Questions about fiberglass imperfections

[cthunter01]

Hi guys!

So I finally decided to stop worrying about messing up some cardboard tubes with fiberglass and just dive in and try glassing some tubes. Best case I learn a new skill and get super smooth tubes, worst case I just learn a new skill and get the opportunity to try again...

I think they turned out okay actually. There are some imperfections I'm hoping to get some advice on, but overall I think they're decent for a first try.

So I got some soller composite sleeves (6"/light, 9.5 oz), 7.6" composite heat shrink tubing, and West System 105/206 epoxy. Well I already had the epoxy because I like constructing with it along with some 406 silica thickener. But the fiberglass and heat shrink is new. The tubes are 5.5" LOC cardboard.

I tried glassing two tubes, each in a slightly different way.

For the first one: I put the sleeve over the cardboard tube dry, mixed up enough resin and hardener so I wouldn't have to stop mid-work to make some more, then applied the epoxy. I wetted it thoroughly enough to make sure the fiberglass was completely transparent, then slid the heat shrink tubing over the tube. After trying to shrink it with a heat gun, it didn't quite shrink tightly over the tube. I thought I sized the right shrink tubing (I did size it correctly, but this was my first attempt and I got scared that it would ruin the finish so I cut it off). I took some more shrink tubing, split it to make a sheet, then just wrapped the tube as if it was a mylar sheet.
After waiting about 8 hours or so, I peeled the wrap and was pretty pleased. It does, however, have some "dry" spots that will need filling (I think?) I'm a little unsure how there are so many, as it was wetted to the point of transparency before I wrapped it with the shrink wrap. Though, I think I might have squeegeed out too much epoxy after wrapping it. And the cardboard may have soaked up more than I anticipated or realized. It's still as solid as a rock, but it's rough in areas. Picture below:

So, what to do with the rough areas? I did a little research and came up with using epoxy w/ microballoon filler. Just apply that to the tube and wipe it smooth. Then I *should* have a sandable surface once it cures, and I can sand it smooth. Or should I do something else to fill the rough areas?

The second tube: This is a smaller one. Based on the outcome of the previous tube, I left more epoxy on the tube after wrapping it with the shrink wrap. Also this time, I tried the shrink tube again and just gave it more time and more heat and it did eventually tightly shrink over the tube. *However*, it left some wrinkles near the edges of the tube. Possibly or probably because I erred on the side of leaving too much epoxy in place, whereas before I didn't leave enough. So after removing the shrink tubing (6 hours later), those wrinkles left wrinkles in the epoxy. The fiberglass is still tightly bound to the cardboard and smooth as near as I can tell, but the resin is wrinkly in some areas. Also, there's still some "dry" spots, but far less than before. Picture below (red circles show wrinkles in resin, green is a dry area):


My next question is: what am I going to do with those wrinkles? I suppose I just sand them down, but does anyone else ever get them? They're pretty small, but not nothing. I couldn't get rid of them while applying heat and shrinking the tubing, so they cured that way. I'm thinking I might just avoid using shrink tubing in the future. Anyone else have success with shrink wrap and fiberglassing cardboard tubes?

 

[cthunter01]

I scaled the image sizes way down so they load fast for people that might not have fast internet connections. But it reduced the quality by quite a lot. I can upload higher res pictures if those aren't clear

 

[Hobie1dog]

I suggest abandoning all the extensive labor and frustration, and still ending up something that's not smooth?... why don't you just start using fiberglass tubing? it's as smooth as a baby's butt, with no work involved at all.

 

[tfish]

@cthunter01

For your first glass job it looks much better then my first one!

Don't worry about what other people say...some of us like building and learning things.

I would sand down the high points, fill the low areas paint it and fly the hell out of it.

Build another and keep learning, flying and having fun.

Tony

 

[cthunter01]

I suggest abandoning all the extensive labor and frustration, and still ending up something that's not smooth?... why don't you just start using fiberglass tubing? it's as smooth as a baby's butt, with no work involved at all.

Haha, why indeed! I have some smaller fiberglass rockets that came that way, but I wanted to see about building something larger that’s also strong yet a lot lighter than solid fiberglass would be.

Plus I would like to learn more about it. Maybe the biggest reason to do it was how I was kind of afraid of doing it for fear of making mistakes. And not doing something because I’m afraid it’ll be hard doesn’t sit well with me.

