# Glassing a built rocket

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#### billdz

##### Well-Known Member
I have seen a few videos about glassing airframes and fins prior to construction of a rocket, but have not seen any about adding fiberglass to the fins and body of a pre-constructed, painted cardboard and wood rocket. It seems straightforward (apply epoxy, press on fiberglass cloth, squeegee off the excess) but I'm sure there are fine points that need further details. Can someone please point me to a video or tutorial?
Thanks,
Bill

#### cavecentral

##### Well-Known Member
I'd take off any buttons or lugs. Then glass the body above fins. Then tip to tip on fin can.

#### billdz

##### Well-Known Member
Thanks for the replies. I had forgotten about the buttons and lugs, they do need to be removed. The videos were helpful but I still have questions, are there any other sources of info? For example, do we use regular epoxy or something special for fiberglass (in the store, there was "fiberglass resin" for sale next to the cloth)? Are there any alternatives to peel ply (someone suggested wax paper)? Does the first layer have to dry before the second is applied?

#### timbucktoo

##### Well-Known Member
Staff member
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Global Mod
Tony's videos are pretty thorough. What I have done is put on two 6 oz. layers followed by a 3 oz. layer followed by peel ply all in one setting. What you are trying to accomplish really dictates how much glass you add. I was only re-enforcing a tube. Some people use mylar film instead of peel ply.
Many use West Sytems 105/205 or US Composite 635 resin with 3:1 hardener. US Composites sells glass cloth too & they are in West Palm Beach.

https://www.uscomposites.com/

#### ActingLikeAKid

##### Well-Known Member
Thanks for the replies. I had forgotten about the buttons and lugs, they do need to be removed. The videos were helpful but I still have questions, are there any other sources of info? For example, do we use regular epoxy or something special for fiberglass (in the store, there was "fiberglass resin" for sale next to the cloth)? Are there any alternatives to peel ply (someone suggested wax paper)? Does the first layer have to dry before the second is applied?
I can answer these, as I was very recently a glassing novice. Well, I'm still a novice but now I'm a novice who's done it once
1. Yes, you 100% need a different epoxy. The epoxy you use to build (whether it's the cheapo 5-minute stuff from Lowe's or Rocketpoxy or whatever) is "structural" epoxy. It's for gluing things together. What you want is "laminating" epoxy. It's much thinner and can be painted on (whereas structural epoxy is very very thick). As Timbucktoo says below, you can get good stuff from US Composites.
2. If you're shopping at a marine supply store, the resin and hardener may be appropriate. If you're in the Bondo section of Lowe's or Walmart ...just don't. I believe Bondo uses a polyester resin and you'll NEED a respirator for that. US Composites epoxy (you'll need resin and hardener) is good stuff.
3. You don't "need" the peel ply or mylar unless you're vacuum bagging. They will help you get a smoother finish, but in my experience, they can add some challenge to glassing for a first-timer (like me. Huge mess. Didn't go well). If you don't use them, be prepared to sand.
4. WEAR A MASK AND GOGGLES WHEN YOU SAND. You'll need to sand quite a bit to get things nice and silky smooth (and probably fill in some stuff too. The dust from sanding fiberglass is bad stuff. Get AT LEAST a fiberglass-rated mask, ideally a proper respirator. And eye protection.
5. You'll either need to let the first layer cure completely before adding a second layer OR put them both on at the same time.
6. I would HIGHLY recommend doing some practice. For your first attempt, get a piece of scrap wood. Mix resin and hardener, paint it on the wood. Put glass on the wood. Paint more epoxy over it. Smooth it out. Check for air bubbles. Look in direct sunlight. REALLY look. Let dry. For your second...what I did was take some scrap tubing and balsa and make a fake little fincan, then glassed it. I learned a LOT. Having nice big fillets helps a ton, because there's less of a crevice to poke the glass into at the fin/body junction, if that makes sense.
7. I don't know why I numbered this list.
8. What would probably be simplest for this project would be glassing the body tube down to the fin can, letting it dry, then glassing tip-to-tip on the fin can, with the top of those layers overlapping what you did in the previous round. There are some great videos on how to do this. Are you going to glass the nose cone? Having done this, I'd say that unless there's some specific reason to do it, I'd DEFINITELY go with buying a commercially-available nose cone. Glassing a nose-cone is hard and messy and REALLY challenging to get pretty results.

