Elevator throw

Is 28-30 degrees sufficient elevator throw on an Oriental?

Note: This ship is destined to compete in Beginner. Assuming I make it to the full pattern, I will be using a different ship.

You should not need more than 30 degrees ever. Any more just adds additional drag with very little added help in throw.

Tom,

I use 1-1 Flap to elevator on all my classic era ships. I stop the bell-crank movement to allow no more than 30 degrees. I have found that more movement is detrimental as it can cause to plane to stall in a turn and actually increase the size of the radius and cause other problems. I have no engineering data to backup that statement. It just has worked out that way for my stunt planes and style (?) of flying over the past four years. Smoothie, Hurricanes, Mustangs, Skylarks and Shark .35.

Len is right that more than that will induce drag particularly on the flaps. Some people are proponents of 1-1.5 movement with 30 flaps and 45 elevator. I don't like this setup myself but we all have different views when it comes to this stuff and it definitely makes a difference in what plane it is on.

I am building an Oriental myself and will use 1-1 30 degrees on this plane.

Phew, I feel better now

I was a bit concerned that I had messed up, but it sounds like I'm in decent shape. I do have it set up for 1-1 so I'll assume all is well.

Thanks!

JOHN,
Just a comment on your statement that you install
a bellcrank stop, would there not be a possibility
that at full up or down you could load the control system
to the point that all the weight is supported by one
line only.If you had any wear in the lines or leadouts
,instant kit, at a time that would make you unhappy.
BUSBY

Bus,

After having a bellcrank get jerked around past full throw and whipped to a backward position (spinning the bellcrank around backwards in flight just never comes out well), I have put in stops. Never had a problem flying on one line and while I suspect it doesn't really do all that much good, it somehow makes me feel better. On my last 4 or 5 planes, there is a stop set in each direction to limit the max throw.

As a newer builder, I most often go by what the instructions say. But in this case, I did add another "stick" to make sure that the bellcrank threw equally in both directions.

Just seemed to be the logical thing to do.

In my "early" days I used to put stops on the belcrank, too. I didn't know any better. It was never a problem, however. Now we just build where full throw is no more than 30 degrees and then control the amount of throw at the handle. Narrow the spacing until you can't (or won't) go beyond the limits. Eventually you might find yourself narrowing the spacing to the point where you don't go beyond even 20 degrees or some such. Once you get the hang of it or the feel of it you won't need physical stops at the belcranks. But, for now, it should be no problem.

Hi Len,

Yea, with me it's more a security blanket thing. I don't suspect the bellcrank ever touches the stops when flying, but it's doesn't cost anything and somehow makes me feel better. One bad incident has generated a lifetime of caution.

My current plane has about 15 degrees of elevator movement at maximum deflection. I doubt I use it all. But that has a lot to do with the design and really long control arms. It just doesn’t need more.

Frank Zaic introduces the section on Control Line Stunt Models in his 1951-52 Model Aeronautic Yearbook thusly, "Through no fault of ours, all we know about them is what we read in the magazines." He then goes on to provide reasonable calculations and theory to answer many of the aerodynamic questions raised on SSW. He suggests that an elevator at 30 degrees deflection may well be stalled.

>reasonable calculations and theory to answer many of the
>aerodynamic questions raised on SSW. He suggests that an
>elevator at 30 degrees deflection may well be stalled.

I would think that within some reasonable limits the "stall limit" or max deflection before stall is a function of CG location, tail moment, and ratio of stab/elevator area to wing area.

Don't know how to calculate it, though, so I usually end up going with 30 degrees as well.

V/r

Frank Zaic goes into some of those effects.

> He then goes on to provide
>reasonable calculations and theory to answer many of the
>aerodynamic questions raised on SSW. He suggests that an
>elevator at 30 degrees deflection may well be stalled.
>

Depends on the pitch rate. An 50/50 stab with the elevator at 30 deg. deflection and no pitch rate has an AoA of 15 degrees, and probably is stalled. A 50/50 stab with the elevator at 30 degrees, with a 24" tail moment (CG to Cl), 78 fps forward velocity, at 360 degrees/second, has only about 4 degree AoA, and is probably not stalled. Of course the first example is pretty hard to achieve, since how to you get to 30 degrees deflection instantly enough to have no pitch rate?

