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Old Feb 08, 2012, 10:16 PM
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Joined Jan 2012
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wingspan, cord and thickness ratio - with the MH32 - help

Hi RC community,

Please help me!
I have read a lot about wings and how they are designed to reduce induced drag caused by lift, and how high aspect ratios are good indicators for this. A 'high' aspect ratio show that you have long thin wings, and therefore low induced drag and this is desirable. However, what I have not read is what a good aspect ratio really is, ie I have a foam wing that is 4.4m x 0.2 this gives an aspect ratio of 22, is this a "high" enough number?

I have also read that the thickness ratio of a wing can help determine the amount of drag, and how important it is in a airfoil design. However I have not been able to find much information about how much thickness I need to stabilize a wing. I was really hoping to find some sort of formula to calculate it, or some rule of thumb. My wing is made out of EPP foam and is 4.4mx0.2m, and I am thinking about using the MH32 airfoil but it only has 8.714% thickness which means I would have a 2cm thick 4.4m wing. I am not sure this will be structurally strong, can anyone please help me. How thick should I make my wing??

Thank you to all you smart people out there!
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Old Feb 10, 2012, 11:00 PM
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Tucson
Joined Nov 2009
1,034 Posts
An aspect ratio off 22 is huge. I don't think that your wing will be strong enough to fly, with the 8% thickness.

Have you thought about sheeting it with balsa? Vacuum packed fiberglass wings are sometimes as thin as 8%, but they have carbon fiber spars, and a fiberglass skin for strength.

A rule of thumb that I have seen for high performance gliders is about 3.5 m wingspan, about 70 square decimeters of wing. This works out to a 136 inch wingspan and about a 7 inch chord. So you are in the right ballpark. 136/7 = aspect ratio of about 19.
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Old Feb 16, 2012, 10:30 AM
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eye4wings's Avatar
Ware, herts. U.K.
Joined Sep 2008
3,504 Posts
Are we supposed to be looking at a design like the Gossamer Albatross or a Lockheed Starfighter?
Seems to me everything depends on what purpose the wing is being designed for. Light or heavy loadings, soaring or speed.... etc.

If we're just talking theory with nothing to relate it to there is a dedicated
aerodynamics forum where that sort of information is swapped ... but brush up your maths before venturing in!
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