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Old 07-12-2006, 21:37   #1
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Foam Floatation...What Is best?

I am presently looking at adding foam floatation to my hard dinghy to make it safer in the case of a swamping or tipping situation. Does anyone have any recommendations for what is the best type of foam to use to maximize the flotation effect of the foam. I have both a fore and aft locker that can be partially or fully filled with foam. Weight is also a factor in this, as always.

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Old 07-12-2006, 22:48   #2
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If you can cut a block to size and get it in the locker, Then Polysytrene would be your best bet. It doesn't absorb water and it is the lightest material you will find next to air. If you have to pour in something, then your best bet is Polyurathane foam.
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Old 07-12-2006, 22:55   #3
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Quote:
Originally Posted by Alan Wheeler
If you can cut a block to size and get it in the locker, Then Polysytrene would be your best bet. It doesn't absorb water and it is the lightest material you will find next to air. If you have to pour in something, then your best bet is Polyurathane foam.
Actually Alan, the white polystyrene with the little balls does suck up water, but i'm sure you were thinking about the blue Styrofoam

http://www.dow.com/styrofoam/what.htm

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Old 08-12-2006, 07:22   #4
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When cost is no object, always use a pour-in polyurethane foam. The lightest density is 2 lbs per cu. ft. If cost is a factor, use a piece of styrofoam (the blue kind preferably) and fill the gaps with spray-in isocynate foam (the kind that comes in a can from the lumber yard).

Remember to calculate how much foam you will need to float the weight of your dink and make sure your lockers will hold enough. The coast guard web site has a pamphlet on how to do the calcs.

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Old 08-12-2006, 11:55   #5
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No Dave, I meant the white one. Never heard of blue. The White doesn't actually "suck up" water as such. the little balls of polyS are only stuck together loosly. Water can migrate between the spaces, but not into the ball itself. Even saturated with water, it still remains the lightest material, with poly expanding faom second. By the way, Poly expanding also takes in water if you damage the hard skin surface. It can migrate into the lattace work of capileries. Just like the PS, the foam itself does not absorb water however
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Old 08-12-2006, 11:58   #6
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Oh yes, now I remember, the blue PS is used in construction industry here in wall insulation.
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Old 09-12-2006, 20:02   #7
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The White doesn't actually "suck up" water as such. the little balls of polyS are only stuck together loosly. Water can migrate between the spaces, but not into the ball itself.

Quoted by Alan


Fair enough Alan,
I just remember a cat over here where the front nosecone of the bridgedeck panel was made from the white stuff and when doing some modification's to it water ran out of the foam for quite a few days.

I just figured that the foam was absorbent in some way.

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Old 09-12-2006, 21:14   #8
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I may be totaly wrong here Dave, but I was under the impression the Blue stuf was fire retardant, hence being used in building construction.

Wow!water pouring out!! That wouldnt' be good. Hmmmm, so I imagine there is some rather major issue there. One, how did water get in? how did it get in there specificaly and why was there so much?
I wonder if the water was filling some void in there somewhere. Because the PS takes water up within the spaces between the little balls, it doesn't tend to run back out again if it did manage to get in.
There are variouse "densities" of the PS. I have seen large expanded balls that are very "loose" fitting and the more familiar we have here, is a very dense tight packed ball.
We have a manufacturer here in my town. I have watched a large "slab" of the PS being made. It starts off with the guy tipping in a container of these little white granuals. Then the mould is closed and high pressure steam is blown into the mold. The hot steam makes the little gainual expand and stick together. A few minutes later the mould is opened and out slides this huge slab. They then cut to variouse thicknesses using a hot blade on a table.
When they make an insulated packing box, same thing happens, but the mold is in the shape of the box.
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Old 10-12-2006, 13:24   #9
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i was actually just talking about doing the same today with our "leaky tiki" dinghy. Actually i'd like to add in a little bilge pump and to do this I would need to connect the forward and aft compartments, at the same time I was thinking i would fill it with the dow waterproof foam from home depot.
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Old 10-12-2006, 14:23   #10
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What is STYROFOAM?

