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NACA profile for Hi wing Trainer

Old 10-25-2009, 06:25 PM
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hillbillynamedpossum
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Default NACA profile for Hi wing Trainer

Im studying to scratch (stick balsa) build a hi wing trainer. Im looking at around 60" wing span and about 5 degrees dihedral. I need some rules of thumb for tailfeather proportions, fuse proportions, and id like some recomendations for a proper NACA profile.


Thanks guys,
Possum
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Old 10-25-2009, 07:21 PM
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JetPlaneFlyer
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Here's a good guide to overall proportions: http://www.palosrc.com/instructors/basicdes.pdf

As for airfoils; the good old Clark-Y really does take some beating for a trainer/ sports model. It's got nice flying properties, a gentle stall, and due to it's mainly flat bottom makes building in balsa very easy.

Steve
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Old 10-25-2009, 07:50 PM
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hillbillynamedpossum
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I dont have a generator for a Clark-Y profile....can you reccomend one?

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Old 10-25-2009, 08:00 PM
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Profili: http://www.profili2.com/eng/default.htm

You can plot all your ribs with Profili including spar/LE/TE notches etc. and produce a basic wing plan. You can also run virtual wind tunnel analysis on your chosen airfoil.

Or if you are simply looking for a plot of the airfoil then see attached..

Steve
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CLARK Y.pdf (8.4 KB, 324 views)
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Old 10-27-2009, 01:18 AM
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Thanks JPF,

I really like that prgrm.
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Old 10-28-2009, 04:06 AM
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I thought I'd make a glider first. I may even put a small motor on it. Heres some pics that should go to a build thread, but any way.....

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Old 10-28-2009, 08:00 AM
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Nice light looking structure.

Hope you don’t mind some comments:

Is there an outer panel going on the wing or is what we see all there is? If that's it then it looks to be very low aspect ratio (AR), perhaps 3:1. The design guide I linked earlier says AR between 5:1 and 7:1, which is much more normal.
A very low aspect ratio makes the wing inefficient, it increased the drag and means you need higher angles of attack to produce lift.. It would still fly providing you had enough wing area and power but just not as efficiently as, say, 6:1 AR wing. Generally the higher the AR the higher the efficiency which is why full size sailplanes have super high AR (very long ‘skinny’ wings).

On the construction.. Are you adding any sheeting? What you have will be ok for a small test model but for the full size plane a sheeted ‘D’ box (sheeting top and bottom as far back as the spar) will massively increase stiffness. If you don’t add sheeting than at least add a turbulator spar or two (or three) on the upper surface between the LE and mainspar.
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Old 10-29-2009, 12:47 AM
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JPF,

Thanks for the tips. This was just a 1 hour quickie to prove I could cut out balsa still. I havent stick built a plane in a few years, and Ive never built one from scratch. I did build a U cut it kit 20 years ago, but It was a static modle and everything was printed on the balsa.

My ultimate goal is to build something that I can fly in a 40' X 60' building, VERY SLOW. You seem like a great source of knowledge, Do you have any recomendations? My goal is a 3 channel, hi wing, hi dihedral, balsa and saran wrap wing.

Possum.

PS
I covered the wing in saran wrap and it did look pretty good, then I did "destructive testing"....the dog helped.
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Old 11-11-2009, 02:38 AM
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This website www.gliders.dk/ has a few NACA foils mentioned in the airfoil section.
I'm just wondering about your NACA generator and what number foils you can generate.
I have Compufoil3D which has a NACA generator. It can plot 4, mod 4 ,5 ,mod 5 and 6 number NACA airfoil.
I have seen that a few recently built gliders use a NACA 6 Airfoil which are low drag profile.
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Old 11-12-2009, 12:46 AM
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the profile generator JPF suggested is fantastic! I never knew there was that many. I even paid the $13 or so to register it. Good stuff!

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