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flight problem need help

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flight problem need help

Post  oldguy on Sat Jan 09, 2016 7:25 pm

I built this plane, it's 15 size 30" wing, just before I quit doing the hobby about 8 years.I did try flying it several times with no luck.Now the problem.
Every time I tried to fly this plane all it wanted to do is come in on me right off the launch.I had to move out of the way the last time I tried to fly it or it would have hit me.I have been told a warped wing, but the wing looks dam straight and measures out good.Can you guy's give me a list I of things I can checkout to correct the problem.Two things I tried was shifting the leadouts back more, and shimmed the engine to give more thrust outwards.
Thanks Jim





Last edited by RknRusty on Sat Jan 09, 2016 8:09 pm; edited 1 time in total (Reason for editing : Added IMG tags to the picture link)
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Re: flight problem need help

Post  TDbandit on Sat Jan 09, 2016 7:41 pm

Make sure you have the engine offset to the outside this can be done by installing washers under the engine mounting lugs on the front holes. Two washers should help being a combat wing may need more also make sure the wing don't have a twist in them. I know you said that the wern't warped but twists can aleron it towards the inside also tip weight helps too. The pylons that attach the elevator can act as a rudder too if they are bowed towards the inside. Another thing if your lines are too long or heavy that can drag the models nose toward the inside .15's should be on around 52 feet Hope this helps! (Bandit)
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Re: flight problem need help

Post  RknRusty on Sat Jan 09, 2016 8:07 pm

Jim, hold the plane by the wingtips with the stabilator at eye level, and gaze over the stab to see if it's parallel with the wing. If it's not parallel, it may be turning the plane. The things you did were the correct first steps in finding the problem. But sometimes these combat wings need more radical engine out-thrust than ordinary airframes, so it may need more than the usual 2 or3 degrees. Like Bandit said, make sure it's not light on tip-weight. If that doesn't do it, go ahead and either twist the outboard wing up(easy with a heat gun if it's shrink wrap covering), or tape an aluminum trim tab to it to act as an aileron.

If any of that gets it flying, have someone watch and see if it flies with the wings level(a straight extension of the lines). If not, it may need more or less tip weight. If you are able to fly some inverted laps, that will tell a lot more. If, for instance, it flies (outboard)tip-high in normal flight, and tip-low in inverted flight, then the trim tab is the necessary adjustment. You may very well need to go back and forth between tip-weight and trim tab adjustment to get it fine tuned.
Let us know how it goes.
Rusty

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Re: flight problem need help

Post  oldguy on Sun Jan 10, 2016 12:02 am

Bandit wrote:Make sure you have the engine offset to the outside this can be done by installing washers under the engine mounting lugs on the front holes. Two washers should help being a combat wing may need more also make sure the wing don't have a twist in them. I know you said that the wern't warped but twists can aleron it towards the inside also tip weight helps too. The pylons that attach the elevator can act as a rudder too if they are bowed towards the inside. Another thing if your lines are too long or heavy that can drag the models nose toward the inside .15's should be on around 52 feet Hope this helps! (Bandit)

RknRusty wrote:Jim, hold the plane by the wingtips with the stabilator at eye level, and gaze over the stab to see if it's parallel with the wing. If it's not parallel, it may be turning the plane. The things you did were the correct first steps in finding the problem. But sometimes these combat wings need more radical engine out-thrust than ordinary airframes, so it may need more than the usual 2 or3 degrees. Like Bandit said, make sure it's not light on tip-weight. If that doesn't do it, go ahead and either twist the outboard wing up(easy with a heat gun if it's shrink wrap covering), or tape an aluminum trim tab to it to act as an aileron.

If any of that gets it flying, have someone watch and see if it flies with the wings level(a straight extension of the lines). If not, it may need more or less tip weight. If you are able to fly some inverted laps, that will tell a lot more. If, for instance, it flies (outboard)tip-high in normal flight, and tip-low in inverted flight, then the trim tab is the necessary adjustment. You may very well need to go back and forth between tip-weight and trim tab adjustment to get it fine tuned.
Let us know how it goes.
Rusty

Bandit/ Rusty
Thanks for the info.With the thoughts given I will have to try more shimming of the engine and more tip weight.the stab to wing alignment is straight, I was using 48' lines at the time so I don't believe it is line length.I have seen some combat models that the engine pointing outward quite a lot so maybe it just needs more.If that doesn't help, I will try a trim tab to see what that does.it's going to be awhile before I can get out to fly, it's cold wet and snowy out here now.it's good building weather, plus my gout is giving me hell in my left foot.I will post back about this topic when I get to try the plane with some adjustments.
thanks again guys.


