Kaos Rulz

Anyone know the pro's and con's of using fiberglass rosin vs epoxy when reinforcing a wing's center section using fiberglass cloth?

ED

pinball-RCU

I may be wrong, but my understanding is that there are two types of what I think you're calling "fiberglass resin": 1) epoxy based resin, and 2) polyester-based resin.

I personally think the epoxy-based resin is great stuff, and that's what I use. It is somewhat pricey, about $30 per quart, and it's a little hard to find in smaller quantities (although Great Planes now sells it). On the other hand, polyester resin is very easy to find since it's used on boats and car bodies, and it's a bit cheaper than epoxy. I've never used it because I've heard folks question its fuel proofness, so I figure why take a chance? On the other hand, if you're going to cover it anyway, it would work fine.

The nice thing about epoxy resin (which is why I use it) is that everyone agrees it's very fuel proof, so you can use the same stuff to paint the engine compartment and the tank area, as well as glass the wing.

Lastly, I'm not sure if you're referring to plain old epoxy, but a lot of folks take regular old 30 minute epoxy and thin it with alcohol or acetone or use heat to thin it out, methods which I think are a bit risky, but others swear by.

DMyer

My Feedback: (2)

I have used both for many years without any failures from either.


Pros

Polyester resin -

Cheap
Can control cure rate by varying amount of catalyst used
lighter


Epoxy

Very user friendly - very little smell
Very Strong

Cons

Polyester resin -

Stinks to high heaven
Will not cure over epoxy
Can become brittle if too much catalyst used

Epoxy

Heavier
Much more expensive for a good resin(West Systems)

I only use epoxy these days... I have not used Polyester Resin in over ten years.


Good luck.

BlackBart

Ed-
polyester resin IS fuel proof. Iv'e worked with it for the better
part of 40 years on boats, with alot of pretty potent fuels. Look
at r/c boating with their high nitro content fuels!! But, I prefer
epoxy because it is stronger. As far as cost, you know how the
saying goes, " My wife says, You better find a cheaper hobby
or i'm leaving you! I'm sure gonna miss her."

Bruce L Prater

The other concern with polyester resins is it is flamable and can even start burning if too much catalyst is put in the resin.

BlackBart

A-MEN to that Bruce!!!!!!!!!!!!!!!!!! Polyester resin burns like
there's no tomorrow. When it's done burning, all that's left is
the complete FIBERGLASS CLOTH MATERIAL outline of the boat, (and the aluminum puddle in the back that used to be a 60hp Evinrude. Don't ask how I know this.)as only the resin burns. As you said, kick it too much and it'll go off in the can, bucket, or
whatever. If in doubt, go light on the M.E.K., it may take longer
to go off, but go off it will. If left long enough, ONE DROP of
catalyst will kick off a comlete 55 gal. drum of resin. In can be
some nasty stuff if you aren't carefull. NEVER EVER pour left-
over resin, (that's been catalized) back into the main batch.
Sorry about this ramblin' on. I tend to get carried away with
a subject. It's just my $4.27 worth.

Kaos Rulz

Thanks for the good info folks,

I din't know that fiberglass was poly or epoxy. I've always used the poly to fuel proof engine and fuel compartments, as well as glass wings, however, I'm not always thrilled with the way monocoat sticks to it. Is the heating of 2-part epoxy dangerous due to fumes or flare-up, or both? Is Pacer's "Z-Poxy" epoxy based fiberglass, or epoxy?

Thanks again for helping me out,

ED

Steve Lewin

Fibreglass is just that, glass. It's the resin used with it that is either polyester or epoxy. Z-poxy is epoxy.

BTW another pro/con. Epoxy resin can be used direct on polystyrene foams. Polyester resin destroys foam. If you're glassing sheeted foam wings with polyester resin make very sure that the sheeting is sealed ).

Steve

monocoupe

My Feedback: (40)

Pacer "Z-poxy" is as the name implies, an epoxy resin. It can be used in place of polyester resin. I only use epoxy resins these days, unless I'm making molds that require a lot os resin, then I'll use polyester because it's cheaper. I have been using Z-poxy for surface finishing with .6 oz. cloth, as well as for laying up fiberglass parts like cowls etc.
As for getting Monocoat to stick to the resin surface: Most polyester resins have wax in them which forms a film on the sufrace of the resin, which seals the resin from the air, and allows it to cure. this waxy surface must be removed with solvent/sandpaper before putting anything on top of it. Epoxy resins do not have wax in them, but should still be sanded and cleaned with solvent prior to painting, or re-coating, or applying monokote. What I do when I have to get Monokote to stick to cured resin, is clean & sand the area to be covered, then brush on a coat of Balsarite. You'll find that the Monokote will stick much better....you may need to use a little more heat than normal in these areas as well.
I hope this is of some help to you...good luck!

Cheers, Nigel