Styrofoam and plywood

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Jeffrey

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I don't know what is the best kind of foam to use, bot would it be styrofoam? Could I secure styrofoam to my floor with Liquid Nails, and then secure 1/4" plywood to the styrofoam with Liquid Nails?

The styrofoam would bridge the channels that run lengthwise on the boat so wouldn't keep water from draining to the back. Since the plywood would rest directly on the styrofoam it wouldn't need to be very thick. It would essentially protect the styrofoam.

What would be the downside to this approach? One downside I can think of is how difficult it might be to remove and replace the plywood someday, although I don't know how securely the Liquid Nails would hold it all together.
 
I'd be surprised if the floor and foam would stay in the boat should it ever sink. I would expect it to tear away. But as you said, it would be a mess to remove and replace if you ever did. I think you would be a lot better off to screw the wood to the ribs or use some sort of aluminum angle at the sides to secure the wood.

I used the blue foam board that lowes sells in my boat. You can see it in my build pics. Link is in my sig.
 
In that case would you try to get foam that is the same height as the ribs so that the decking would rest on the foam? I guess otherwise the decking would have to be strong enough to span the ribs and not sag?
 
Would it be more quiet if I made the foam a layer taller and covered the ribs with foam? Then I would screw through a layer of foam into the ribs? I haven't done this before but it seems like if there is any movement at all between the plywood and ribs then it will make noise.

Also, regarding this type of foam, are there voids that will be full of water, and can saltwater damage the foam?
 
There are no voids in the type foam I used it's closed cell foam so it won't absorb water. I'm pretty sure salt water won't have any effect on it but I've never seen in writing that it would or would not affect it. As for adding another layer over the ribs, logically that would seem to make sense that more foam would do more for sound elimination. I'm not sure how much you'd gain from that or if it would be worth doing though.
 
I don't know if I should start another thread to ask this question, but if I decide to use aluminum deck plate, should I still put foam insulation underneath? Seems like I would smoke the insulation a bit when welding the decking down.
 

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