Using the fin pattern generated from RockSim, I started with cutting the fins out using 3/16ths birch plywood. Next using my new circle cutting jig, I cut all the center rings and the bulkhead. Taking time to measure right and get the center for cutting out the motor tube cuts on the center rings was a challenge. Using a compass and a steel ruler, I found the center of the motor tubes. I drew the pattern on the per cut center ring from the template from RockSim. Then I found the radius of the motor tube circle by using the compass set the radius of the circle. Place the compass point on the edge and draw a slight arch in the middle of the circle. Do this about every 1/4 way around the circle. Where all the lines meet in the middle is the center of the circle. Since I wanted to duplicate this on all three center rings, I did the pattern on one ring and stacked them in a body tube. This allowed me to drill the center holes in both motor tubes for the tube cutting jig in the same place on all three center rings. Next I started cutting the motor tube rings out. Using my jig again, I cut out the motor tube rings. Note the small test ring to the upper left in picture 4. This was used to get the exact motor circumference of the tube. I used the router and jig to slowly cut the circle bigger and bigger until it fits. I do not cut it all the way around, because then you lose the ability to keep your circle round when cutting. After cutting all the rings out, I test fit the motor tubs in all the rings. A nice tight smooth fit for all of the motor tubes. You may need to do a little sanding. The Jig will leave a small area from the cut. This will need to be sanded down. The next thing I did was to measure, drill and install the T-nuts for motor retention on the bottom ring. After installing the T-nuts, I epoxied them into the center ring.
Using my routing table, I cut the fin slots for the fins. Next I centered the center ring in the fin can. Using the tube coupler to make sure it was flat and level in the body tube, I epoxied the center ring into the fin can. I test fit the fins next. I had to cut a groove into all the fins to fit over the middle center ring. Because this is a dual motor rocket, I had to cut the root edges of two of the fins to touch the motor tubes. Then I started to epoxy all the fins in. I made sure the motor tubes where straight and not twisted. Using the upper and lower center rings to help keep the motor tube centered I glued the upper part of the fins first. I worked on the fin fillets on the bottom side of the center center-ring again using the end center ring to keep the motor tube straight. I drilled the hole for the rail button and epoxied in the button T-nuts. Then I put epoxy on the inside of the body tube and slid the end center ring into place. After I let this dry, I did the same thing for the upper ring. I finished up installing the U-bolt and epoxying the bulkhead into the tube coupler. Next I finished up all the external fin fillets and the lower center ring. The last part of the fin can was to glass the fins.
