I have been working to get the wings level on my S1 Ringmaster. The wing needs an outboard tip tab to lift up as the ship flys inboard wing high in level upright and low inverted. I have been trying a wedge under the outboard tip which gets it done but if the ship gets a little off wind it wants to wander loose. I have had other ships where a trim tab was needed and use to use a tab off the trailing edge. I got the idea to use the wedge from the free flight guys flying catapult glider. The wedge looks nicer since it is under the wing out of sight. I am wondering if it is causing a funny airflow around the edge that causes this looseness in less than perfect conditions? I seem to remember Paul W having an issue with a tip tab on one of his ships that he was trying to use a section of the tip as a trim tab and it caused all kinds of trim problem, he made it fixed, no up/down position and used the flap tweak and all the trim issues were gone. What do you think wedge or tab?

Best,   DennisT

Find and remove the warp causing this or you will just go nuts.

Ty beat me to it -- but I was doing this long writeup.  So:

Neither tab nor wedge.  The Ringmaster wing is held in torsion by the covering, and is very easy to unwarp.

'Coat or tissue & dope, it's easy to unwarp (or warp) the wing with heat (and moisture, if dope is involved).

First, inspect the wing for warp.  I do this by putting the spinner on my toe, and sighting down the fuselage from the back.  Line your eye up to the very back of the fuselage, and tilt the plane in pitch so that you're looking right down the airfoil at the wing roots -- i.e., you want to see an equal amount of wing above and below the trailing edge at the root.  Then, move just your eyeballs out to the wing tip -- you should see equal amount of wing above and below the trailing edge at the tips, and everywhere in between.

If you don't see that equal spacing then the wings are twisted.  If they're twisted to roll the airplane to the outside of the circle when upright -- congratulations, you've found the real problem.

The luckiest (least unlucky?) twist is even, from root to tip.  To fix that, hold the tip to straighten the wing out, plus just a little bit of "anti-warp" (how much to go past "correct" depends on the plane and the covering, so plan on trying once or twice to get it right).  Now re-shrink your covering and check for warp again.  Repeat until there's no visible warp, then go fly your new plane.

To re-shrink 'coat, just use a heat gun like you did when you shrunk it.  Hold in the anti-warp with one hand and go over the covering on one side (top or bottom) with the heat gun.  You may see diagonal ripples in the covering where you're stretching it -- that's normal, and means things are working.  Keep holding in the anti-warp, and make the covering look good.  Now check for warp again, flip the plane over, and repeat on the other side (bottom or top).  Use what you found out checking the warp to decide just how much anti-warp to hold in while you do this.

Keep in mind for this part that I'm quoting other people -- the only plane I've tried this on has way too much plasticiser in the dope and it just won't stay shrunk.  To re-shrink whatever-and-dope, you want to hit it with moist heat.  The recommendations I've gotten are to hold it over a kettle, pull towels out of a kettle of boiling water, or some other solution that involves steam.  It takes more time (the moisture needs to penetrate).  Because the heat and moisture will penetrate, you need to hold the anti-warp longer -- to the point where you may want to make a fixture, or plan on sitting and watching TV for a while while holding the wing.

While you're checking out the plane, you also want to check to see if the trailing edges are bowed -- this will show itself as a warp that gets worse toward the center of the wing then gets better at the tips.  If it's not severe, you can fix this the same way, you just have to hold in some anti-bow while heating the covering (or you want to heat the TE itself -- see the next little bit).

And, among all that, you also want to check if the horizontal stab is tilted: when you're sighting down the plane, with the elevator out of the way, tilt the plane in pitch until you can just see the wings under the stab.  You're looking to see an even spacing between the stab tips and the wing.  If you don't see this, the stab is tilted.

Fortunately, on a profile, you can fix this, too.  Balsa will take a set if you twist it and bend it, and the covering will help.  So, get out your heat gun, then twist the fuselage until it's twisted at least as far in the opposite direction as the actual twist.  Then spend a good long time getting the fuselage between the wing and the tail as hot as you can.  Then take the heat off and hold in the back-twist until it's cooled and check the warp.  If it's gotten better -- good.  If it's twisted the other way -- better.  In that case you might just let it settle out for a day to see if it doesn't end up spot on.  If it's not twisted at all, or not nearly enough, then you'll need to do surgery to the tail to level the elevator.

The first advice I got about tightening head bolts was "torque it until it breaks, then back it off half a turn".  For heating the fuselage you want it just short of messing up the covering or paint, and you want the wood under the paint to be warm.  So, be patient, be bold, keep feeling it for how warm it is, and remember that it's already twisted up, so bubbling the paint or covering isn't really going to make it worse, technically.

I have a Jim Walker Firecat that was like that, with one trailing edge bowed down and one bowed up.  No amount of heating would make the thing straight.

I ended up cutting off the trailing edges, breaking each rib loose from the leading edge, and essentially rebuilding the wing.  It was a stupid amount of work for the plane -- but hey!  It flies now!

I'd go with a tab, and maybe more steam, or if you get mad at it, strip the covering and rebuild.

Folks tend to assume that superposition applies to aero stuff.

Folks tend to assume that superposition applies to a lot more than it actually does.  It does make the math easier though.

Problem is I have tried to steam out the twist and got most of it but since it is not just a warp the glue is holding. I didn't build it and don't know what kind of glue the guy used. So not wanting to spend too much time on this though a simple trim tab/wedge would do.

   Depends on how crooked it is. Presuming that the wing is tissue/dope, you can wrap it with a bath towel,  hold it straight, and have someone you trust pour boiling water on the towel on both sides. You will feel it let go, hold it straight for 10-15 seconds, then have the helper take the towel off and let it cool.

   If the residual warp is tiny, I would probably prefer a tab over a wedge, just because it does not have a significant effect on the side-to-side drag. Or, cut out a small aileron into the trailing edge stock, and make it adjustable.
 
      Brett

I use clear stiff plastic and attach to the trailing edge (or rudder) with double sided tape. Works a treat and hardly visible. Some wings just cant be trued, unless an enormous amount of work is done, but can fly well for most purposes with trim tabs.

In free flight and some CL, quick cheap, free tabs come from cut up Coke cans. How simple is that?

    Soft drink cans are handy for a lot of things, and I have used them for quick and dirty trim tabs. My first SIG Primary Force ARF had one of those hard to cure warps, so I got a Werner's Lemon-Lime can from John Garret to make one up. I doubled up the material to get some more stiffness out of it and it road along on the airplane for a long, long time. Then one day I was flying the airplane and it came flying off. I though the tape had just came loose, but on looking at it, the metal cracked along the bend I had made in it and it finally fractured and broke off.  Soft drink can stock is pretty thin, ( about .005 to .007" depending on where you are)  and Coke at one time experimented with going even thinner, and had to put facets , or bends, in the cans  to give them some vetical strength, or you couldn't stack cases and pallets of them very high. That didn't work out and they went back to what they had. The faceted cans were absolutely useless for anything like head shims as you could not flatten them out.
   Type at you later,
   Dan McEntee

I decided to try the good old tap. After as couple tweaks the S1's wings level through maneuvers and feels solid on the lines. Trimming the leadout position and tip weight, very close on both.

Best,    DennisT

Charles.  The twin electric stunter was an experiment.  Two motors flew fairly well, but it needed a bit more power.  I added a pusher motor, making it a tri-motor.  That flew even better.  Looking at the tri-motor, I imagined a fourth motor in the nose.  After installing a fourth, the first flight with 4 motors was short and spectacular.  First time going inverted, it went free-flight with slack lines and crashed into a million pieces!  The result is shown in www.flyinglines,org under "numerous pieces"