that is built in. Being tail heavy and a bit overweight are more than likely contributing to the problem, so more careful building would probably minimize or eliminate it.

WOW! This is great stuff. Thanks.

Wow! I can't wait to try all these ideas on my son's
sheet wing Sig Buster trainer; he will dominate!!

Great stuff, keep it coming!!!

Later, Steve

>Wow! I can't wait to try
>all these ideas on my
>son's
>sheet wing Sig Buster trainer; he
>will dominate!!


What is the stall rate of a 1/8" flat sheet?

Figuring for that 24% stab is so much easier, just cut it into quarters!

Huhhmm, let me my calculator...

I flew the plane today with the new super flaps. It is all in order now. This plane turns and sits flat on the exits. I am really pleased.

I did not seal the hinge lines today. It flew well regardless. I am going to seal them and try it next time.

Now I feel the elevators are not powerful enough. I have the handle spacing pretty far out. 4 3/4 inches. It can go farther and I will try it.

It is not that the controls are slow. It just feels like I have to pull so hard on it to get it to turn. I mean really pull on it. There is no binding in the controls. It just feels that the stab does not want to turn.

I will go down the same path with elevators that I did with the flaps. Start adding area and see how it turns.

The big full span flaps worked. Lesson learned: pay close attention to the weight range of the plane. If you are going over the weight range added flap area is an easy fix.

DMoon

>I flew the plane today with
>the new super flaps.
>It is all in order
>now. This plane turns
>and sits flat on the
>exits. I am really
>pleased.
>
>I did not seal the hinge
>lines today. It flew
>well regardless. I am
>going to seal them and
>try it next time.
>
>Now I feel the elevators are
>not powerful enough. I
>have the handle spacing pretty
>far out. 4 3/4
>inches. It can go
>farther and I will try
>it.
>
>It is not that the controls
>are slow. It just
>feels like I have to
>pull so hard on it
>to get it to turn.
> I mean really pull
>on it. There is
>no binding in the controls.
> It just feels that
>the stab does not want
>to turn.
>
>I will go down the same
>path with elevators that I
>did with the flaps.
>Start adding area and see
>how it turns.
>
>The big full span flaps worked.
> Lesson learned: pay
>close attention to the weight
>range of the plane.
>If you are going over
>the weight range added flap
>area is an easy fix.
>
>
>DMoon


Hi Doug,

glad you're making progress. I'm anxious to hear the outcome of sealing the elevators.

You've discovered, through your experiments, one of the realities associated with larger chord surfaces of any kind, and...parenthetically...one of the reasons that some of us prefer to find solutions in another direction.

It is an unfortunate corollary of increased moveable chord that control pressures increase significantly. I odn't recall precisely the exact percentage increase but this is a subject that Wild Bill Netzeband covered at some length in his classic articles on the control system form about a century ago.

This (higher required control loads) is exactly one of the reasons that I chose to go to narrow chord, but consistent percentage flaps on my designs. I "prefer" a control feel that is light but constant since I find that a lot of line tension requires to much effort simply to hold onto the handle and makes refined control inputs more difficult to obtain. Lots of line tension is an absolute requirement of an airplane that requires lots of load on a line to obtain the response desired. I hasten to add that I've been whipped more than once by those who prefer the heavier feel...not only Al but a several times nats champion name Jimmy Casale, as well.

Your experience corollates exactly to the feel you noted with Al's Mustang. This is likely also the reason Al uses a much larger than most line spacing at the handle.

I once again urge you to experiment with both the sealed hingeline on the tail and also to try out the temporary more rounded leading edge. If these areas yield the control feel you prefer and still do away with the stall it might be a win, win proposition.

By the way, I think this thread is developing a number of good areas with which to proceed independent of your particular ship...a discussion on airfoils and their effects, in particular. I'm going to try to launch some discussion on those areas specifically in the next day or two so the info doesn't get lost in the noise of this more diverse discussion

Ted

Ted

You are right it felt exactly like Als Bearcat. This is something I dont understand. My other Bear, exact same wing, turns very light on the lines. A very solid but not heavy amount of line tension. Even when the plane has medium line tension the contrls feel heavy. Personally, I cant stand it. somehow I have to get that easy control feel into this plane. If I can do so I know this will be a good one.

Another question. If I decide to build an Impact, how heavy can it be before it suffers? Also if I build it right off of the planes will it have the slow heavy controls? If I build your plane how heavy can it be? Will it have the light on the lines feel? Also If I give it a different profile(look from the side) will it change the way it flies????

