As the build progresses, we came to the subject of hatches. How many hatches, what type, location, and which rules apply? One of those events where our owner's rep, Akan Dumrul, started asking questions, and we needed to understand an appropriate answer.
To which hatches are we referring?
The rear engine room access door sits below the main deck, exposed to the sea on the swim platform. It needs to be watertight and secured from the inside. It can have a small glass panel but the size is limited under UK MCA rules.
Cabin light/access hatches.
These three are also at the main deck level; they are glazed but will also need aluminum storm shutters. They need to be watertight and secured from the inside. One is internal and needs to be arranged so as not to foul the saloon furniture when opening.
Engine room hatch.
A construction detail for engine room access. We will probably weld this closed for strength and watertight integrity. There is also a tiny escape hatch, similar in construction to the cabin escape hatches but with solid aluminium cover per MCA Regulations. . We cannot glaze it per UK MCA regulations for machinery spaces.
These are internal to the vessel. The forward engine room door needs the be fire rated, noise blocking, and watertight. The forward cabin door needs only really be weathertight.
Helm door hatches
Helm door is above the main deck and need to be both weathertight and securable from the inside. This door needs to be either sliding or pantograph due to a narrow port side walkway. If hinged, it must open forward per UK MCA, sliding doors can open aft. Height is 1.5m so its a step up and out grabbing a rail on the cabin roof for support.
Saloon door hatches
The rear saloon door is to be secured externally also as it is the primary access to the vessel.
is secured at sea and watertight. If we want to access at sea, the coaming must be 300mm higher than the main deck. Hinges must be on the forward edge so any head sea forces it shut.
Swim step access platform. I'm of two minds here as its so near to the waterline it seems like a leak just waiting to happen. Naval are investigating access from within the engine room as an alternative.
Hatches invariably open outward, forcing them to shut by seawater pressure. Additionally, all watertight hatches have limit switches that trigger an alarm at the helm if left open. That way, we can confirm hull integrity before venturing forth.
All deck hatches are flush fit, fully welded construction to maintain hull integrity and save stubbing toes!. The pipe bottom left is a drain for the seal that leads water to a convenient overboard discharge point. All internal metalsurfaces will need EPDM insulation to limit condensation.
I have called out the phrase "main deck"; it is a UK MCA stipulation in so far as :
At or below the main deck level, all external hatches must be watertight and secured at sea.
Above the main deck level, weathertight hatches are also acceptable.
While we are on the subject of definitions:
Weathertight for our purposes means able to withstand water from mainly one side when at sea.
Watertight means able to withstand water from both sides to maximum head about 2.0 meters after which Vanguard's fate would be sealed as this is greater than the freeboard.
We understand that there are other far more rigorous definitions, for example within SOLAS and that a marine approved wheel marked door may be more capable but these are ours for our purposes.
During this process, it became rapidly evident to us that hatches are not simply doors. A good number of regulations govern their design and use, developed no doubt, from harrowing experience over time.
If anyone had told me about the level of detail needing consideration in building a yacht, I might not have believed them at the outset. In my last career, we built custom homes of similar cost, but shipbuilding is not like construction. The detail and scope are relentless, though, to be fair, the end is now coming into sight. XPM Hull No 4 may just be a walk in the park!