 

[Hobie1dog]

John Coker weight chart:

Common Name	Manufacturer	Material	Weight¹	Thickness	Grooves
cardboard	Loc/Precision	paper	103	0.060"	light
phenolic	Public Missiles, Ltd.	paper phenolic	143	0.069"	medium
flexible phenolic	Giant Leap Rocketry	paper phenolic	149	0.067"	medium
Blue Tube 2.0	Always Ready Rocketry	vulcanized paper phenolic	174	0.060"	light
MagnaFrame	Giant Leap Rocketry	vulcanized paper phenolic	174	0.067"	heavy
canvas phenolic	MAC Performance	cotton phenolic	185	0.060"²	none
seamless phenolic	Black Cat	phenolic	182	0.063	none
fiberglass	Performance Rocketry	filament wound FG	248	0.063"	none
carbon fiber		filament wound	163	0.045"	none

¹ The units here are grams per foot (yes, tha

 

[Grog6]

I'd add epoxy to the dry areas and anywhere else that needs it, and give it some time on the pump.

 

[Hobie1dog]

I know it's been done on here before, but too hard to search for, is how much weight you end up with by taking cardboard tubing and adding fiberglass to it then all the resin.

 

[cthunter01]

Maybe “ a lot lighter” is an overstatement. But my 2.6” all-fiberglass rockets are chonkers. Relative to similarly sized cardboard rockets anyway. I just suspect wrapping cardboard with a single fiberglass layer and laminating it would be lighter than all fiberglass, but I don’t know that for sure. It’s all a learning experience for me. and actually, I quite enjoyed painting on that fiberglass surprisingly enough. Very satisfying actually! hopefully next time it’ll be both enjoyable and a great smooth outcome.

I’ll come back and update this thread after I try smoothing the tubes, and report how that goes.

 

[Ez2cDave]

why don't you just start using fiberglass tubing?

 

[boatgeek]

I'd just sand the wrinkles to make them smooth enough. For filling the weave of the cloth, a couple of coats of a pancake-batter-consistency mix of epoxy and microballoons works well, applied with a squeegee to get into as many crevices as possible. Sand lightly between coats to take off the high spots without cutting into the glass too much and coat with a clear epoxy (or just filler-primer) to fill pinholes when you're all done.

I've found using a grooved roller (like these, widely available elsewhere too) really helps with pushing the glass down to the surface to eliminate bubbles. I also like to use a perforated ply or peel ply on the first cure. They don't squeeze the tube as much as heat shrink, but I've had reasonable luck getting a nice surface without a lot of sanding as long as you're careful to pull out wrinkles before the epoxy sets. If you use peel ply, you'll need to roller on a thin layer of clear epoxy to fill surface roughness before you move on to other finishing.

 

[kjhambrick]

I'd just sand the wrinkles to make them smooth enough. For filling the weave of the cloth, a couple of coats of a pancake-batter-consistency mix of epoxy and microballoons works well, applied with a squeegee to get into as many crevices as possible. Sand lightly between coats to take off the high spots without cutting into the glass too much and coat with a clear epoxy (or just filler-primer) to fill pinholes when you're all done.

I've found using a grooved roller (like these, widely available elsewhere too) really helps with pushing the glass down to the surface to eliminate bubbles. I also like to use a perforated ply or peel ply on the first cure. They don't squeeze the tube as much as heat shrink, but I've had reasonable luck getting a nice surface without a lot of sanding as long as you're careful to pull out wrinkles before the epoxy sets. If you use peel ply, you'll need to roller on a thin layer of clear epoxy to fill surface roughness before you move on to other finishing.

boatgeek --

I REALLY like those grooved aluminum rollers.

Do you have a favorite diameter / length wrt airframe diameter ?

Do you try to clean and reuse them or are they disposable ?

Thanks !

-- kjh

 

[Hobie1dog]

View attachment 586420

But how much of the precious remaining time left in your life do you want to spend trying to reinforce an inferior product to start with? So you have to go out and gather up costly materials like fiberglass cloth, resin, tools, etc. along with exposing yourself to hazardous chemicals, and cleaning up a big mess. I don't get it

 

[tfish]

But how much of the precious remaining time left in your life do you want to spend trying to reinforce an inferior product to start with? So you have to go out and gather up costly materials like fiberglass cloth, resin, tools, etc. along with exposing yourself to hazardous chemicals, and cleaning up a big mess. I don't get it

Yes. Your emoji says it all.
You just don't get it.