DMoon

>Ted
>
>You are right it felt exactly
>like Als Bearcat.
>This is something I dont
>understand. My other Bear,
>exact same wing, turns very
>light on the lines.
>A very solid but not
>heavy amount of line tension.
> Even when the plane
>has medium line tension the
>contrls feel heavy.

It's not the same wing anymore! You said you greatly enlarged the flaps. Deflecting the larger flap to even the same angle will take more effort. The fact that it also causes an adverse pitching moment means that you have to deflect it further. Both conspire to make the control loads higher.


Personally,
>I cant stand it.
>somehow I have to get
>that easy control feel into
>this plane. If I
>can do so I know
>this will be a good
>one.

You're kind if stuck between a rock and a hard place. To reduce the control effort I would move the CG aft (which was previously at around 20% if I managed to correctly decipher your cryptic notes thereon). Note that it's even further forward now, since you added chord, the position on the fuse stayed about the same, but the wing effectively moved back.

You might try sneaking the CG back to maybe 22-23%. This should lighten the control load, but may get you back to the same problem again. A more complete solution would be to enlarge the tail by adding 3/4" or so to the LE, full span, so you could safely move the CG even further. Your tail volume is down due the enlarged flaps as well.

>Another question. If I decide
>to build an Impact, how
>heavy can it be before
>it suffers? Also if
>I build it right off
>of the planes will it
>have the slow heavy controls?
> If I build your
>plane how heavy can it
>be? Will it have
>the light on the lines
>feel? Also If I
>give it a different profile(look
>from the side) will it
>change the way it flies????


Howard's flies exceptionally well, and it's built exactly to plans, with emphasis on *exactly*. Until you have a good idea how it will fly, I recommend building it exactly to plans, with *no changes*.

The controls will not be heavy at all. The very aft CG will act like power steering.

Paul and Howard can tell you more, but we have all had out butts kicked collectively and repeatedly by 63-65 oz Impacts with 40VFs. If it can win the NATS 5 times, it's good enough for you and me. I have seen some up around 70, but if you just build it neatly it will be around 62-63 or so. The extreme light wing loadings (55 oz/680 squares) are not necessary, and I would debate how beneficial they are on models like the Impact and Trivial Pursuit.

As an example, David's latest Trivial Pursuit/Star Gazer is lighter than the rest at 57 oz. It needed the flap travel reduced slightly relative to the elevator compared to the rest which are 62-68.

Brett

Brett,

Thanks for the notes and suggestions on the numbers of my plane now that it has new big whopping flaps. I will deffinently try moving the cg back. I can easily take out the big nose weight under the spinner.

Is Howard's Impact take apart. I have been looking over the plans. I pauls plane has alot of "wood" in it to be in the 58 to 60 oz range. I read the Article in Flying Models this weekend. I really want to build one of these. I would like to try the take apart. I am just real worried I would blow it and get it out of alignment or something.

DMoon

Doug,

Same kind of worrying I'm doing about take apart. See my new thread on the same. Someone suggested buing Windy's videos - but my model budget doesn't include enough $$$ to buy videos too.

Jim Pollock

Doug,

Another way to reduce the increased loading you are experiencing with the larger flaps is to add "stabilators" to them. I think this is the correct name for them.

They are like an additional flap cut into the trailing edge of the main flaps. They have a horn on them and a pushrod fixed to a horn on the main wing. When the main flaps go down these "stabilators" go up. It's like power steering. The size of them is a learning curve in itself.

I messed with these on a model about 13 years ago. Too big and as soon as you deflect the controls at all they activate and overide your inputs and you find yourself fighting them, smaller is better than larger. At a guess something like 3" long and about 1/2" wide would be a starting point. They are at the root of the wing.

Another bloke here in Oz has been using them for the last 5 years that I can think of. I flew his model at our nats in 98. They worked a treat on his model, but for my own personal preference they were too active. He was used to them though and could fly the model very well.

You may find they work well to lighten the load on the controls, in fact you would be amazed as to the effect they have.

BRI

I have seen two types of aerodynamic balancing on 1:1 scale "models". We frequently see the tips cut off the stab and glued to the elevators (SIG Chipmunk), but what about the type with the small wing mounted on a pylon and angled ahead of the hingeline? It would seem to be a good solution for Doug's heavy controls. Since the flaps and elevators are hooked together, it seems to me that wherever you mounted these, flaps or elevators, it would help reduce the heavy feel. I believe I would mount them fairly close (5"?) to the fuselage on the flaps, both sides, and of course top and bottom. Anybody tried it? Steve

Bri i did some research on Stabilators and found only flying stabs on fighter jets. I did however see some aerobatic planes that have a litte extra flap hanging behind the flap not as an internal part of it. These looked to be attached on a fixed rod and horn.

