Builders' Forum Archives
Re: Bulkhead Hatches
Posted by Dave Houser on Mar 9, 2007
The front hatch is a long reach. The advantages of bulkhead hatches are a clean deck and if you stay in the boat they are assured they will not leak (mine are almost air tight so water in the cockpit does not leak past the hatch anyways). The big disadvantage is in the unlikely event you have do drain a compartment at sea it is nearly impossible. I use floatation bags for insurance and also to secure the gear.
There is only one t-nut and it is on the crossbar. There are two flat washers between the biscuit-shaped knob and the hatch. I grind two flat sides on the threaded end of the round-headed screw and epoxy it to the biscuit knob (after assembly) so the screw spins with the knob. The head of the screw prevents the parts from being screwed apart during use. When the knob is screwed all the way out the screw head jams against the t-nut flange and the biscuit knob axis lines up with the axis of the cross bar. This makes it easy to do the blind positioning of the crossbar when installing the hatch cover during use. If you count plys you will find there are two layers of plywood and one of gasket between the back of the hatch lid and the cross bar on the opening’s flange and on the back of the hatch cover there is one layer of plywood and the square gasket. This allows some deflection of the hatch from the clamping force. The hatch lid also has a little camber in it from the addition of the stiffener so the far ends on the major axis of the ellipse touch first to also help assure compression of the whole gasket. The square gasket seals the screw hole. Many builders will argue to leave it out so compartment pressure will equalized faster. I often have to wait a few seconds after loosening the biscuit knob for the vacuum in the compartment to hiss out (in?) before I can remove the cover.
In Response to: Re: Bulkhead Hatches by LeRoy on Mar 7, 2007
- Re: Bulkhead Hatches by LeRoy on Mar 9, 2007