stunthanger.com
Building Tips and technical articles. => Building techniques => Topic started by: Randy Powell on June 24, 2008, 10:03:34 PM
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Last weekend at a contest, I was having problems with a slight yaw that was obvious during outside corners. More obvious at the 45 degree corners at the top of the outside squares. Didn't seem to have a lot of effect on the flightpath, but it bugged me. A lot. It was suggested by one trim expert that I trust that it could be because there's an almost undetectable warp in the outboard flap of the plane. Sort of a slight downturn as the flap reached the root. Another guy that is also very good at this stuff suggested that the leadouts were too close together. That rang a bell. If I move the leadouts farther back. Say 1.25" behind the CG, the problem mostly goes away, but the line tension above 45 degrees also pretty much disappears. I had hit a compromise that somewhat minimized the yaw while maintaining some line tension above 45 degrees. It was suggested that if I split the leadouts (make them independently adjustable) that I could keep the front (up) leadout at the best location and move the rear one back to help with the yaw issue. This seemed to make some sense.
So, what to do? What I did was cut a hole in the bottom of the wingtip and remove the leadout slider (not so easy since it was a boxed system with the slider in the middle). I machined two new sliders that each have a set screw. Hopefully, I can finish it up tomorrow and recover the hole I cut and repaint it by the weekend. Then we'll see what we have. Since the new PA plane (currently covered and awaiting fillets and primer) is much the same design, if this works, I'll retrofit it with a similar system. The only question now is, since I have to repaint the bottom of the wingtip, is it worthwhile to go ahead and fix some other minor hanger rash that the plane has accumulated.
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Randy,
I dont know maybe you should go ahead and strip it do a compete refinish, then you can take care of all the little spots. or heck, dont bother, finish the new pa plane and put this one into reserve for future consideration, lol,,
I dont know man honestly, just fix what you need to, dont be overdoing, adding weight, and spending finish time you need on the new weapon!
Like I should talk right, I have the profile 109, the built up 109 both waiting for finish and what I really want to do is start building the New Avenger! sigh,,
I feel your pain,, really!
By the way, I neglected to make clear, GREAT flying sunday, you were looking real sharp man,, keep it up
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Just my thoughts Randy. If the new independent leadout slider works out to be the cats meow. You'll be flyin the SLIDER alot until the new one is done anyway. I say as long as you got the paint mixed and the gun out, go for it. Remove all that hanger rash, why do it twice, because if it flys good you gotta look good. Your just that kinda guy. No less than what I expected. y1 LL~
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Randy, in my feeble mind I would think that you would fuel proof the area of changes until you see that it is going to work. I vaguely remember guys making changes on planes after they had flown them without the final finish. Of course in those days about 10 coats of dope was a super finish. Now does it make a difference on which leadout is in front? DOC Holliday
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I am glad Randy is flying better while I keep getting worst. 23's and twenty fours just for my squares just don't cut it. Maybe I am just getting old or my scores are. HB~> HB~> HB~>
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Yes, Leo, it's the scores that are old. LL~
There isn't much to fix. A little scratch here. A slight ding there. I imagine that when I finish the fix on the leadouts, I'll probably at least fix the areas that are the same color as the fix area.
The more pertinent thing is, if this works as planned, I really need to re-work the setup on the new plane. It's going to be a lot more complicated due to the design of the new wing tip. It will take some figurin'
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Got the leadouts all redone and put a patch over the hole. Hope I can sand it out tomorrow and get some more dope on the patch. Then paint it soon. I hope to have the repair done so I can do some flying this weekend, but I'll fly it with the patch just doped if not. I'm dying to see if this works.
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Last weekend at a contest, I was having problems with a slight yaw that was obvious during outside corners. More obvious at the 45 degree corners at the top of the outside squares. Didn't seem to have a lot of effect on the flightpath, but it bugged me. A lot. It was suggested by one trim expert that I trust that it could be because there's an almost undetectable warp in the outboard flap of the plane. Sort of a slight downturn as the flap reached the root. Another guy that is also very good at this stuff suggested that the leadouts were too close together. That rang a bell. If I move the leadouts farther back. Say 1.25" behind the CG, the problem mostly goes away, but the line tension above 45 degrees also pretty much disappears. I had hit a compromise that somewhat minimized the yaw while maintaining some line tension above 45 degrees. It was suggested that if I split the leadouts (make them independently adjustable) that I could keep the front (up) leadout at the best location and move the rear one back to help with the yaw issue. This seemed to make some sense.
Hmmm, Gyroscopic precession? Which way is it yawing? Is the "down" line in front or in back?
Looking forward to seeing if your individual line adjustment mod yields a solution...
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Dennis,
This was a standard layout with the down line in the back. Problem was, the leadouts were about a half inch apart in a one piece slider. If you slid the slider back far enough to kill the yaw in the outside corners, all the line tension was gone above 45°. If you slid it forward until you got pretty good tension above 45°, you got a wiggle on hard outside control. I hit a compromise spot where the wiggle was minimized and the line tension was OK, more or less.
On hard outside control, at the end of the turn, the outboard wing was ahead of the inboard wing. The plane has a ton of side area aft of the CG, so it tends to stabilze pretty quickly, but causes a little rocking on the yaw axis.
Paul just suggested that if the leadouts were independently adjustable, then I could locate the line angle in the right place and move the leadouts apart a little at a time using the line angle point as a center until both problems went away. Like I said, we'll see if it works. It was worth trying since nothing else seemed to help.
It's not a bad problem. But it's there and bugs me.
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Well, it's all done (though I have to say I didn't do the best job with the patch and particularly the new inklines. But it is on the bottom (sigh). Seems to work pretty well as far as being about to adjust them individually. We'll see what we get.
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Glad to see it is done, now for the flight reports!
Mongo (who BTW always tries to put the up line in front)
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Bill,
Well, it won't get a flight test for a week or so. I couldn't get out yesterday and I had some surgery today. Doc says I can't lift anything heavier than a pencil for at least a week. Man, I am sore.