Barrier coat or Epoxy for coating bare wood hull

[ajay73]

Back in the early 90's I built a 15 ft sloop rigged sailboat with plywood and epoxy and covered inside and out with a 6 0z glass set in epoxy. This boat was framed and the plywood skin adhered to the frame with epoxy. Never had a failure in that boat and it's still around today with another owner. There are a whole lot of boats built with plywood covered with glass set in epoxy. Most have long lives. Just because of my allergy I'm looking for alternative. But because the dinghy is only a 10 footer I may try to get someone to help with the final coating.

[Jim Cate]

First, get the wood fair.

Next, Put up a layer of really thin veil glass over the entire surface using vinylester. Tiny. Just like 6oz cloth or thinner.

this might be kinda hard to do on a lapstrake hull...

Applies to all the suggestions of glassing over the hull.

Jim
Jim

[Chotu]

Originally Posted by Jim Cate

this might be kinda hard to do on a lapstrake hull...

Applies to all the suggestions of glassing over the hull.

Jim
Jim

Guess you didn’t read his initial post completely.

It talks about glassing it being a possibility, if straight resin won’t cut it, which it won’t.

[Jim Cate]

Originally Posted by Chotu

Guess you didn’t read his initial post completely.

It talks about glassing it being a possibility, if straight resin won’t cut it, which it won’t.

Guess I did too read it, neener, neener, neener.

Seems to me that he was asking if glassing was a feasible option, and I reckon it is awfully hard to do on lapstrake hulls.

Have you succeeded in doing this? And if so, how did you avoid voids at the roots of the strake joints?

Jim

[fourlyons]

You said the boat will never be stored outside or left in the water full time. You don't need to epoxy coat the ply. The ply you quote is high quality and does not check, therefore all you need is a quality paint job. I have done this a number of times, in one case the boat was stored outside through three New York state winters and faired well.

How many traditionally built wood boats are coated in glass and epoxy before being painted? Not many, and quality plywood is much more stable so holds paint even better.

[ajay73]

I think fourlyons is right but I will just coat the outside and inside with regular epoxy. The meranti hydro-tek is very good ply and does not check like fir does. So I shouldn't end up with splits in the surface of the epoxy where water would get in.The epoxy will keep any water from soaking into the wood and possibly compromising the lap joints.

[Manateeman]

I’ve built a number of all wood boats and as unbelievable as it sounds, without epoxy. There are actually wood boatbuilders still doing this...no epoxy, no plexus, no high tech, high toxicity coatings.
I’ve seen wooden boats stored inside for decades till you could look through the plank seams and again, unbelievably, have seen them cleaned, caulked and painted ...they swelled up and make perfectly fine boats.
I learned wood boat building on Beetle Cats which are carvel planked but a well built lapstrake hull will not require any epoxy whatsoever, to give years of service. I would not use any hard, high tech coating on wood.
The most beautiful lapstrake dinghy I ever watched being built was in Norway. The planks were split not sawn. One center mold. Copper rivets. They soaked the interior in processed fish oil but the old timer fishermen just used the smelly stuff. That dinghy will be used day in and out for a lifetime.
Real tung oil, menhaden oil, pine tar, Kirby paint...you would find these in every wooden yacht yard because they worked.
The U. S. S. Constitution wasn’t built with, nor is it held together with, epoxy.
Happy trails to you.
Captain Mark and his eggnog and mistletoe manatee crew

[MicHughV]

My very first dink was a homemade plywood job....it was nailed together and varnished and surprisingly, considering I had never built anything before, held up very well for quite some time.
Then it started to leak, about which time I was also introduced to WEST system, so all the original varnish had to come off and be recoated with WEST.
As the dink was already put together, I was not able to get the WEST in the various joints.
This I solved by making a thick cove at all the joints and corners, etc, with WEST and some filler.

Then the dink got sanded and painted with some cheap hardware store epoxy paint, on the outside only. No primer, no undercoat.
Never had any problems with it afterwards. Dink lived on deck, out in the open for a number of years. It saw a lot of abuse...a lot....the paint (color green) did chalk after a number of years, and landing on a sandy beach did wear some paint off the centerline skeg and runners, which were made from oak, but all told, lived a happy long life.

[Capt. Lace]

Epoxy is water proof. And should not fuss over a boat you pull out everytime after eaxh use. Maybe over kill but i like epoxy. Water proof and doesnt stink

[Ken Fry]

I have been very careful with epoxy through the years, including not doing any sanding until fully cured, and always wearing gloves, and a respirator when sanding. If I had a sensitivity, I would give up boat building, I think*. I'll end my preaching in a second... but I'd be wary of using any epoxy product if I were in your shoes. I would not use 6-10, for example, or i2000. People who have not been sensitive to epoxy suddenly develop sensitivities -- and if you know you have the propensity why push it?