Is this what you are talking about???

DMoon

I'm hastening to add to Pauls' statement re: take apart airplanes. "Once you try them, you won't want to go back."

Over the years, I've built most of my planes this way to one degree or another. The first, The Pathfinder 40 I built in '94 for the '95 Nats only had the wing removable. Over the years, I've seen a lot of planes built with removable features, and the main thing I've noticed is the tendancy for first timers to over engineer the process.

It doesn't take a lot of wood and hardware to get all the stregnth you need, and on a stunter, more is not always better, esp. when you start adding on the weight. Several years ago, I built Sheeks Stagerwing Beech for classic. I powered it with a Wankel engine, on the thought that a round cowl deserved a round engine. It has plenty of power, but the engine weighs a ton and the plane is too heavy to be competitive. I mention this plane because it was the first one I made totally take apart. I don't believe the added weight would be more than an ounce and a half at the most. One of these days, I'll repower it with a lighter engine. I'm sure it will be a better plane with less than half the weight out of the nose.

I only use 4-40 screws to hold everything in place, and only a few at that except for the 3/16" nylon screws that hold the wings in place on the Staggerwing. I use two locating dowels, 3/16" dia at the leading edge into a ply bulkhead ala RC fashion to take the flight loads at the leading edge. I use two more at the trailing edge, but they are at 90 degrees to the wing chord. They also mount, or key into ply plates. This assures alignment of the wing as well as taking the flight loads. The 4-40 screws, one at the front, and the other at the pack take none of the flight loads. They are there to keep the wing tight and the alignment dowels engaged in their key blocks.

I use a similar technique for the stab and elevator. Thre is only one 4-40 screw tying the entire unit into the keying blocks. The alignment pins take most of the load in this case, though the bolt takes about half the load. So far it's working just fine.

The Zephur will also be a total take apart. I took a while, but with a copyof the plans, a pencil and a straight edge, and it's all worked out. I mention this to point out that it's much easier to figure a system out before you start building thatn to try and figure it out when the magor components are all built. Don't ask me how I learned this. It was a mess doing it that way.

Paul, being an engineer, has worked out a good sstem with his Impacts. I would recommend the easiest method would be to follow exactly what he has onthe plans and in his article.

John

>
>
>Is Howard's Impact take apart.

No

>I have been looking over
>the plans. I pauls
>plane has alot of "wood"
>in it to be in
>the 58 to 60 oz
>range. I read the
>Article in Flying Models this
>weekend. I really want
>to build one of these.
> I would like to
>try the take apart.
>I am just real worried
>I would blow it and
>get it out of alignment
>or something.
>
>DMoon

Doug,

Once you go to the take apart construction, you'll never want to go back. Don't worry about allignment. It's no different than a normal stunt plane. The take apart feature allows close inspection on the inside and access to all the controls, for adjustment, monitoring, etc. A big bonus.

Howard's IS STONE STOCK except for the vertical tail shape. That shape is from my '96 Sweeden version of the Impact. If you want, I can send you the outline of that!

Weight.....62 to 64 seem to work the best. No question! I had success mostly with the 40 VF, not with the bigger more powerfull engines. That design with 2-cycles was always superior with the 11.3" dia 2 blade prop, and I have tried every size and shape.

I wish you luck Doug, and Steve too.

Hi,

If you want to be able to give more steering power with less linetension, use a larger bellcrank. I have been using 5 inch bellcranks for years now and I haven't noticed a bad side effect (yet).
Off course the linespacing at the handle has to follow the increase in bellcrank size with the same percentage.

Paul

>>Wow! I can't wait to try
>>all these ideas on my
>>son's
>>sheet wing Sig Buster trainer; he
>>will dominate!!
>
>
>What is the stall rate of
>a 1/8" flat sheet?
>
>Figuring for that 24% stab is
>so much easier, just cut
>it into quarters!
>
>Huhhmm, let me my calculator...

I know Godzilla is saying this tongue in cheek, however...

Although not a particularly good airfoil, a flat sheet is an airfoil nonetheless and can do a surprisingly good job of flying. I wouldn't have believed how good until hearing about and eventually witnessing a flapped, flat sheep wing on a moderately sized stunter fly very well indeed down in Australia.

I first heard about this fellow (don't recall his name) from Big Art Adamisin who had judged the ship during one of his "good fellowship tours" down under. On a trip to Sydney a year or two ago I visited the Kuringai Model Flying Club's site north of the city and saw the ship fly. It wasn't going to win our nats...but it wouldn't have come in last either!

Ted

Here is two photos of the plane in question.

The first photo shows the plane with the original flaps.


