Opinions on foam filling a boat?

[Flex]

Hello all,

about to put some larger fuel tanks in my sharkcat. So I'm redoing the whole floor while tanks are up.

currently there are inspections ports for each compartment aswell.

im contemplating the pros/cons of filling it with foam and fully sealing the floor.

I'm also considering leaving out the inspection ports in the floor(about 8 of them.) except the back two.

as nice as it is, the do leak here and there.

on the flip side it is nice to visually see inside each one.

thoughts?

[Noelm]

if the foam is the right type, and done properly, there was a thread a long time ago done by a guy on another site that did a full sharkcat rebuild, and he put sort of false floors right at the bottom to allow for drainage, and to keep the foam out of any water, I would do it for sure, the inspection ports I personally would leave out.

[Chris Tucker]

Definitely worth doing but don't use expandable foams.

start with a couple of pool noodles in the bottom. Round shape means water will be able to drain through gaps. Then use sheet foam for the rest. If there is a local Ali boat builder near you most will sell you the right foam as it's cheaper for them to buy it in bulk. Otherwise try specmar.

Keep the front and back inspection ports, loose the rest.

[Michael Sharp]

A mate of mine is doing up a 5.5 shark cat at the moment and he did the same, he put false floors down both hulls for drainage then foam filled and sealed leaving out inspection ports. The only thing is make sure you have your shit together with whats under your floor (fuel clamps etc) nightmare job pulling full up.

[Noelm]

Not too sure if it breaks some sort of forum rules, but I found the old thread relating to rebuilding an 18' Sharkcat.
http://www.fishnet.com.au/forums/viewtopic.php?t=76926&start=0

[scottar]

Pros - Boat cant sink, will possibly make the boat quieter for occupants.

Cons - Many a totally sealed cat hull has had water mysteriously appear - easier to let water out than keep it out - unless the cavity is full of foam and you cant get in there. If you decide to fit additional accessories/wiring foam filling can be a nightmare. As mentioned by Michael above, maintenance of under floor equipment is substantially more difficult without access.

[Flex]

Cheers for the replies,
thanks for the link Noel,
i read that thread a long time ago and the guy did a great job.

one thing I though strange was the false floor. He sealed it totally so what happens if water gets above False floor?

i know expansion foam can absorb water as the middle doesn't cure fully. I had a thought of putting a big block of high density foam in each compartment with 2 inch gap around it. Then fill that gap with expansion foam. That way middle is less likely to absorb water and easier to remove if needed.

[tropicrows]

Don't use pool noodles, they break down and absorb water. Nothing wrong with expanding foam if it the correct type and done correctly. IMO I would not use foam I would prefer to have sealed chambers down each side. Foam would be my second choice, many boat builders (fiberglass and alloy) use it.

[Shark Poker]

Tropicrows is indeed correct if you never can access the chambers again
Also, Tropicrows and myself have this mate who poured expanding foam into his aluminium boat with terrible consequences. Ended up carrying somewhere up to 200kg of wet foam.

But the the problem with air chambers is that they turn into water chambers the moment they are pierced. The transition from positive buoyancy to negative (ie. you r sinking fast) is instantaneous.

Applying closed cell foam is a great idea. Have a look at this thread:
http://www.ausfish.com.au/vforum/showthread.php/195929-Successful-DIY-Boat-Flotation/page2?highlight=flotation+foam

The 2x1m sheets of foam are really easy to use, and can be purchased around $60 a sheet.

The important thing is not to compress it. Do NOT squeeze extra foam into the chamber because:

1. You are just squeezing the air (flotation component) out of it.
2. It will want to absorb water after that.

I have proven that it will absorb water after you compress it.
So, IMO, closed cell foam sheets cut into strips, with inspection ports.

Cheers, Pauly