Now that I have solved the problem where my motor tube was too large, I can now complete the fin can!

Completing the Fin Can

As soon as I finished sanding the crap out the motor tube centering rings so I could put the parts together, I went ahead and finished it up by epoxying it all together.

The next step was to insert the motor tube assembly into the lower air frame. I used the method I learned earlier in this process and put the inner ring of epoxy in first, then slid the motor tube in half way and put a second ring around the base. This worked like a charm. I let this section dry for a few hours, and prepared for the next step in which I would put the third centering ring up near the end that would eventually connect to the rest of the rocket.

The epoxy had fully set before I started this process, and I am very glad I let it because otherwise it would have destroyed the fin can because the extra epoxy on when inserting the last centering ring caused a VERY tight fit that ended up putting a lot of pressure on the motor tube.

I had dry fit this section and planned it out fully before I ever glued the motor tube in place, so I knew better than to try and dry fit the last centering ring after the motor tube was stuck in place. At this point once you put the last centering ring in, taking it out would be almost impossible.

The basic plan goes like this:

1. EYE BALL IT, MAN, DOUBLE CHECK, TRIPLE CHECK!
2. Mark the coupler/bulk plate assembly half way with a pencil
3. Put a bunch of epoxy around the edge of the tube
4. Slide the centering ring in just over a half inch
5. Insert the coupler/bulk plate assembly, spinning it as it goes in until it gets to the pencil mark
6. Turn the entire assembly upside down and hold it in place

Attaching the Fins

Once the motor tube, all centering rings and the bulk plate assembly have dried and are firmly in place, the next step is to attach the fins. I differ from the kit instructions when it comes to fins. The instructions call for you to leave the bottom centering ring off, tack the fins in place and drain epoxy along the fins. I prefer to tack the fins in place, drill a hole next to the fins and use a baby feeding syringe to insert epoxy into a closed cavity.

Either way you have to tack the fins in place. This is easy enough, just put a nice generous amount along the fin slit and a strip along the edge of the fin which will attach to the motor tube. Then insert the fin and use tape to hold it in place. Using this method you can put all the fins on at once and be prepared for the fillets a few hours later.

The only bit of advice I have for the fillets so far is to use tape to mark off where they should end. This makes clean up significantly easier by removing the need to sand off the excess. Just make sure to pull the tape off well before the epoxy starts to harden.