What is a crash bulkhead? The term watertight volume would be more appropriate. This bulkhead actually is designed to create a watertight volume in the boat so it can increase the buoyancy in case of emergency like a capsize situation. In the design of the JEFFCAT 44, the bow section of each hull includes a crash bulkhead, this is the case with 99.9% of the catamarans out there most probably.
The design shows how the crash bulkhead goes from the bottom of the hull upwards and ends just below the forward beam. This plan also shows an extension of the watertight volume towards the left just underneath wat used to be the sail locker.
I had always been worried about the condition inside that unaccessible volume. The fact some holes had been drilled outside on the hull in that same area made me fear for some water intrusion. Best way to find out is to dig deeper, right?
The idea is to cut out a part of the bulkhead: big enough to see what is going on behind but small enough to be able to close it up again afterwards and make the panel watertight again. One anomaly that pops up right away: shouldn’t a watertight surface be laminated completely? It is well visible on this picture that only the sides of the plywood have been tabbed to the hull, the rest of the wood is still exposed. Not really reassuring for what is to come I would say…
Two main observations after opening of the crash bulkhead. The wood is wet, very wet on the inside, meaning the volume is indeed a watertight compartment… but on the wrong side! The other observation is how the recommendation of the architect “fill with 340l foam” has been implemented in the real world. The volume is actually filled with various scrap parts of styrofoam and a small portion of injected foam at the bottom. In other words, the volume is still full of air and the foam is not made out of closed cells at all. Being this far in the process, there is only one way forward: open more of the area and assess the damage caused by the water but also what the origin of this infiltration could be.
In total I emptied 3 and a half bucket of water that had been collected in the forward bilge. This means over 30 liters of water that was inside the watertight volume.
A quick look in the emptied area does not reveal any visible opening in the hull surface. But there is a suspicious zone: the connection of the main beam with the hull.
So the conclusion is simple: there is a leak inside the beam and the water is accumulating inside it partially and then flowing downwards inside the watertight volume of the crash bulkhead. Let’s have a closer look at the beam in this case.
The beam on a Lerouge catamaran is unique, it is like the trademark of the models designed by this famous French naval architect. Most catamarans carry an aluminium bar attached to hinges on each side of the hulls, but not with Lerouge. His beams are actually part of the structure, piece of it is in the deck mold, other pieces are produced separately and then laminated to it and to the hulls.
This kind of beam design increases the global stiffness of the catamaran. This of course provided the construction has been carried out correctly and according to the plans of the architect.
The only way to confirm the assumption concerning the origin of the water intrusion was to open the way further to the inside of the beam.
So, at this stage it is clear the water is originating from the beam. But how does it get into this volume? An external inspection on the beam is the only way to find the truth and draw final conclusions.
There is one major final conclusion here: the beam has not been constructed as an end to end element like depicted on the plans of the architect. Instead of multiple tabbings to the hulls, it has been single side tabbed to the inner facet of the hull. Most probably, this construction did not bring the required stiffness to this critical area of the catamaran that is subject to a lot of torsion and transversal efforts. The end results is appearance of cracks followed by water intrusion.
The way ahead is to have everything dry completely first, remove the old tabbing laminate, add connector plates in extension of the beam contours to the outer hull and laminate + tab these using preferably an unidirectional cloth for increased longitudinal stiffness. I will wait before putting back and closing the crash bulkhead and observe if water keeps coming in from the beam once the cracks have been repaired. Most likely a reinforcement will also be required on the outside at the junction of the beam with the hull. 99% chances the situation on the port side will not be any better.
You think this is all? Wait until the next post! Stay tuned!