Another Foam Question

[brents]

I have yet another foam question for you all. I plan on using exandable foam and was trying to figure how much I would need. The weight rating on my boat is 1050 lbs. It is a 15' 1968 Chrysler Del Ray, all aluminum. I am not sure of its weight. When adding foam, do I need to add enough to offset the weight rating on the boat, or how should I go about this? The motor alone is 195lbs, does the aluminum offer any self flotation, or will I need to compensate for it? Also, there are no stringers in the boat, the floor is attached to wood that is attached to the cap. Will 2lb be enough density to walk on under plywood or should I go for atleast 4lb? Thanks for all the help!

Brent

 

[Bondo]

Re: Another Foam Question

Ayuh,........

I'd start with the 4lb. stuff,..... The 2lb. stuff will just gather more water, sooner......

The weight of the boat,+ it capacity isn't of concern,.....
What you need to figure out is the Volume of the area you have to put the foam Into........
Then buy enough of the product to Fill the Volume of the Void..........

 

[brents]

Re: Another Foam Question

Well, that was my original thought. However, with my boat not having stringers I know the foam must provide some support, the existing foam was expandable so I would imagine there would be some specific weight rating I should apply. Most of the expandable foam I see for sale has a weight rating of say 4lbs, then it says a qt will provide 100 - 120 lbs of flotation. If its 4lbs per square foot, then I would imagine that would cover up to 30 square feet right? Which is to much for my need. How much foam is typically used to fill a boat, a qt, or a gallon. Or is it manufacturer specific to expandable rate and temp applied?

 

[Robj]

Re: Another Foam Question

My guess it that is the density of the foam, 4lbs per cubic foot. I think it will expand about 20 times its original volume. That 120 lbs floatation is
(density of water-density of foam)*volume of foam in the can = floatation. If I remember correctly the density of water is 62.4 lbs/cubic foot. Therefore a can is roughly about 2 cubic feet. It is best to do that on a hot day to ensure full expansion of the foam. Make sure there are no leaks in your hull or that foam will get waterlogged awefully quick.

Good luck and have a great day,

Rob.

 

[oops!]

Re: Another Foam Question

try reading the first thread on cg rules.
(if you can stay awake)!

cheers

 

[rebuilt]

Re: Another Foam Question

2lb and 4lb pourable both offer right at 60lbs of flotation per cubic foot of expanded foam.. There is a site that offers a fairly complex way to compute how much you will need. The computation takes into account factors such as density of the hull, (fiberglass, wood, aluminum-different densities) total weight of the vessel, waterweight required to sink the vessel, and estimated passengers. (Lifejackets take care of that) I've lost the doggone link, but it is out there. The way it broke down for a fiberglass boat with motor worked out to be about 16 cubic feet for 1600 lbs. About a foot per 100 lbs for a glass boat. Bear in mind, 4lb is twice as expensive as two lb. It's twice as dense. For your application, since you're looking for structural help, probably the 4lb as a minimum. 2lb is more than ample for a stringered boat. It's all the coast guard requires. 4lb just adds weight in an application like mine.A good source for both the foam and info is
shopmaninc.com/foam.html Add the www. The guys name is Mark. USComposites. The stuff likes warm ambient temps to expand. The warmer it is, the more expansion you get up to 25 times by volume. Good luck. KR