Styrofoam sheet floatation ??

Getting ready to build an aluminum hull, approx. 18 feet long. Planning on a wooden floor spaced two inches off the hull skin. Would like to fill this area with two-inch Styrofoam sheets, the type carried by the local home improvement stores. This would become my primary floatation skystem. They have different types, I have been told by the store salespeople that some of them absorb water, other do not. What should I look-out for? Is it a good idea to place them directly on the aluminum skin, if not, why? Etc. Etc. - - - Any and all thoughts/comments greatly appreciated.

 

Biggest problem with this plan is if the boat did flip over it would want to stay flipped over, the majority of the floatation would be in the bottom of the boat, which if the boat's inverted would then be on top. Would be next to impossible to right it without outside help.

Bill H.

 

Old Grumann aluminum canoes had a alum. welded air chamber in each end. You could do a similar weld job and fill the spaces with "marine expanding foam". Keep the chambers up high, also under the seats.Hope you never need it. Nice to know you did the job right, if you need it.

 

More info.

Sorry, I should have put in more information. Beam almost eight feet, if she flips, I don’t think I will be able to bring her back. She also has other floatation on sides, etc. What I am interested in, and my question is, about using the sheet product for floatation.

 

Do it yourself foam. IS NOT RATED FOR-- SUNLIGHT --GASOLINE --OIL--OR ANYTHING ELSE!!!!PERIOD. LEAVE IT ALONE. I am totaly correct on this subject.

 

The blue Styrofoam brand made by Dow will not absorb water. The common white foam which crumbles into beads will allow water to travel around in its interior.

 

Ask yourself if you need the extra floatation. Looks to me, with the space available, it will not have a significant effect.

 

The average blue styrofoam (depends on where you live, around here a similiar product is pink) won't degrade with water contact, but as mentioned oil, gasoline and sunlight will eat it alive. You'll still need to glass it to protect it from everything other than water.

Bill H.

 

Thanks for the comments, guys. Hey Richard, what type are you referring to when you say, " Do it yourself foam"? Are you talking about the foam sheets, or the liquid, two part mix type?

 

Lowe's and Home Depot stuff. I called Owen's Corning to see what it is not attacked by. They said it needs to be painted or covered by another material to protect it against almost any thing. It was and is designed for roof insulation. Everybody else is on their own to protect it.

 

There are many foams out there. Use a MARINE FOAM.

 

I use the blue board against aluminum to insulate my fish hold and cover it with another sheet of aluminum to give me a working surface. Sounds like you are wanting it to float the hull if you get swamped. I bought some marine two part foam once. If I run into a place to buy it again, I'll let you know. It was a mess to spread but it would be worth it.
Most of the commerical skiffs up here in Alaska have no flotation - it's a Southern Thing. Just let her sink - Just kidding!
There are some skiffs that have so much flotation, they are self-bailing. That is what you want if you are going to do anything.

 

One big problem is most of this foam burns with a vengance!!

Should a wire or other ignition source start a fire , it will be VERY hard to get out as you breathe poisin from the combustion.

SEAL it really well, and it will work as insulation and flotation.

FAST FRED

 

Fred, you brought out a REALLY important fact of foam. TOXIC FUMES. USCG specifys spark proof wiring for fuel vapors. But what about spark proof FOAM. I did not see that with the fuel dangers. What gives?