Now that I have my mind right concerning plywood, what about bottom protection? Greg Tatman advocates the use of UHMW plastic and Roger Fletcher and others seem to prefer using 1/4 ply with fiberglass and graphite. What are the thoughts on this.

Also, what about the use of adheasive between the frames and side panels? I would think that it would go all the way but in the book it says below the water line.

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So far so good, I used UHMW on my boat. I really like the choices it allows for both camp tie ups and lower flow runs. I do a lot of multiday trips with three people and a ton of both necessary and decadent gear. Prior to installing the UHMW I applied two coats of epoxy and a layer of glass to the entire outter hull. Also, I glassed the inside hull with a strip of glass on top of the chines and coated the entire hull inside and out with several coats of interlux paint. I also filled each screw hole with 5200 as I installed the UHMW. I might regret my decision in the future, but boating on whitewater with lower flows helped make my decision easier. Marc
Mike,

That is a great illustration. You are right- the S&G guys do glass inside and out and they don't have the impact issues that the rest of us with framed boats use. I'm glad someone took the time to research this, because it will be an awesome thread to re-post the next time bottoms come up!

Dave
Hmmmm, Dave, what do you mean that they don't have the impact issues that the rest of us with framed boats use? Obviously if they are on the same water we all hit the same rocks.
Randy, Not what I meant to say!

Obviously, they do have the same impact issues we have! What I mean though is the plastic or foam bottoms loaded up with kevlar and glass don't exhibit the same reaction to impacts. I should have clarified! Not to mention without frames, those bottoms are more flexible as noted and distributes an impact.
Roger clearly has more knowledge then most when it comes to design, building and materials but, I have used black graphite mixed into epoxy. I can't say I think it makes a difference. I also have not rowed side by side boats and pulled them over the rocks to see if they slide better.

One of these days I will epoxy up 2 pieces of scrap one with graphite the other without. I will then load them with some weight and drag them over a rough surface to see if it really makes a difference.

I have had to make a few bottom repairs and sanding the stuff is no fun. Kind of like sanding a giant black pencil. I no longer use it just because of this reason and I can't say I notice any difference.

I love running rivers but sadly my rowing ability is not equal to the skill required for many of the places I row. I also only get to be on the water about 30 days a year so it's hard to get better. I say this because I have had to make a few repairs now and then. Now when I build most of my emphasis is geared to maintainability and ease of repair. There are thing I have stayed away from because I know repair will be more work after I bash a rock. That's kind of boring but it's the right approach for some. A classy wood boat like anything is a different issue. They are great too but, it takes some effort to keep them beautiful. An old truck you just drive around and never do anything to it until is stops running. It's the issue of the right tool for the job.

The plastic bottom cover needs to be held in place with screws. The screws mean you can't just install it and forget about it. It's a place for rot to start if we don't pay attention to them.

With glass on the bottom you do need to take a look now and then to see if it has been cut all the way through to the wood. If it has it needs to be patched. Just takes a little time and it's not the maintenance headache the Clacka people will say it is. Some rivers are tougher on boats then others which factors into the maintenance issues. A molded glass boat might require very little attention but, I wouldn't run one down the Yampa at 15000 CFS. After it gets swamped and goes to the bottom of the river it might never need any maintenance again. It's just not built for that kind of water.
Over the years I dealt with some nightmarish pins and submersions with rubber boats (ie Upper Yough & Upper Gauley with bucket boats). I feel like the conversation is overly optimistic in terms of energy transfer. At the end of the day, I feel both framed and S&G boats will sustain damage if it's a big enough hit with a loaded boat. However, the end story will be a lot more fun to reminisce about in another year or two. Marc
You are right on the money Marc. No boat can take too big of a hit. We need to decide our compromises, as always, and the differences in construction vs damage are a very fine point.

The bigger issue is to design for performance and safety in the water that you run the most often. Each person will prefer a boat designed for their home water. Then fix the thing when you have that fender bender so you can go do it again.
Hey Marc, the Yough is my home water.
You are absolutely correct Marc but, some materials will hold up better then others. 3/8 inch plywood on the bottom will make a lighter boat but, it's not strong enough. Heavier plywood and fibers like kevlar can make the difference between having to fix a hole in the boat and continuing with just a crack in the floor or a duct tape fix. I don't think anyone here is trying to say that we can build something indestructible. There are composites which will take much bigger hits but then it's not a tradition wood boat. There is a limit to what we can expect from the traditional wood boat. In defense of wood, no matter what you do to a wood boat if you can float out the pieces it can be put back together.

PT boats were build from plywood then moved to honeycomb. Aluminum is about as tough as you can get but I don't want an aluminum boat.

After years of development the wood framed boat is about as refined as it's going to get and they are running the Colorado river every day.

This is a very good discussion in that people can learn about different option and how assembly and materials can help. This is what moved us from planks to plywood, plywood to foam core and kevlar. It's all good stuff.

My first run down the Yough was way back in 1978.
I was 4 years old in 1978.
I graduated from High school in 1978
Hello, Lady's and Gentlemen
I am a newbie at boat building and going to give it a try with my father-in-law. I have experience in Wood Working
and a former Home Builder and have wanted to give it a try. I have been fly fishing basically my whole life and so the madness begins!!!! I have read alot of the forums about Lowe's Home Improvement and Merant i& Okuome ply and Marine grade ply. I know they don't have this in stock but confirmed from a vendor of Lowe's that it's in stock at there location. BLUELINX has it in several thickness and trying to get the $$$$ will post asap and hopefully help several of us find it a maybe a better price and quick ship. I am sorry I am in the Atlanta Market(area).
Thanks a million for such a informational forum and site Jeffery Wood

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