Fiberglass questions

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Dec 1, 2009
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I plan on fiberglassing my next rocket which will be the LOC magnum. I figure I will need 3 yards of 50" 4oz cloth. How much resin and hardener do I need and which one? I think I will only be doing one layer.

The first thing I'll say is, you don't need to fiberglass that rocket to fly it on the recommended motors. Even going up to one of the 54mm L motors shouldn't need glass.

The second thing I'll say is, go for it. Glassing tubes is a lot easier then I thought it would be. I would put a double layer on right away. I used the US Composites 635 Thin Epoxy with 3:1 Medium Hardener. A Quart of resin with the hardener, P/N EPOX-635312 $20.75, should be more then enough. It shouldn't take more then half the quart of resin.

You can use the remaining clothe for tip to tip on the fins and if you mix the epoxy with alcohol, you can soak the insides of the tubes to harden them too, it's cheaper then using CA on the ends of the tubes.

Let us know how it turns out.
You can use polyehster resin or epoxy. I like west epoxy. As for how much, the ideal ratio is 50/50 glass to resin/epoxy by weight. As this is your first layup you will probabily be a little resin rich. Don't sweat it if you are, for this aplication it won't hurt.
good luck.
A Loc Magnum will fly on L's without any problem & can even take most M's
I know people that have done this....

You're just adding weight unless you plan on 3+ layers of fiberglass.
If you choose to do so; go for a 3" motor mount because the added weight will require bigger motors.

A Bruiser really needs a 3" MM as well & needs at least a large K to get it going.

I've built 2 Magnums; one mostly stock & the second one was more of a clone with allot of upgrades: larger fins, 6 outboards, & larger payload section & all I did for that one was to peel away the glasine coating & apply epoxy then sand smooth. I flew the second one on K 700's & various clusters involving K 1100's.

Polyester resin is a real pain to work with. I tried it once or twice & it is hard just to get the mix ratio right.

It's better to do 2 layers at once.

In order to get a balanced resin to cloth ration you really need to vacuum bag the tubes. Which requires allot more prep work.

I'd buy the gallon kit & usually start out with about 6 pumps of each; hardener & resin. If I need more I'll mix up another batch.


You can use polyehster resin or epoxy. I like west epoxy. As for how much, the ideal ratio is 50/50 glass to resin/epoxy by weight. As this is your first layup you will probabily be a little resin rich. Don't sweat it if you are, for this aplication it won't hurt.
good luck.
I use West Systems Epoxy, Also 1 layup of 4-6Oz fiberglass will be PLENTY! Before you glass the LOC tube though either peel the glasine off the tube or sand the crap out of it with like 80 grit sandpaper.
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The ideal glass to resin ratio for maximum strength is generally 60% glass and 40% resin. Most of us end up closer to 50-50. The "weight" given for glass cloth is ounces per square yard, so if you figure out how many square yards of cloth you are going to use, you can figure out how much resin you need. I'd get as much resin as the weight of the cloth because you're going to have to apply extra resin and then remove the excess to make sure everything is wet out.

To get the glass firmly against the body tube and to remove excess resin, a vacuum bagging technique is commonly used. First, you have to plug the ends of the airframe with something so the vacuum bag doesn't get sucked in and pop. Ask me how I know that... Spare nose cones work or make up some plugs from circles of wood bolted together. Whatever you use, cover it with plastic wrap so it doesn't get epoxied into the ends of the airframe.

The glass and resin are applied to the rocket, pulling the glass tight to avoid wrinkles. I use a small foam trim roller (Home Depot paint aisle) to apply the epoxy. It pushes the cloth down and does not distort the weave. Next, a peel ply (typically dacron treated so epoxy won't bond to it) is wrapped around the glassed tube followed by one or more layers of "breather" which is loose cotton felt. All this is slipped into a plastic bag, the ends of the bag are sealed, and a vacuum pump connected. Then you spend a while chasing leaks.

There's a variation where you wrap a heat-shrinking tape around the layup instead of using a vacuum bag. I did a variation on that where I wrapped the layup with Monokote (heat sensitive plastic covering for RC airplanes) and shrunk it with a heat gun. You won't get quite the pressure with either of these, so you won't get as much excess resin pulled out, but you don't have to invest in a vacuum pump.
As others have said, you don't need to fiberglass it. But you can, if you want to.

You can fiberglass without compression material, but you will use more resin, and thus add more weight. That can be alleviated by vaccuum bagging (which requires a lot of equipment investment), or using shrink tape (you can shrink it with a heat gun, if you don't have an oven, though it's time consuming and you won't get as much compression.).

If you go the shrink tape route, don't use West Systems Epoxy, especially if you use a curing oven -- shrink tape requires a temperature somewhere in the 150 - 160 range to begin to shrink, and West Systems Epoxy begins to break down if exposed to 120F for very long.

No matter what you do, if you're going to apply heat, be aware of the affects of temperature on the epoxy you're using, and what its limits are. Some epoxies don't like to go above about 180F, and with shrink tape, you get maximum compression at around 180 - 190F.

You can do "poor man's shrink tape" using basket wrap from a craft store with a hair dryer. Just apply wax to the basket wrap before you put it over the epoxy, or you'll never get it off. Been there, done that, have the Merit Badge. :rolleyes:

Thank you for all the good advice. I do not plan on vacuum bagging or heat shrinking. Just rolling it on. As for the reason I plan on fiberglassing is to with stand the damage on landing. For my level 1 flight, my rocket landing on a dirt road, the end of the booster section bounced and put a dent on the top of the tube. I bent it back easily but it kind of hurt my pride.

Thank you
another opinion...

Look at braids, they can be applied by hand, end up with a good laminate and wont need to be tape wrapped or vacuum bagged. Realistically, you will end up with around 40-50 percent fiber BY VOLUME, be careful, many people use fiber by weight not by volume.

A couple of important notes, best to get the resin working up from BELOW, for your tube brush on the resin directly to the part, remove the outer layer of the tube before hand (don't bond to shiny stuff). You can work the resin into the braid using your hand (yes gloves) using the space between the thumb and finger as a squeegee.

If you haven't done wet layup, figure you will throw away as much resin as you use on a small project.

Lots of techniques you can use (I work on aircraft composites as the day job), epoxy and braid are simple with good results.

Another suggestion for West System's epoxy. The 105/205 Resin/hardener is just great. Check it out at Soller CompositesThe 'kits' come with metering pumps so you get a precise mix. Jon the owner is greatand will answer any questions..

Also check out their fiberglass or carbon fiber sleeving and heat shrink tubing..makes layup easy and fairly painless.