Last edited by RknRusty on Sun Jan 10, 2016 12:17 am; edited 1 time in total (Reason for editing : fixed Bandit's quote tags)
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Re: flight problem need help

Post  RknRusty on Sun Jan 10, 2016 12:15 am

You can give it radical engine offset at least long enough to make it fly laps so you can get eyes on the wing attitude. Then when you get the airframe problems all sorted out(tip-weight, trim tab, twist, leadout position, etc), move the thrust angle back to a more reasonable angle. Good luck.
Rusty

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Re: flight problem need help

Post  oldguy on Sun Jan 10, 2016 12:25 am

RknRusty wrote:You can give it radical engine offset at least long enough to make it fly laps so you can get eyes on the wing attitude. Then when you get the airframe problems all sorted out(tip-weight, trim tab, twist, leadout position, etc), move the thrust angle back to a more reasonable angle. Good luck.
Rusty

That is probably a good idea and a good place to start.One thing at a time so i know what is fixing the problem.
Jim
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Re: flight problem need help

Post  fredvon4 on Sun Jan 10, 2016 8:14 am

Hey OldGuy

Older guy here...I presume

what engine, what prop, what size lines, where is CG, who is launching, where is the wind relative to launch point what is weight of the plane

wing is straight: check
engine offset: check
Stab to wing in line; check

CG forward enough for first trim flights?
lead out exit behind CG?
Enough engine?
correct propeller for the weight, size and engine?
launching with wind to back? first half lap need to be down wind until airspeed is enough to complete the lap into the wind
launching pointed tangent to the flight circle? Is the launch RPM and thrust enough that the plane does NOT need to be pushed but just let go
are you stepping back several paces at launch until some airspeed gives good line tension?

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Re: flight problem need help

Post  Ken Cook on Sun Jan 10, 2016 8:33 am

Twists are not always easily detected. This become increasingly harder to detect when the nacelle is in between the panels. Block the plane up on a table. Lay an arrow shaft approx 24"-30" long from the trailing edge to the leading edge. Put one on the inboard side right against the wingtip and one on the outboard side against the tip. Standing back looking from the side ( Pilots view if flying) the arrow shaft on the inboard wing should cancel out the arrow shaft on the outboard. If need be rubber band them onto the wing to insure that they are tightly pressed against the surface. Straight wooden dowels would also suffice but rolling them on a table to insure that they're true is a must. The shafts will quickly reveal if the wing's outboard and inboard wing are in the same plane. Ken
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Re: flight problem need help

Post  RknRusty on Sun Jan 10, 2016 9:27 am

Here's a wing test using two CF tubes like Ken suggests. Of course it easier when it's just bones. The rods should be parallel so the back one disappears behind the front one when you crouch down and eyeball it.

If you're looking at the pic on a phone the black rods might be invisible. You might get a big view if you click on the pic, I uploaded a giant size.


And Fred thought of all the other factors the rest of us overlooked. Particularly when I launch a combat type plane, tell the launcher to point it up and out, both of you confirming tight lines, holding it out to his side(so it doesn't loop around and hit him in the back). Neutral or slightly up-elevator. When you wave him off, he/she should just open their hands as if dropping it(and get the hell out of the circle). And you immediately start back peddling. Tail wind becomes a beneficial crosswind 1/4 lap later.
Rusty

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Re: flight problem need help

Post  pkrankow on Sun Jan 10, 2016 10:09 am

Wing tip weight and engine offset. If balanced on the point the engine is mounted the outboard wingtip should drop.

Also how are you launching? Is someone launching for you or are you using a stooge of some type? Sometimes launching with a little more nose-out of the circle may help...slower speed but more line tension initially. Having it "thrown" with some velocity is better than being dropped.

Get your running shoes on and check wind direction. Hand launching should be between downwind and crosswind, while with wheels is downwind so it has speed on the crosswind. In both cases crosswind to upwind is where it is really getting flying. Backing off at an angle can help maintain line tension through this process.

(And everything everybody else has said)
elevator twist
"fuselage" twist or elevator to wing misalignment
wing twist
engine offset

Phil


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Re: flight problem need help

Post  oldguy on Sun Jan 10, 2016 7:01 pm

fredvon4 wrote:Hey OldGuy

Older guy here...I presume

what engine, what prop, what size lines, where is CG, who is launching, where is the wind relative to launch point what is weight of the plane

wing is straight: check
engine offset: check
Stab to wing in line; check

CG forward enough for first trim flights?
lead out exit behind CG?
Enough engine?
correct propeller for the weight, size and engine?
launching with wind to back?  first half lap need to be down wind until airspeed is enough to complete the lap into the wind
launching pointed tangent to the flight circle? Is the launch RPM and thrust enough that the plane does NOT need to be pushed but just let go
are you stepping back several paces at launch until some airspeed gives good line tension?


