%)@%$ trim issues!! Sorta' solved

[Clint Ormosen]

Nine trial flights this morning and I STILL have the same problem.
OK, here it is. Airplane is about 430 sq. in profile with smallish flaps and elev.. OS LA25 with stock muffler. Model makes a beautiful corner from level flight inside or outside. Inside corners from 45 deg. are good too. BUT, try an outside corner from 45 deg and get ready to run backward. The outboard wing will come up and the model banks inward. Tip weight helped some, at about 3/4 oz right now. More than that and the outboard wing starts to dip on the turns. Flap tweaks did nothing positive. Faster lap time did little, and made the round stuff hard to fly.
 The wing is not warped. There is zero offset on the engine and rudder, but engine offset is the next thing I was going to try. It's mounted on aluminum, so I'll have to figure a way to do it better than washers under a lug.

Soooooooooo. Any Ideas?


P.S.  The plane does not have adjustable leadouts. Well, at least not easily adjusted ones.

[Jim Morris]

Try checking the cg then see where the leadouts are relative to the cg. forward leadout  should be oprox 3/4 in behind cg to start with.

[Airacobra]

I posted the same issue months ago. I have been flying a 40 powered Scimitar. I went through the normal trimming process like you, tip weight and moved the leadouts forward a bit. That all helped, but what made the difference for me was adding a clear plastic trim tab that increased the area on the outbaord flap and I sealed the hinge line from the tip to just past the added trim tab towards the root.

[Clint Ormosen]

I checked the CG this morning and the front leadout is about 1/2" behind it. Pretty close.
I DID NOT seal my hinglines! So I'll do that and see what happens. Also I'll try the trim tab if I have to, but I hate the way they look.

That's two good things to check out. Thanks guys.

[Charlie Pate]

You could trim the inboard flap if you d,ont like the outboard tab,.
This has been done by others , but is very sensitive and if you go too far kinda hard to put back.
 I saw Bob Palmers , differential flap T Bird and it appeared over .125 in. had been removed from the inboard flap.
 Tom Dixons, VSC winning T bird had approx. a 4.5" clear tab on the outboard with about .5 in. exposed(as I remember) and did NOT use the differential flap set up.
 He told me that it was impossible to do a descent SQ. eight before the trim change was made.

[Jim Morris]

Before permanently adding a tab or whatever. You could temp install a tab using a good tape,then fly and see.

[Airacobra]

Jim, that is exactly what I did. I will see if I can post a photo later this evening.

[Marvin Denny]

  I hate to put this in, not knowing the experience level of the builder,  but if the stab and elevator is mis-aligned with the wing,  that could be a cause.  If the stab is tilted up on one end and down on the other (not parallel with the wing when viewed from the front or rear) and also if the stab to elevator hinge line is not parallel with the wing (one end ahead of the other when viewed from the top) then either of those two items could cause that problem.  Even as little as 1/8th inch on either misalignment is sufficient to cause the problem.

  Bigiron

[Dennis Adamisin]

Clint:
Wow, you are getting a lot of ideas here, the tilted stab Marv mentioned would fit your symptoms to a T.  Lucky that is pretty easy to check.  Couple other possibilities:

* LE radius.  If it is a little sharp or not quite smooth top to bottom, you COULD generate a stall turning one way or the other, and the stall could occur on just one wing or the other.  Can ruin your whole day!  On my recent Oriental ARF thread I mentioned that blunting the LE overcame an issue where that bird would stall on inside corners but not outside.

* Elevator neutral side to side.  On ships with a wire joiner sometimes you can get a twist where one side of the elevator is slightly up or down versus the other side.  This does not quite fit the problem where it apprentlly turns OK inside and not OK outside, but when you go looking for gremlins you never quite know WHAT you are going to find!

* Do you have a large rudder?  With a lot of offset?  If so it could be inducing a roll that is OK upright but working against you inverted.  Again this is a stretch but see previous comment on gremlins!

* Also agree with the sealed hingelines - seal them then fogetaboutit!

...oh keep us posted, I think there is going to be a GOOD thread here!

[Airacobra]

This what I did guys, as I explained earlier.

[Clint Ormosen]

OK, I checked (or re-checked in some cases) theses few items.
Stab is dead straight to the wing.
Elevators are the same (neutral) both sides.
I do have a rather large rudder, but with no offset.
The leading edge is rather blunt preformed solid balsa. The wing is similar to a Buster with a little less chord.

