Pink/blue foam - what about white foam?

[1lhorn]

I went to HD looking for pink or blue sheet insulation foam and didn't see any. The only sheet insulation foam they had was white sheets up to 2 in thick. Says it's polystyrene and looks exactly like the foam that's used in cheap foam coolers or is used in padding when you buy a microwave or TV, etc. One side had a silver like film on it. Would this be OK? On the shelf tag by this product is indicates that it's resistance to moisture is "low." I guess "low" is relative. I've never been concerned that my foam cooler was getting water logged and I don't plan on water sitting in the bottom of the boat for long.

My boat is a 1998 Klamath. It's got similar polystyrene foam in the front and rear areas but nothing under the floors. At first I thought it was the company skimping but then I thought that it might be their effort to place the foam higher up so the boat wouldn't flip over if it got swamped and to prevent the foam from getting water logged. It worked. The old foam is very dry and I plan to reuse it but thought I would also put some foam under the floor boards for added level of protection and because I want to remove a little of the foam in the front area to create more storage.

I suppose I would try to put the silver coated side down expecting it to offer some protection against minor contact with water.

On a side note I was at TAP Plastics (chain plastics store) and they sell their own epoxy. On the shelf that had small pieced of material coated with the epoxy to show how it worked. They had what looked like polystyrene foam coated with their epoxy. Seemed like a good idea but maybe a bit pricy and overkill.

 

[DaleH]

FWIW I know guys that have wrapped similar foam or foam peanuts in contractor-grade plastic bags, glue sealed closed with care, and used that for additional flotation. Many examples abound all over the 'stitch & glue' DIY build-a-boat websites.

I haven't done it, but it works ...

 

[1lhorn]

Doing a bit more research I guess while they are all polystyrene, the pink and blue (color is at least in part an indication of their manufacturer) are consider XPS (extruded polystyrene) and white is EPS (expanded polystyrene). EPS is lighter. I guess it's considers water proof and is sold as floatation for docks (https://univfoam.com/floatation).

I found this article interesting. Seems to be pro- EPS (and anti expanding polyurethane which I never considered due to cost). Again I don't know the difference between EPS(white) or XPS(pink or blue), but EPS seems to be OK.

https://www.valleymorningstar.com/coastal_current/news/something_extra/article_ddfb54a2-5b4a-11e2-83d8-0019bb30f31a.html

"When the Coast Guard regulations regarding flotation in recreational boats came to be years ago, the most common types of flotation were air chambers and blocks of foam, typically expanded polystyrene (EPS) referred to as Styrofoam. Because air chambers could not be part of the hull or in direct contact with it should a hull penetration occur, few boats used this type of flotation and most builders used closed cell EPS foam block instead. After all, EPS foam was water-proof, would not become water-logged and was relatively inexpensive.
There were a couple problems though with EPS foams, the first being that it had to be cut and shaped to size. Secondly, because fuels would melt it, it would have to be sealed away from fuel sources. Both of these increased labor and material costs significantly, so when Dow Chemical first introduced a two-part liquid expanding polyurethane foam that could be made in small batches, required almost no labor and would form a fuel resistant foam block, boat builders jumped on this for their boat’s flotation.
It was not until years later that this so-called “closed cell” foam, that by the way is still approved by the Coast Guard, would raise its ugly head and contribute to water-logged and rotted wooden components in boats, but also to numerous sinkings, fires and explosions.
You see, in a controlled environment, expanded polyurethane foam forms an exterior skin which is what makes it water-proof. But if that skin is breached in any manner the foam becomes a literal sponge. Breaches happen whenever the skin is cut by a screw, bolt, or even cut or ground down to size by the builder.
Also, over time, with high internal boat temperatures during summer months, the foam can re-expand and crack the skin wide open. Not only will it now soak up and hold water, but it will also soak up and hold fuel. This obviously reduces its ability to float the boat in an emergency, but also makes it a floating bomb!
Odds are that your boat has the two-part expanding polyurethane foam for its flotation, but you can contact the builder to be sure. If it does and has wooden reinforcements, it’s a good idea that at the first sign of wood rot to not only replace the floors and decks, but at the same time replace the foam flotation with EPS blocks of foam."

 

[acabtp]

go to a different supply yard that has XPS sheets

 

[rscottp]

You gotta use the XPS foam. The other kinds will absorb water.

 

[mbweimar]

I was doing some research on the subject myself and just found this link. It explains all the differences.

https://www.diversifoam.com/xeps.htm

 

[rscottp]

Interesting info about the 2 part Polyurethane foam! That was my experience with it in my Lund, first of all most of it was shaved to make it fit thus breaking the skin and all of it was all waterlogged. I litterally pulled out 300-400lbs of soaked foam when I redid my boat! I have replaced all my foam with XPS foam or packaging foam I got for free(same stuff pool noodles are made from). Rig is way lighter now and I am much happier.

 

[SumDumGuy]

I used the white foam in my boat. I figure if it is good enough to be in those docks I see out there that have been in the water for the last 50 years and not absorbed water and sunk then it is good enough to use as flotation in my boat that is not going to have prolonged water exposure.
Further, the stuff I removed from my boat (1968 Crestliner Flying Crest) was original, white foam (that's creeping awfully close to 50 years, too). Apart from some deformation due to fuel contact the foam was in perfect shape (re-used as much as possible) and not water logged.
I think the blue, pink, purple or whatever color of foam is a waste of money. - the "white stuff" works perfectly fine.

Perhaps I'll snap a picture in 10, 20, 30 years when I pull up the floor again. :twisted:

 

[rscottp]

I think the only problem with the white foam is that when it falls apart you get those annoying little balls all over the place.