Trimming

I'm getting back into C/L after many years absence and have to say this forum is a fantastic source of information. I am currently getting a Tanager ready to fly and have a few questions:

- How much flap travel should the model have? It seems that more than just a few degrees of flap would give more drag than lift.

- Flap/elevator ratios. Should this ratio be 1 to 1 or should we have more elevator than flap travel?

- Rudder offset. Should I use no rudder offset or just a few degrees? What about a rabe rudder setup? What effect does rudder offset have on the model while flying?

Thanks in advance for any information.

Doug Wood

Hi there;Flap travel...... As long as the hinges allow 30 deg. in each direction you will have ample for any flying and you probably will use much less , Butr I just feel better knowing that its there incase I need it.Flap elevator ratio..... Best start with equal and I think if yoiu look at the horn lengths shown on the plan it will work out that way. If ,on the other hand , you use an adjustable elevator horn such as the one from Tom Morris you always can reduce the flap to elevator ratio easily. If the plane ends up much lighter than the designer weight you may find it somewhat nicer with less flap. Rudder offset..... mostly the very old plans called for large amounts of rudder offset, but in this enlightened age we have found that rudder offset only helps you when you dont need it and can cause unwanted yawing during manoevers. The best plan would be to have an adjustable one then you can satisfy yourself by experimenting. Many people using Rabe rudders ( wiggly rudders) do themselves more harm than good. The ones that seem to help out in particular cases have a very subtle action andas a retread or beginner you probably will have enough to contend with just trimmimg out your ship with the rudder straight ahead or slightly to the right. Thats how I build mine.A wiggly rudder is one more thing to go wrong. Keith Varley. My appologies to any one that is a fan of wigglies (Dan)

Doug,
I have a Tanager myself I have crashed it 3 or 4 times. If you go to the search area and type Tanager, also repairs you will see a photo of me and some of the problems I have faced sence the middle of last summer when I finished it. I went by the plans. The adjustable rudder is the way to go, or about a 15 degree offset. Mine was set at what the planes called for. about 30 degrees. That is before I knew about the adjustable. I will not get into any details on this right now as you need to go to the search areas. I have equal elevator flap ratio. But I through my flight today am having trouble trimming mylevel flight. I will have to adjust the elevator or flaps as even though they have equil ratio I think I need more up. As no matter what I do to the handle line adjustment my handle was always higher in the up position to stay level. I was also timing my lap speed which at over 5 sec. lines are not pulling hard enough and having to much haw only wing overs were done. I am in the process of the speed adjustment and level fight adjustment. This is the first thing I would do before any next steps. Tell me where I'm going wrong, or tell me what I'm doing right.

>Doug,
>I have a Tanager myself I have crashed it 3 or 4 times.(snip)
>I went by the plans. The adjustable rudder is the way to go,
>or about a 15 degree offset. Mine was set at what the planes
>called for. about 30 degrees. That is before I knew about
>the adjustable.(snip)

Well, you are part way there. I, too, would agree that if you use any offset, you should make it adjustable. Back in the "good old days" people thought you needed lots of offset in order to maintinain proper line tension. The plans probably reflect the "good old days". A lot of the problems back then were caused by the engine or lack of power from same. With modern power plants we can solve power problems and get on with proper trimming. Really, you should need very little, if any, rudder offset. It appears to me that you may have far too much with even 15 degrees off offset. You need adjustable leadouts (I hope you have them) and then you can adjust the leadout position for your line length, tension, lap times, etc. This will get you the tension you need.

>I have equal elevator flap ratio. But I through my flight today
>am having trouble trimming my level flight.

OK, tell us about this. You want to make sure you wings are level in upright and inverted. If not, make the proper adjustments. (outboard tip up or down both ways, adjust tip weight. If up one way and down the other, twist flaps or add a trim tab and twist.) What is the CG like? How does it track in level flight, and how does it glide when the engine quits. You may have to adjust the nose weight--enough to track in level flight and glide well when the engine quits, but may need more rearward position if it does not turn well. Also, check the flap and elevator to see that they are neutral with one another. OR, that the elevator is just "slightly" up with the flap is at neutral, and NEVER the other way around.

>I will have to adjust the elevator or flaps as even though
>they have equil ratio I think I need more up. As no matter
>what I do to the handle line adjustment my handle was always
>higher in the up position to stay level.

I do not understand this at all. Moving the "up" line higher in itself will not affect how the plane tracks in level flight. It will only add more pressure causing you to pull harder in that direction. This may be a matter of how you hold you hand, and you will need to adjust neutral different. And if you have a "hunting" problem with the plane (nose wanting to bob up and down and not track level) go back to the above.

