Under deck buoyancy, what to use?

chewy · 30 August 2009, 18:29

Have got a new project and wondered whats best to use for underdeck buoyancy. Have seen some polyurethane foam which is two part and provides 27kg of buoyancy per cu ft. I know Powercats use some sort of small ball a bit like a ping pong, and the HR223 used empty coke bottles.
Any one else used something different or which would be best?

Thanks

alystra · 30 August 2009, 21:20

Quote:

Originally Posted by chewy

Have got a new project and wondered whats best to use for underdeck buoyancy. Have seen some polyurethane foam which is two part and provides 27kg of buoyancy per cu ft. I know Powercats use some sort of small ball a bit like a ping pong, and the HR223 used empty coke bottles.
Any one else used something different or which would be best?

Thanks

IMHO I think foam is the very worst stuff to use. Whatever the manufacturers say, it does soak up water because the closed cells are rigid and they get progressively crushed as time goes by. Dell Quay Dories suffered badly from this. Provided there's a hatch to get them out if you need to, I would go for ping pong balls or plastic bottles.

Or, as with my boat, nothing at all.

codprawn · 30 August 2009, 23:02

Do NOT use foam!!!!!!!!!!!!!!!!

I wouldn't bother - that's what tubes are for. If you must fill a void another fuel tank is a great way to do it. Even when full of fuel they will keep you afloat but when empty they provide even more lift.

m chappelow · 30 August 2009, 23:50

the amount of scrap boats that our club has broken up over the years,sailing/ power/ply /grp have showed that a lot of so called foam filled would have been death traps ,ok most boats were from the 60s 70s and a few from the 80s so they were old ,but what was worrying was the amount of open cell foam used in bouyancy tanks ect,voids ,any leaks into these area s and the water just stayed there or very little drained back out again ,the amount of water weight was brow raising, and we have seen the home d.i.y using empty coke bottles/ gallon containers most which over the years had gained water .though having said that the cavity wall foam used in building seemed to fair up well .

m chappelow · 30 August 2009, 23:56

the amount of scrap boats that our club has broken up over the years have showed that a lot of so called foam filled would have been death traps ,ok most boats were from the 60s 70s and a few from the 80s so they were old ,but what was worrying was the amount of open cell foam used in bouyancy tanks ect,voids ,any leaks into these area s and the water just stayed there or very little drained back out again ,and we have seen the home d.i.y using empty coke bottles/ gallon containers most which over the years had gained water .though having said that the cavity wall foam used in building seemed to fair up well .

chewy · 31 August 2009, 06:41

Quote:

Originally Posted by codprawn

Do NOT use foam!!!!!!!!!!!!!!!!

I wouldn't bother - that's what tubes are for. If you must fill a void another fuel tank is a great way to do it. Even when full of fuel they will keep you afloat but when empty they provide even more lift.

I know this is in the RIB section buts it actually for a Tremlett 23. I can do anything at the movement as its a bare shell.
Am I best just having sealed compartments wiith inspections hatches?

Tim M · 31 August 2009, 08:24

Polystyrene is a good option if you do decide to fill it with something. Buy a big sheet, break it up and stick it in. I think I personally would seal it all up, put hatches in and leave it empty.

Jizm · 31 August 2009, 08:47

Ask a packing company (spare parts) for a couple of sacks of the polystyrene chips that look like wotsits!

Poly · 31 August 2009, 10:22

Quote:

Originally Posted by Jizm

Ask a packing company (spare parts) for a couple of sacks of the polystyrene chips that look like wotsits!

If you do go down that route then (1) make sure they are Polystyrene - many places now have moved over to biodegradable ones which slowly dissolve in water! (2) think about the implications of a fire in that space.

Personally I would say that anything small like that is fairly pointless - as a big hole will let them all out! I agree about foam filled being a giant sponge.

I would tend to leave it empty - and consider fitting a bilge pump (or fitting where you could connect a self priming pump - with tube to the bottom of the void on the inside) - if you are really worried.

Heart-trouble · 31 August 2009, 10:33

dont fill it with foam, like everyone else has said, it will get waterlogged, heavy and it is a nightmare to remove. i would fill the void with air. best not put anything there. the less stuff you have on the boat, the less stuff you have that will go wrong.

chewy · 31 August 2009, 10:49

Think I'll do a few and have hatches fitted. Will just have them full of air as everything else seems to have a downside.