I'm modifying each lazarette to hold a 5 gal. horizontal propane tank. Starboard tank for heater and stove. Port tank for BBQ. Problem: Existing lockers are too small. Solution: Make them bigger. This means not just the interior of the locker, but the opening as well. I also wanted the opening to match the profile of the original hatch opening so, although it will look a little different from the original, it won't look like it wasn't part of the original design. I started with a mockup of the enlarged interior to make sure everything needed to meet ABYC guidelines will fit inside. *

Once I knew space could be made to hold everything. I jumped ahead to the most difficult part of the project - building a gas-tight hatch closure. I wanted to do this first because if it proved not doable then I would go back to plan B which was to use smaller propane bottles and a smaller off-the-shelf sealed hatch, like the newer 22s have.I designed the locker lids on a CAD system. Each lid (port and starboard) was built as three separate components. The lid top and the o-ring channelwere then epoxied together. The lid base will be fiberglassed into the top of the hatch and the top will be secured with hinges and latches.

First I made the lid bases. At right of photo I've assembled the four mold parts for the lid base for the starboard locker. On left of photo are strips of 1708 ready to wet out and lay in the mold.

Here's the assembled mold ready to fill with epoxy resin and fiberglass. The molds were constructed from MDF, painted white with three coats of lacquer, and then sealed with six coats of mold release wax.

Mold has been filled with fiberglass and West System 105 epoxy resin with white color additive. I waited three days then I sanded the excess cured resin from the top of the mold before disasssembling the mold and releasing the part. I was nervous about it releasing but it easily popped free.

Here's the finished part, which will be the new opening to the lazarette, and is large enough for a 5 gal. propane tank to pass through. Next - make the lid with a channel to hold an O-ring. Then do the same on the port lazarette. *

Although I had a CAD design for the channel, I decided to not use it and trace off the rim of the lid base instead, to compensate for any way in which the finished base deviated from the CAD design, since proper fit would be critical.

I then glued 1/4" wide MDF strips to a base of flat plywood. This will be the "opening" that holds the 1/4" o-ring.

Here the three molds for the port channel are in place and screwed down to the plywood base.

Epoxy is poured and curing.

One day later I used a multitool to remove most of the excess epoxy.

After three dyas of curing I sanded the top of the channel smooth. I had pre-drilled small holes under the edges of the channel, on on each of the five sides, and filled them with wax. This allowed me to insert the flat end of a drill bit and tap on theh channel to help pop it from the mold.

The mold for the port lid top is ready for laying up with 1708 and epoxy. There are several 1/2" holes in the bottom of this mold which are filled with wax. This gives a means to tap on the back of the mold with a 1/2" dowel to help pop the part free.

Here the mold has been layed up with fiberglass, the o-ring channel has been inserted, and a strip of stainless steel has been inserted as backing for hinges. Also note that the whole assembly is resting in a box. This was done so that a jig could be clamped to the top edges of the box. This jig has strips of MDF on it that were tied directly to the o-ring channel with monofilament line, to ensure the the o-ring channel was positioned exactly flat, with respect to the top of the lid. The monofilament line was then simply cut to remove the jig once the epoxy was cured. Sorry I neglected to photograph this step.

Here the o-ring material is being inserted (friction fit) into the channel. The o-ring material is .250" Buna-N 70 O-Ring Cord Stock, from theoringstore.com. The glue is Vibra-Tite 388 Super Glue (specifically for gluing rubber) from Amazon. I used the chisel to make clean out the channel and ensure it was fit to hold the o-ring. The reinforced area (extra later of fiberglass) alongside the long side of the lid is where two latches will be installed. Next up - build the hatches!