Hope this helps.

#### billdz

##### Well-Known Member
Great info, thanks much. I actually was in the Bondo section of Walmart yesterday, thanks for steering me away.

I suppose there are different techniques for doing this. This video:
was interesting, although it does not specifically involve rockets. Unlike Tony, who first put epoxy on the rocket then laid the fiberglass over it, this guy put down the fiberglass first, then applied epoxy. He also dilutes the epoxy with alcohol to make it like water. He didn't wear gloves.

I assume I need to sand down the existing paint on the rocket before applying the glass? And wax paper is not an adequate substitute for peel ply or mylar?

#### timbucktoo

##### Well-Known Member
Staff member
TRF Supporter
Global Mod
Putting resin down first will help keep the glass cloth from sliding off. I tried it both ways and found resin 1st is the way to go.
Make a practice run on some scrap tube first. It is a lot easier than I thought!

#### BDB

##### Absent Minded Professor
I have been learning how to glass rockets over the past 6 months, and it is not as bad as I thought, though it does take some practice. Here's a link to three of my threads on my learning process. (Three posts on the topic means I probably obsess too much about this stuff.)

https://www.rocketryforum.com/showthread.php?136266-Glassing-my-first-tube/ (post #33 is the list of materials that I ordered)

The best advice I got through the process was "Go for it!" I'm far from an expert, but I like doing it now. I'm planning to glass my first fincan on a built rocket this weekend.

#### Steve Shannon

##### Well-Known Member
TRF Supporter
ActingLikeaKid's post should be framed.

I would only add this, referring to his bullet point 5 (which perhaps explains 7 as well):
It's easy to wind two layers onto a body tube in one go, especially if you're not vacuuming. It will cure nicely as long as you go slowly. Dave Triano put out a set of videos (on VHS it was so long ago) that showed a very good technique. TFish38 has the best videos on YouTube for this now.
It's possible to put down one layer and put another layer on later. According to West Systems if you apply the second (or third, fourth, etc.) within 24 hours the epoxy will actually cross-link with the previous epoxy, resulting in the best bond between layers. If you wait until after it has completely cured then the most you can hope for is a mechanical bond between layers.
Most laminating epoxy has a "leather" stage, where it is still slightly soft. That's when I would apply an additional layer, especially if I wanted to vacuum bag.

Steve Shannon

#### ActingLikeAKid

##### Well-Known Member
Great info, thanks much. I actually was in the Bondo section of Walmart yesterday, thanks for steering me away.

