Adding a waterproof bulkhead?
As some of you may already be aware, I'm currently restoring an early Fletcher Arrowbolt (21' inboard cuddy) and as this has become more of a rebuild than a restore, I intend to use the opportunity for some subtle 'modifications' and updating.
Beneath the original cuddy floor was filled with buoyancy foam together with some under cushion GRP storage lockers. The very front of this section was open however and yet the foam filled section was sealed off aft with a GRP barrier from the main bilge (which ended just inside the cuddy area). After some 30 odd years (open boat) water had inevitably found it's way in - and although not excessive, had been drawn into the foam in a sponge effect. Once there, this was largely sealed in by the GRP cuddy floor adding weight and negating the purpose of the foam.
Either side of the engine bay, two boxed off sections were created with the bottom half of each also being filled with buoyancy foam. On top of this was a ply 'floor' topped with GRP forming two small storage areas - used for battery etc. These will be recreated. The main bulkhead between the engine bay and cockpit area stopped at about 3" above the keel - leaving a triangular hole such that the bilge under the cockpit ran through to the stern.
I'd like to change this layout and make the engine bay 'sealed' by taking the bulkhead right down to the keel such that any compromise of this section caused by a failed hose etc could only ever flood the engine bay and not the main sections.
Obviously this would mean adding a separate bilge pump for the cockpit area as any water from spray, rain etc would not be able to drain back to the main bilge in the engine compartment or out via the bung when ashore. I have however figured a couple of bigger issues:-
1) would I be wasting my time? If the engine bay flooded and overwhelmed the bilge, would the extra weight drag the stern so low that water would pour over the bulkhead or bust it anyway? How would I calculate this?
2) In order to access the engine for maintenance, the centre section of the new bulkhead needs to be removable! I don't think this is impossible and although space is limited, I envisage either an 'insert' that can be fitted from the engine bay side or a top 'slide in' section. These comprising perhaps two joined layers of GRP coated marine ply with the first made to fit the 'hole' in the bulkhead and the second over-sized, such that water pressure could not push this through?
I should add that forward of the bulkhead sits the fuel tank and rear bench seating (tank beneath seat base). I will be replacing the buoyancy, but ensuring that the sections are sealed and water cannot ingress. The vessel will be primarily be used as a family boat for extended coastal exploration...
Any idea's, pitfalls and other wisdom of the forum greatly appreciated!
Fletcher Rally: swfbr.org.uk