Good Day, all... While in Home Depot today, I ran across some 'Bondo' All-Purpose Fiberglass Resin for $15 per quart. I have never attempted to glass anything before, except for the center section of a wing. Is this good stuff or should I keep on looking??? What are your thoughts or opinions??? Thanks in advance for all of the info...

DF

....it will work fine, it is a general purpose laminating resin. It is good for repairs
or new lay-up....I have used it.

FBD.

Though it's unlikely to be an issue, I'd just like to remind everyone that when cured polyester resins, unlike epoxy, are not waterproof. No, it doesn't disolve in water, but when boat builders use it, the gelcoat, not the fiberglass layup, is the hull's sealer.

First of all I do not use polyester resin at all. Hardware store polyester has all sorts of additives to preserve shelf life. There is no consistancy or repeatable quality. Polyester stinks the house out. The hardener is very dangerous and should not be allowed in a domestic house. Most polyester will not cure over epoxy glues. They might cure over 5 minute epoxy but even that is unpredictable.

Use epoxy resin only for constistant results.

Ed S

Not that I know (that's why I ask), in the picture you can see the can states "water proof repairs". Perhaps this stuff is not polyester?

Then leave it alone. for your small usage Purchase "West Systems" epoxy resin or "Z-poxy" finishing resin from the local hobby store.

Ed S

I've not worked with polyester myself, as I use West Systems, but there are a lot of champion scale builders who do. One of the advantages often mentioned is ease of sanding, the other is cost. With Polyester, the glass is applied much like epoxy, with the glass being whetted out on the balsa, then excess being squeegeed off. But often a second thicker wet coat is added to fill the weave of the glass and then sanded smooth. It would be a lot of work to try doing that with epoxy as it is much harder to sand. Odor is another issue. Polyester resin has a strong odor and needs very good ventilation. If you want to see the process, get the Building and Fiberglassing series of videos from Dave Platts Black Art series. These are good videos even if you choose to use epoxy.

Scott

Right on, Scott....[sm=thumbup.gif]

The West epoxy systems are great, but they are designed for marine applications, where a few
or several different materials are bonded together, ending up with a finished product all done
at once....nothing wrong with that. The epoxy resins are more water proof and long lasting than
the polyester resins in marine applications as well....nothing wrong with that either. Epoxy is very
difficult to sand.

However, for "glassing" a wing or a fuselage, common polyester resin is the way to go. The regular
(polyester) resin is readily available, and not expensive. The thinner is acetone, again readily
available and cheap. The catalyst....MEK is not problematic, but like just about anything else it must
be used in a well ventilated area.....like outside or in the garage with ventilation.

Once the initial glass job is completed and squeegeed dry it is allowed to set up completely. Then a
second coat of resin is applied to fill the weave....this is "sanding resin." This finish coat is real easy
to sand....it is designed that way. Then simply prime, sand, and paint for a nice finish. Most of the
resin gets sanded away, and the weight is reduced.

A gentleman by the name Joe Bridi advised me of this process. It works well, and is easy to do.

Don't worry about the "wax" in the sanding resin, it's not regular wax, and it doesn't keep primer
or paint from sticking.

FBD.

It's all "Horses for Courses"
Polyesters cure fast, are easier to sand but shrink more whilst curing (Typically 3 - 5% by volume) and often have some porosity issues (mainly due to application techniques)

Epoxies have all sorts of cure regimes, have lower shrinkage (Typically 1 - 3% by volume) and are harder to sand.

Polyesters generally will not bond well to epoxies and they tend to smell more as they cure.

Make no mistake - the hardeners for both are especially nasty. MEKP (Methyl Ethyl Ketone Peroxide) is used to cure Polyesters and is a particularly awful chemical - It will permeate through tissue layers and kill tissue such as skin and fat layers.
Many epoxies that we use use polyamines as a hardening agent - they are almost as toxic as MEKP, just not as fluid.

Caution should be used when handling either products.