Coating inside of body tubes with ______ (?)

[shanejohnson2002]

I've tried the search function, but after sifting through 10 pages without finding my answer I'm just going to ask it here:

I've seen/heard multiple threads about coating the inside of standard, thin-wall cardboard body tubes in order to make them easier to clean and a bit tougher. I have tried some different things with varying degrees of success. I'm about to start on a homebrew modular BT70 rocket and I'd like to try some new techniques with it.

here's what I've tried in the past:
- Wood hardener - Seems to work but it is more "fuzzy" than glassy / slick.
- CA - works, but it builds up in 'rings' as you coat the tube. It's also difficult to coat the inside of longer tubes.
- wood glue - Works, but ends up pretty thick. Also tends to pool at one of the tube, requiring constant rotation.

I would ultimately like to simply soak the sides of a foam brush with whatever hardener I'm using, and 'bore brush' the inside of the tube with it. I'm hoping it to be hard/glassy/easy to wipe clean, and drying WITHOUT pooling or requiring rotation.

I have seen 'thinned epoxy' mentioned. Which epoxy (finishing epoxy / laminating resin? 5 minute? 15 minute? Aeropoxy?), and how was it thinned?

I'm leaning toward BSI 20-minute, BSI 30-minute, or ZAP ZPoxy.

Thanks!

 

[samb]

I’ve used Elmer’s Glue-All and even school glue and Gorilla polyurethane on thin-walled Estes tubes. I don’t recall using it ion anything larger than a BT-60 (1.6in).
I stuff one end of the tube with paper towel at the level of the forward end of the motor tube. Then load up some glue onto the towel and push it forward with a dowel. Sometimes a second pass is needed. Don’t see why epoxy wouldn’t work as well.

 

[Dave S.]

I coated the inside of a 4" cardboard tube with West Systems epoxy.

I applied it with one of those small foam paint brushes. Cut the handle off first so I could reach all the way in there.

Made sure to have gloves on and my arms covered/protected all the way up to my elbows.

 

[David_Stack]

What about something like Minwax polyurethane or polycrylic? Seems like epoxy would be adding a significant amount of weight...

Or go old school and source some butyrate dope.

 

[shanejohnson2002]

What about something like Minwax polyurethane or polycrylic? Seems like epoxy would be adding a significant amount of weight...

Or go old school and source some butyrate dope.

Agreed about the weight, but it's still significantly less weight than fiberglassing the outside, or buying phenolic / qt / fg tubing.

Not as strong either, but I'd be willing to experiment to find a good trade-off.

poly might work. I have a can of it already.

Also have some shellac but it's in the spray can. I could get the quart of liquid and test it on some scrap.

 

[SolarYellow]

Deft sanding sealer seems relevant. Or high temp paint.

 

[shanejohnson2002]

I coated the inside of a 4" cardboard tube with West Systems epoxy.

I applied it with one of those small foam paint brushes. Cut the handle off first so I could reach all the way in there.

Made sure to have gloves on and my arms covered/protected all the way up to my elbows.

I was thinking of the same thing, only with a 1/4" dowel attached to a foam brush head, chucked up in a drill on a low speed setting.

 

[Back_at_it]

I've used MinWax brand sanding sealer with good results. On small tubes, I've dipped a small foam roller in it then shoved it down the tube a couple of times. Makes them water proof and they clean easily. Just be sure to wipe away the excess.

On larger tubes, thinned epoxy works extremely well and doesn't add much weight. You need to use something that is slow curing like T-88. Mix it well then get it warm so that it is really thin. Paint it on the inside of the tube then use a hair dryer to keep it warm for a few minutes. Use a towel damp in rubbing alcohol to wipe away the excess. I've also done this to the outside of smaller rockets to give them some additional strength.

If you wipe the outside of an Estes tube with rubbing alcohol it will remove the shiny outer coating. T-88 will soak right in afterwards.

 

[Blast it Tom!]

If you wipe the outside of an Estes tube with rubbing alcohol it will remove the shiny outer coating.

I'll take that tip just to keep from sanding the tubes before finishing! Thanks!