[photo not recovered: 3c79b7b567f76352.jpg]


Photo two shows the plane with the new BIG WHOPPING FLAPS!!

[photo not recovered: 3c79b7f76840d03a.jpg]

After 30 flights and alot of testing this plane is starting to show a LITTLE promise. It still really wants to tighten up on the inside manuvers. It seems to want to get tighter and tighter during consecutive loops on the inside only. I have to fight it to keep it from looking like it is going down the drain.

After tweaking on the elevators some it seems better but not quite there yet.

I dont know if you can tell but in the second pic I have a giant glob of clay on the tail. The new flaps really moved the CG forward. I used to have two ounces under the spinner. Now I have it on top of the stab.

I had to shrink the size of the photo so much to get it down to 50kb it killed the clarity. How do you all post with such clarity at only 50kb????

After further thought I think I finally realized where I made my fatal mistake.

When building the control system I used Tom Morris horns. That is not the mistake the way I set them up was. The flap horn has the first hole at 1" from the 1/8 wire and the second 1 1/4" away from the wire. Well I wanted really fast controls, as I always do. I decided to hook up the bellcrank Prod to the 1" hole on the flaphorn. This placed the Erod to the 1 1/4" hole away from the wire. The elevator horn has a hole that is 1" from the 3/32 wire. You can now see how much more elevator than flap I have. Also the Elevators are larger than the one on the plans giving them even more power. This is why I had to make such large flaps because they are not moving much. I have heard of many pilots dialing in more elevator than flap. But a 1/4 more on a plane that is at its weight limit. I dont think it is a good idea. I think this is one of the major contributors to this planes stalling problems. Not enough flap deflection in relation to the elevators.

The Bear builds his controls with about an extra 1/16 of an inch on the flap horn to give it just a (quote) "teeny tiny" bit more elevator. The quater inch I put in there was deadly.

Do you think this could be the culprit?

DMoon

Doug, you are not compressing your photos enough. you are down to about half the height and width that you need to be. I took the same photo and saved in in LView Pro and compressed it from your 50K down to 16K in size and can't see any difference in quality. You should be able to compress a 640 x 480 to the same size as this one and get a much larger image but compressed more so it loads at the same speed.

Nice looking plane, however. I would suggest you go to an adjustable elevator horn which would allow you to crank in more or less elevator travel as needed. Matt has had the opposite problem you have. He started with larger flaps, thicker airfoil, lighter wing loading, and had to crank in more elevator. But with the adjustable elevator horn it was easily accomplished.

The days are getting longer and soon we will be out in the evenings again.

Leonard Neumann

I know the adjustable elevator horns are the trick now. It is a little late for this one. I would have to practically destroy it to get in there and change it out.

I did some measuring last night. God zilla loaned me one of those degree arcs you can put on the wing and measure the throw of the surface. At full up the Elevator has 60 degrees of travel and the flap is 40. It 15 degrees where you are really using the elevator there is only 9 degrees of flaps. Not nearly enough huh?

Len, once I have the file saved on my desktop how do I compress it? I am using adobe photoshop. I have to save it as low resolution to get it small enough.

DMoon

Doug,
I don't remember your stating in the original post that you had more elevator travel than flap travel. It seems obvious that to obtain the lift you need, you must have either bigger flaps or to move them farther. I think all of your problems happened when you lengthened the flap horn substantially. If you had built the airplanes controls as Bob designed them, this thread would likely not exist. To make lift, flaps must have area or travel. You reduced the travel. To compensate, you had to increase the area. For what its worth, since I depend on flaps making a lot of lift, I've found my airplanes fly best at a 1-1 ratio and this applies to handling characteristics as well as making lift.
Al

Yep you are right. If I had built the controls the way Bob did this thread would not exist.

I really did not realize how I had set the controls up wrong until I was looking at what controls I have to put into my two new planes that I am building right now. I am building a new BIG BEAR for a PA motor and a new BIG BEAR for a YS 63 4s motor. It was here where I figured out how far off my throws were. I almost punched myself in the eye for making such a drastic offset in the control throw.

I guess the knife will be making an apperance. The only tough part is getting the flap horn out. It is one of those offset horns from Tom Morris. I cant just reverse the hookup. It needs to be removed and turned around (read that bend a new one). This ought to be interesting. I put 6 oz carbon cloth with West Systems epoxy in the pipe floor to give it tremendous strength and a real cool look. Now cutting through it is going to be real difficult.

Wish me luck.

I have learned so much on this plane. It is incredible what a real big Foul Up can teach you.

If anyone has any suggestions on how to get that horn out without destroying the plane please post away. The flaps are removable so that helps.