Here's something else. I built this plane as an elevator only sport model and added the flaps later. I don't remember having this problem until the flaps were added, but it just didn't turn very tight without them. Maybe I just didn't notice it because of the lack of turn.

I won't have another chance to fly now it until at least Thursday afternoon. I have sealed the hingelines and am going to add some engine offset.

[Bootlegger]

 Clint, Don't know if this was mentioned or not, but you might check and see if the stab is the same distance from the wing on both sides measured from the same distance out from the fuse. Also check to see if fuse is twisting in manouvers..
               Hope that this helps...

[Airacobra]

Not trying to be difficult, but how possibly can you see if your fuse is twisting?

[Bootlegger]

    The only way that I have been able to see that the fuse was twisting was some of the guy's seeing it from outside the circle. Your point is well taken, and I didn't take it as a "shot at me".  We are all here to help any way we can. No offense taken...

[captcurt]

I have seen some of the arf profiles twisting the elevator tip perhaps 3/4 to an inch visible from outside the circle.

Curt

[Ted Fancher]

OK, I checked (or re-checked in some cases) theses few items.
Stab is dead straight to the wing.
Elevators are the same (neutral) both sides.
I do have a rather large rudder, but with no offset.
The leading edge is rather blunt preformed solid balsa. The wing is similar to a Buster with a little less chord.

Here's something else. I built this plane as an elevator only sport model and added the flaps later. I don't remember having this problem until the flaps were added, but it just didn't turn very tight without them. Maybe I just didn't notice it because of the lack of turn.

I won't have another chance to fly now it until at least Thursday afternoon. I have sealed the hingelines and am going to add some engine offset.

Clint,

Some clown published an article on a ship called the Doctor in Stunt News several years ago.  It was designed with no flaps for precisely the reasons you suggest in your second to last paragraph above.  Flaps on  a stunt ship are a pretty good idea for flying precision stunt.  They aren't a particularly good idea for "ease" of flight trim.  They complicate every facet of doing so.

Seal the hingelines!!!!

Ted Fancher

[Clint Ormosen]

Clint,

Some clown published an article on a ship called the Doctor in Stunt News several years ago.  It was designed with no flaps for precisely the reasons you suggest in your second to last paragraph above.  Flaps on  a stunt ship are a pretty good idea for flying precision stunt.  They aren't a particularly good idea for "ease" of flight trim.  They complicate every facet of doing so.

Seal the hingelines!!!!

Ted Fancher

I've seen your Doctor fly, Ted. If my model flew half that good without the flaps, believe me, I wouldn't have added them.

Hingelines sealed!!!!

[Clint Ormosen]

Clint, Don't know if this was mentioned or not, but you might check and see if the stab is the same distance from the wing on both sides measured from the same distance out from the fuse. Also check to see if fuse is twisting in manouvers..
               Hope that this helps...

I hadn't thought of that one so I just checked. Measured from hingeline to hingeline, at the outermost point of the stab, the outboard distance is 1/16" closer to the wing. I have no idea if this is enough of a flaw to get the problem I'm having.
As far as the fuse twisting, I kinda doubt it's moving much. It's pretty stiff.

[Clint Ormosen]

Sealing the hingelines didn't cure the problem. Neither did engine offset, but that one was no surprise.
Just for fun I tried going from a 9x4 to a 10x3 prop. It's hard to say, but I think the problem got worse.
How about if I cut down the outboard flap? Take maybe 1'' off the end?

[Steve Helmick]

"I checked the CG this morning and the front leadout is about 1/2" behind it. Pretty close."

Probably not close enough. Most guys think moving the leadouts 1/8" is a coarse change. Up high is where it matters most, not level flight to 45 degrees. Change the leadouts to adjustable...it's possible, and it will teach you a lot. Don't pass up this opportunity to learn... Steve

[Clint Ormosen]

After a great flying session this morning with Tom and Chris Hagler, I went out this afternoon with the troublesome model to try once again. I taped a 1"x3" trim tab to the outboard trailing edge. It made the plane fly OB tip low so I cut it down to 3/4" and tweaked the flaps just a little. This seemed to be the trick as the model still wants to bank a little into the circle on hard outside corners, but it is much better and the plane is a least flyable. I don't think it will ever be good enough to enter in a contest, but it sure is a good tool for learning how to trim. I don't know, maybe with some tuning it could get much better.. I'll work on it.