OT - What Do You Think?

I was thinking about posting the following to some usegroup that deals with sailboats. What do you think?

Ken

So what if we do not shape the model airplane wing leading edges?

Consider the power we have in our engines/motors.

Consider the turbulation we would get from those wings when flying at a high angle-of-attack.

OK, I propose the following. Build a general sort of trainer and only shape one leading edge.

Fly said model. I venture that the square wing will lift first, will stall last, and appreciable yaw won't occur until well up in speed.

If the wing is a "D" section, the covering can be put on the wing to the trailing edge of the leading edge stock, leaving the leading edge bare wood.

After testing that way, then leave the tip third of the span square and slowly shape the leading edge as it approaches the root.

Fly again. The yaw will be a little less, the speed up a bunch, and the square wing will still stall last...and possibly at nearly the same angle.

By the way, leaving the square leading edge stock uncovered would be a good idea. It can be shaped later and covered. Even if both wings were to have square leading edges, I would not cover them with film. I think I would not even sand them but just brush some butyrate on them...and not sand after that either.

Or I could just be all wet about all this. But if you think I am, say why.

Reply to
Ken Cashion
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Reply to
Geoff Sanders

Yes, Fluid Dynamics is what the NASA folks call it when they work out the expected results for their test articles before they turn on the wind tunnels. For some experiments it takes a lot of computational power, which they have. It helps to mathematically make the predictions before spending the resources looking for results. One of the things that happens is the observer looks at the right place to see the results...

Reply to
Six_O'Clock_High

| Hydrodynamics and aerodynamics are similar, but I doubt than many boat | types would think so.

They're more than similar -- they're pretty much the same thing, just in different contexts.

Far-subsonic (less than mach 0.3 or so) aerodynamics is generally based on the approximation that the air is not compressed, and in this realm it doesn't really matter if you're talking about air or water -- the same rules apply, though of course the properties of the fluid are different.

What matters is the Reynolds number, and if the Reynolds numbers match, and the airfoil (or whatever you call it) matches, then the results will match, even if the fluids and/or speeds involved are radically differnt.

For example, there's this case --

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where they built a model of a fruit fly, but make it much larger and had it flap slower (so it would be easier to study) but made it `fly' in mineral oil rather than water so that the Reynolds number would be the same and so it would work the same as real fruit fly wings.

| I guess the term, "fluid dynamics" applies to both, though.

Yes it does. To be more specific, fluid dynamics is more general, encompassing the other two.

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Reply to
Doug McLaren

About 5 or 6 years ago I recall a website for RC airplanes talking about wing design. There were diagrams and photos and charts, but not more than generally technical. The part I remember is that they attached the wing of a high wing trainer with the trailing edge in front. It flew just fine. Aileron control was sloppy, glide was a little below the expectations of a properly attached wing, but overall the results were quite similar with the wing either way.

Reply to
Charlie

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