Extinguishers rated for a specific volume are all well and good but.....
In my experience, you need more. The initial inrush of Halides or CO2 is a very temporary solution. It will knock down the actual flame, but the other 2 sides of the triangle still exist, namely heat and fuel
. After your gas replacement system is empty, the fire is out but the components are merely waiting to get some oxygen to restart, and sometimes will do so explosively as flammable gasses will be releasing. Ideally, boundary cooling
and direct cooling
will be needed, then ventilation.
The best system is the HiFog, where flame suppression and cooling happen simultaneously.
To answer your initial question, size it according to specs, then increase it.
It might all be completely useless anyway, as your bulkheads and access hatch
are plastic and will burn. Your internal hoses should be in steel
up to above waterline, otherwise they will burn through and admit water
, (thus helping with the cooling, but adding another problem.)
Do you have external fuel
shut off valves? Is there a battery
in the same compartment? Is fuel, gas, propane
, cans of spray, lubes stored in the same compartment?
Fire is my biggest fear on board.
Maybe look up Lloyds 100/A1 requirements for an idea.