This boat is a lapstrake stitch and glue, in Okume. Every inch is covered in fiberglass in epoxy -- inside and out. Avoiding wrinkles at the laps is a bit of a pain, but not too difficult. The outside is painted, so any goofs could be sanded and filled. But the inside is finished bright, so bubbles in the lap filets would show. So I was quite careful, but also came back in about an hour and sliced the bubbles with a razor, and pressed the cloth back into place. Then, before adding a later of epoxy to fill the weave, I first touched up any little slits.

The outside is finished with Brightside, and has held up well -- better than I would have expected. Thorough prep is a key to having it stick well to the epoxy. The interior varnish needs a good UV absorber.

For the way you plan to build the boat (if someone else does the gluing) just painting with brightsides would work well. Advantages of using fiberglass cloth everywhere are layer thickness control, abrasion resistance, and surface toughness. But for light use, you don't need much of any of those things.


* (Or do what I did some years ago with home depot exterior ply and construction glue, and latex paint: a $50 pirogue. Turns out, it worked fine. Hundreds of miles in streams and in the ocean. Finally after 20 years I just gave it away, and its still doing fine.)

[Ken Fry]

Originally Posted by ajay73

I think fourlyons is right but I will just coat the outside and inside with regular epoxy. The meranti hydro-tek is very good ply and does not check like fir does. So I shouldn't end up with splits in the surface of the epoxy where water would get in.The epoxy will keep any water from soaking into the wood and possibly compromising the lap joints.

Didn't you just say you are sensitive to epoxy? If you are gong to risk coating the boat, you might as well fiberglass it as well -- it's not the fiberglass that is giving you your reaction.

[Jim Cate]

Originally Posted by Ken Fry

I have been very careful with epoxy through the years, including not doing any sanding until fully cured, and always wearing gloves, and a respirator when sanding. If I had a sensitivity, I would give up boat building, I think*. I'll end my preaching in a second... but I'd be wary of using any epoxy product if I were in your shoes. I would not use 6-10, for example, or i2000. People who have not been sensitive to epoxy suddenly develop sensitivities -- and if you know you have the propensity why push it?

This boat is a lapstrake stitch and glue, in Okume. Every inch is covered in fiberglass in epoxy -- inside and out. Avoiding wrinkles at the laps is a bit of a pain, but not too difficult. The outside is painted, so any goofs could be sanded and filled. But the inside is finished bright, so bubbles in the lap filets would show. So I was quite careful, but also came back in about an hour and sliced the bubbles with a razor, and pressed the cloth back into place. Then, before adding a later of epoxy to fill the weave, I first touched up any little slits.

The outside is finished with Brightside, and has held up well -- better than I would have expected. Thorough prep is a key to having it stick well to the epoxy. The interior varnish needs a good UV absorber.

For the way you plan to build the boat (if someone else does the gluing) just painting with brightsides would work well. Advantages of using fiberglass cloth everywhere are layer thickness control, abrasion resistance, and surface toughness. But for light use, you don't need much of any of those things.


* (Or do what I did some years ago with home depot exterior ply and construction glue, and latex paint: a $50 pirogue. Turns out, it worked fine. Hundreds of miles in streams and in the ocean. Finally after 20 years I just gave it away, and its still doing fine.)

Looks a nice dinghy, Ken! And good onya for getting the glass worked into the corners of the strakes. On a simple three-strake hull I guess it can reasonably be done... my advice to avoid glassing posted upthread was based on a more traditional lapstrake hull with many narrow strakes forming compound curves in the hull. Something more like this one:

https://images.app.goo.gl/ieawVn9uHNQ8bSNy7

Getting the glass right on such a hull would be a serious challenge!

Jim

[ajay73]

What about this process? Use chop strand mat set in vinyl ester resin and then apply a gel coat as a finish. CSM conforms really well to tight turns. Remember, the dinghy will not stay in the water. I still would use Six10 to glue the lap joints.

[Ken Fry]

Originally Posted by Jim Cate

Getting the glass right on such a hull would be a serious challenge!

Jim

Jim, Jim, Jim. I could have the inside of that properly glassed (to be finished bright) in less than two years of full time effort... if I hired a helper... and didn't take time to eat. No big deal. Of course I am insane, which is a huge help.

[Ken Fry]

Originally Posted by ajay73

What about this process? Use chop strand mat set in vinyl ester resin and then apply a gel coat as a finish. CSM conforms really well to tight turns. Remember, the dinghy will not stay in the water. I still would use Six10 to glue the lap joints.

Sounds like torture to me. You have listed most of my least favorite materials to work with. But if you like working with the smell and toxicity of styrenes, and are willing to experiment with unusual methods, don't worry about using epoxy, and want to put in the work to get a CSM layer smooth... then it would be interesting to hear how it goes.

Personally, if I were building a small lapstrake dinghy, and were not concerned about weight, I'd do it as a traditional wooden boat.

https://www.clcboats.com/forum/5/thread/14408.html