Arlington Washington

The early wildly asymmetrical designs (like the All-American) were just examples of not entirely thinking the problem through. The ideas was that you could just scoot the fuselage over and use that instead of tipweight. Unfortunately, I think they forget to consider several factors, most importantly, the thrust line offset to the CG, and that in moving the fuselage, they also moved the tail.
I think they (and by "they" I pretty much mean Hal "Pappy" DeBolt, who if he didn't invent the idea, certainly was the first to utilize it on a wide scale) never stopped to consider why the thing needed tip weight to begin with. The ideal situation would be that the lateral CG and lateral CP would stay right on top of each other at all time, thus causing no tendency to roll from aerodynamics. For this to work, some degree of wing asymmetry is required. Unfortunately, its a pretty complicated problem, and I don't think that anyone has a reliable analytical solution.

I personally don't think that the weight saving is a particularly important factor. If it's light but out of trim, or even untrimmable (like the All-American) it's really not going to work very well.

>The larger outboard
>flap makes sense.I will follow
>your outlines and determine the
>weight i need-this came at
>the perfect time Carlton
>Zeigler AMA10168

The larger outboard flap seems to be pretty much univerally needed, to make the roll in both round and square maneuvers be the same. I would also point out that we are still universally building our tails centered on the fuselage (just like "Pappy" did). Coincidence? You be the judge!

The only reliable way to determine the correct tip weight is by trial and error. But it's fairly easy to predict the range. Both Matt's and mine are pretty representative of our different approaches. If it's way off what we have, I would look for some other factor that might be effecting it.

Tommy built one that looked very nice, with the stars and bars like Hal's box art. His was pretty heavy, and didn't fly right. We didn't know a lot about trim then. It seemed to fly better with tip weight added. We never got his sorted out before its lines caught on a big Sunflower plant's stem in some high grass and flew right at the pilot (me.)

I dropped to my knees, and got turned around. Before I was reoriented back on my feet, it hit the end of the lines and yanked the handle from my grip. It free-flighted at about 20 feet high in wide circles, climbing slowly and dragging the handle through the stubble. Both of us chased madly behind the bouncing handle until it caught on some more tough stems close to the curb on Kampmann Boulevard, east of Jefferson High School.

The plane performed a wing-over and glanced off the front bumper of a large car moving slowly. It hit the pavement very hard and the car stopped practically immediately. We never did find all of the pieces of the Fox engine, which was shattered. I always thought that the cylinder part must've bounced up under the Buick and lodged on the front cross-member.

Of course. I merely state that this is not in trim in the sense I understand it. For instance, I don't consider models intended to roll wildly in the maneuvers to be "in trim", even if that was what DeBolt wanted it to do.

I have flown
>mine for nearly ten years
>now, won the nationals once
>and placed second once with
>it. Sounds as if
>it is trimmed fairly well
>for OLD TIME STUNT to
>me.

Lots of out-of-trim airplanes get through OTS patterns.

Note that this a repost- I answered this last night, too, but now the post is missing...Leonard?

********

Untrimmable doesn't mean unflyable. If you can get it off the ground, it will fly fine through round maneuvers, and you can fudge it through the square loop. What you will have trouble with is getting it to fly tangent to the circle, and with getting rid of the wild rolls in the maneuvers. The rolls are intentional to "get more line tension", which gives beginners a bit more security, and only hurts the squares, of which there is only one, (at least in OTS). It's not the machine of choice for the modern pattern.

The caveat is that you have to get it off the ground first. With a normal release and takeoff, it has a nasty tendency to yaw in at you, and come loose on the lines for a while. A technique suggested by WAM pioneer C. Lee Mckown, and tested extensively by Walt Pyron and myself is this: Have the holder hold the airplane by the tail, with a hand on each side. Hold the tail off the ground to the point that the fuse is level, or even a little nose-down. DO NOT yaw the airplane outboard, just hold it tangent to the circle. Hold in neutral elevator, and then have the helper just let go - no pushing, no outboard yaw. Then just let it take off, not horsing it into the air. Only pull back on it if it comes loose. Holding it level prevents and p-factor and GP adding to the tendency to yaw inboard as the tail pops up. Holding it tangent to the circle avoids the possibility that pulling back for more line tension will yank the inboard wingtip back, making it nose in.

Don't worry, it will fly OK, if not great, once you get it in the air.

Now, if you want to talk about a plane with problems, how about Palmer's Thunderbird which not only had a bunch of assymetry, but also had more movement on the inboard flap. Talk about a plane doing the "wiggle-waggles" at the intersections!

>Now, if you want to talk
>about a plane with problems,
>how about Palmer's Thunderbird which
>not only had a bunch
>of assymetry, but also had
>more movement on the inboard
>flap. Talk about a
>plane doing the "wiggle-waggles" at
>the intersections!

Somebody got a look at the original on the way to a museum (AMA?). The inboard flap had been cut about 2/3 of the way out to the tip, and the free end made fixed to the trailing edge. Bob's a pretty sharp guy.

Guess I was probably the guy who got a look. Actually had the ship in my shop for a few months as we worked its way back to (at that time) the AMA in Reston, VA.

To be technically accurate, as I recall the length of the inboard flap hadn't been changed. The trailing edge had been trimmed off appx. 3/16 to 1/4" for its entire span. The Bare wood edge was still there all the way. Don't know whether this was done before or after writing the magazine article discussing the virtues of the assymetrical flap movement. Hmmmmm?

As Brett stated, Bob's a pretty sharp guy.

I stand corrected. That's what I get for passing on second-hand information. I may have mixed some stories together. I have so many...

He makes his wing ribs in one stack numbered 1 to ? whatever is the last rib in the total set for a wing. Therefore, No1 has the greatest chord and the last one is the smallest. Claus designs his models with the inner wing 20mm longer that the outer. Rib No 1, the longest, becomes the root rib for the inboard wing, rib No2 the root rib for the outboard, etc. So, in addition to a wing with 20mm less span on the outboard 'half', the wing chord is that fraction of a percent smaller as well.

I do not know how important these differences are, but Claus applied the same theory to his Loriot, designed in 1974, and Escapade, his most recently published design—Aeromodeller October 2000.

Another thought for consideration.

I sorta got my All American to fly O.K. Just pretended that it had a nasty warp and put a big trim tab on the outboard wing!
Even then it still would roll slightly in the round maneuvers.
Now I have a Viking in the works - only 1" assymetry on that one according to Z-Man who I am told did extensive research on the plane.

For all those of you looking for a way to trim some of the roll out of an All American. I just put a big old trim tab on the outboard wing and pretend that it has some kind of nasty warp! It Works!

Putting that trim tab on the outboard wing wouldn't hurt. Also there's nothing that says how large a trim tab can be is there?

Just so happens that mine needed the trim tab (wing warp)

The plane should just fly somewhat inboard wing high due to the extra lift in level flight. The wing waggle comes when angle of attack and loading is put onto the extra inboard wing pannel (increased the rolling force somewhat) if the wing is build dead straight anyway! If you fly one fast enough the cintripeal(sp) force applied should keep the plane from rolling too excessively.
Fortunately the OTS pattern lends itself to flying faster than the modern pattern. Or you could build a Viking like I am going to do!!!!