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Unequal winghalfs

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Unequal winghalfs

Old 09-14-2006, 07:58 PM
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CoosBayLumber
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Default Unequal winghalfs

I have recently come across my third Old timer plan which has unequal length wing halves. The right wing is about 33 inchs and the left half is a good 5/8 inch less.

As mentioned, this is not the first time, but the third time now. All having to do with Pre-WW2 designs for Free Flight. Most of the Pre-WW2 designs I have come across have wings panels of equal halfs.

Any thought here as to if this prevalent to the era, to avoid installing engine offset or thrust?


Wm.
Old 09-14-2006, 11:12 PM
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mesae
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Default RE: Unequal winghalfs

Seems to me some of the free-flighters were set up to climb under power in a gentle left turn due to propeller left-turning tendency, then when the engine quit, the airframe design resulted in a gentle right descending spiral. The differing wing lengths may have been one method to achieve this.
Old 09-15-2006, 02:20 PM
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Default RE: Unequal winghalfs

It's definetly a mistake. I suspect it's got more to do with taking prints off old plans that may have shrunk due to exposure to moisture or that were photo copied and suffered some sort of distortion in the copy process.

It has to be a mistake, at least in the vast majority of cases, because in many cases the old plans only showed you 1/2 a wing along with squares to aid blowing up curved portions and measurements for rib spacing and span. Nowhere in any of the articles I've seen does it talk about assymetrical wing construction.

The flight trim is always set up using warps or drag tabs and control tab offsets combined with thrust offset angles.
Old 09-15-2006, 06:09 PM
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mesae
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Default RE: Unequal winghalfs

Yeah, I was guessing. I don't really know.
Old 09-15-2006, 07:15 PM
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Default RE: Unequal winghalfs

Nope, the right and lefthand wing halves are pretty well parallel and right next to one another. It shrinkage were to happen, it would then affect them both. The spacing of the ribs is about 1/32 per greater on one half than the other.

There isn't any downthrust or right thrust indicated for the engines. Wonder if the unequal length of wing halves was one way to adjust for this.


Wm.
Old 09-15-2006, 10:25 PM
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Default RE: Unequal winghalfs

I still say it's a mistake. Check the ribs for parallel or some convergence of the rib lines. None of the articles and plans I've seen from any of the magazines have ever said anything about this.

To help research this though, what 3 models are we talking about here?
Old 09-15-2006, 11:46 PM
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Default RE: Unequal winghalfs

I assembled a kit and in the assembly instructions was a statement that due to the tendency of paper to expand and shrink with humidity, the precut notches in the leading and trailing edges for the ribs may not exactly match the spacing on the plans. So, I think that it may be a result of the original plans shinking or expanding. We used to shrink silkspan and tissue by wetting it in the good old days before Monokote.
Old 09-16-2006, 12:08 PM
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Jim Thomerson
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Default RE: Unequal winghalfs

What airplanes are you talking about? If we knew, we might be able to give you better information.
Old 09-16-2006, 08:08 PM
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Default RE: Unequal winghalfs

I've experienced different wingtip and stab half shapes on some reproduced oldtimer plans. I don't know if it was a fault in the reproduction process or a fault in the original drawing, but I doubt it was an intentional difference. Those things were drawn before CAD and sometimes guys just screwed up.
Old 09-17-2006, 03:04 AM
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davidfee
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Default RE: Unequal winghalfs

I've definitely built some rubber-powered FF models with asymmetric wings, but these were indoor models with props that were about 1/2 - 3/4 of the wingspan. The asymmetry was required to react against motor torque. I don't suspect you're dealing with the same thing, but anything is possible. What model designs are these?
Old 09-17-2006, 09:13 AM
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Default RE: Unequal winghalfs

Right now, am working on the new Pacific Ace by Modelcraft. Original design was in 1939, but seemed to be in production up into the early 1950's. One of the few that jumped the gap caused by WW2.


Wm.

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