Asking for trouble? 38mm Powered BT-80 based rocket?

So, would a standard BT-80 tube hold up to the stresses of a 38mm powered rocket, or am I just begging for a shread?

Presuming that it wouldn't, is there any full length coupler material that could reinforce it sufficiently?

I'm sure I could probably make one w/fiberglass strong enough if not for three issues.

Smell
Expense
Experience.

Thanks!
Jim

Yes, I've done it and the way you suggest. Parachute section is double walled with couplers but the lower is supported by the Giant Leap 38mm tube. There's 4 rings down the 36" length of the MMT. The SEMROC BT80 tube seems to be the highest quality plus there is always the heavy wall version. I have some BT60 full length coupler from Totally Tubular and it's real nice stuff. Use Gorilla Glue on the coupler and dampen the inside of the BT with water. It will not grab when you assemble and the glue swells up and fills all the space. If you look at it the chemical reaction forms microscopic bubbles pushing the glue to fill in the gaps. Once it sets up it's the best join ever, make a mistake and you cut it out, no peeling back the cardboard, you cut the bad place out and start over

Totally Tubular and Balsa Machine Service has the long tube and I think SEMROC has some left. Mine flew on a H242 with a balsa nosecone and too small of a lag eye screw, it pulled out but I found it. When I got home I put a bigger eye loop in it

If you're going to double wall it, why not just get LOC 2.56" tube and be done with it?

You could put a layer of fiberglass to reinforce the tube.


Kirk

1tree said:

You could put a layer of fiberglass to reinforce the tube.


Kirk

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Agreed, this is my suggestion as well. Nothing like just two layers of lightweight glass will do.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

K'Tesh said:

I'm sure I could probably make one w/fiberglass strong enough if not for three issues.

Smell
Expense
Experience.

Click to expand...

1tree said:

You could put a layer of fiberglass to reinforce the tube.

Click to expand...

SinfulDarkLord said:

Agreed, this is my suggestion as well. Nothing like just two layers of lightweight glass will do.

Click to expand...

My build area is inside my living space (light colored carpet). I don't have a area outside where I can work and leave my stuff out. Nor do I have resources needed to glass up a tube.

DizWolf said:

If you're going to double wall it, why not just get LOC 2.56" tube and be done with it?

Click to expand...

+1. Just use LOC tubing. And then if you still really want to put something stoopid in it to power it, you could double wall that with a coupler and use a stiffy to join sections.

K'Tesh said:

My build area is inside my living space (light colored carpet). I don't have a area outside where I can work and leave my stuff out. Nor do I have resources needed to glass up a tube.

Click to expand...

I do all this in my room, which also has a carpet, along with a dog that sheds a lot of hairs and I vacumm my room to do all this. I have yet to mess it all up with epoxy.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

Good laminating epoxy has very little smell to it. A project that small can be done on a countertop covered with newspaper. Aeropoxy is not too costly and goes a long way. You'd only need a scrap of lightweight glass cloth and you can purchase that in most automotive sections if you don't want to mail order a bunch of it.

As far as experience, this is the perfect type of small project to get some on.

Binder Design said:

Good laminating epoxy has very little smell to it. A project that small can be done on a countertop covered with newspaper. Aeropoxy is not too costly and goes a long way. You'd only need a scrap of lightweight glass cloth and you can purchase that in most automotive sections if you don't want to mail order a bunch of it.

As far as experience, this is the perfect type of small project to get some on.

Click to expand...

Most agreed


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

This all assumes he wants to glass.... which if he does that's cool.

If you want to avoid it..... a LOC tube is $6.88 for 30" https://www.apogeerockets.com/Building_Supplies/Body_Tubes/High_Power_Tubes/2.56in_LOC_Body_Tube

DizWolf said:

This all assumes he wants to glass.... which if he does that's cool.

If you want to avoid it..... a LOC tube is $6.88 for 30" https://www.apogeerockets.com/Building_Supplies/Body_Tubes/High_Power_Tubes/2.56in_LOC_Body_Tube

Click to expand...

Thanks for that... I talked to Apogee, and they checked an Estes BT-80 nosecone in the LOC body tube, and there was a bump caused by the larger diameter tube.

The reason for all these questions is I'm pondering a BT-80 based design, and the BT-80K nosecone (or the TLP-26L) would be a good match for the nosecone/boat tail in that design (and would compliment the 29mm Powered Cherkokee D I'm working on). In doing the calculations on the upscale, I found that at 159% gave me a (IIRC) hole on the back of the boat tail 42mm wide, and a perfect match for a 38mm motor tube. If I'm not mistaken that would be just enough room for a slimline retainer.

I'm still leaning towards the BT-80 tube w/internal couplers to thicken the wall some.

Presuming I'm using a 20" long 38mm motor tube (plus the leftovers from my L1 (Offl) build), and the body tube is ~27", a couple of couplers should be able to fill the space above the forward CR. I may need to redo the shoulder of the NC though.

Still, I'm just pondering. $$ flow problems are back. Perhaps I should just build what I've got for a while.

I'd just go with something like a LOC tube as others suggested, as it's not only the tube itself, but the availability of things like CRs and bulkheads. Lining the bt80 with a coupler could also add more weight than you want. (think of it this way - with lining, you are doubling the weight of the airframe)

I just started using Fiberglass yesterday. It's actually a lot friendlier to work with than I thought it would be.