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Old Dec 19, 2012, 12:33 AM
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Wow, didn't expected this to turn into such a heated discussion.

Yes, I've done indoor duration before and yes for indoor duration you'd want to cover only on a single side and have a very slightly cambered airfoil. If you want, I can post pics of my indoor duration style flying wing.

But this is a peanut. And besides flying, a peanut scale model's primary function is to look pretty. So I don't mind not being able to do 4 minute flights with this inefficient airfoil. Getting past 30 seconds would do just fine and if it can do a minute that would be nice but not really necessary for this project.

Having said that, after actually building it I do think the thickness can be reduced a bit without affecting the structural strength of the wing. So I'll probably try a thinner airfoil later.

And it does fly - with modifications. It doesn't have anywhere nearly enough twist to be stable. I had to add additional "elevons" from scrap balsa to get enough reflex for a glide. The calculated CG was fairly good. Only had to move it a couple of millimeters to get an acceptable glide.

Will post pics of the (failed) finished wing later. For now, here's a revised set of plans with 10 degrees of twist and built-in dihedral.
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Old Dec 19, 2012, 12:36 AM
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Originally Posted by nmasters View Post
I wouldn't say that stating that thick airfoils won't perform as well as a flat, or slightly curved, plate at the Reynolds numbers of a 1.5 inch chord rubber model is a logical fallacy. It's simply a demonstrated fact that at Re<50,000 a plate will have lower drag than a thick section. Better pitch stability can also be expected because of separation on the lower surface. Using several thin spars instead of one thick one would also help.
Yes, it's not a logical fallacy at all. It is in fact true. But it is also an unnecessary optimization in this case.
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Old Dec 19, 2012, 07:27 AM
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I wouldn't say that stating that thick airfoils won't perform as well as a flat, or slightly curved, plate at the Reynolds numbers of a 1.5 inch chord rubber model is a logical fallacy.
Norm:
What you mentioned (quoted) was not the logical fallacy to which I referred.
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Old Dec 20, 2012, 07:39 AM
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Another fallback would be the Worlds Foremost Authority, aka Prof Irwin Corey.
http://www.irwincorey.org/

At least he was a comedian.
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Old Dec 20, 2012, 07:42 AM
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Originally Posted by nmasters View Post
Carlo Godel also called himself "the world's foremost authority" but he always wrote it in crayon. I wouldn't say that stating that thick airfoils won't perform as well as a flat, or slightly curved, plate at the Reynolds numbers of a 1.5 inch chord rubber model is a logical fallacy. It's simply a demonstrated fact that at Re<50,000 a plate will have lower drag than a thick section. Better pitch stability can also be expected because of separation on the lower surface. Using several thin spars instead of one thick one would also help.

--Norm
Hey, why didn't I think of that ....?!

Thanks,
Lee
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Old Dec 20, 2012, 07:51 AM
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Originally Posted by slebetman View Post
Wow, didn't expected this to turn into such a heated discussion.

Yes, I've done indoor duration before and yes for indoor duration you'd want to cover only on a single side and have a very slightly cambered airfoil. If you want, I can post pics of my indoor duration style flying wing.

But this is a peanut. And besides flying, a peanut scale model's primary function is to look pretty. So I don't mind not being able to do 4 minute flights with this inefficient airfoil. Getting past 30 seconds would do just fine and if it can do a minute that would be nice but not really necessary for this project.

Having said that, after actually building it I do think the thickness can be reduced a bit without affecting the structural strength of the wing. So I'll probably try a thinner airfoil later.

And it does fly - with modifications. It doesn't have anywhere nearly enough twist to be stable. I had to add additional "elevons" from scrap balsa to get enough reflex for a glide. The calculated CG was fairly good. Only had to move it a couple of millimeters to get an acceptable glide.

Will post pics of the (failed) finished wing later. For now, here's a revised set of plans with 10 degrees of twist and built-in dihedral.
OK, of course!

It's YOUR baby!

For many, incl. me, pretty also involves pretty flying, and extra-large props, tissue-covered wings and all that has to go into a small rubber-powered model is neither scale* nor particularly pretty either.

However, Beauty IS in the Eye of the Beholder .... in any/every case!

It would be very nice to post FLYING-video results of both your "scale"* thick- and later thin-winged versions.


Lee
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Old Dec 20, 2012, 08:01 AM
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Lee, perhaps you should read this site about logical fallacies. Appeal to authority = fail.
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Old Dec 20, 2012, 09:25 AM
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And as 4x past president of the Philosophy Honorary Society, which was mainly focused on Sematics & Logic, I am constantly checking & re-checking for fallacies.
Oh, the irony...

lulz
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Old Dec 21, 2012, 08:00 AM
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Old Dec 22, 2012, 08:59 AM
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Old Dec 22, 2012, 09:01 AM
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Old Dec 22, 2012, 09:01 AM
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Old Dec 24, 2012, 05:11 AM
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thinly disguised

Only to further illustrate the ONLY point I was trying to make [thick vs thin wings for small slow models], which has in fact been recognized and considered, as a example here is my micro F-22.

Since both very low Rn flying surfaces AND supersonic flying surfaces can be shown to work much better when thin, rather than thick, the thin wings on the 20 cm F-22 are reasonably scale. To maintain a SCALE flying speed range, from lowest to highest, I made the wings in a smoothed-out approximated version of the landing & max.-maneuverability configuration, in which both leading- and trailing-edge flaps would be deployed to camber the wings [incl. the conical camber of the fullsize F-22].

This toy was sold by ITC as Transformers Starscream and then as MicroFighters, unfortunately with the motors moved w/o my permission from the original vertical stab-mounted position to the wings ... which sadly only removed the low end* of the performance envelope that is shown in the below video.




Indoor Aircraft Carrier Landing (0 min 5 sec)






Micro Fighter /StarScream RTF R/C F-22 ORIGINAL version (0 min 42 sec)





* By stupidly moving the motors fwd to the wings, ITC ruined the very delicately balanced CG, moving it fwd and thereby making the toy only capable of "normal" fast flight .... while at the same time removing the unique nose-"pop-up" feature [2-ch acting like 3-ch] when power is abruptly cut [CL vs CG vs thrustline], which feature was disabled in the software in the Default Mode 1 & slightly less in Mode 2, but allowed in unfiltered Mode 3, which ITC kept hidden from consumers!
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Old Dec 28, 2012, 06:35 PM
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Originally Posted by slebetman View Post
Yes, I've done indoor duration before and yes for indoor duration you'd want to cover only on a single side and have a very slightly cambered airfoil. If you want, I can post pics of my indoor duration style flying wing.
So how did it fly?
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Old Dec 28, 2012, 07:36 PM
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Originally Posted by Cap_n_Dave View Post
So how did it fly?
You mean my previous wing? Quite well actually. It's based on my Planktastic design. The best time I managed on it was around 2 minutes. I'm sure it can do better with some adjustment and trimming. Haven't flown it in quite a while. The last time I flew it a hard landing broke the spar in several places so it either needs repairs or, since I now have more experience building indoor rubber planes, I'd just rebuild it from scratch and end up with a better, lighter version.

I've attached a picture of it below.

As for the subject of this thread. I'm afraid I've put it on hold for the past couple of weeks - had other projects to work on (so much to build, so little time). I'll most probably continue building the penut wing next week unless something else comes along to distract me.
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