Wing tip trim HELP

Got in my first flights on my Nobler ARF today. My trim problem is this! At level flight plane looks perfect, except for slightly crooked decal. All I see is the profile of the wing. When I go inverted, I can see the whole bottom wing or outside wing tip is way to high. I first started with wing tip weight, but that just caused outside to sag when landing. Tried tweeking outside flap up some or as much as I could , but no change there. Do I need a trim tab? Thanks

It sounds as if you do have a slight warp in the wing. The outboard wing tip upward warp or the inboard tip TE down slightly. Also the outboard flap should be tweaked DOWN to correct the problem as you describe it.
Tape the leadouts at the wing tip so the controls are in neutral, then block up the fuselage so that you can get back behind the plane about 20 feet and be in line with the thrust line. You should be able to see the entire length of the wing without turning your head back and forth. Now does the wing appear straight? Move the tail up or down or otherwise get so you can get an alignment sight line from the TE of the wing to the upper spar. Does the wing still look straight? If you do have a warp, a heat gun or Mono-Coat Iron should do the trick of working the warp out. Just hold the warped wing in the opposite direction of the warp and heat one side and then the other all the while holding the wing in the opposite direction of the warp. It shouldn't take a lot of twist . Be careful not to over do it. Always recheck for any warp after twisting and heating. To tell if you have gone far enough OR TOO far.

WHAT old rusty said:+

Yes--What BigIron Said.

Remember--wing warps and flap twist make the wing do the same RELATIVE to THE PLANE upright or inverted. ie wing high upright will also be wing low inverted (relative to the ground or pilot perspective)

Tip weight always acts toward the ground (local apparent ground for the physics savvy) in level flight--ie wing heavy, flying low upright will also fly low while inverted.

If it is level upright and high inverted, there is a combination of the two involved. First get it the same upright and inverted with tip weight, then make it zero-zero with flap tweek, unwarp, or trim tab.

Fine adjustment of tip weight may be better evaluated when trimming the plane in squares. I think many stunt ships drop the outboard wing during landing.

Best thing is get some experienced observers to assist. It can be pretty challenging to observe proper trim while flying.

Just MHO

I have a follow-up question on trimming.

I stayed up pretty much all night Saturday and got the major parts attached on my IgNobler ARF. When I was done, I weighed the outboard wing tip on a gram scale. I supported the plane by the crankshaft and on the tip of the vertical stabilizer with the plane level. The outboard tip was only 22 gm (3/4 oz.) heavy when measured at the tip rib. The plans are a little ambiguous in that they say to add an ounce, but there was obviously already some tip weight installed. (I had a fairly early kit, even so there were lots of things the plans said to do that were already completed.) On this plane, I replaced the leadouts with .027 stranded stainless. Obviously, that would reduce the outboard weight bias. I also installed the stock O.S. .40LA muffler which ends up on the inboard side. (Never had that problem with my Pukey Profiles!) I'm going to weigh the muffler tonight when I take the cowl off again. Anyway, I assumed it would be best to go try it the way it was. Not sure if this attitude was based on a lack of sleep or an unshakeable belief in following the instructions.

Well, maybe not. The plane balanced fore and aft about a half inch forward of the 2-1/2 inch dimension specified. For the first flight, I thought that might be a good thing. In retrospect, it seems like the forward CG would have a similar effect of yawing the plane and adding line tension. So if I add tail weight, I have to retrim for line tension? Without adjustable leadouts...?

I got one slow flight in on Sunday. An observer (Thanks, Ron!) said the wings were level in upright flight. It had more line tension than my SuperClown at the same speed, but I wouldn't try a loop with the S-Clown at that speed. I need a little more confidence in the engine before I try to fly it inverted. (Ok, that's a lie. It took me forever to put it together, and there was NO WAY I was going to face sweeping up the debris and shoveling it into the oh-so-conveniently provided refuse receptacle! I first got aquainted with Mr. Pavement. He introduced me to Mr. Can. And I'm trying to keep Mssr. IgNobler away from that kind of company!) You guys are saying I can't be sure I don't have a warp since I haven't flown it inverted. Man, I hope not!

How much tip weight should a Nobler have? Someone said about two empty rolled up Ambroid tubes. How much is that? Are the trim numbers any different for the ARF version? Would I be able to tell if I had the right amount without attempting square corners?

