Location of Load Bearing Structure

[IrishDave]

Hello,

I am currently designing a model plane using the Clark Y Airfoil. I have been searching high and low on the internet without success for information on where the load bearing structure should be in terms of distance from leading edge along chord? I have designed my spar system but I just don't know where to locate it along the chord.

The only information I have found on the internet suggest 25% chord for a symmetrical chord length, but Clark Y is cambered. Does anyone know where it is best located for Clark Y?

I am talking about my spar to take span wise loading. The design involves a system of wing ribs and then spars connecting them together and then covered in fabric.

Thanks
David

[JohnR]

Aircraft Design is way beyond me, but the book “Basics of R/C Model Aircraft Design” has all kinds of information that I don’t understand. It may be too basic for someone like you but it dose have a chapter on weight distribution in design. Maybe somewhere in the book there could be an answer to your question. Good luck with your design and please post a photo when it is done.

[whitecrest]

Small world! I recently designed a park flyer using the same Clark Y airfoil. I put the spar at the thickest part of the airfoil, which is around 33 percent from the leading edge I believe. I think if you are in this general area you will be OK. I have a spar top and bottom at this point to form an I-beam. With thin, plywood dihedral braces and vertical-grain balsa webbing, it has proven to be very strong.

I am very happy with the flying characteristics of the Clark Y. It glides very well and appears to be very efficient. My ship has a 48-inch span with 360 sq. inches of total wing area. AUW is about 16 oz. with brushless power system. Good luck with your design.

[JohnR]

Can either of you post a photo of your designs?

[IrishDave]

Hey, thanks whitecrest. I was thinking of moving to 33 percent. Mine is actually a large scale glider for the Bognor Birdman competition (google). It's part of a uni group project. I'll post photos when we get the solidworks done. We are making using an IBeam as you have mentioned with a canard layout. It's going quite well so far. Just need to sort out a few detail points and start manufacturing.