Fiberglass Sealant recommendations?

DON · October 28, 2017, 11:49 AM

Anyone have suggestions as to what to use to seal coach fiberglass. Fiberglass down to hairs of fiberglass. Want to seal to save for future paintjob. Thanks.

Oz · October 28, 2017, 12:01 PM

I worked a couple years in fiberglass molding, layup, and finishing for trains and heavy construction equipment.

Before the actual fiberglass is sprayed, the mold or flat panel is "painted" with gelcoat. After it's dry, the fiberglass is then sprayed on top of it. Typically, the thickness of the gelcoat would be 3mm thick but could vary up to 5mm for heavier applications.

However, I'm sure there are alternatives which would be less expensive, more readily available, and work just as well. I'm thinking Bondo body filler since it's hard and durable and can be painted.

Also, fiberglass patch/filler. It works the same as Bondo but is specifically made for fiberglass use. I've used it several times and when it dries, it's even harder than Bondo. Prep and paint as you would with Bondo.

CapnDirk · October 28, 2017, 03:37 PM

Brush some catalyzed fiberglass resin on the area to strengthen and bond the fiberglass fibers. Then you can spray on the gelcoat (available at marine supply stores). Skuff the area around the patch to clean and provide a bond for everything. Bondo will work and is fiberglass resign with catalyst, but i would put a catalyzed (two part) primer over it.

Oz · October 28, 2017, 05:23 PM

Great tip, CapnDirk!

The resin is a good alternative, depending on how deep the area is you need to fill. If it's shallow, maybe up to @ 1/8", the resin is good. Remember, it is thick, but it's basically a thick liquid and can sag like when you put on a layer of paint too thick, especially if you don't put in enough catalyst. On the other hand, too much catalyst and it will begin to harden too soon. So, the amount of catalyst and timing of application is critical to do it without getting the sag and before it hardens too much to apply smoothly.
Practice with it first to get the hang of it.

The fiberglass filler is a good option if the depth of the area to fill is greater than 1/8", I'ts more of a pasty solid, like Bondo, and gives you a bit more flexibility since you can add less hardener, giving you more time to apply and work it to the desired fill before hardening. Again, practice with it first.

Rickf1985 · October 28, 2017, 06:14 PM

There is a product I have user for years in rotted wood and also as a wood preservative. It is wood based epoxy resin so it does not get rock hard, it always has a little "give" to it. Perfect for working on RV's. The produce I am thinking about for what he is looking to do is called CPES and has the constancy of diesel fuel. It is a two part resin and mixes 50/50.
Do a search for Rot Doctor. They are located in Washington State. I have dealt with them foe many years. They have an entire line of products to do any type of repair you need. One caveat, Wood based epoxy is a it more expensive than polyester epoxy for the main reason that it is a better product. You get what you pay for. I figure that I don't particularly like working with resin so do it right and don't have to do it again.

Sorry if it sounds like a plug for them but when I find something that works I push it.

Warren · October 28, 2017, 09:42 PM

X2 what Rick said.
http://www.smithandcompany.org/CPES/

The CPES is an excellent product. Highly recommend.

Rickf1985 · October 29, 2017, 10:12 AM

Interesting, I was not aware of two places selling it. I wonder if they are related?

DON · October 29, 2017, 10:55 AM

Thanks to everyone for the info. This is not a "spot", but most of the exterior of the rv. Been sitting outside in the El Paso sun for years. Just trying to postpone complete paint job.

Rickf1985 · October 29, 2017, 08:27 PM

Well, The CPES would be a good product for sealing that up. Try a small spot to get a feel for it and then go for the rest of it. This stuff does not set up fast like a lot of epoxies, it is designed to have a slow setup time so that it fully absorbs into rotted wood and such before setting up. Once the solvents evaporate out then it catalyses. I am not sure how it would work on the vertical surfaces though. I would call either of the companies and ask. I sent e-mails to both and it is the same product with Smith being the manufacturer. Rot Doctor does carry more in the line of fiberglass repair products.

Warren · October 29, 2017, 10:55 PM

Looks like this company likes questions. I would encourage you to call them and discuss your situation.

Keep us posted on how it all works out.

http://www.epoxyproducts.com/penetrating4u.html

Rickf1985 · October 30, 2017, 08:56 AM

Well, Right on their home page they make this statement.

"Don't be fooled by amazing claims. Penetrating epoxies are much less than they claim to be."

That statement right there turns me off to that place because I have been using CPES for 20 plus years with great results. You are not going to resurrect a totally rotted out piece of wood with it but if the wood is only partially rotted or dry rotted this material works great. You can call them but I would be sure to call Smiths or Rot Doctor also and get both sides of the story. Just for the hell of it I am going to call this place and ask why they make this claim against the CPES when I for one have had so much success with it and I can name at least ten others who have had equal success. I am curious to see if they are as friendly as they say they are or if they just hang up on me.