buoyancy foam for catamaran

are there any issues with placing expanding foam inside plywood hulls for buoyancy?
are there good and bad expanding type foams?
will the foam contribute any significant weight to a 6m power cat
sean

 

Thought you might find this link of interest, also calculates the amount of foam required

http://www.dpi.wa.gov.au/mediaFiles/mar_cv_foam_bouy_calc.pdf

 

i have a 2 part 3/4 full 4 l tins of polyurethane foam it says it has a density of 35kg/m3 does this mean that a full tin can make roughly a quarter of a cubic m of foam ? or does it tend to make much more than this?
sean

 

35 kg/m3 means what it says.
If the resin has a SG of 1.1 then 4 lt = 4.4 kg

4.4 kg / 35 kg/m3 = 0.1257 m3 which is about 1/8 th of a m3 per full can.

Of course poly foams often have different densities depending on the temperature that they are cured at. Higher density on the edges compared to the center which reaches a higher temperature.

 

as it is a 2part foam and each conatainer is 4l then i should only get a 1/4 cubic of foam this does not sound like much i thought these things were supposed to expand like mad, is 35kg/m3 quite a dense foam then?
sean

 

we fill all of our sponsons with 2 part poly foams. no weight issues and quiets the ride. and we use plywood for our floors.

 

Thats a foam with a bit over 3% solids, which is very low density.

 

ok thansk for that its just that in my imagination 1/4 cubic doesnt sound like much
sean