Tony

 

[boatgeek]

boatgeek --

I REALLY like those grooved aluminum rollers.

Do you have a favorite diameter / length wrt airframe diameter ?

Do you try to clean and reuse them or are they disposable ?

Thanks !

-- kjh

I use one that's around 1" diameter (OD of grooves) and 4" long. That's fine for all kinds of airframe work where you're rollering the outside of the tube. If you were doing small inside corners you might want a smaller one.

I clean and re-use. They'd get expensive as disposable items. After many times trying to clean them up enough with solvents while the epoxy was still hard, I just settled on setting the roller on parchment paper or wax paper when I'm done for the day. The epoxy in the grooves settles down ont eh hard surface below. Then I come back later and chip the epoxy out of the grooves with a hammer and a center punch. You have to hold the roller in place with a pair of vise grips, but otherwise it goes pretty quickly. I think it usually takes 5-10 minutes, which is less time than fiddling with solvents. Use eye protection--the epoxy shards can go all over.

 

[kjhambrick]

Thanks @boatgeek !

I will either wrap an Apogee BT-55 with a layer or two of glass or I might trim-and-stuff-and-glue a 34-inch Totally Tubular Coupler inside the 18-inch BT-55 tube ... I've not decided yet ... I need to check my masses.

I am leaning toward the glass -- I've not done any for 25 years or so and this is an opportunity to practice a tad.

Thanks again !

-- kjh

EDIT: does epoxy NOT stick to parchment paper ?

That would be good to know for next time !

 

[boatgeek]

EDIT: does epoxy NOT stick to parchment paper ?

That would be good to know for next time !

Nothing sticks to parchment paper. Epoxy, tape, you name it. That's my go-to mandrel release for rolling tubes since it's relatively readily available in rolls or large sheets.

 

[kjhambrick]

Nothing sticks to parchment paper. Epoxy, tape, you name it. That's my go-to mandrel release for rolling tubes since it's relatively readily available in rolls or large sheets.

Yes !

My wife, Steph keeps a metric ton of the stuff in the pantry ... Waxed Paper ... not so much ...

THANK YOU FOR THAT INFO

-- kjh( the more I hide my small purchases, the more motors and electronics I can 'explain' )

 

[tfish]

-- kjh( the more I hide my small purchases, the more motors and electronics I can 'explain' )

I remember those years...

Tony

 

[boatgeek]

Yes !

My wife, Steph keeps a metric ton of the stuff in the pantry ... Waxed Paper ... not so much ...

THANK YOU FOR THAT INFO

-- kjh( the more I hide my small purchases, the more motors and electronics I can 'explain' )

About 12 hours after I made a motor order (for me and next year's TARC team), the bank called my wife and asked if it was a fraudulent purchase and could she confirm amounts.

To be fair, she did know I was making an annual motor order, and she's fairly well clued into what that means in terms of dollars spent.

 

[OzHybrid]

Rocketry falls into several camps. Buy a Kit, Fly it High, Fly it Fast, Make it Pretty. Make it Weird. Build it from Scrap. Make all the Bits from Scratch. and a few others.

Making your own tubes is a lot of fun once you get through the fear of stuffing up.

Any tube has to be fit for purpose. Strong enough to survive the flight profile you intend to use it for. Light enough to be able to fly.
Glassed cardboard gives you an easily accessible former to use rather than having to get a fiberglass tube off a mandrel.
It has its place as a tube. The FG tubes you can buy are usually much stronger than you actually require for a safe flight. So they are too heavy. So there's a potential weight saving from making your own tube.

There are many weaves and weights of fiberglass cloth available that could give you a better strength to weight property with a finer weave/ lighter cloth. Buy some small samples and have a play. Using the sock technique will give you an initially coarse result that will have to be refined by sanding.
Unless you plan to fly to M2(where the heating from surface imperfections starts to get ugly), don't worry too much about small holes. Filling them with epoxy will add little strength, but significant weight relatively. It's the glass that gives you strength. The epoxy or polyester resin is just there to lock the glass in place.
Good luck on your adventure.

Wear a mask. Don't stand on the wet epoxy on the floor and walk through the house....

 

[kjhambrick]

Rocketry falls into several camps. [Snip] ...
Wear a mask. Don't stand on the wet epoxy on the floor and walk through the house....