fred it's a fox 15x slant plug,have treid my standard  8 x 4 MA prop,and a 7x 6 also, i was using 48' foot .015 steel lines could use .012, but don't have any at the time.CG is about 3/4" aft of leading edge.An i always launch back to wind.I have flown other similer combat type planes without issue that i have built, haven't had any issue with getting them going.But this bird has been a problem child.It weighs 12.5 oz's with engine.It should move pretty well, and does, you can't backup fast enough.It's like it hates me, it comes after me on launch.I will be checking everything here you guy's have mentioned an will post back with results when i have some.
thanks again guys.Here's a small video of a small combat type plane I built with a cox golden be.
https://www.youtube.com/watch?v=bqYFxuVMhZI
jim


Last edited by oldguy on Sun Jan 10, 2016 7:42 pm; edited 1 time in total
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Re: flight problem need help

Post  RknRusty on Sun Jan 10, 2016 7:24 pm

Haha, Jim, sounds like a badass combat plane with a seriously foul attitude. Maybe strap a little league size baseball bat to your other wrist and if it keeps chasing you after all this, just haul off and clobber it back to kit-form! lol! Be sure the camera is rolling.

I'm gathering you're an experienced flyer, able to fly inverted and loops, 8s, etc, am I right?
And, you're quite welcome. This is the stuff we're here for.
Rusty

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Re: flight problem need help

Post  Ken Cook on Sun Jan 10, 2016 7:44 pm

Jim, I fly a lot of combat. I know that foam and wood framed wings are night and day but this may or may not apply here. One thing I found very apparent with foamie wings using external controls is the way the bellcrank is setup high on the wing. The end result is the leadout guide keeps the lines close to the airfoil and the bellcrank sits about 1/2" high above it. The vertical CG is off and the wing almost always flies outboard tip high. More tip weight will help get the plane flying but too much weight is certainly going to prove problematic in the maneuvers. For instances like this, I use golfers lead tape that comes in a roll. I cut a piece and form it tightly around the leading edge and tape it on for test flying. The fact that the engine is mounted sidewinder is already offering tip weight. My question is, where are the leadout tubes glued on your wingtip, above or below the wingtip? If they're above, I would try and swap to the underside just to try it. Some of the similar problems we were having on the foamies where fixed by inserting Nyrod through the foam from the bottom of the wing to the top . I know you mentioned sliding the leadouts back in the earlier portion of this post. Are they adj. leadouts? I would caution adjusting them back too far due to it wanting to make the plane bounce on the lines during launch. I would keep the prop load light like a 7x4 woodie.
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Re: flight problem need help

Post  oldguy on Sun Jan 10, 2016 9:51 pm

RknRusty wrote:Haha, Jim, sounds like a badass combat plane with a seriously foul attitude. Maybe strap a little league size baseball bat to your other wrist and if it keeps chasing you after all this, just haul off and clobber it back to kit-form! lol! Be sure the camera is rolling.

I'm gathering you're an experienced flyer, able to fly inverted and loops, 8s, etc, am I right?
And, you're quite welcome. This is the stuff we're here for.
Rusty

Rusty yes, I was able to do all the manuvers you mentioned but it has been awhile.But I can't fly like the big boy's that fly  the pattern.

https://www.youtube.com/watch?v=xTCkjOMYZ14


Last edited by oldguy on Sun Jan 10, 2016 10:10 pm; edited 2 times in total
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Re: flight problem need help

Post  oldguy on Sun Jan 10, 2016 9:52 pm

Ken Cook wrote:          Jim, I fly a lot of combat.  I know that foam and wood framed wings are night and day but this may or may not apply here. One thing I found very apparent with foamie wings using external controls is the way the bellcrank is setup high on the wing. The end result is the leadout guide keeps the lines close to the airfoil and the bellcrank sits about 1/2" high above it. The  vertical CG is off and the wing almost always flies outboard tip high. More tip weight will help get the plane flying but too much weight is certainly going to prove problematic in the maneuvers. For instances like this, I use golfers lead tape that comes in a roll. I cut a piece and form it tightly around the leading edge and tape it on for test flying.  The fact that the engine is mounted sidewinder is already offering tip weight. My question is, where are the leadout tubes glued on your wingtip, above or below the wingtip? If they're above, I would try and  swap to the underside  just to  try it. Some of the similar problems we were having on the foamies where fixed by inserting Nyrod through the foam from the bottom of the wing to the top . I know you mentioned sliding the leadouts back in the earlier portion of this post. Are they adj. leadouts? I would caution adjusting them back too far due to it wanting to make the plane bounce on the lines during launch.  I would keep the prop load light like a 7x4 woodie.

Ken the leadouts come out of the center of the wing, and I did put a adj. leadout, it's all the way aft now.
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