Thread: need plans for fwd hatch

Construct it so the hatch closes over a cofferdam like so... otherwise it will allow water in

Hatches (all types) are generally "application specific", meaning each is unique. Engineers and designers typically develop "systems" they can rely on. Once they do, subsequent versions will share a family resemblance for this reason.

All my hatches have similar traits, derived from what I've found that works. A lip, as Darce calls a coffer dam, is a common ploy to keep water on the weather side of the hatch. Often you'll see a "U" shaped channel to trap water, possibly funnel it off so it doesn't pool or drip inside the boat. Hinges are easy and usually the "over center" type, with several mass produced versions available. As are supports, stops, braces, latches, etc.

The basic requirements for a good hatch are: a strong cover, preferably one you could step on if necessary, a tight seal to keep out breaking seas and boarding water, a scupper system to remove water that might be trapped by the hatch, a positive latch that provides reasonably uniform pressure around the seal, strong carlins (what the hatch is bolted to) so it can support the hinges, a hefty hatch, etc. Don't forget the ability for the hatch to shed water and naturally it should look good and on a sailboat, be as low a profile as possible with very rounded edges, so as to not catch a line or trip crew.

This is likely much more then you ever wanted to know about the thought processes that go into a hatch. My hatch test is two fold. I take a 5 gallon bucket of water and I toss it directly at the deck just in front of the hatch. This simulates a breaking wave and forces water under the hatch edge and tests the seal. If it's just a "coffer dam" you'll have a large percentage of the 5 gallons inside the boat. Though if you put a good gasket on top of the dam and this is in contact with the hatch cover, you'll fair much better. The second test is the garden hose on full blast, directed at the edges of the hatch. I'm testing the seal and trying to force water past it. Some water (a few drops) is normal, noting is perfect, but you don't want much.

thanks - i really appreciate the trouble you took over that response - i might take a harder look at the hatch thats already in place - its very low profile and i didnt think about the possibility that a raised hatch might interfere with the rig. Might be possible to improve its waterproof-ness. Because the boat is quite high sided it doesnt let in sea water, its mainly heavy rain that gets in.

A hatch I made last year. The images aren't very good, but you should get an idea of the simple nature in the assembly, particularly the home made hinges. The whole hatch is about 30 mm tall when closed on the deck. This helps prevent lines getting caught under it or by it's sides. The planking is simulated, with 1/16" and 1/8" thick veneers of teak and mahogany. The hatch coming, hinge pieces and carlins are live oak. A barrel bolt serves as the hinge pivot, so there's no nut or bolt head sticking out to catch stuff too. Naturally the hinge base is through bolted to the deck.