Can't figure out how to make a proper wing

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Merlin

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I'm curently trying to design a 2 seat high wing with struts. So far the welded cromoly tube chassi is almost complete but i'm having trouble with the wing.
i want to use Douglass fir wood but the simulation results (Solidworks) are not reassuring and basically i can't get a wing strong enought (5g) with an acceptable weight.

i would really aporeciate your advices.

thank you.
 

Victor Bravo

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Spars made out of 2024-T3 aluminum will resolve your problem, but will require adjustments to your wing ribs to fit the spar.

Spars made out of a Spruce or Douglas Fir core, with a calculated amount of "Graphlite" carbon fiber laminated on the top and bottom, then wrapped in two layers of 45 degree fiberglass cloth, and vacuum bagged correctly during the curing process, will resolve your problem, give you a much stronger spar than the wood alone, and not require the ribs to be adjusted.
 

fly2kads

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I think we need a bit more information. What gross weight are you designing to? There are several different ways to design wood spars (e.g.: plank, box, I-beam, C-beam, etc.). What spar configuration(s) are you trying to use?
 

Norman

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How thick is your airfoil? The strength of a beam is proportional to its depth so any increase in wing thickness gives you an equal increase in spar strength almost free. Also, as fly2kads is getting at, the cross section makes a big difference to the weight.
 

wsimpso1

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i want to use Douglass fir wood but the simulation results (Solidworks) are not reassuring and basically i can't get a wing strong enought (5g) with an acceptable weight.
Merlin,

Strut braced wooden wing and you can not get it strong enough? Sounds like a calculation problem somewhere. First the wing shear and moment diagram should look like the illustration here post 10. Not same numbers, but the shapes should look similar.

Next, once you have the bending moment and shear diagrams, the calcs for stresses can be done closed form really easily right in Excel or even with a pencil, paper and calculator. SW is nice, I love it, but hardly needed. All this stuff was easily done with paper and sliderule a long time ago.

You can share your loading and process on here or contact me through a PM. Then we can start trading Excel and SW files to find the bug...

Billski
 

Merlin

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I think we need a bit more information. What gross weight are you designing to? There are several different ways to design wood spars (e.g.: plank, box, I-beam, C-beam, etc.). What spar configuration(s) are you trying to use?
My gross weight is 450kg, using plane rectangular spar
 

blane.c

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That is all normal sized. There is not a logical reason it won't work considering empirically it has been done so many times before.

Try a different program for the math?

Or copy something like an Aeronca.
 

blane.c

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I wonder if an aeronautical program is already factoring load like 3.8g,s and if you are putting 5g,s times or additional to it?
 

Merlin

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That is all normal sized. There is not a logical reason it won't work considering empirically it has been done so many times before.

Try a different program for the math?

Or copy something like an Aeronca.
Can you recomand me a program?
 

mcrae0104

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Can you recomand me a program?
A pocket calculator is plenty effective. You will need to learn the basics of statics and beam theory. But you need to learn that anyway to be able to trust FEA. Look up Jeff Hanson's YouTube channel to get started.
 

Dana

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A pocket calculator is plenty effective. You will need to learn the basics of statics and beam theory. But you need to learn that anyway to be able to trust FEA. Look up Jeff Hanson's YouTube channel to get started.
Thatone

FEA attached to CAD is a useful but not necessary tool. You need to understand the underlying theory to know if the FEA results are meaningful (GIGO)... and for a simple wing design like you're describing, once you understand the theory the hand calculations aren't any more difficult than setting up a realistic FEA model.
 
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