>I was also timing my lap speed which at over 5 sec.
>lines are not pulling hard enough and having
>too much yaw only wing overs were done. I am in the process
>of the speed adjustment and level fight adjustment. This is
>the first thing I would do before any next steps. Tell me
>where I'm going wrong, or tell me what I'm doing right.

OK, if you are using 60 foot lines (or less), which is quite common on a plane of this size, then you will probably need quicker lap times. 4.7 second lap times are quite reasonable, and this will not only get you a proper maneuvering speed on the airplane and give you better wind penetration, it will also help you with your tension problems. Go back to the above and adjust the leadouts and rudder (maybe get rid of the rudder offset completely, then adjust the leadouts). That can get rid of your excessive yaw and get you back to flying where you should be.

What engine are you using and what is your flying weight?

Leonard,
I would have to cut my rudder off and repair it to get rid of the offset. I will try to adjust the lead outs 1/8 inch forward first. I have 63.5 line length. I will adjust the throttle a little faster to get that lap speed to udder 5 sec. Whats to fast?
As I remember the outside wing is fairly level up or inverted. But a outside person could see that better. It glides really well when the engine dies so I feel the CG is real close. What do you mean by a Hunting problem? I really don't see haow I could seal the hinges at this point, but I'm sort a confused exactly how?
As the elevator I think it's a slight bit higher then the flap ratio. I will have to go outside to the shop and re check it.

>Leonard,
>I would have to cut my rudder off and repair it to get rid
>of the offset. I will try to adjust the lead outs 1/8 inch
>forward first. I have 63.5 line length. I will adjust the
>throttle a little faster to get that lap speed to udder 5
>sec. Whats to fast?
> As I remember the outside wing is fairly level up or
>inverted. But a outside person could see that better. It
>glides really well when the engine dies so I feel the CG is
>real close. What do you mean by a Hunting problem? I really
>don't see haow I could seal the hinges at this point, but
>I'm sort a confused exactly how?
>As the elevator I think it's a slight bit higher then the
>flap ratio. I will have to go outside to the shop and re
>check it.
>

If you have a lot of yaw, you may need to "adjust" the rudder. And if it means cut it off and reglue it, well, that isn't too bad. With 63.5 inch line length, you can go a little slower, but you may still need to run at 5 seconds or so. If the engine is running too rich, by all means lean it a bit. If it is running correctly, then adding a bit of pitch can help. Check the other trim areas. Sealing the hinge line can be done simply by putting strips of tape in from the bottom while giving full control to the surface being sealed and then making sure the tape does not bind.

Leonard,
In using tape, do you mean temporarily? And what kind? Just the bottom side? Do you stick half the tape on the trailing edge and give up elevator and stick the rest on the flap? And does it go the total lenghth of the flap area? And do you do both sides? WOW lots of questions.
I just cut off my rudder. I will glue it on straight or make it adjustable. Any tips on the constucting of the hinges or control rod?
Thanks!

>Leonard,
>In using tape, do you mean temporarily? And what kind? Just
>the bottom side? Do you stick half the tape on the trailing
>edge and give up elevator and stick the rest on the flap?
>And does it go the total lenghth of the flap area? And do
>you do both sides? WOW lots of questions.
>I just cut off my rudder. I will glue it on straight or make
>it adjustable. Any tips on the constucting of the hinges or
>control rod?
>Thanks!

Well, forget the adjustable, I glued it on straight. Well not exact. I laid a steel strait edge on both sides agaisnt the fus and stab after I glued on the rudder. the right side showed about 2 or 3 degrees off set above the elevator and about 5 degrees below the elevator. The left side shows somewhat different. about 6 to 10 degrees offset above the elevator, and about 10 degrees off set below the elevator. Strange I know. But I beveled the left side of the fus from the wing to the tail end to help with the wind drafting. I guess if in the beginning when I was in constuction with the tail I should of left the rudder straight. Because the beveling and the leadout adjustment would of been enough. I left the engine straight also,(No offset)but the planes suggested 2 degrees. So, can you see what I'm explaning about the difference in the offsets? Can you vision what it may look like, given of what Iv'e said? It sure looks alot better though. Please reply to the previous about the tape hinging. Thanks again?

