Fiberglass hull repair?

[Jdege]

The hull of my boat has a fairly deep gouge in the hull where someone scraped along some rocks.

The boat had been on the hard for a couple of years before I bought her, and she's still on the hard waiting for warmer weather, so the area is dry.

I've attached a couple of pictures. You can see that there's a fairly thick surface layer that's been compromised, but the underlying glass layers look to be untouched.

How then to fix it?

First question epoxy or polyester? The boat dates to 1978, so I'd assume the hull was originally laid up with polyester resin. I've never worked with polyester, though I've done a bit with epoxy, and I have some West Systems 105/205. Can I do the repairs with epoxy?

I'm assuming I'll want to sand this back to provide a solid base, but then what? Fair it smooth with thickened epoxy?

I'll be painting the bottom before I put her in the water - Interlux VC-17. (She's on Minnesota's Lake Pepin - fresh water, and VC-17 is the go-to up here.)

So what else, between the epoxy and the bottom paint? Some sort of barrier coat?

What does she need before I put her back in the water?

[Randy Bogardus]

I would clear out all of the compromised glass and lay in a succession of epoxy and fiberglass cloth…..something like 6oz….. cloth until the repair area is slightly proud of the adjacent surface. Then I would sand/fair it back to the original form, then seal the weave with epoxy. Start with small patches and work out gradually overlaying the patches with subsequent patches. Keep the cloth full of epoxy but not overly saturated.

[Jdege]

No suggestions on what to do over top of the epoxy?

[CSYChip]

I would do the underlying glass work with polyester first because the hull is and second because most glass is coated to wet out with polyester. This makes getting the bubbles out and getting good adhesion easier. After fairing it out, a coat of epoxy makes a good undercoat for painting. Barrier coats like interprotect 2000 call for putting the barrier over epoxy while the epoxy is still slightly tacky.

[Spot]

Originally Posted by Jdege

No suggestions on what to do over top of the epoxy?

I don't have experience with VC-17 but was told (by someone who knows) to directly paint over the epoxy on my plywood rudder cheek and blade and not to apply a barrier coat. So I am wondering if VC-17 would stick once any amine blush from the epoxy is removed and it is sanded to have a little tooth.

[Jdege]

Originally Posted by CSYChip

I would do the underlying glass work with polyester first because the hull is and second because most glass is coated to wet out with polyester. This makes getting the bubbles out and getting good adhesion easier. After fairing it out, a coat of epoxy makes a good undercoat for painting. Barrier coats like interprotect 2000 call for putting the barrier over epoxy while the epoxy is still slightly tacky.

The existing polyester is decades old. Anything new will have to rely on mechanical binding, and AIUI epoxy usually does a better job at this than polyester.

[Jdege]

Originally Posted by Spot

I don't have experience with VC-17 but was told (by someone who knows) to directly paint over the epoxy on my plywood rudder cheek and blade and not to apply a barrier coat. So I am wondering if VC-17 would stick once any amine blush from the epoxy is removed and it is sanded to have a little tooth.

From what I'm reading, "barrier coats" are essentially a layer of epoxy over the top of polyester, so as to provide better waterproofing. If the patch is epoxy, that might be all that's needed.

Though West Systems has an epoxy additive - 422 - that's supposed to improve their epoxy's performance when used as a barrier coat.

[Cheechako]

That doesn't look very deep, unless the hull is quite thin. I would probably treat it as cosmetic. Or just use resin with glass strands in it then grind back. It's what.. 1/16" deep?

[Frankly]

I posted this last week for a keel repair but most steps are applicable.

Grind away the old damaged gelcoat and take a close look to see the underlying glass layup. A single layer of 1708 material might make the most sense to help fair the patch. Then fair with West Epoxy paste and use the visqueen to control/ smooth the repair. Scuff sand the final epoxy surface and apply bottom paint or add an epoxy barrier coat if it makes you sleep better.


If you have acess to compressed air, make a trip down to Harbor Freight and buy a small high speed angle grinder and some small (like 2" coarse sanding disk).

Laying on the ground compressed air is safer than electricity (works better also).

Wear a mask and set up a small fan to blow the grinding dust away.

Heat lamp can help with the drying process.

Don't consider using anything other than epoxy for the repair. Over the years (there has been a lot of them) I have found 1708 biax stitched fabric usually works best.

Want to practice this before jumping into the repair so make a small test patch of a couple of layers of 1708 on a piece of scrap plywood. Get some Visqueen (large sandwich bag will work) use duct tape to hold one edge of the Visqueen in place, lay the Visqueen over the test patch and use a plastic squeegee to milk the patch out flat and remove excess resin. Tape the opposite edge from blowing in the wind. The epoxy will stick to the Visqueen while wet but will release after it cures.

