Vintage homemade rowboat cosmetic restoration

My lake neighbor has an old rowboat that her brothers built from plywood and fiberglass about 50 years ago. It appears they used fiberglass mat along the exterior joints and coated the whole thing in fiberglass resin. It has sat outside and the fiberglass coating has shrunk, cracked and peeled where there is no reinforcement, and all of the mat reinforcement let go of the plywood to where I could get a scraper under the edge of the mat and peel it off. The plywood is in remarkably good condition and there is minimal rot on hardwood reinforcements to the bow and transom. After repairing the rot, my plan is to use epoxy resin (as opposed to polyester resin?) to reinforce the exterior joints with fiberglass mat as it was built originally. I will also need to seal the interior joints, but I am unsure of what to use. I intend to use Rustoleum Marine primer and topcoat paint to finish it.

I realize for a boat that would be in the water for extended periods of time, topcoat paint would not be a suitable finish, but this is purely a cosmetic restoration and I'm footing the bill, so I want to keep it as inexpensive as possible, as well. I want it to look decent and for it to float if they want to put grandkids in it down by the dock to take putt around, take pictures, etc. It will be stored in a shed most of the time. Here are my questions: 1) What would be a suitable sealant for the interior joints that can be primed and painted? 2) Is epoxy resin the appropriate material for the fiberglass mat exterior joint reinforcement? 3) Searching for such on Amazon turns up mostly table top epoxy resin. Would that work? Thank you in advance.

 

Buy fiberglass tape, 4 inches wide, and a good 2 part epoxy resin. Clean up the exterior and interior by sanding to clean, bare wood. Put a coat of epoxy resin about three inches wide on all exterior joints and put the tape on the joints. Before it cures put another coat of epoxy on and wet out the tape. It might need some smoothing or sanding after cure. You may want to put another coat of epoxy on after it cures. Do the same on the interior joints. This is essentially what is called stitch and glue boat building. Then after the epoxy cures just paint it with a good marine or exterior grade paint. It won't leak and will look like new. I have two small wood boats and I use the same technique.

 

Welcome to the Forum JMO.
I just saw that Ike beat me to it!

Do you have any photos of your boat?
Will it be possible to strip off all of the old fibreglass on the exterior fairly easily?
If you can, it would be worthwhile doing so.
And then use epoxy ideally (rather than polyester) and glass cloth to reinforce the joints.
You can buy glass cloth as a roll of tape, where the tape is available in different widths (eg 2", 3", 4") - this is much easier than trying to cut narrow strips from a sheet of glass cloth.
What is the interior of the boat like? Is it painted? If it is mostly bare plywood, and in good condition, then that is good. Ideally you could also use epoxy and glass tape on the interior joints as well. The cost of doing this should be relatively modest.
And if you have lots of bare plywood, and it is dry, then it would be worthwhile sealing it with a thinned coat of epoxy resin before you paint it.
How do I thin Epoxy for certain applications? https://support.promarinesupplies.com/hc/en-us/articles/360016083552-How-do-I-thin-Epoxy-for-certain-applications-

Re type of epoxy to use - WEST System epoxy is probably the most common, but there are others for marine use.
Here is the gallon size WEST epoxy on Amazon, complete with measuring pumps for US$ 145 -
https://www.amazon.com/System-105-B-Epoxy-Hardener-Metering/dp/B07JKYCV8G/ref=sr_1_9

Or a gallon of Totalboat epoxy (also with pumps) for US$ 125.
https://www.amazon.com/TotalBoat-Epoxy-Quart-Fast-Hardener/dp/B00HR85152/ref=sr_1_12

Here is a typical type of glass cloth tape (4" wide) which you could use on your joints.
https://www.amazon.com/YIKAI-Fiberglass-Cloth-Reinforcement-Glass/dp/B07DDFWXFB/ref=sr_1_4

 

I've tried various brands. I have pretty much settled on System Three. It's a bit expensive compared to others (except West which is about the same as System Three) but I have never had any problems with it. Some of the cheap brands I tried didn't cure well, or bubbled like mad in the sun, and so on. If you haven't had much experience using epoxy look here for guidance. Instruction manuals, book, videos & workshops - WEST SYSTEM Epoxy https://www.westsystem.com/instruction-2/ It's by West System, but their instructions apply to any type of marine epoxy.

 

Oh yeah, I just looked in my tool bin and the last job I did this summer on my 8 foot sailing dinghy was West System Epoxy. I bought that because where I am living now I could get it in smaller batches than System three for the small job I was doing. I would have had to drive 20 miles to get System Three and I don't buy on line if I can get what I need locally. Anyway it worked great. I was doing exactly what you are planning to do. The boat isn't as old but it need refinishing.