Boy howdy, @RocketScientistAustralia, I'm not sure there's room to build rockets in the doghouse

-- kjh

 

[PSLimo]

The method that works for me to fill in heavy weaves is to stretch pantyhose over the tube and wet it out with epoxy. The pantyhose will hold the epoxy and fill all the grooves leaving you with an easy to filler primer / sand to a smooth tube.

Phil

 

[tfish]

Rocketry falls into several camps. Buy a Kit, Fly it High, Fly it Fast, Make it Pretty. Make it Weird. Build it from Scrap. Make all the Bits from Scratch. and a few others.

Making your own tubes is a lot of fun once you get through the fear of stuffing up.

Any tube has to be fit for purpose. Strong enough to survive the flight profile you intend to use it for. Light enough to be able to fly.
Glassed cardboard gives you an easily accessible former to use rather than having to get a fiberglass tube off a mandrel.
It has its place as a tube. The FG tubes you can buy are usually much stronger than you actually require for a safe flight. So they are too heavy. So there's a potential weight saving from making your own tube.

There are many weaves and weights of fiberglass cloth available that could give you a better strength to weight property with a finer weave/ lighter cloth. Buy some small samples and have a play. Using the sock technique will give you an initially coarse result that will have to be refined by sanding.
Unless you plan to fly to M2(where the heating from surface imperfections starts to get ugly), don't worry too much about small holes. Filling them with epoxy will add little strength, but significant weight relatively. It's the glass that gives you strength. The epoxy or polyester resin is just there to lock the glass in place.
Good luck on your adventure.

Wear a mask. Don't stand on the wet epoxy on the floor and walk through the house....

How strong are homemade (hand layed, not vaccumed, 'boat epoxy') FG body tubes ..gets asked all the time. 10+ years ago I set out to show how fast, hard and how high you could 'send it'...There are a bunch of your tube video on the build n and a thread here...

https://www.rocketryforum.com/threads/my-next-project.19534/
To cut to the chase...just under mach 2 and just shy of 35K for the first flight ...


Tony

 

[OzHybrid]

How strong are homemade (hand layed, not vaccumed, 'boat epoxy') FG body tubes ..gets asked all the time. 10+ years ago I set out to show how fast, hard and how high you could 'send it'...There are a bunch of your tube video on the build n and a thread here...

https://www.rocketryforum.com/threads/my-next-project.19534/
To cut to the chase...just under mach 2 and just shy of 35K for the first flight ...


Tony

What weight and weave do you use?

 

[tfish]

What weight and weave do you use?

post #8
https://www.rocketryforum.com/threads/my-next-project.19534/post-174464
the above post link describes all the details..

Tony

 

[OzHybrid]

post #8
https://www.rocketryforum.com/threads/my-next-project.19534/post-174464
the above post link describes all the details..

Tony

link for FG goes to 404 not found. @tfish

 

[tfish]

link for FG goes to 404 not found.

this is a 12 year old thread/project..lots of the links probably won't work..might take some research to figure it out.

I'm mentoring a kid and we layed up a 3" tube and used Tap plastics Boat C https://www.tapplastics.com/product/fiberglass/fiberglass_fabrics/boat_c_lightweight_7533/81

we went with 8 layers (40" long by 84" wide) 7 layers would have worked better. plenty strong for the 54mm motor mount and video camera flights...part of a local University program and NASA grant.

Tony

 

[tsmith1315]

Do you try to clean and reuse them or are they disposable ?

After many times trying to clean them up enough with solvents while the epoxy was still hard, I just settled on setting the roller on parchment paper or wax paper when I'm done for the day. The epoxy in the grooves settles down ont eh hard surface below.

We used to clean polyester resin from rollers in a pan of acetone. It took a few minutes, but left them clean. My father used two rollers on a fairly regular basis for years without replacing them. Epoxy might be more trouble.

 

[OzHybrid]

this is a 12 year old thread/project..lots of the links probably won't work..might take some research to figure it out.

I'm mentoring a kid and we layed up a 3" tube and used Tap plastics Boat C https://www.tapplastics.com/product/fiberglass/fiberglass_fabrics/boat_c_lightweight_7533/81

we went with 8 layers (40" long by 84" wide) 7 layers would have worked better. plenty strong for the 54mm motor mount and video camera flights...part of a local University program and NASA grant.

Tony

Any reason you're not using S type FG to get the higher strength to weight ratio?