troubleshoot me

[Dan Berry]

Here is what I have:
Profile Oriental, Tower 40 running fine. It's wings level in level flight. I don't have excessive line rake and I'm probably not comfy going further forward.
A smidge of engine offset, fin is on straight. I have a metal offset tab on the fuse side under the stab.
Flaps seem parallel. Wing might be straight .... ish. The stab looks parallel to the wing and even with it for and aft.

Here is the problem:
From level flight, up elevator will drop the outboard tip.
Down elevator will raise the outboard tip.
It isn't severe enough to crash the plane but it is there.

I worked on the stab last night. I felt like the outboard stab tip was a bit high and did a bit of wedgification. It looks level now.
When flying today the wing lifting/dropping was less than before but is still there.

I am open to suggestions. Wondering if a tab on the wing might be in order. Or maybe a tweak of the flaps.

Thanks for any advice. I've no one to watch it where I am.

[Brett Buck]

Here is the problem:
From level flight, up elevator will drop the outboard tip.
Down elevator will raise the outboard tip.

    Sounds like it has too much tipweight.

    Brett

[Tim Wescott]

Dan, how is it inverted?

Like Brett said, it has too much tip weight.  If it's wings level in level flight then it's probably because the flaps are slightly tweaked to give the thing a roll to the left, which counteracts the roll to the right from the tip weight.  If I'm right, then when you go into inverted level flight the outside tip will be down by a lot.

Since you have two problems, you need to do two fixes: reduce the tip weight until it doesn't roll on the corners, and then tweak the flaps for even line tension on insides and outsides.

If you're flying alone (and, for that matter, when you're doing the last itty bitty tweaks) sometimes it's easier to tell that the flaps need to be tweaked by comparing line tension on inside and outside maneuvers -- if it gets light on the lines on insides but stays nice and tight on outsides then you need to tweak the flaps for more left roll.  If this isn't apparent now, as you start taking out tip weight to correct the roll in sharp turns it'll become apparent, and you can fix it.

I'm pretty sure the Oriental has leading edge sheeting, which means that the wing should be at least somewhat warp-proof (and a lot warp-proof if it has shear webs).  Given that, you should be able to tweak the thing into near-perfect trim.

[Perry Rose]

With two popsicle sticks attach one on each flap close to the fuselage with a spring clothes pin or two sided tape so each points towards the stab. Raise and lower the flaps and check the alignment of the sticks as they go over the fuselage. Do the same with the elevators.

[Dave_Trible]

I would approach this as a flap assymetry issue- inboard flap a little too powerful.  Try tack gluing on a small strip of balsa, say 1/8 or 3/16 thick,  3/8 x 4 on the trailing edge of the outboard flap out near the tip.  When you fly you'll know right off whether too much or too little.  When you get a sense of how much then you can trim off a small strip from the inboard side or add a strip outboard.  From the building board I make my outboard flap 3/32" wider chord full span.  The outboard flap has a touch more area.  I can carry a few grams more tip weight which I think adds line tension.  In the 'olden days' the design thought was to make everything inboard larger.  Not my take at all.  I use equal span wings and a larger outboard flap.  
Another method I've used on a finished airplane is to make a smallish flap chord extension strip from clear acetate sheet- canopy material attached with cement or silicone.  It mostly vanishes to look at the airplane but does the job.  Doubt anyone would give you guff about changing the design any- it's minor trim.  I remember one Nats in particular Bob Gieske had about 5 slices off his inboard flap and said he might Dremel out his tip weight box till he got his G Nobler trimmed up.
Dave

[Dan Berry]

Wings are level inverted or upright.
I am trying to imagine why too much tipweight would raise the outboard with application of down elevator-this is from normal upright flight.

[tom hampshire]

What Dave said.  The elevators move down, so the flaps move up.  The inboard flap is too big, so it drops the inboard panel more than the outboard.  The line tension prevents the inboard panel from dropping, makes it look like the outboard tip is rising.  Minor quibble, I'd approach the tab sizing with a piece of manila folder creased tight, and taped to the top and bottom of the outboard flap.  You can pull the tape and adjust the effective flap width without cutting or gluing anything.  With a little luck, you can find the right width in one trim session.

[Motorman]

Wings are level inverted or upright.
I am trying to imagine why too much tipweight would raise the outboard with application of down elevator-this is from normal upright flight.

because the plane is going down but the tip weight wants to stay where it is.


MM

[Dan Berry]

because the plane is going down but the tip weight wants to stay where it is.


MM

OK. That clears things.
I'm thinking that trimming fast gas Free Flight planes might be easier than this stuff.

[Tim Wescott]

Wings are level inverted or upright.
I am trying to imagine why too much tipweight would raise the outboard with application of down elevator-this is from normal upright flight.

If you're at 5 foot altitude and it's a sharp downward turn, it won't raise the outboard tip for long.

I hadn't thought of it being a flap asymmetry issue, but that certainly sounds right.  How do you tell that the wing is level?

[Dan Berry]

If you're at 5 foot altitude and it's a sharp downward turn, it won't raise the outboard tip for long.

I hadn't thought of it being a flap asymmetry issue, but that certainly sounds right.  How do you tell that the wing is level?

Yah. I did the testing at higher than 5 ft.
The asymmetry seems weird on a proven design but I'm willing to play with anything.
I did have an observer-Jason Greer- two weeks ago watching for level. He said level. It was windy and I don't fly great so seeing the problem I'm working on would've been harder to spot.

I assume that I shouldn't try 3 or 4 different adjustments all at once. That's what they said about FF stuff.......
I'm gonna check that the flaps are even--the stick trick seems easy enough.
Removing tip weight is easy enough and will give instant gratification.
Then, playing with a tab.......
 

[Tim Wescott]

I'd trust what Jason says.

If you're good enough, you can gauge wing level by flying at eye level with your hand at eye level.  You should see the wing tip superimposed on the wing root, with equal area above and below.  Do the same thing upright and inverted.

And yes -- you shouldn't try changing more than one thing at once, at least not until you're pretty good at flying a plane once and knowing all of it's problems.

[Dan Berry]

Well, we have a winner.....
Tip weight.
I checked the flaps for even with each other and they seem pretty close.
Took out 3/10 oz weight and went flying.
It was better.
Snipped off some more. Seemed better.
At the field I took off weight 3 times.
Total including at the bench is a bit over .575 oz removed.

The wind starts laying down in the evening but goes right to a setting Sun. This isn't a good thing for me and my......skills.
Squirrelly weather here this time of year.

Thanks to all for the advice.