>>Leonard,
>>In using tape, do you mean temporarily? And what kind? Just
>>the bottom side? Do you stick half the tape on the trailing
>>edge and give up elevator and stick the rest on the flap?
>>And does it go the total lenghth of the flap area? And do
>>you do both sides? WOW lots of questions.
>>I just cut off my rudder. I will glue it on straight or make
>>it adjustable. Any tips on the constucting of the hinges or
>>control rod?
>>Thanks!
>
>Well, forget the adjustable, I glued it on straight. Well
>not exact. I laid a steel strait edge on both sides agaisnt
>the fus and stab after I glued on the rudder. the right side
>showed about 2 or 3 degrees off set above the elevator and
>about 5 degrees below the elevator. The left side shows
>somewhat different. about 6 to 10 degrees offset above the
>elevator, and about 10 degrees off set below the elevator.
>Strange I know. But I beveled the left side of the fus from
>the wing to the tail end to help with the wind drafting. I
>guess if in the beginning when I was in constuction with the
>tail I should of left the rudder straight. Because the
>beveling and the leadout adjustment would of been enough. I
>left the engine straight also,(No offset)but the planes
>suggested 2 degrees. So, can you see what I'm explaning
>about the difference in the offsets? Can you vision what it
>may look like, given of what Iv'e said? It sure looks alot
>better though. Please reply to the previous about the tape
>hinging. Thanks again?
any takers? really would like some tips on the hinge sealing.

Warren
Nov-07-02, 01:34 PM (CDT)
10. "RE: Flap Sealing Tape"
>Len and Warren: What is better:
>3/4" width, or 2"? Inquiring
>minds want to know.

The 3/4" width is just perfect for me. By the time you fold it down into the gap to the hinge pivot line, and then back out, it leaves a little over a 1/4" on each surface, so it doesn't look conspicuous. You certainly wouldn't want to use the full 2" width on your plane, or you might have to put some postage on it !! <g> And trimming down the 2" width to something less, would be tricky.

You'll notice on the package, that the roll is 650" long, so you can get 8-10 planes out of one roll.

>Do you deflect the flaps in
>one direction to the max,
>and then apply the stuff?

Here is a sketch that Brett Buck sent me one time. It shows the procedure clearly. Thanks Brett.

I only apply the tape *between the hinges*. So I cut each piece to the
correct length, then stick half of it (length wise) to a piece of "release paper"....the backing for Ultracote/Monokote works nicely for this. Then you can position the tape on one surface and gently rub it down. Then I use a thin, plastic squeege to force the tape down to the pivot point, and up the opposite side. Then remove the release paper and rub the tape down on the second surface.

Someone (I think it was TF) once suggested that after you do each
section, check the control surface to make sure that you did not increase the stiffness. If you did, remove the tape and do it over again.

You do have to use care, because over 60-65" of hinge line (wing and
stab) you can introduce considerable stiffness to your control system,
which of course you don't want.

Have fun. Cheers, Warren W

All the above was saved to my computer from posts on SSW. I would add, however, that the 3M tape seems to change names and numbers on an annual basis. I'm not so sure it makes a difference, but get the clearest stuff, and don't worry about it. Just be sure to apply it per the instructions, to a well cleaned model, BUT do oil the hinges first. Steve

Thanks Steve!
The attachment looks good. It doesn't tell you to tape the top or the bottom. Leonard says to do it on the bottom. I would think over time that as dust sets in the crack, it will eventualy gum up sticking to the tape. Has anyone had that happen? Or is their a solution for that?

HI GREG. I sent you everything today. Hope it helps. Do the Bottom of the flaps in your tapeing. Glad you re-worked the rudder. Move your lead outs back 1/4", NOW see what happens when you fly.

Scott(thanks for your call)Riese

Scott, a little sanding and a little paint on the rudder. Re mount the engine, thanks to the threaded insert, and cna't wait to she how she performs. Are you going to Mac on Friday, if it's fair weather?

>Thanks Steve!
>The attachment looks good. It doesn't tell you to tape the
>top or the bottom. Leonard says to do it on the bottom. I
>would think over time that as dust sets in the crack, it
>will eventualy gum up sticking to the tape. Has anyone had
>that happen? Or is their a solution for that?

Hi, I am late in getting back to this one. But, yes, do the bottom so it is less visible. And, yes, over time it can get dirty, grimy, full of fuel residue, etc. If so, then peel it off and clean the hinge line and redo. A lot will depend on how big a gap you had to begin with. Matt makes his very tight to begin with (or, at least that is the goal). He, also, tapers both the flap and the trailing edge of the wing to a 45 degree point. It makes both taping and cleaning easier and seems to work fine. Matter of fact (Ted, you didn't see this) on most of his planes he cannot tell a difference with or without tape. Still, I will go with Ted and recommend doing it. Unless you get things stiff, it can't hurt.

>I'm getting back into C/L after many years absence and have
>to say this forum is a fantastic source of information. I
>am currently getting a Tanager ready to fly and have a few
>questions:
>
>- How much flap travel should the model have? It seems that
>more than just a few degrees of flap would give more drag
>than lift.
>- Flap/elevator ratios. Should this ratio be 1 to 1 or
>should we have more elevator than flap travel?

