Double-Coaming Bow Hatches

As you may have guessed from the length of time since my last post, work on the Tiki 26 has slowed due to other obligations and considerations. I'm expecting to pick up the pace again shortly, despite the arrival of colder weather which interferes with the curing of the epoxy.

One project that I have been working on is building the double-coaming hatches that provide access to the forward storage compartments in the bows. These compartments are sealed off from the main cabin areas by watertight bulkheads that go from the keel to the deck, so having totally waterproof hatches here is not absolutely necessary. It will be nice, however, to not have to worry about these compartments filling in rough situations where solid water might sweep the decks, so I have elected to go to the extra trouble of building double coaming hatches, rather than the simple lid hatches shown in the plans.

This type of hatch is the most waterproof design you can build with wood and epoxy, and does not require a gasket-type of seal to keep the water out. The design consists of a high inner coaming and then an extra outer coaming about half as high that meets the overhanging hatch trim. The outer coaming turns away most of the water, but if any gets in, it is stopped by the inner coaming and then drains back out via a couple of drain holes in the rear of the outer coaming.

The first step in building these was to make and install the inner coamings. These are 3 1/2 inches high and made of two layers of laminated 6mm ply. The first layer was screwed into the sides of the deck stringers that run under the decks parallel to the hatch openings on each side. The second layer was laminated on from the outside and filleted to the adjoining deck surface. This makes for a very strong and rigid inner coaming.

The front and rear pieces were then fitted to the adjoining sides, with epoxy fillets in the corners to reinforce them. After the clamps were removed, epoxy fillets were made all the way around to the decks, then the outside corners were rounded off to a nice radius with a belt sander.

An overhanging lip of 6mm ply cut to 3/4 of an inch in width was epoxied on the top edges of the coamings. The extra 1/4 inch of overhang is designed to further aid in turning away water that might otherwise squeeze between the top of the coaming and the hatch cover.

To insure that the hatch lid lies completely flat on the coaming, I sanded across the finished coamings with a rigid longboard to take down any high spots and keep everything level.

The hatch lids were then built using 9mm ply and an outer, overhanging lip of 1/2-inch ply to match up to the outer coamings. These hatch lids are larger than the inner coamings by about 3/4 of an inch all the way around, to allow for a channel between the coamings where any water that gets in can be contained and then drain away.

The first step in building the outer coamings was to align the hatch lid over the opening and then carefully mark the locations of the two outer side pieces. The installed outer sides of one of the outer coamings is shown here. The extra length will be trimmed when the athwartship pieces are fitted.

Here is how the hatch lid fits over the coamings. When closed the flat panel of the lid will rest on the top of the inner coaming. The outer lips of the hatch lid will mate with the top edges of the outer coamings all the way around.

Fitting the front and rear pieces of the outer coaming was the most difficult part of the job, as the bottom edges of these have to match the deck camber and the fore and aft placement of them has to exactly match the locations of the hatch lid overhangs. Here is a view of one of the rear pieces. You can see the drain openings cut at each rear corner. These are the lowest spots on the coaming and being to the rear are less likely to get wave action forcing water through them.

This is the other rear outer coaming. I installed both of these today, so now the hatches only lack the forward pieces before they are complete. When finished, the hatch lids will be attached using stainless steel piano hinges along one side and a locking latch on the other. All of this is a lot of work, but it will be nice having these large storage holds that are both dry and lockable.

I'm heading to Florida tomorrow to help David show his Tiki 30 at the St. Petersburg Strictly Sail Boat Show. I'm looking forward to a few days of hanging out on a boat, particularly a Wharram, and talking to people about sailing, boatbuilding and design. Reuel Parker will be there as well, so I'm sure that after a good dose of inspiration from him and David, I'll be ready to get back to work on Element II.