I have a H9 Cub on GP floats (60 size). The floats seam to be set up properly according the post from the Ontario Club and it lifts off the water nicely - but once in the air the plane has a strong tendancy to roll left. I have never set the plane up with landing gear so I don't know how it would respond on wheels therefore I'm not sure if one of the floats may be causing this. The stab looks perpendicular / parallel to the fin and main wing. The main wing has 2 deg positive to the floats.

To counter act the left roll I need to add 10 clicks of right aleron - this moves the trailing edge on the aleron one thickness (~1/8") up on right wing and down on left wing. This seems excessive and I was wondering if there is another way to fix the roll? The plance CG width wise is close to the middle (right side alittle heavy).

Can you use he elevator (since it is in two halves) to help compensate for the roll or would this create a bigger problem? If so, how?

Thanks for any help!

Are the floats tracking properly with the chord line of the fuse? If the front of the floats are kicked off to the right or starboard this will want to roll the airplane in the manner described.

Did you balance the main wing ? Remove the main wing and check the balance - add weight as needed in the wingtip.

1. Don't try to use the elevator to correct a roll problem. Besides putting a twisting stress on the fuselage, the roll correction (if any) will change with both airspeed AND elevator input. Ick!

2. The floats may be contributing to this, but the first place I'd look is the wing. It's probably got a warp in it. Assuming it's covered with a heat-shrink material such as MonoKote, you can heat the covering while holding it straight (maybe overcorrect slightly). Repeat until the ailerons trim flush with the TE.

3. Lateral balance may also be contributing, but I'd eyeball the wing for warps before adding wingtip weight. Rx for lateral balance is to compare inside loops with outside loops (assuming the airplane is capable of outside loops). If it rolls the same direction both inside and outside, lateral balance is not a factor; the problem is purely wing twist. OTOH, if it rolls left on an inside loop and right in an outside loop, the left wing is heavier than the right. Or it could be a mix of wing twist and lateral balance. Work slowly over many flights and you'll eventually get it dialed in.

Duane Gall
RCPRO

I have an update to my findings:

1) The floats are straight to the fuse - I plummed a line from the CL of the floats to the CL of the fuse down the length of the fuse and it is parallel all the way down. Top of floats are level.
2) The wing looks straight with no warping or loose ultrkote.
3) Ailerons are trim flush and straight with TE of wing
4) Weighed wings and both came in @ 1# 3.8 oz exactly. Connected wings (no fuse) they balanced perfect (didn't balance cord wise)
5) Don't think I can do outside loops with a Piper Cub - at least I didn't try.
6) This was my maiden voyage and I noticed that the plane is very tail heavy. I am placing weights on the float tips to get the CG to suggested spot and I'm picking up the plane under the wing and balancing to get the main wing underside level with the ground. Is this correct?
7) Can a very tail heavy plane cause the rolling problem?

See pictures for details

Thanks for the help and keep any other info coming!

pictures:

I agree with Duane, I think you have a slight warp in the wing or you may be creating a warp when attaching your struts. Use a level on the bottom of one wing tip, at the last rib, and shim up your floats to get the wing level, then go to the other side and check. Another way is to hold a yard stick under the wing tip and measure from the ends of the stick to the floor (table). Shim the floats till both measurements are the same. Now go to the other wing tip and check the measurements.
Seaplane

Update -

I shimmed the right float up 1/8" off floor in order to get the wing tips to match height off ground once connected. Attached is the picture of what I have found by taking measurements around both wings from the edge of wing to a level surface.

It seems the right wing may have a twist at the end of about 3/8" - 1/'8" around the end of the wing. I guess this is in the right direction to cause a left roll.

What do you guys think? How do you fix or compensate? This is a ARF and I'm not taking the ultrakote off.....

Thanks!

It looks like you found the problem. I don't know if the right wind TE is twisted down or the left wig TE is twisted up or both. Either way they should measure the same. I think you can get the twist out, but you'll need another person to help. While one person is untwisting the wing, use a heat gun across the wing top and bottom. After cooling re-check your measurements. Hope this helps

Seaplane

Thanks for the help!

I don't know if one is twisted up or the other down but since this is a new plane Horizon Hobby said they would replace the wings at no charge - so I think I'll take them up on it! I guess 3/8" is enough to do cause the problem!!

Thanks!

Looking at your first picture I'd say the beer bottle on the left float is causing your problem. [sm=lol.gif]


Really though, if you look at that first picture it looks like you have a warp in the wing, of course that could just be an illussion from the picture.

One way to check for a warp is to make up a special tool to check it. Cut 2, 2 " squares out of some scrap ply, then drill a hole in the top center 1/4 " down from the top for a dowel ( I use arrow shafts ) and insert the shaft through the hole all the way ( making it look like a hoe ).
Now take the tools and place one on each end of the wing ( at the end ) with the dowel end sitting on the leading edge of the wing and the hoe end sitting on the trailing edge just short of the aileron. NOW > stand back away from the end of the wing and look down the wing ( level with the wing ) The dowels should line up, if they don't you have a warp.

It's crude but it works. Sorry I can't do pictures. ENJOY !!! RED

Red Head -

Thanks for the advice and you are right about the beer! Actually the first picture does show a bit of the warp - the TE at the end of the right wing is 3/8" lower than the left wing causing the left roll problem. As I said, since this is a new plane Horizon Hobby argeed to replace the wings at no cost! I just hope the new wings are not twisted.

Thanks for the advice!

Unless the wing is fully sheeted in front of the spar, you can twist out the warp. Maybe even if it IS sheeted.

Get some beer cold, and ask a buddy to come over. Have him twist the wing in the appropriate direction and you go over the covering with the heat gun until the wrinkles disappear. Do the top and the bottom of the wing. Once you have both wings the same you are good. On a Cub it is not a bad idea to twist a little washout into both wings.( Washout: trailing edge higher at the wingtip) . I agree with previous posts that in the first picture i t appears that your right wing has some wash-in. Since this is a Cub, the V-shaped struts can affect the rigging angles, so check the wings both with the struts arrached and without. You may just be able to correct the problem with the struts.