Basic Fiberglass repair

BT · Last edited by BT on Mon Jul 06, 2015 7:27 pm; edited 1 time in total

I scraped the keel of my 1989 22' cruiser on a rock and I'm looking for repair advice. I've attached 2 images. there is probably a total of 15 lineal feet of this type of damage (both sides of the keel were damaged). The damage does not seem to penetrate into whatever core material is in the keel.
I have limited fiberglass experience and have never worked with gelcoat.

I'm looking for any specific advice on how to approach this repair as if i had never done anything like it before (how would a professional approach this?) especially what materials to use and how to accurately maintain the shape of the keel.

I'm also looking for general repair resources to help me with the approach people end up recommending (websites, threads, books, etc)

thanks in advance for the help.

i couldn't get the images to display so here's the links
https://imageshack.com/i/ex77vuDij
https://imageshack.com/i/eyvSjeNFj

[img]https://imageshack.com/i/eyvSjeNFj[/img]
[img]https://imageshack.com/i/ex77vuDij[/img][/img]

rogerbum · Posted: Mon Jul 06, 2015 7:27 pm Post subject:

Here's the two images.

ssobol · Posted: Tue Jul 07, 2015 9:11 am Post subject:

If this is the keel down the center of the boat, I would just fill the gouges with fiberglass resin and leave it at that. It will be pretty hard to see. You could repair the gouges and the gelcoat if you wanted, but gelcoat repair is trickier to get looking good.

You could also mix up some thickened epoxy and repair it that way too. Wet the gouge with regular epoxy and then fill it with thickened stuff. WEST 610 would probably be a good choice. IMO epoxy would be easier than FG.

You have damaged down to the fiberglass mat. You need to make sure that it is completely dry before doing any repair.

SEA3PO · Posted: Tue Jul 07, 2015 12:01 pm Post subject: Yep ya did it..

Fairly easy to fix..luckily it is in a place that does not show...

I would use West Systems Epoxy for the fix...you can get it at West Marine.
The first coat should be a wet coat of non-thickened epoxy.... it will wick up into any exposed fibers and seal the scrape.... then after that cures I would add several layers of thickened epoxy.... West Systems sell a light weight thickening agent.... it's pyrogenic silica... cabosil is the trade name..not sure what West Systems calls it....you can make several layers of thicker and thicker resin....letting each totally cure before the next...... If you want to make a flush repair...you can finish over the top of your epoxy coats with what is called "light weight Bondo"
Both Polyester and Epoxy have an affinity for each other and will adhere well.... all "LW Bondo" is Polyester resin and Cabocil....lots of Cabocil..don't use regular Bondo as it's thickening agent is wood flower.

SEA3PO · Posted: Tue Jul 07, 2015 12:03 pm Post subject:

You can buy Light Weight Bondo at any discount parts store....
Or you can just keep thickening the epoxy resin with thickening agent and applying that....... just remember on your finish coats to work it into shape before it totally cures....darn stuff becomes hard quickly...

Joel
SEA3PO

SEA3PO · Posted: Tue Jul 07, 2015 12:22 pm Post subject:

West Systems is a First Class company and used to have instructional videos available for free.... they probably have them online.

thataway · Posted: Tue Jul 07, 2015 6:51 pm Post subject:

I have always had an issue with polyesters adhering to epoxy (not the other way around). I am sure it can be done. Vinylester resin is better than the polyester.

One thing you need to watch with epoxy is to clean off each layer before you put the next layer on--because of the amine blush which comes to the surface as the epoxy drys and hardens. (There some epoxy which do not have the blush).

A quick and easy way is to use Marine Tex. Not a professional repair however.

I like epoxy because its secondary bonding is far better than polyester. I use a lot of cabosil for thickening epoxy. When you get to a fairing stage, you may want to mix microlight (filler from West Systems), as your thickening agent. It is easy to sand and fair.

I would grind out any of the loose fibers, and gel coat. It is far better to get rid of that now, than to have a potential adhesion problem down the line. A professional repair, would be to lay in some glass fibers with the repair--either epoxy or vinyl ester (my first choice here, if you want to gel coat after to make it cosmetically acceptable.

Good on you for wanting to tackle the repair yourself. Good time to get a Dremel tool, or a rotozip, with a flexible shaft, and collet so you can use Dremel bits. (The RotoZip will be a much heavier duty motor than the Dremel.