Invented by Dow more than 50 years ago and identified worldwide by the distinctive Blue** color, STYROFOAM* products are the most widely recognized brand in insulation today. In the early 1900s, The Dow Chemical Company invented a process for extruding polystyrene to achieve a closed cell foam that resists moisture. Recognizing its superior insulating properties, buoyancy and "unsinkability," it was originally adopted in 1942 by the Coast Guard for use in a six-man life raft. That was the start of many other wartime applications by the Coast Guard and Navy. Today, the Dow STYROFOAM brand includes a variety of building materials (including insulated sheathing and housewrap), pipe insulation and floral and craft products. But there isn’t a coffee cup, cooler or packaging material in the world made from STYROFOAM.
These common disposable items are typically white in color and are made of expanded polystyrene beads. They do not provide the insulating value, compressive strength or moisture resistance properties of STYROFOAM products. In order to protect the Dow trademarked name “STYROFOAM”, such other material should be referred to by the generic term “foam.”

Doesn't this sort of say that the white stuff get's thirsty ?

That Oz cat I mentioned Wheel's, had done some serious offshore work and an around Australia race in company with "Steinlager II ".

I'd reckon water got in through holes that had been drilled for trampoline and catwalk attachment points that had flogged out a bit over the years.

Also a stint with the "Roll 'em over racing team" may have put that section of the boat underwater for a day or two.

For the job description above the white would more than likely be fine, but the blue stuff doesn't cost much anyway, so i'd get the blue if it was me.

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Old 10-12-2006, 20:38   #11
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Arrrrr yes, Styrofoam. Same but very different ;-)
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Old 11-12-2006, 22:18   #12
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Thanks for the discussion everyone. The BLUE or PINK closed cell foam used in construction has absorbed a certain amount of water over the YEARS while acting as an floating insulating lid to my above ground pool, but then it is in constant contact with water. I feel that this may be a good choice since in the dinghy it is usually dry.

I also thought about closed cell urathane foam as used in kayaks for padding and support beams but it is quite expensive!

I don't want to use poured or blown foam so I can remove the flotation if I have to repair my old, well used wooden dinghy.

I know from experience in kayaks that the white ball type foam is NOT a good bet. I just wondered whether people had any other ideas than the ones I had and it looks like the closed cell blue or pink may be the most economical and quickest way to go.

Thanks all!
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Old 12-12-2006, 10:07   #13
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"Doesn't this sort of say that the white stuff get's thirsty ?" If the white stuff all got thirsty, I could use my coffee cup as a water purifier, right?<G>

I think there's a difference in the quality (density) of the white expanded foam. Some is dense, designed for cups. Some is light, designed for more air and insulation with less plastic expense.

And then there's the white stuff that is more like florists' foam, which is open-cell and absorbs water very nicely. Maybe THIS stuff is what is causing more of the confusion, because IIRC folks use it for making displays and molds when they want mainly air and light weight, low cost?
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Old 20-12-2006, 18:00   #14
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foam flotation

Try Bubble wrap Packaging, cheap, but protect it from UV.
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Old 21-12-2006, 00:51   #15
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How does anyone suggest securing the styrofoam to the hull of the boat? I know it is easy to stuff a bunch of blocks into the lockers etc. but what if you have places that are exposed to foot traffic or weather.
I know someone who had a 13 ft aluminum work boat. He needed all of the space he could afford so rather than putting big chunks in the cabin he sprayed foam into the many nooks and crannies of the boat. How he could know that this would afford him buoyancy in a time of crisis is a mystery to me but the thing actually sank on he mooring during a blow and well, didn't sink - if that makes any sense. Anyway the point of this diatribe was to see if anyone had any thoughts of spray foam vs. styro chunks.
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