In reply to "Thanks", posted by Brent on Mar 30, 2002:
>First of all I would like to take a minute to say thanks for allowing the fishing world to experience the talents you have building boats. They are beautiful boats!
>
>The purpose of my email is to have you share some of your knowledge about wooden boats. I am considering purchasing a Tatman 16'standard boat as a project to build for my father who lives in Missoula. There are several questions I have in regard to building a non-fiberglass reinforced boat.
>
>You may ask why am I asking you instead of Greg.......
>Just wanted a different opinion.
>
>While viewing your web-site and boat pics there are several items that I would like to incorporate into the boat I build.
>
>1)With Greg's kits he recommends UHMP for bottom and side applications for obvious reasons, while it appears as if you use a coating of sorts for the bottom and up the sides.
>What is this material?
>
>2)What is the difference in material for the sides and bottom between AA fir plywood, sepelle plywood, meranti plywood etc. Which is the best to use?
>
>3)Is it better to paint the outside of the boat for protection from possible cracking? Or is it better to finish the boat in a epoxy and varnish combination?
>
>Last, it looks like your buffalo boat is the exact boat I owned when I lived in Bozeman. We purchased it from a kid that used to build them there at his house. Same exact color, finish, and oars???????? I will have to email you pics of it.
>
>Thanks for your time.
>
>Brent
Brent,
Uhmw (Ultra High Molecular Weight plastic) is great stuff. Very tough very slippery. But it's got a couple problems. One is that nothing sticks to it, not epoxy not paint, not Sikaflex. So it must mechanically fastened to the boat, which means hundreds of screws.
The other bad thing with it is that it has a very high coefficient of thermal expansion. It expands and contracts in the sun like nothing else. I mean , you can actually see it move if it goes from a cold river to a hot sunny trailer. That makes the screws get loose and eventually they
eakout of the wood. Another by product of this expanding and contracting is that the plastic eventually gets very
ittle and it will
eakup.
At our shop, we pull old plastic off several kit boats a year.
The material I use is not UHMW but is a very strong polyurethane material. WWhat is actuallyin the mix is a trade secret for the company that makes it and I have no idea what is all in there. But it doesn't expand or shrink and it doesn't mind the cold water and it's almost as tough as the UHMW.
The bad news is that you can't pu it on your kit boat. If you do you are creating a plastic pan that the boat sits in and all the water that gets in from the inside of the boat and weeps in through the frames and small voids in the joints will eventually sit on the bottom of the wood in the plastic pan.
The best thing to do is to fiberglass both sides of the bottom panel very well and then attach it with screws and sikaflex caulking sealant to the bottom. It will last for years and when you need to you can easily remove it and replace it with a new one easier than one that is epoxied on.
The best plywood to use is BS1088 Okoume. It's a lightweight mahogany plywood with beautiful grain and good working characteristics. Fir needs to be glassed on both sides to prevent checking, Sapele and Meranti are other tropical mahogany subspecies which are fine but are heavier than Okoume. Fir is better for the bottom panel though if you are using plywood for the bottom panel. It has longer grain and will take hits better than mahogany. Baltic birch works too, it's just very heavy.
Paint won't stop checking if th outside of the hull isn't glassed. I paint the outside of my boats because I have a personal thing with seeing scarf joints on the outside. I would only
ight finish the exerior of a boat that is made of real wood. i.e. plank on frame dimensional lumber boat. To me it's like seeing fake wood on the side of a station wagon. I'm in the minority on this I know, but I have a hard enough time with varnishing the plywood on the inside.
Varnish is harder to maintain than paint on the outside and yo can see flaws easier, screw holes and plywood flaws etc.
Glass, epoxy and paint on the outside in my opinion, there's plenty of wood to go around on the inside.