DMoon

Don't mess with the flap control horn, get an adjustable elevator horn from Tom Morris and replace the present elevator horn to get it back to one-to-one. That is less drastic than cutting out the flap horn. Talk to Tom and tell him what you want to do. It appears to me that you have enough room in the tail to do it.

Tom McClain

That is an option. Do you by chance have a number for Tom? If not I will call him tonite so I can find out if his slider horn goes out to 1 1/4"

DMoon

Do you really have to modify the airplane further? If the big flaps adequately substituted for lack of travel, there may be little to be gained by cutting into the airplane. My second choice would be to cut into the tail and scab on a elevator horn extension to give the length you need. With a piece of 1/16" steel, some copper wire and a soldring iron, it should be possible. But then your new flaps may be too big. If the airplane flies well enough, personally, I'd just practice with it until I was comfortable enough to win. There is no such thing as a perfect airplane. At some point we have to accept the short commings of any airplane and learn to live with them. Trimming and practice can cover a lot of building mistakes.
Al

If you can get into the flap horn, can you put Robart-style ball ends on both pushrods, and bolt them both to the same 1" hole, one on each side of the flap crank arm? A hole saw on an electric drill should do a decent job of putting a couple of holes in the carbon pipe tunnel floor, then connect the two holes? Steve

If the flaps are to big what will be the symptoms?

What can I expect?

DMoon

>If the flaps are to big
>what will be the symptoms?
>
>
>What can I expect?
>
>DMoon

The tail won't swing fast enough and the plane will appear to climb in the corner instead of simply rotating. It is caused by too much flap or too light a wing loading. Matt had that problem with his last plane and had to dial in more elevator throw (hence less flap travel) to compensate. Just the opposite of what you were experiencing. His new one has about 10% less flap area, but will still have that adjustable elevator horn.


Leonard Neumann

Doug,

Tom's number is 256-820-1983.

Also, your brother and his partner are kitting the Impact. I have seen examples of Impacts that had elevator extension added because the incorrect horn length was used on the flaps. Hopefully, the kits contain the correct length horn for the flaps. Check the plans, I think the flap horn is suppose to be in the neighborhood of 1.4 inches.

Jim Pollock

>
>
>Len, once I have the file
>saved on my desktop how
>do I compress it?
>I am using adobe photoshop.
> I have to save
>it as low resolution to
>get it small enough.
>
>DMoon


Download LViewPro. (Most download places have it. Go to Zdnet.com and click on downloads.)

It won't take really big files (like 1 meg) but it will take some pretty huge pictures and when you save the picture in JPEG format (or resave in JPEG) it will compress it. You can even change the default to an even higher rate of compression and my eyes can't tell the difference on the screen. I have even bounced back and forth between the original and compressed version and couldn't tell the difference.

Oh, yes, you can also flip pictures, turn them upside down or sideways, convert a GIF to JPEG or visa versa, change size, do a bunch of things. Not a bad little program.

Leonard Neumann

Leonard is correct. I use both LView Pro & PhotoShop.
I may be a beginner at C/L stunt, but I do know computer
graphics. Increasing the compression of a JPEG image
will reduce the file size. JPEG (Joint Photographic
Expert Group) is by nature a "lossey" compression
scheme, but serious image degradation doesn't occurr
until something like 70% of the original information
is discarded. JPEG does support 24-bit color.
GIF (Graphics Interchange Format) files are smaller
because GIF uses 8-bit indexed color. However, images
which were originally 24-bit color and contain subtle
hues will exhibit an "isophote" appearance when
converted to GIF, unless dithering or diffusion is
used to smooth the image. Dithering will often
impart a "grainy" appearance to the image.

I generally start with images as 24-bit Bitmap
or uncompressed TIFF (Tagged Image File Format),
do any manipulation in that format, then save to JPEG
or GIF.

Like Ed I'm a CL novice but I make a living as a graphics professional at a newspaper. We should remember that we usually view any pictures we see on the web at "screen resolution" which is somewhere around 72 dots per inch. Web browsers frequently default to this setting and will enlarge the pic to conform to it which is why if you get a hi-res file in an e-mail you sometimes only see a portion of the image in the browser window and have to scroll around to see the whole thing. Don't know about LView but in Photoshop it's a simple matter to save a photo at 72 dpi and when it's downloaded by anyone it should pop up on their screen at approximately the actual size (say 5 inches) you saved it. A 5" by 3.5" color RGB image at 72 dpi is about 250K uncompressed. Saved in Photoshop in JPEG format at a #4 quality level gets you about a 50K file. That should be fine for any web use and have adequate clarity. Anyone with more specific Photoshop questions can give me a shout anytime---Mark