waltr
Well-Known Member
Ok, do what works is key...
The slots and rocket build does look real good.
The slots and rocket build does look real good.
3 inch 29mm Scratch Build
- Thread starter Dane Ronnow
- Start date
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Thanks, Walt.
I decided to finish out the upper and lower body tubes before attaching the fins. So, coupler first, then the ejection baffle.
This is a 6" coupler, with bulkheads in both ends. The forward bulkhead will have a 5/32" eye bolt for attaching a nose cone tether. The aft bulkead will use a heavier 3/16" eye bolt for shock cord attachment, and a reinforcing disk, since this bulkhead will bear the force of ejection.
After securing the eye bolt in the aft bulkhead, I glued a .625" piece of split coupler into the end of the tube for bulkhead reinforcement, then epoxied the bulkhead behind it. After the epoxy had set up, I epoxied the forward bulkhead/eye bolt assembly into the other end, then set everything aside to cure.
The baffle is a standard design—two opposing plates (cut to my specs by Rocketry Works) with holes offset from each other—with the addition of two short tube sections. The smaller diameter tube attaches to the aft plate; the larger tube to the forward plate. This choke/collector setup confines the flow of hot particles from ejection, without restricting the flow of gases.
I attached a 3/16" eye bolt to the forward plate for shock cord attachment, then cut the short tube sections and epoxied them to the plates with J-B Weld.
I let the J-B Weld set up for several hours, then epoxied the forward plate into the tube, behind a .375" reinforcing ring.
This is a 6" coupler, with bulkheads in both ends. The forward bulkhead will have a 5/32" eye bolt for attaching a nose cone tether. The aft bulkead will use a heavier 3/16" eye bolt for shock cord attachment, and a reinforcing disk, since this bulkhead will bear the force of ejection.
After securing the eye bolt in the aft bulkhead, I glued a .625" piece of split coupler into the end of the tube for bulkhead reinforcement, then epoxied the bulkhead behind it. After the epoxy had set up, I epoxied the forward bulkhead/eye bolt assembly into the other end, then set everything aside to cure.
The baffle is a standard design—two opposing plates (cut to my specs by Rocketry Works) with holes offset from each other—with the addition of two short tube sections. The smaller diameter tube attaches to the aft plate; the larger tube to the forward plate. This choke/collector setup confines the flow of hot particles from ejection, without restricting the flow of gases.
I attached a 3/16" eye bolt to the forward plate for shock cord attachment, then cut the short tube sections and epoxied them to the plates with J-B Weld.
I let the J-B Weld set up for several hours, then epoxied the forward plate into the tube, behind a .375" reinforcing ring.
Next up, installing the coupler in the upper body tube. But first, I cut slots for the canards. The forward end of the coupler will be .75" above the aft end of the slots, and I want to be able to slot the coupler body before the epoxy hardens completely.
I attached a braided Kevlar nose cone tether to the forward eye bolt, stuffed it into a plastic drinking straw to keep it out of the epoxy, then ran two beads of epoxy around the inside of the body tube—one, just below the bottom edge, and the second, 1" below the slots. Then I slid the coupler into the tube, up to the halfway mark at 3".
Then I slotted the coupler, marked the canard tabs and notched them to fit the coupler bulkhead, then did a test fit.
I attached a braided Kevlar nose cone tether to the forward eye bolt, stuffed it into a plastic drinking straw to keep it out of the epoxy, then ran two beads of epoxy around the inside of the body tube—one, just below the bottom edge, and the second, 1" below the slots. Then I slid the coupler into the tube, up to the halfway mark at 3".
Then I slotted the coupler, marked the canard tabs and notched them to fit the coupler bulkhead, then did a test fit.
Back to the ejection baffle, I sprayed the interior and the fire side of the aft plate with several heavy coats of Rustoleum high temp paint. Once that dried, I epoxied the aft plate into the tube, flush with the end.
I've still got a little work to do on two of the fins—rounding the leading edges—but I got all of them papered using Avery full-sheet labels. Due to the length of these fins, I ended up adding a short piece of label above the forward tab, but the edges butted together nicely.
I cut a fin guide next, using foam core and a template from payloadbay.com. I cut the slots using my aluminum angle and a box cutter with a fresh blade. The foam cut easily, with straight, even edges.
I did have one small problem: The instructions from payloadbay for this particular template says to cut at the outside edge of the black line. When I did that, the slot was a scant 1/32" too wide (see the horizontal cut in the second picture). I corrected for that on the second cut. Apart from the two opposing slots that are slightly wider, the fit is just right, with body tube and guide slots lining up perfectly.
I did find that the foam bends quite easily when sliding it along the tube. So I reinforced it with a second layer of foam.
I guess that's it for now. More later.
I cut a fin guide next, using foam core and a template from payloadbay.com. I cut the slots using my aluminum angle and a box cutter with a fresh blade. The foam cut easily, with straight, even edges.
I did have one small problem: The instructions from payloadbay for this particular template says to cut at the outside edge of the black line. When I did that, the slot was a scant 1/32" too wide (see the horizontal cut in the second picture). I corrected for that on the second cut. Apart from the two opposing slots that are slightly wider, the fit is just right, with body tube and guide slots lining up perfectly.
I did find that the foam bends quite easily when sliding it along the tube. So I reinforced it with a second layer of foam.
I guess that's it for now. More later.