I suppose there are different techniques for doing this. This video: (snip) was interesting, although it does not specifically involve rockets. Unlike Tony, who first put epoxy on the rocket then laid the fiberglass over it, this guy put down the fiberglass first, then applied epoxy. He also dilutes the epoxy with alcohol to make it like water. He didn't wear gloves.
I was going to recommend exactly that video. As Timbucktoo just said, painting resin on first helps the glass stick and I had a lot of success with that. I did resin - glass - more resin - squeegee/wipe and it worked great.
Wear gloves. Epoxy is less dangerous than polyester but it's still not something you want on yourself. People who work with it unprotected can develop a severe reaction to it (to the point that they can't work with it any more). A box of nitrile gloves is like $7 for 100 at Walmart. Just get the gloves and wear them. And if you end up with epoxy where it shouldn't be, alcohol works great to take it off. I used isopropyl but denatured alcohol is even better, I think. I also thinned my resin like the guy you posted (using 90% isopropyl) and it worked great. I assume I need to sand down the existing paint on the rocket before applying the glass? And wax paper is not an adequate substitute for peel ply or mylar? Yes and yes. Longer version: Sand off the paint if you can. Wipe everything down with a tack cloth or damp rag. Unlike with paint (where you want a mostly-smooth surface with just enough roughness for the paint to stick) you want a nicely roughed-up surface for the glass to stick to - it'll cover up any roughness. I went over the pieces I was glassing with 100 grit, I think. More tips: The guy in the video above uses a razor blade to trim excess fiberglass. That works, but I got impatient on my first practice piece. I said "This feels leathery....i guess?" and started cutting and the glass started coming off. DO NOT try to trim or do anything while the glass is still even remotely sticky. It should feel dry before you start trimming it. I had more success by letting it cure overnight and then sanding the excess away, particularly on the fins. I used pieces that overhung the edges by 1/2" or more, let it cure overnight, then sanded along the edge of the fin, with the sanding block at a 45 degree angle to the fin. The result is that the sanding "cuts" the excess fiberglass off. Go slowly. I don't know if wax paper works, but I know some folks use parchment paper because it will not stick to anything. Again, practice with some scrap and you'll quickly find out what works. I think I would be ready to try using parchment paper if I were doing a flat piece - just layer something hard and smooth, then parchment, then the glassed piece, then more parchment, then something hard and smooth and heavy, then let it cure for 24 hours. But something complex like a built rocket? Yeah, I would spend my time and effort sanding instead of peel-ply-ing. Another trick I figured out: When you do glass your rocket, glass a piece of scrap as well. Doesn't need to be big, just a little piece of wood is fine, but it will work as a tester. Drying times can vary quite a bit with temperature (literally 10 degrees can be the difference between "it's done before supper" and "it's done before bedtime")... and I'd much rather say "This looks dry, let me double check" with a scrap piece than with the rocket. Also - After you've glassed everything, you'll probably want to fill it. Imagine wrapping your rocket in a wet piece of denim. Think of how the surface would feel and look ... not quite ready for paint. The heavier the glass cloth, the more pronounced the cloth texture is. Sanding will help a bit, but you can't really sand off the texture or you're sanding into the cloth and weakening it. There are two ways to address this: -What I did, which is kind of like what they call gel-coating, I think: Once everything's cured and you've sanded off the imperfections, mix up a nice batch of epoxy and paint your rocket with it. It will act like a thick paint that covers up all of that weave. Keep in mind, though, that epoxy is pretty thin and will run. What I did was 4 sessions (which took forever but came out really well) because it's a four-fin rocket... basically paint one side of each set of fins at a time. So if you have a four-fin rocket and you're looking down at it, you have two fin-sides facing north, two fin-sides facing east, and so on. Put the rocket so the north-facing fin sides are horizontal and facing up, then paint them with epoxy. Let cure, rotate 180, paint the other sides. Let cure, rotate 90, paint the up-facing fins. As long as the surface you're painting is flat and horizontal, you're good. One of the things I found when I was doing my test bit was that if I painted on resin and had the rocket horizontal and the fins making an X from the back... all the epoxy runs down and leaves the fins uncovered and the body tube coated with a THICK layer. -What they do in body shops, which is smearing a layer of filler over the glass. This will give you a smoother surface and you can (I think) do the whole rocket in one shot. BUT you'll need to double-check the protective gear (I think it's the evil polyester again) and practice a lot. Also that stuff ain't cheap - I think it was like$30 for a can of the good stuff, and you already have a big jug of epoxy anyway, so that's basically free