In that high pitchimg rate you can have separation (buble) at LE on positive pressure side (inside the camber) - that is what makes difference between shap and blunt LE on stab or sence of turbulators.

>In that high pitchimg rate you can have separation (buble)
>at LE on positive pressure side (inside the camber) - that
>is what makes difference between shap and blunt LE on stab
>or sence of turbulators.

Yes, just like many undercambered airfoils at low AoA. Lot's of drag.

I tried my best to explain the "separation bubble" to a self-styled boost-glider expert on the model rocketry USENET groudp a few years ago, as part of an explanation of why you don't want to use heavily undercambered airfoils on a model that climbs ballistically at 300 mph. I knew I was in trouble when he declared that "undercambered" was a meaningless terms that he had never heard before.

Hello Tom I built mine with controls as per plans .I was concerned some also as it seemed throw was minimal.With plane balanced as per plan and handle spacing one hole past middle on one of Teds handles, the controls where to fast.This is a very nice flying plane with lots of control authority.As Leonard stated just move handle spacing in until you tame it to your liking. Lets see some pictures ?
Dennis

In case you do find yourself hanging on one line you might want to ensure that the force is not all transmitted to a control horn. A stop, if needed, can prevent that.

>Is 28-30 degrees sufficient elevator throw on an Oriental?
>
>Note: This ship is destined to compete in Beginner.
>Assuming I make it to the full pattern, I will be using a
>different ship.

Hi Tom,

As others here have pointed out, 28-30 degrees of elevator is plenty. It is also really important to be sure that your control system is extremely "free" in its operation with minimal friction when operated even to the limits of the throw. This includes having your hinge pivots lined up so that you don't get "spring back" or binding at any point in the deflection of the controls.

LAST EDITED ON Jun-04-04 AT 07:44 PM (CDT)
 
>Is 28-30 degrees sufficient elevator throw on an Oriental?
>
>Note: This ship is destined to compete in Beginner.
>Assuming I make it to the full pattern, I will be using a
>different ship.

That's plenty. But the speed of the response matters, too. By speed, I mean how much the elevator moves relative to the handle movement. You can have +-30 degrees with a tiny twitch of the wrist, or +-30 with full wrist and arm movement. Set it up so the handle angle more-or-less matches the elevator angle.

I asked this same question about the Nobler that I built probably 8 months ago. My wing flaps were 20 deg compaired to 30 deg elevator and my airplane refused to turn. I could not turn sharp enough to do a wing over. I changed it to 10 deg flap and 30 deg elev. it turned much better. I changed it again to 5 deg flap and 30 deg elevator and it flies much better. I built another Nobler with the fuselage 1.5" longer than before this time the flaps are 10 deg and the elevator is 20 deg and this airplane will turn circles around the other one. The extra 1.5" fuselage length made a world of difference and it made the airplane balance without LEAD tail weights. I have learned that a lot of experementing is required to make it work and each airplane is different.

>I asked this same question about the Nobler that I built
>probably 8 months ago. My wing flaps were 20 deg compaired
>to 30 deg elevator and my airplane refused to turn. I could
>not turn sharp enough to do a wing over. I changed it to 10
>deg flap and 30 deg elev. it turned much better. I changed
>it again to 5 deg flap and 30 deg elevator and it flies much
>better. I built another Nobler with the fuselage 1.5"
>longer than before this time the flaps are 10 deg and the
>elevator is 20 deg and this airplane will turn circles
>around the other one. The extra 1.5" fuselage length made a
>world of difference and it made the airplane balance without
>LEAD tail weights. I have learned that a lot of
>experementing is required to make it work and each airplane
>is different.

Gary;

One of the first things that you look at when a ship will not turn is the CG location. The more noseheavy, the less the turn response. A lot of ships from the classic era tend to come out noseheavy when we use modern engines, as they were originally designed for the much lighter (and less powerful) Fox 35, Veco 35, OS 35, etc. These ships also tended to have shorter tail moments than is popular now. To get to a size that presented well with the limited power of the engines (compared to today), airfoils tended to be thinner. The additional lift needed during maneuvers comes from the flaps. If you have built light and have a modern engine capable of generating more thrust than classic era mills, you might be able to get away with less flap movement and still get through the entire pattern.