If I need to add weight, can anyone describe where the factory weights are glued in? That might reduce the exploratory surgery with the Exacto. I was thinking of adding a weight box so I can fool with the amount without repeated surgery.

Dave
LA_Flyer
"Newbie Pukey Profile Pilot with first full body stunter"

>How much tip weight should a Nobler have? Someone said about
>two empty rolled up Ambroid tubes. How much is that? Are the
>trim numbers any different for the ARF version? Would I be
>able to tell if I had the right amount without attempting
>square corners?

You can get awfully close looking at round loops - close enough to do round loops, anyway.

There is no set amount, since the lateral balance is so highly varianble. The Nobler tends to take less than some other airplanes because the inboard wing is so much longer. which tends to roll it out aerodynamically. If you want to get close, balance it laterally with about 3/4 oz temporarily on the *inboard* wing. get ti to balance, then remove the inboard weight before flight. That takes the building variations out of the equation.

Near as I can tell, the wing is a very close copy of the Green Box Nobler kit from 1957. Most fo the rest of it is functionally equivalent.

Then see (or have someone else see) if the airplane rolls away from you on round maneuvers. Too much is better than not enough. Way to much will begin messing up figure 8 maneuvers, since it will be rolled one direction on the inside loop, and then want to roll the other way on the outside part. There will be an abrupt and disruptive yank when it goes from on to the other in the intersection.

>If I need to add weight, can anyone describe where the
>factory weights are glued in? That might reduce the
>exploratory surgery with the Exacto. I was thinking of
>adding a weight box so I can fool with the amount without
>repeated surgery.

Good idea.

Brett,

Thanks for the trimming help. Now I'm a little better prepared to tackle things this weekend. Didn't think to look for problems at the intersection on the eights. I also found your article on initial trim settings at www.aeromaniacs.com/Benchtrim.htm. That helped a lot, too. Really appreciate the advice!

Next I need to learn how to start an inverted engine! My old "Pukey Profile" technique of no battery, thumb over venturi, turn prop thru three times forward, remove thumb, turn prop thru six times forward, add battery, forward flip, hold on tight--ain't making it! Can't get my finger, much less my thumb, between cowl and prop. A drip or two into the venturi with the plane inverted is a pain. And sometimes causes hydraulic lock. Plus I really don't want to flip the plane over with the engine running. Just doesn't seem very safe to me. And it means I can't fly off a stooge....

I'm thinking of leaving the cowling off while I develop some new techniques. The only other thing I can think of is to mount the engine in my test stand inverted just so's I can practice. Rebuilding test stands isn't nearly as much fun as flyin'....

Make a "Choke Stick"-- a small dowel with a balsa or rubber plug on the end that you can use to stick up into the venturi for choking.

Inverted starts are iffy at best in my experience.

Curt,

Ok, I get the idea on the choke stick. I think I'll try molding a rubber plug in the venturi with a short piece of cord thru it and a red ball on the other end. That way I can press it in and yank it out easy. And find it on the ground after every flight. There really isn't room for much more than a plug.

Looks like I'll still need to practice in a test stand to learn how to avoid over-choking, flooding and lockup. Lots to learn about these wide-body airplanes....

Thanks!

YEs, it will help to practice alot on the ground first. Mid air re-starts are a Bi%^^h.

Seriously though..you are right about the safety issue of turn-overs. If not well rehearsed they can be high risk.

I think the secret is having alot of experience with the engine and being "tuned in" to how they react to different conditions. ie first start of the day, cool morning, hot afternoon, etc.

It is better to under-prime it and have to do that twice than over-prime and hydraulic loc it. After choking, always flip hard several times to get the fuel vaporized.

Also, try to store your plane upside down to prevent the residual oil from draining into the plug.

If you get up to about 30seconds of no-joy, after the signal to judges, strongly consider a pass. (unless you just want to practice!)

The stick can be a pencil with a large eraser carved to the correct shape.

Also, consider leaving an opening so it doesnt completely seal off the venturi. If it completley seals, the fuel is pulled in from the tank but just sits on top of the choke plug--if there is about a 1/4 venturi opening to air, fairly high velocity air will go through along with the choke fuel and help transport the fuel to the innards.

I do this manually even for profile or upright installations. perhaps one or two pull-throughs full choked, then two or three 1/2 choke to get the fuel into the crankcase. might take more or less depends on engine, temp, installation etc. (practice and keep mental or written notes)

Anyway,

Keep the digits out'n da prop arc!