Hi Steve, Fred,
This is carbon fibre tape from Dave Brown Products (CFTP-5220), having the width 1/2".
It does not feel like being epoxy impregnated as it is not sticky like typical pre-pregs. The individual fibers move freely and I can smooth, align and separate them relatively easily by finger tips. I used thin CA to attach the 6" long, 1/4" wide piece of this tape to 1/4"x1/4" x 6" hard balsa piece.
I did not sand and did not clean with alcohol the tape before gluing. Then, I glued with thin CA the 1/16" thick balsa on top of the already glued tape. The bending stiffness of this specimen was at least twice of the bending stiffness of the specimen without tape.
Then, I destructively tested both specimens, bending them in my hands until they broke. The balsa specimen reinforced with the carbon tape failed in compression and the specimen without tape failed in tension. The in-plane shear strength between tape and balsa was sufficient and there was no in-plane shear generated separation. Simply put: balsa broke but tape stayed attached to balsa.
Then, I peeled off the carbon tape with 1/16" balsa strip on top and inspected its surface, seeing that balsa was ripped off from the 1/4" x 1/4" x 6" hard balsa piece. This indicates that the tape to balsa CA connection was stronger than balsa itself.
I will sand lightly the tape, clean it with acetone and let it dry. Then, I will spot attach the 1/4" wide x 20" long pieces of it to the central portion of the wing spars. By "spot attach" I mean a single drop of thin CA where the spars to ribs connections are. By doing this, I will secure the tape to the spars but will not fill the entire spars surface with CA. Then, I will attach 1/16 balsa sheeting with pins and fill the entire connection with CA.
The weight penalty will be around 5 grams but I hope the wing will be much stronger in bending.
Best Regards,
M