 

[SolarYellow]

I believe water accomplishes the same thing.

 

[Alan15578]

I've tried the search function, but after sifting through 10 pages without finding my answer I'm just going to ask it here:

I've seen/heard multiple threads about coating the inside of standard, thin-wall cardboard body tubes in order to make them easier to clean and a bit tougher. I have tried some different things with varying degrees of success. I'm about to start on a homebrew modular BT70 rocket and I'd like to try some new techniques with it.

here's what I've tried in the past:
- Wood hardener - Seems to work but it is more "fuzzy" than glassy / slick.
- CA - works, but it builds up in 'rings' as you coat the tube. It's also difficult to coat the inside of longer tubes.
- wood glue - Works, but ends up pretty thick. Also tends to pool at one of the tube, requiring constant rotation.

I would ultimately like to simply soak the sides of a foam brush with whatever hardener I'm using, and 'bore brush' the inside of the tube with it. I'm hoping it to be hard/glassy/easy to wipe clean, and drying WITHOUT pooling or requiring rotation.

I have seen 'thinned epoxy' mentioned. Which epoxy (finishing epoxy / laminating resin? 5 minute? 15 minute? Aeropoxy?), and how was it thinned?

I'm leaning toward BSI 20-minute, BSI 30-minute, or ZAP ZPoxy.

Thanks!

I have finished the inside of piston tubes with epoxy, but unless you are a committed contest flyer, it is just plain nuts.

 

[billpr]

I've sprayed painted the inside of some tubes with black heat paint. Weight was a little heavier. I let it dry and then sanded a little with 400 paper on a long dowel to get a little smooth . I didn't get any on the motor end of the tube, just beyond it for the exhaust gases.

 

[K'Tesh]

Ok, now that I've read this (I'm inclined to wood hardener), I wonder how good whatever Future floor wax is calling itself these days would do.

 

[lakeroadster]

2 parts yellow Wood Glue, 1 part water

 

[Daddyisabar]

I have mostly used the cheapest CA I could find and a scrap piece of Balsa from a kit fin sheet as a smoothing stick. You must have the patience of a Jedi and good lighting is essential. When you see it smoking too much use breath control as you back away, you are applying too fast! (cough cough spit!) Don't dilly dally around either. Wear junk clothing. Have some newspaper under your work. You will eventually gain the skill to get nice even, glasslike coverage. You are making Poor Boy Phenolic. ALL COATED SURFACES MUST ALREADY BE GLUED! Very light, very strong but not cool. Surface imperfections can be sanded if desired. Using CA to build and strengthen entire oddrocs is a sure sign you have fallen to the Dark Side.

Use many of the same techniques for thin, slower cure expoxy carefully applied with a chip brush. Use if even more strength and weight is needed. Use if you have the time to supervise the cure. Very hipsterish and cool. Brag to your friends about using this awesome technique.

Sealers or dope not quite as strong as glues but they work too. But really, how strong does your LPR thin walled tube really need to be? "Well dude, with the high end motors I use, it better be bullet proof!" Old school dope for the dopey old dudes who still have a bottle or can stashed away. Dope worked well on stiffening up the card stock booster cones on my Cosmodrome Vostok. Used finishing epoxy on the cardstock transition. Used thin CA on the bid balsa nose cone. SO MANY GLUES FPR SO MANY DIFFERNT COATING JOBS! IT'S DRIVING ME CRAZY! WHEN WILL THEY MAKE ONE GLUE THAT DOES EVERYTHING!

Titebond II and sometimes III(waterproof) works too, especially if you are broke or lazy and running low on exotic glues like epoxy, CA or dope. A nice thick coating of cheap Titebond II on the bottom of my clustered TLP kits. Trying to prevent hibachi from multiple flights on the thin tube and cardstock. Yuky, what's that smell when recovering the rocket? Burned wood glue and black powder residue. Wipe off the smelly soot, get out the Titebond and recoat! Good as new and no one knows what really happened. Hipster Image saved.

