Help needed for FG body tubes!!

[Deenelson85]

Hey everyone very much new to the forum and to scratch building, but would very much love to get into building my own fiberglass tubes. The problem I’ve been having is the fiberglass doesn’t want to release from my tube forms to slide off. Any suggestions on how to form them a little easier?

 

[dhbarr]

What kind of don't-stick are you using? A coating, some kind of sheet material, etc?

 

[tim cubbedge]

Here’s a thread with some good techniques that might help.
https://www.rocketryforum.com/threads/fiberglass-techniques.154538/

 

[Deenelson85]

I have tried only what I have on hand I haven’t bought anything specially made purpose. I’ve tried wax that had in my shop also tried some clear plastic film like Mylar. That’s one of my reasons for turning to the forum is for some type of ideas on what to buy/use.

 

[n27sb]

Take a look at post # 8.
https://www.rocketryforum.com/threads/another-stuck-tube.159836/

 

[Deenelson85]

Excellent i think this may be exactly what i was needing!!
Thanks for the help, once i go thru it i will know for sure.

 

[Deenelson85]

This was a very useful post thanks! I tried the technique that was used and it worked flawlessly. I don’t yet have a way to vacuum seal with plastic may work on getting that started soon to make the fiberglass a little more even and smooth.

 

[Scrapmaster87]

This was a very useful post thanks! I tried the technique that was used and it worked flawlessly. I don’t yet have a way to vacuum seal with plastic may work on getting that started soon to make the fiberglass a little more even and smooth.

Glad to see my mistakes are bringing people together to help more than myself

If you're thinking if vacuum bagging a tube, I would urge caution. Many many years ago my dad and I tried to bag a tube on a mandrel and it failed miserably. The tube bunched up and became useless for an airframe.

I would suggest using a heat shrink tape or sleeve. I have been having great success with heat shrink tape wound with a 50% overlap.

Heat shrink sleeves
https://www.sollercomposites.com/ShrinkTubing.html
Heat shrink tape
https://compositeenvisions.com/hi-shrink-tape-100-yards-release-coated-220r/
Some day I would like to try vacuum infusion, you'd be able do your wrap dry and make sure it's not bunching up when you pull your vacuum. You're also able to do your leak check before you even mix your epoxy.

 

[n27sb]

This was a very useful post thanks! I tried the technique that was used and it worked flawlessly. I don’t yet have a way to vacuum seal with plastic may work on getting that started soon to make the fiberglass a little more even and smooth.

Ok, so there is even and smooth.
It is easy to get to SMOOTH from EVEN but not so much the other way.
Open sided vacuum bagging rarely gets to EVEN unless the surface is formed by a mold surface.
Vacuum bagging a tube compresses the layup and may lock it on the mandrel.
I find that the best way to get to smooth is to wet sand the cured surface and follow with a layer of thin epoxy.
It may take a couple of coats.
Finish with clear automotive 2 part or sand up to 600 grit and buff.

 

[Deenelson85]

Glad to see my mistakes are bringing people together to help more than myself

If you're thinking if vacuum bagging a tube, I would urge caution. Many many years ago my dad and I tried to bag a tube on a mandrel and it failed miserably. The tube bunched up and became useless for an airframe.

I would suggest using a heat shrink tape or sleeve. I have been having great success with heat shrink tape wound with a 50% overlap.

Heat shrink sleeves
https://www.sollercomposites.com/ShrinkTubing.html
Heat shrink tape
https://compositeenvisions.com/hi-shrink-tape-100-yards-release-coated-220r/
Some day I would like to try vacuum infusion, you'd be able do your wrap dry and make sure it's not bunching up when you pull your vacuum. You're also able to do your leak check before you even mix your epoxy.

i never even considered the shrink tubing or that vacumm bagging would cause such a problem like that. This is one main reason i wanted to check on here before moving forward a lot of knowlegeable rocketeers to pick from there minds.

that said i may end up going with the shrink.

 

[Deenelson85]

Ok, so there is even and smooth.
It is easy to get to SMOOTH from EVEN but not so much the other way.
Open sided vacuum bagging rarely gets to EVEN unless the surface is formed by a mold surface.
Vacuum bagging a tube compresses the layup and may lock it on the mandrel.
I find that the best way to get to smooth is to wet sand the cured surface and follow with a layer of thin epoxy.
It may take a couple of coats.
Finish with clear automotive 2 part or sand up to 600 grit and buff.

yeah i did notice that at some point the resin actually started settling to the bottom side of the tube before it cured up. One side had just a noticeable bit less on top because of the transperency difference. I think a bit of sanding like you said may remedy that. Maybe on the next go before i try the shrink tubing/wrap maybe rotating the mandrel til i gets a good set going.

 

[n27sb]

yeah i did notice that at some point the resin actually started settling to the bottom side of the tube before it cured up.

I set my mandrel up on a modified Gas grill rotisserie motor. It constantly turns slowly until the epoxy gels.
This also helps if you add additional gloss coats.

 

[Scrapmaster87]

I set my mandrel up on a modified Gas grill rotisserie motor. It constantly turns slowly until the epoxy gels.
This also helps if you add additional gloss coats.

My mandrel holder/lathe is also powered. I use the low speed for curing, winding the shrink tape, and gloss coats. I have a foot pedal set up to index it when I'm doing the wrap. Putting on the shrink tape is about the most fun part of the process. I'm using a direct drive motor, so I'll use higher speeds to shrink the tape and much higher speeds for sanding and polishing mandrels.