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Shock cord mount for 29mm MD

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ActingLikeAKid

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Obviously the easiest thing here is just to order a baffle with an integrated eyebolt.
But I'm impatient and also hate paying shipping for just one thing.

I kicked around a few ideas in my head; let me tell you about the rejects, they were good!
1. "OK, I'll cut a disc of plywood and drill holes in it for ejection gases and put in an eyebolt" .... yeah, if I had a CNC router, maybe? 29mm just isn't a lot of room to work with.
2. "Fine. I'll take this dowel that's almost a snug fit in the tube and grind it down to 1/4" thick and 2" long and then put an eyebolt in the end, then epoxy it in" ...OK, better, but I'm not sure that's going to be super secure. Good possibility for a huge mess of epoxy down in the airframe.
3. "OK, how about a coupler in the tube, and I put a barrel bolt through the coupler" Better! I like this idea. But blue tube isn't that thick. Can we get it so the head of the bolt fits between the coupler and the ID of the airframe? That might require enough sanding that we weaken the tube. Also I don't know if my local hw store sells those bolts, and I really don't want to have to place an order with McMaster. Also also, invariably the cord will end up on the threads, which will weaken the cord. A dowel would be better, but wouldn't stand up to ejection gases. Aluminum rod would be perfect, but we're back to a McMaster order.
4. "OK, how about this...."

Take a coupler that fits inside the BT. Drill two 1/8" holes across from each other. Take Kevlar cord and make 3 or 4 loops going through the two holes and over the top(from the side, it would look a little like a bucket with a handle made of thread). Tie the cord to itself very securely (note - the kevlar cord is 200# "thread" and is thin enough to fit between the coupler and the airframe. The coupler is on the loose side.
Smear a thick layer of epoxy around the ID of the airframe about where I want the mount.
Take a long piece of scrap string. Slide a fishing weight onto it, then put one end through the shock cord mount (the "bucket handle). Tie the ends together so you have a loop with a fishing weight at one end and the coupler at the other. The loop is longer than the airframe. Holding the airframe upside down, carefully lower the weight through the airframe, trying to disturb the epoxy as little as possible. Gently pull the string from the other end, sliding the coupler into the airframe until it self-fillets the epoxy. Let it dry. Once the epoxy has cured, untie the string but do not remove it. Tie a piece of kevlar cord to the end of the string and carefully pull the free end of the string, making a double length of Kevlar from the top of the airframe, down to the mount, and back up. Attach shock cord to Kevlar so that the shock cord will hit the edge of the tube, not the kevlar. Tie everything off. Call it a day.

Essentially, this is like what I do with Estes ARF rockets that have the plastic tube connector with an "X" across it; I just loop a bit of kevlar around the "X" and tie the shock cord to that. Way easier & stronger than the tri-fold method.

Thoughts? This ought to work, right?
 

dhbarr

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Stainless sink strainer from your local hardware store.
 

dhbarr

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Bathroom ones slip right inside a 29mm.
 

ActingLikeAKid

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Bathroom ones slip right inside a 29mm.
Update: Got a bathroom strainer. Perfect fit ... inside the body tube. Lip hangs over the edge. Would work if I ground the lip off. Trying to decide if that's worth it.
 

dhbarr

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D'oh, so close!

If I needed to grind the lip off I'd bolt it into my drill chuck and spin it against el cheapo sharpening block or a fine file.
 

ActingLikeAKid

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Well....!@$#%.

Couple of days ago, I'm out for a run, thinking about how great this rocket is going to fly.

Then I have a "wait a minute" moment: 29mm MD doesn't have room for a chute release. Either I make it 38 and it probably fits, albeit snugly ... or I keep it 29mm MD and use a streamer. That's probably a non-starter; even with a nice long streamer, a 3 foot bluetube rocket would probably come in hot enough to hurt people. And trying to cram DD into a 29mm isn't my idea of fun.

Back to the drawing board!
 

dhbarr

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Prairie Twister cable cutter :)

And for trackers the new mini egg or telemini; and get the tailcone closure for an h399 ^_^
 

ActingLikeAKid

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Prairie Twister cable cutter :)

And for trackers the new mini egg or telemini; and get the tailcone closure for an h399 ^_^
Full size EF will fit in the nose. And THEORETICALLY an EF Quark could deploy the drogue and cut the cable cutter. I'm thinking I build this so that it'll be a cool ~1000ft rocket on single deploy; maybe this winter I'll tackle building an av bay for it.
 

ActingLikeAKid

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Related: If you're using a cable cutter, isn't there a risk of the rocket flopping around and eventually yanking the cords out?
 
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