RE: Joining carbon fibre tubes - dihedral !?
If the carbon tubes have the fibers aligned straight (rather than spiral wound), then music wire inside the tube will tend to crack the end of the carbon tube. Once that starts, the carbon tubes split easily. The carbon is strong stuff, but like wood, it can be weak along the "grain". A short bit of bent aluminum tube that the carbon tubes slip into would be better, and probably weigh less than the music wire. I am not sure how strong the bent aluminum tube would be, but it would probably be "strong enough".