Reinforcing Wing Spars with Carbon Fiber  
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All Forums >> RC Airplanes >> Composites Fabrication And Repair >> Reinforcing Wing Spars with Carbon Fiber
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Reinforcing Wing Spars with Carbon Fiber - 9/27/2002 1:57:39 AM   
JDHammer



Posts: 233
Joined: 4/27/2002
From: Slippery Rock, PA, USA
Status: offline 		Hi, here's my example: 84" wingspan, 22lb, all wood, built up unlimited aerobat. You want to strengthen the spruce spars with carbon fiber tapes running along the spar.

Questions: Best way to bond CF to spruce (CA?). And also, where to apply CF (Top and Bottom?, Front and Back?). One more- thickness of CF for the aircraft example above? (Assuming we don't want to add too much weight.)

Wonder how many "Gs" this aircraft could absorb after being properly reinforced?

Thanks for the help, JD
       Post #: 1

Reinforcing Wing Spars with Carbon Fiber - 10/3/2002 5:33:36 AM   
R. Carver



Posts: 154
Joined: 12/9/2001
From: Oviedo, FL,
Status: offline 		Well, since no one else has answered yet, I'll step up...
Use the carbon strips on the top of the top spar and the bottom of the bottom spar. I'm thinking around .010 on bottom and .020 on top, thicker on top because CF and spruce are weaker in compression than tension. Glue it on using a good laminating epoxy like West Systems. Use balsa end-grain as shear webs between the spars. Wrap the spar assembly tightly with kevlar tow spacing the wraps about 1/8" towards the root, 1/2" towards the tip. Brush a thin coat of the epoxy over the whole thing.
Build it like this and the stab will fail before the wing does

(in reply to JDHammer)
       Post #: 2

Reinforcing Wing Spars with Carbon Fiber - 10/3/2002 9:03:16 AM   
JDHammer



Posts: 233
Joined: 4/27/2002
From: Slippery Rock, PA, USA
Status: offline 		Thanks R.C. , that's exactly the information I needed. Sounds like you could use the wing for a diving board after that treatment. I'll give it a try.

(in reply to JDHammer)
       Post #: 3

Reinforcing Wing Spars with Carbon Fiber - 10/4/2002 4:39:57 AM   
Darrinc



Posts: 1028
Joined: 1/22/2002
From: Piqua, OH, USA
Status: offline 		R. Carver seems to have a good system.

I can only make one comment, use the lightest weight balsa square stock that you can find for the spars instead of the spruce, and put one layer of the uni tape on the top and bottom of each of the spar.

Then continue with R. Carvers method, just go very lite on the epoxy!!! This is still overkill, but it will be very light and you will be battling weight with a bipe.

My 2 cents,

Darrin C

(in reply to JDHammer)
       Post #: 4

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All Forums >> RC Airplanes >> Composites Fabrication And Repair >> Reinforcing Wing Spars with Carbon Fiber
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