 

[Daddyisabar]

2 parts yellow Wood Glue, 1 part water

The MIXOLOGIST has spoken. Diluted to perfection for the perfect SMEAR! FLOWS LIKE CREAM. Perfect soak on surface cardboard. Drys thin and shrinks to provide maximum strength and flexibility. Basically the nectar of the Gods.

Like whiskey and water. Don't know exactly how it works, but it does.

 

[dhbarr]

Instead of thinning epoxy, I've considered thickening wood hardener. Either with dissolved scrap plastic, or with epoxy.

Disclaimer: haven't tried it.

 

[Hybrid33]

Try this

 

[shanejohnson2002]

I believe water accomplishes the same thing.

I can confirm water works. I use baby wipes for glassine removal. They're plentiful thanks to having 3 kids.

 

[Zbench]

Shellac. Perfect for what you want. Is light, dries fast and is easy to apply. You can buy it premixed for cheap or mix your own from flakes and alcohol which is what I do.

 

[lr64]

Shellac. Perfect for what you want. Is light, dries fast and is easy to apply. You can buy it premixed for cheap or mix your own from flakes and alcohol which is what I do.

Sorry, couldn't edit yesterday. What's a good source for shellac flakes? Seems like they'd store a lot better than the stuff that's already mixed.

 

[wsume99]

I can't find the thread but in the EX section a member once posted how he coated the ID of motor tubes with epoxy before casting grains. He used laminating epoxy but how he applied it was interesting. He had a thin rubber sheet attached to a long dowel. He'd put the tube over the dowel with the rubber sheet sealing the bottom end and then pour a small amount of epoxy inside the tube from the top end. Once it all settled at the bottom he would pull the dowel through the tube and the rubber sheet would wipe the ID of the tube and evenly spread a thin coating of laminating epoxy. Hopefully you can visualize what I'm describing. This method should work for other liquids you might consider as well.

 

[Zbench]

Shellac. Perfect for what you want. Is light, dries fast and is easy to apply. You can buy it premixed for cheap or mix your own from flakes and alcohol which is what I do.

Here you go:

https://www.highlandwoodworking.com/dewaxed-garnet-shellac1lb.aspx

Get the Platina. That much shellac will last a lifetime. I fill a wide mouth pint canning jar 2/3 full and then cover with everclear. Will take about a week to dissolve with occasional shaking. Once dissolved the impurities will settle to the bottom and you can decant to another container.

Resist the urge to buy cheap “stove fuel” which is a mix of ethanol and methanol. Everclear is cheap and infinitely better. 190 proof is the way to go.

 

[lr64]

Here you go:

https://www.highlandwoodworking.com/dewaxed-garnet-shellac1lb.aspx

Get the Platina. That much shellac will last a lifetime. I fill a wide mouth pint canning jar 2/3 full and then cover with everclear. Will take about a week to dissolve with occasional shaking. Once dissolved the impurities will settle to the bottom and you can decant to another container.

Resist the urge to buy cheap “stove fuel” which is a mix of ethanol and methanol. Everclear is cheap and infinitely better. 190 proof is the way to go.

Yow! That's kind of expensive, considering I have a floor that needs it. I don't know if we have Everclear around here. I remember, decades ago, driving to the next state and they didn't have it either. What's the deal about "wax free"?

BTW, people should know that shellac isn't terribly water resistant.

Do you French polish the inside of your rockets? ;-)

 

[Zbench]

Shellac would be a terrible floor finish. It isn’t a very durable finish but it’s easy to apply and dries fast. It’s an excellent sealer under other paints. I typically paint the exterior of my LP tubes with it. It really takes the paint so much better than over primer or without. There are cheaper versions but you get what you pay for.

Dewaxed is what it says. When the lac beetle poops out shellac, it’s mixed with a lot of wax. By taking the wax out it makes the finish much harder and durable.

 

[lr64]

Shellac is very often used as a floor finish, though, including in our house. For a room that doesn't get very much traffic or moisture, it's ok. Not great, just ok. But I'd want to fix the water damaged or worn areas before putting something else over them, unless it was opaque.

That's a good tip about using before other paint, something I was vaguely aware of before. But only vaguely.