The epoxy/ Visqueen will aid in working/ holding the patch when gravity is against you. Vacuum bagging works best in holding odd patches in odd positions but requires a vacuum pump. I have used 1/2 " soft foam (like ensolite) with a plywood backing and a stake in the dirt to put pressure on the epoxy/ Visqueen patch. After curing the Visqeen will leave a slick surface that will need grinding before the next layers.

Typically I make a paper pattern, cut 3 layers of 1708 to match the grind taper, and lay them on the visqueen while wetting them out. Then lift the whole patch into position, have the duct tape pieces already cut and handy (couple of extra hands can help).

Make a dry run to work out your technique before adding the epoxy. Will not work with polyester

At this for over 50 years and the secret is the epoxy and Visqueen.


Frankly

[Jdege]

Originally Posted by Cheechako

That doesn't look very deep, unless the hull is quite thin. I would probably treat it as cosmetic. Or just use resin with glass strands in it then grind back. It's what.. 1/16" deep?

The hull is more than an inch thick. It looks to me as if the gouge did nothing more than chip off the gel coat. It's closer to 1/32" than 1/16". It looks deeper because the coating layer has separated from the laminate along the edges. These loose areas will be dealt with when I sand it back.

[Jdege]

Originally Posted by Frankly

If you have acess to compressed air, make a trip down to Harbor Freight and buy a small high speed angle grinder and some small (like 2" coarse sanding disk).

Laying on the ground compressed air is safer than electricity (works better also).

I'm in a seasonal storage yard with no power available, so I'm pretty much restricted to battery powered tools. Not ideal, but no electrocution risk.

Wear a mask and set up a small fan to blow the grinding dust away.

I have a full face respirator with lens inserts. I wear glasses, and googles+glasses+half-face-respirator is an uncomfortable combination. I'd been thinking about lying under the boat applying bottom paint, but it will work for this, too.

I have a battery-powered shop vac that I'd planned on using. Blowing glass dust over the neighboring boats isn't polite.

Want to practice this before jumping into the repair so make a small test patch of a couple of layers of 1708 on a piece of scrap plywood. Get some Visqueen (large sandwich bag will work) use duct tape to hold one edge of the Visqueen in place, lay the Visqueen over the test patch and use a plastic squeegee to milk the patch out flat and remove excess resin.

Thanks for ghat. I've been looking for a reasonable peel-ply, but what I've found has been either ineffective or very expensive. I'll give Visqueen a try.

I won't, though, use duct tape. I had a set designer friend recommend gaffer tape, some years ago, and I've never looked back. It works much like duct tape, but it tears more easily and it doesn't leave residue.

[newhaul]

Originally Posted by Jdege

The hull of my boat has a fairly deep gouge in the hull where someone scraped along some rocks.

The boat had been on the hard for a couple of years before I bought her, and she's still on the hard waiting for warmer weather, so the area is dry.

I've attached a couple of pictures. You can see that there's a fairly thick surface layer that's been compromised, but the underlying glass layers look to be untouched.

How then to fix it?

First question epoxy or polyester? The boat dates to 1978, so I'd assume the hull was originally laid up with polyester resin. I've never worked with polyester, though I've done a bit with epoxy, and I have some West Systems 105/205. Can I do the repairs with epoxy?

I'm assuming I'll want to sand this back to provide a solid base, but then what? Fair it smooth with thickened epoxy?

I'll be painting the bottom before I put her in the water - Interlux VC-17. (She's on Minnesota's Lake Pepin - fresh water, and VC-17 is the go-to up here.)

So what else, between the epoxy and the bottom paint? Some sort of barrier coat?

What does she need before I put her back in the water?

As a retired shipwright I would sand out the area and fair it with marine grade bondo. And top with barrier coat and then paint to match . It's not a deep structural issue .
Do this all the time on hard dinghies on the bow area .

[Spot]

If you need supplies, Express Composites in Minneapolis is a nice place to go.

https://www.expresscomposites.com/


Off project wet-out and 'Visqueen' (plastic film) with a foam pressure pad sounds really good for this considering the remote yard location and being under the boat. Real peel ply would help with less sanding and less amine blush.

[Jammer]

That doesn't look serious.


Similar to those writing upthread, I would:
1) grind back to sound material
2) optionally put in a layer or 2 or 3 of 6oz fiberglass saturated with epoxy if it's deep enough to warrant it
3) spread on some epoxy thickened with colloidal silica to provide a watertight barrier and some strength (on top of the wet fiberglass if you did that)
4) allow to cure, sand, fair, and paint to taste


I like to use peel ply.


I like to use ratchet straps and plywood and squishy foam to hold stuff in place.

[Uncle Bob]

Originally Posted by Cheechako

That doesn't look very deep, unless the hull is quite thin. I would probably treat it as cosmetic. Or just use resin with glass strands in it then grind back. It's what.. 1/16" deep?

This. to my eye the pics show minimal glass damage, mainly gelcoat. Break out the flap sander, clean up the small damaged glass area, reconstruct with epoxy and appropriate cloth and repair the gelcoat damage, paint and launch.