The first step in bonding the fins is to sand off the gloss coat of epoxy on the carbon tube, to expose the cloth. I first cleaned the section of tube that was to be bonded with Isopropyl alcohol, and then sanded the tube with 150grit sandpaper until the shine was gone. I then cleaned the surface again with IPA.
You can see a few scratches here, you want it to be about like this; not too much more. It’s important to remember when bonding composites that you want chemical bonds, and not mechanical bonds. Thus, if you rough up the tube too much, you end up breaking the fibers instead of preparing the surface for bonding. 120grit is the absolute maximum that you should use for composite bonding.
I then mixed up a batch of Aeropoxy ES6209. Apply some to the root of the fin, and fit the fin into the alignment jig.
The entire surface is sanded here because i’ll be doing tip-to-tip carbon fiber reinforcement.
Here’s an overview of the alignment jig:
The tube is clamped in the Workmate table, with the jig resting on top. The jig has adjustable spacing between the two blocks to allow for different tube diameters.
The fin is clamped to the side of the jig as shown, and this allows for the fin to be perfectly straight in all vectors.
ES6209 takes about 5 hours to cure with this setup. The other two fins are repeated as shown.