I started off by making a template for the RockSim drawing. After I printed the fin pattern and cut it out, I placed it on a file folder and made a thicker template to reuse if I wanted to. Then I traced the pattern onto the 3/16th's plywood and cut them out with a scroll saw. I also cut out the small bulkheads for the altimeter bay. After cutting and sanding all the wood pieces for the fin can section, I measured the outside circumference with piece of paper and divided by three. Then I made three evenly spaced marks on the paper and put it on the rocket until the paper edges lined up. I then marked the tube for the fin slots. I then measured the fins from the front tab all the way to the back and transferred this measurement to the top of the fin slot line so I would know where to stop. Using a 3/16 bit in my router table and a strong alligator clip as a guide I clipped on the tube for a straight cut, I cut all three fin slots. The slots came out mostly straight.
Once the slots where cut, I then started to epoxy in parts. I epoxied the middle center ring in first. Using the motor mount tube and the rear ring in place to make sure the ring was not tilted sideways. I also used the fins because I wanted the ring to sit on top of the fin tabs. So after the fins and rear ring were in place temporally, I used the tube coupler to put the middle ring down to sit on top of the fin tabs and I tacked it with CA (super glue). Then I removed the fins and rear ring and motor tube and finished epoxying the outside of the ring. Then I glued in the motor tube using the lower and upper center ring in to center the tube and epoxied the tube to the middle ring on both sides. Note I already had the T-nut's for the motor retention glued in the lower ring and I could use screws to get it back out if it got stuck and the upper one I didn't put in all the way. I then epoxied in the upper ring. I first applied epoxy to the inside of the tube and out side of the MM tube just above where the ring was going to be placed. And the using the TC again pushed the ring into place and pulled the TC back out. The tube coupler is 6-inches, so I have the insertion mark at 3-inches. That's how far I pushed the upper ring into the fin can because I want the TC to sit on the upper center ring. Then I epoxied the outer side of the MM and upper center ring only. I'm not epoxying the outer edge of the upper ring until I am ready to put it the TC. This way all the rings get epoxy on both sides for a very strong rocket.
Then I tacked in one fin and start epoxying it in. I finished up with installing the other fins. After making sure the fin is all the way up against the middle ring and straight, it is tacked into place with CA and tape to hold it in place. Then using clear tape at the outer ends for dams, I filled the fin joints with epoxy. When it dries it should look like this. Again I'm using the lower ring to keep the tube straight. I use a small piece of clear tape taped to the inside of the fin can tube over the fin slot gap to keep the epoxy off the lower center ring. You want to be able to remove it to epoxy all the inside points as well. Once the fins are all epoxied on the outside it should look like this. Keep in mind that these joints are all done one at a time. On the inside I started off with standing the fin can on the top end and epoxying the middle centering ring on the inner and outer edges. Then I did the both sides of the fin tabs at the MM tube then last the inner edge of the fin can tube. In picture 11 the fin on the right is finished and the fin on the left is not. Next I needed to drill the holes for my rail button T-nuts. Then I drew a line in between the fins for the rail button placement. I epoxied in two T-nuts into some 3/16 scrap wood. I then drilled the holes and cut them down. I also rounded the outer edge to fit better on the inside of the fin can. When drilling the holes for the T-nuts in the fin can assembly, make sure the hole is in far enough so when you place the lower center ring in that it rests on all the fin tabs and not the T-nut mount. Then drill the hole for the upper T-nut mount and epoxy them both in.
For the tube coupler, I went ahead and fiber glassed the inside of the TC. The stock LOC 3.9 coupler and it was kind of weak. I cut the glass and wicked the ends of the tube with CA. I then poured epoxy into the tube and spread it out. Then I worked the glass into place. I used the old balloon trick. After I glassed the inside, I inflated a balloon inside the TC to push the glass outward and it worked great. I finished the TC by epoxying the bulkhead in. I needed to cut a small groove to clear the upper launch lug T-nut. Then I epoxied the TC into place. I filled and sanded and filled and sanded so more. Then I did the final sanding and finished getting ready for paint.
I then put epoxy around the inner edge of the fin can assembly and the outer edge of the motor mount tube and slid on the lower ring. Next I epoxied the out side on the lower ring. Again by building you rocket this way, you are able to get epoxy on all joint on both sides. The last items I needed to do where to cut a small slot in the tube coupler for the rail button and to glue in the TC. Using a Dremal tool with a cut off wheel, I cut a slot for TC to fit over the rail button. I then placed epoxy around the inner edge on the fin can on the upper center ring and all over the inside of the fin can tube where the TC was going to be. Then I slid the TC into place and let it dry. I still haven't decided to glass the fins or not. I think I will. Otherwise all the needs to be done is to apply micro-filler, sand and paint. So I decided to glass the fins. I used three pieces of glass from fin tip to fin tip. It came out very clean with no air bubbles. I filled and sanded and filled and sanded so more. Then I did the final sanding and finished getting ready for paint.
