A few questions before our first fiberglass job

[Golden Echo]

You are doing the right thing by calling West System. My wife repaired a transducer thru-hull and three for the marine head. She called west system and they walked her through the repair and she did a fantastic job. You can do it but you must follow the instructions to the letter. She did it from the instruction book that West System sells. While writing this my wife says "Don't forget to tell them to get plenty of gloves" ��

[Golden Echo]

Ok on composting heads. Just like everything else on a sailboat there are compromises with a composting head. We have used one since 2008 and never regretted the decision. No smell, no hoses to replace, no holding tank, no through hulls to maintain, no requirement to pump out, non polluting. I've heard good things about Natures Head and it's a well made product. We chose Airhead because of size restrictions.

[ramblinrod]

I use unwaxed polyester resin. Less expensive, doesn't heat up, can do as any layers as it takes, what the boat was made of in the first place, cures
faster, no risk of setting boat on fire with left over materials curing, less likely to become sensitized to it. Quite frankly, I avoid using epoxy for all these reasons.

I would never glue in a plug. If a thruhull is not needed, glassing in he hole vs capping it is far less risky. Lots of boats sink every year due to fail thru hulls and seacocks.

I've never heard of a boat sinking due to a properly glassed in thruhull.

Ramblin Rod
About Sheen Marine

[laika]

Originally Posted by Rainh2o2

I did my below water thru hulls like Hilbert. I did taper it more though on both inside and out. My hull was about 1 3/4 thick in the spots I removed mine. I drilled out the thru hulls with a 3/4 inch hole saw. Made a plug from epoxy and some fiber glass matt. More epoxy then matt. Filed the plug down to fit really snug inside the hole and then epoxied that in the hole. The plug was only about 1/4 inch thick. After the plug dried in I started adding fiberglass patches and fiber matt in alternate layers. I only had time to add about 5 or 8 layers at a time before the epoxy would start to get to thick hot and sticky. I alternated fiber matt and fiberglass to improve strength. The matt does well to fill while the glass holds the strenght. I did this on both sides. Smoothed it out real nice on the outside and painted. Inside I knocked all the sharp edges and ridges off and just painted but didn't feather as much because of the mess of sanding inside the boat.

That' was pretty much my process too. The hull was quite a bit thinner--about 5/8"--and I had some 12ounce biaxal cloth already so used that and no matt. Took a good number of layers to build up on both sides from the plug to the edges of the tapered hull area. I believe the technique WS recommends is starting with the largest diameter circle of cloth and going progressively smaller towards the center, maximizing the bonding strength of the epoxy/cloth to the existing hull with one massive primary bond.

I used intelux 202 and plenty of clean rags to clean before beginnign the layup. Nasty stuff. Then WS #407 to fair/finish.

If you go with a slower cure epoxy (like WS 206) there's less issue with the thing cookin while you're in the middle of the layup. Also depends a lot on ambient-mixing temps. Keep the mixing batches small, only a couple of pumps at a time.

And tons of gloves for sure!! Also plenty mixing containers, stir sticks and chip brushes at the ready. helps to either have a helper cutting the cloth as you go, or to cut everything beforehand.

It can get messy fast, but otherwise easy peasy.

[Rumlater]

If you are using West epoxy do not use stranded mat as the sizing to hold the strands together do not let the epoxy penetrate the strands

[Viajero]

I think that most of this advice is overkill except wiring and capping existing through hulls. Holes for 1" or smaller through hulls can be cleaned and filled with thickened epoxy. Hot glue a thin wood batten over the hole on the outside with wax on the batten where it covers the hole to keep it from sticking to the epoxy. Fill the hole from inside then thoroughly sand an area around the filled hole with 40-60wt. sandpaper. A sanding disk in an electric drill would be adequate for this. The sanded area doesn't need to be larger than 6" by 6". It should smooth out any weave prominent in the fiberglass. Add a layer of fiberglass mat and one of biaxial roving in epoxy resin. Don't worry about the polyester sizing in the mat, it won't cause problems. The mat will form a good mechanical bond with the glass. Remove the wood batten and fair with thickened epoxy if necessary. For the 1 1/2" through hull hole you might want to apply another, larger laminate of biaxial cloth. The repaired areas will be stronger than they were with the through hulls in place.