I would not be surprised if your first Nobler was noseheavy, and that your subsequent Nobler with the longer tail helped to redress that problem. I would also not be surpised that if you moved the CG back by either using a lighter engine or lighter muffler or added weight to the tail, you would find the original Nobler a much better flyer, even if you go back to a 1-1 flap/elevator ratio. It might be worth an experiment.

V/r

My first Nobler was nose heavy. I removed the muffler and swithed to a wooden prop and it flew better. With tail weight it would fly great but I do not want to added weight. After crashing it 3 times I built another Nobler. This time I made the fuselage longer and used the elevator, fin, stabilizer as a balance to get CG where I wanted it. I slide the (elevator, fin, stab) assembly along the fuselage until the airplane balanced then I glued it there. The airplane has an OS Max 40 LA engine. Balance is perfect and it flies much better than the other airplane did.

The LA engine is heavy, Gary. When you add that much extra weight in the nose compared to a Fox 35 or similar around which the plane was designed, it makes a difference. Adding an ounce or ounce and a half of lead to the tail to bring it into balance is the price we pay to get a good flying plane under those circumnstances, however. True, we don't want to add more weight than necessary, but in this case it becomes necessary. Balance is important. No, more than important--it is crucial!

If you are building a Nobler, however, then my feeling is, build a Nobler. Lengthening the moments is definitely going to change the character of the plane. In this case it might help it, but I never heard of moving the tail to balance the plane. We design the plane around certain areas and moments and then lengthen or shorten the nose for balance. In your case, shortening the nose of the Nobler would have been the preferable treatment. In neither case would it now be legal for Old Time. You could enter it in Classic with a loss of fidelity points, and if it is just for fun, "who cares"? But then, why not build a plane that is designed around the size and weight of engine you propose to use?

LAST EDITED ON Jun-06-04 AT 06:57 PM (CDT)
 
>My first Nobler was nose heavy. I removed the muffler and
>swithed to a wooden prop and it flew better. With tail
>weight it would fly great but I do not want to added weight.
> After crashing it 3 times I built another Nobler. This
>time I made the fuselage longer and used the elevator, fin,
>stabilizer as a balance to get CG where I wanted it. I
>slide the (elevator, fin, stab) assembly along the fuselage
>until the airplane balanced then I glued it there. The
>airplane has an OS Max 40 LA engine. Balance is perfect and
>it flies much better than the other airplane did.

Gary;

Welcome to "trimming 101."

Understand that the moments for the Nobler, be it Green Box or '52, were designed around the much lighter unmuffled Fox 35 in the nose. Put in a LA 40 and muffler, and you increase the engine weight considerably. However, tail moments are usually much longer than nose moments, so it takes less weight in the tail to bring the CG back to where it needs to be.

Now, here comes the fun part. I know that all of us would prefer not to add weight if at all possible. Greater weight means greater lift needed to get through the maneuvers. The extra weight doesn't bother level flight much. However, once you are going through the pattern or series of maneuvers, weight will have an impact. If the wing is going to stay the same, then you are going to have to increase your flap deflection to generate the lift needed in maneuvers. Increased flap movement generates drag. That means you need more thrust if you are going to fly at a constant speed (or as constant as possible). With the LA 40, you can generate considerably more thrust than a box stock Fox 35. So, once you get the CG about where it needs to be for crisp response, the next thing is to get the flap deflection where it needs to be to generate the lift necessary. If you are a scratch builder, this is the time to make sure you put adjustable flap and elevator horns. An adjustable tip weight box is also a good idea, as are adjustable leadouts and taill weight box.

Kept within reason, you can compensate with many classic designs to fly well and still keep them as the designers built them. For those who compete in classic events, this is essential. However, with many of the classic era designs the increasing of the fuselage by two inches and increasing the total stab and elevator surface elevator area to 22-24% of the total wing area can also make a very flyable ship, albeit competing with it in classic may not be possible.

For trimming a ship, it is hard to beat Paul Walker's trim chart. Copies have been posted on this board a couple of times.

Best of luck.

V/r