Drain and flotation

[Guardian]

Hi, Can I please get get some help with a project Im doing at the moment. Im putting in a new floor in a Guardian 5 m half cabin. The underfloor is made up of 10 ribbed stringers/bulkheads running across the boat.
Ive pulled all the old stuff out out as it was rotted etc...There is a hollow square tube of fibreglass that runs down the spine to the rear bung.(it only goes 2/3 of the way to front..)
My main concern is do i seal up all of the 10 chambers and fill with foam so there is no drainage or do i put pieces of conduit in each bulkhead for drainage? If it Is sealed up to floor I am not expecting any water to get into chambers if they are glassed and gelcoated. If I allow for drainage and fill with foam will this stop any water from being able to drain out. Also I thought having sealed compartments would mean if I hit a rock at sea only that chamber will fill with water not the other 9.
Any advice would be appreciated.

Justin

[MERCMAN]

Hi Justin and Welcome to The Board.

I feel I understand your question. The first thing, I wouldn't fill the chambers with foam for many reasons.
To me, it makes very good sense to install small pieced of conduit say 20mm diameter (and as low as possible) between each bulkhead.

If you do hit something at sea, water won't enter a chamber faster than the air can get out. A decent pump can look look after what ever flows out of a 20mm conduit.
 
Underneath the splash well near the transom, make a cut out in the floor and install a Ronstan Inspection Hatch into chamber closest the transom, then install a decent 12V Bilge Pump.

I'm assuming there is already a Bung installed in the transom. If there is, your entire under floor area should be air tight, thus water tight.

Personally, I'm not fond of automatic pumps as the can have dramas. Generally, I'm on my boat when it's in the water and I will switch my pump on, if I'm ever trouble. Simple!

MERCMAN.