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#### soopirV

##### Well-Known Member
Also - After you've glassed everything, you'll probably want to fill it. Imagine wrapping your rocket in a wet piece of denim. Think of how the surface would feel and look ... not quite ready for paint. The heavier the glass cloth, the more pronounced the cloth texture is. Sanding will help a bit, but you can't really sand off the texture or you're sanding into the cloth and weakening it. There are two ways to address this:
-What I did, which is kind of like what they call gel-coating, I think: Once everything's cured and you've sanded off the imperfections, mix up a nice batch of epoxy and paint your rocket with it. It will act like a thick paint that covers up all of that weave. Keep in mind, though, that epoxy is pretty thin and will run. What I did was 4 sessions (which took forever but came out really well) because it's a four-fin rocket... basically paint one side of each set of fins at a time. So if you have a four-fin rocket and you're looking down at it, you have two fin-sides facing north, two fin-sides facing east, and so on. Put the rocket so the north-facing fin sides are horizontal and facing up, then paint them with epoxy. Let cure, rotate 180, paint the other sides. Let cure, rotate 90, paint the up-facing fins. As long as the surface you're painting is flat and horizontal, you're good. One of the things I found when I was doing my test bit was that if I painted on resin and had the rocket horizontal and the fins making an X from the back... all the epoxy runs down and leaves the fins uncovered and the body tube coated with a THICK layer.
-What they do in body shops, which is smearing a layer of filler over the glass. This will give you a smoother surface and you can (I think) do the whole rocket in one shot. BUT you'll need to double-check the protective gear (I think it's the evil polyester again) and practice a lot. Also that stuff ain't cheap - I think it was like \$30 for a can of the good stuff, and you already have a big jug of epoxy anyway, so that's basically free
I'm a novice at this too, but my advice here (worked for me, YMMV!) is to thicken your resin with something that is sandable. I traced the tube radius onto a thin piece of plastic (think it was a lid from a ricotta cheese container, don't remember), and cut it out. i then applied a thick paste of resin mixed with Q-Cells from US Composites. I used the lid to squeegee the paste onto the tube, and let it cure. Thickening made it not run, and the q-cells kept it very sandable. Once that cured and I sanded, I had a few pin holes to contend with that I filled with bondo spot putty.

#### ActingLikeAKid

##### Well-Known Member
ActingLikeaKid's post should be framed.
Thanks!!!!

Slightly off-topic, but I remember hearing about a revolutionary way of teaching physics ...
Basically, students were given a reading in a book, then the next day in class, instead of the professor reviewing the concepts, the students were tasked with answering a dozen or so questions. But it wasn't a quiz and it wasn't open-book. It was "talk to your neighbors and see if their answers agree with yours", in the hopes that if the answers didn't match, the students who had just figured it out could explain to those who didn't get it yet.
The idea was that people who have just learned a basic concept of a complex realm like physics can - sometimes - be better equipped to explain it to someone who doesn't yet get it. From what they were saying, it vastly improved comprehension.
And that was key - it wasn't about improving test scores; before this method, they did a survey of students who had just finished first-year physics and found that while they could answer test questions accurately, they had enormous basic gaps in their knowledge. They'd memorized (for example) a formula but couldn't tell you why that formula worked. Or they understood Concept A and Concept B, but didn't understand that the two concepts could work together to give you Concept C.

All in all, a fascinating idea.

#### billdz

##### Well-Known Member
Is the procedure pretty much the same for carbon fiber cloth instead of fiberglass?

#### ActingLikeAKid

##### Well-Known Member
Is the procedure pretty much the same for carbon fiber cloth instead of fiberglass?
I believe so, yes. Some epoxies play better with CF than others, though. Also CF (as I understand it) does better under vacuum, in which case peel ply and release agent go from "optional" to "mandatory".

I would wait until you've got some glassing experience under your belt before you go trying carbon fiber, though. If for no other reason than CF is both more expensive and (I think!) more challenging to work with. You don't want a messy pile of expensive carbon wrapped around what used to be a cool rocket...

#### Q-Aero

##### Well-Known Member
..... He also dilutes the epoxy with alcohol to make it like water. .
Because he is using the wrong epoxy for laminating , he is using cheap hobby shop 1:1 epoxy. Do not use 1:1 epoxy , and do not thin epoxy with alcohol, if the epoxy need to be thin it's because you are using the wrong type; use laminating epoxy . You only use alcohol to thin the laminating epoxy to apply over the peelply.

Also if someone use West, better get the 206 hardener instead of the 205, it give more working time

#### Q-Aero

##### Well-Known Member
Is the procedure pretty much the same for carbon fiber cloth instead of fiberglass?
Carbon fiber is a pain to work with, it does not come transparent like fiberglass, so it's hard to see if you have dry spot under.