I would stick to what the plans say, which is almost certainly 1:1. It is possible and sometimes desirable to alter the ratio of elevator to flap, provided you really, really know what you are looking for in turn quality, but even then it's usually just a tiny change that's required.

As far as travel goes, it should be able to go +-35 degrees. But the rate of movement is more important than the total throw, within reason. You should be able to get about +- 30 degrees with full normal travel on your wrist. Of course, the handle spacing is in the equation too.

For reference, I just measured how much my leadouts move. My controls go roughly 45 degrees each direction, total. When it's at 45 degrees, the distance between the end of the leadouts is just a hair under 3". That's what I use on my airplane with a handle spacing (at sea level settings) of about 3 1/4". The result is a control rate that is comfortable for me with my CG in a moderately aft location, and modern moments. Overall, it's probably about in the middle of the road in terms of control sensitivity compared to the other airplanes I fly.

Once again, the plans presumably show some ratios, and I would probably use them as shown unless it's grossly faster than my example.

>- Rudder offset. Should I use no rudder offset or just a
>few degrees? What about a rabe rudder setup? What effect
>does rudder offset have on the model while flying?

I'm a big advocate of no rudder offset, or at least carefully trimming the rudder offset (which, if you follow my trim ideas) will inevitably lead to effectively no rudder offset. But BIG CAVEAT - it will wind up with 0 rudder offset presuming everything else is as straight as a die. The reason rudder offset has been shown on virtually every C/L plan since the event started is largely to *hedge one's bets* concerning alignment and construction variations. If you just glue it on "straight", and anything else is a little crooked in the wrong direction, your first flight could involve a lot of running.

I definitely think the rudder offset should be adjustable. Of course, adjustability could involve a saw and some glue, but on this particular model it should be easy to hinge the rudder and provide an adjustable stop (I use a plain old control horn and some kwik-links - by the way, the only place you should ever, ever, use kwik links - never, ever, on the flap or elevator). Start with some offset, and then as you gain confidence and learn what to look for, you can adjust it for minimum yaw transients in the corners (use the search function to look for many previous threads on the topic of trimming the leadouts and rudder position). I stick mine almost straight ahead right on the first flight, but then I am highly confident that the alignment is right elsewhere - which could easily prove wrong and skewer my ego if I ever build another airplane.

In general, the effect of rudder offset is to yaw the airplane out, and usually to set up a situation where the line tension limits the yaw angle. This will give you a lot of line tension in level flight, that usually gets messed up in maneuvers as the line tension varies. And a lot of yaw from any source tends to really mess up the overhead tension. My plan is to always set the airplane to fly as tangent to the circle as possible.

Unless you really know what you are doing, and are a very good observer, I would avoid using a Rabe Rudder. Al's work well, a few other people's work well, but by far most of them cause more harm than good. Not because the principle is wrong, or that Al's instructions on adjusting it is wrong, but that most people seem to be unable to see or feel the effects necessary to adjust it properly. This includes multi-time NATs Top-5 pilots. Two problems, really - either people can't detect when it's right or wrong, and, once you have a movable rudder, people tend to fixate on the rudder adjustment as the cause of, or cure for, every trim ill that comes along. When in fact it's just one more possible cause, out of dozens.

I would suggest that the a fixed. adjustable rudder will get you close enough that not having it move in flight WILL not be a limiting factor on the performance. If you decide to do it anyway, first, study the linkage very carefully and make sure you really understand it and know how to accomodate all the different adjustments that it permits. Second, make darn sure you can make it fixed, and trim the airplane with it fixed/static adjustable FIRST, then only add the movement to trim the residual yaw.

Brett

p.s. I might also add that the hinge sealing instructions that someone posted originally included the information that it should go on the bottom of the airplane. Not that it really matters from an aerodynamic standpoint, but who wants that tape on the top where you can see it? I strongly advocate sealing the hinge lines before you even fly it - there's no good reason not to, and it solves so many potential trim issues that it's simply a no-brainer. But you have to do it properly to avoid binding the controls up.

After hearing about Keith's Trostle's trimming horror story with the Glufhawk Bearcat, I agree that if your just starting stay with a fixed adjustable rudder. After a few years and knowing what you want and why you want it that way then you may decide to experiment with the in flight moveable rudder, also known as a "Rabe" style rudder. The best working one I have seen is the one on Keith's Glufhawk Bearcat, but by his own admission it wasn't easy to get it set-up right. See the So Cal visit thread for a little more info if you like. Hopefully, Keith will get that article published eventually.