New scratch build, now "Binary Effusion"

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Time to work on the half moon baffles for the motor tubes. I cut discs out of 3/16" plywood with a 1-7/16" hole saw, then cut them to final size on the lathe. After drawing the cut lines off center, I filled the pilot holes with epoxy. Then cut them with the bandsaw. This is the easiest way I've found to make the half moons.

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Using a length of 1/2" PVC pipe with depth markings, I pushed the half moons into the epoxy. After the epoxy set, I put fillets on the exposed sides. Repeat this three times for the three half moons in each motor tube. I also coated the motor sides of the baffles with epoxy to help protect them from the hot ejection gasses.

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Got the motor mount epoxied in. The aft centering ring hasn't been epoxied yet, I'll need another jig for that. Also, as I always do on my zipperless builds, I flooded half the coupler with CA, and sanded/polished it on the lathe. I guess I really do have jigs for everything!

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I decided to use 3/8" plywood for the baffle plate for the extra strength. I cut it with a 4-1/4" hole saw, and sized it on the lathe. I need to make a template to mark the locations of the vent holes.

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And the other jig. For setting the position of the aft centering ring at 1" from the bottom of the body tube.

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Lookin' good, Cap! I'd say the cluster bug has bitten you and the venom is just now getting to your nervous system;)
 
Normally with my 4" zipperless designs, I drill eight 3/8" vent holes equidistant around the perimeter of the baffle plate. But in this case, I didn't want any of the holes directly above either of the motor tubes. The half moon baffles keep burning particles from passing through, but there's still a lot of heat. So I decided on six 1/2" vent holes arranged so that they're to the sides of the motor tubes. Out of curiosity, I figured the area of 3/8" and 1/2" circles. Six 1/2" holes have a larger total area than eight 3/8" holes.

Using a template I made with the template from Open Rocket, I marked the positions of the vent holes on the plate. I must have been drilling too fast, it kept catching the plywood and spinning it out of my hand. Made me cuss. It also chewed it up a bit. But I got the holes drilled, finally.


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I love those nylon spacers! I have used them for so many different things with my scratch builds. In this case, I'm using 1/2" long spacers to place the baffle plate at the proper position inside the coupler. I also covered up the torn areas on the plywood with epoxy.

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Normally with my 4" zipperless designs, I drill eight 3/8" vent holes equidistant around the perimeter of the baffle plate. But in this case, I didn't want any of the holes directly above either of the motor tubes. The half moon baffles keep burning particles from passing through, but there's still a lot of heat. So I decided on six 1/2" vent holes arranged so that they're to the sides of the motor tubes. Out of curiosity, I figured the area of 3/8" and 1/2" circles. Six 1/2" holes have a larger total area than eight 3/8" holes.

Using a template I made with the template from Open Rocket, I marked the positions of the vent holes on the plate. I must have been drilling too fast, it kept catching the plywood and spinning it out of my hand. Made me cuss. It also chewed it up a bit. But I got the holes drilled, finally.

I hate it when that happens. I've learned that when possible, to sandwhich the part between two other Scrap Pieces while drilling to prevent the chipping.
 
I hate it when that happens. I've learned that when possible, to sandwhich the part between two other Scrap Pieces while drilling to prevent the chipping.

I just need to take my time. I was over-confident.
 
Time to see if my retention idea will work. I'm using my favorite 1/8" aluminum bar, 3/4" wide in this case. It's just a matter of marking and bending it in the vise. I use a hammer to get sharper corners. Then drill the holes for the screws.

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Two 6-32 screws go into the tee-nuts to hold the clips down. Then I drilled two holes in the center of the clips, for a long screw to hold them against the motors. It doesn't need to be very tight, just enough to keep them from flexing outward. Of course, I'll use lock washers on the short screws, and a lock nut on the long through screw. I think it'll work!

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I wanted something with a bigger footprint than just a fender washer for the forged eyebolt. So I cut a 1-1/2" long piece of 2" x 1/8" aluminum bar, and drilled a 1/4" hole in the center of it.

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I got the fin slots cut and couldn't resist a dry fit. The tabs weren't quite long enough, so I sanded the fins a bit with my handy-dandy 1" belt sander. I also got the nose cone in the mail yesterday. It's a 5:1 conical gel coat fiberglass. Pretty wicked looking!

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Using my handy-dandy fin alignment guide, I got all five fins epoxied on. My second five finned rocket.

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Man thats one pointy nose cone, I'm courious what this bird with turn out weight wise, looks plenty strong.
 
Very nice! I'm curious, do you plan on doing internal fillets, and if so; how?


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