A New Hatch That Leaks Air
The clever new Seabreeze acts as a ventilator, but can an extruded hatch be as good as one made from cast aluminum?
It has been more than three years since we thoroughly examined deck hatches. There were lots of good ones—with Bomar, Lewmar, Nicro and Atkins & Hoyle leading the way.
Whether you want an offshore version that will withstand anything the sea can dish up or a lighter and less expensive hatch for less rigorous duty, our review in the July 1, 1994 issue has become an important guide for those faced with replacing hatches.
Nothing much has happened since then—until Jim Kyle marched in the office with the new Bomar Seabreeze. Almost as proud as a new father, Kyle spent months working on the Seabreeze. He’s one of the better engineers in the marine field.
His idea was simple: Build a hatch that keeps water out, but lets air in. Although it may appear, as in Maine, that “you can’t get there from here,” Bomar’s Kyle has found a way to avoid both that fetid, closed-up boat odor (and the attendant mildew) and the claustrophobic stuffiness of sailing in bad weather. The new Bomar hatch leaks…air only.
Here’s how it works.
Except for a substantial flange, the deck part of the hatch is fairly straightforward, in both the plain and spigot models. (A spigot model has a collar that extends down into the boat to which finish trim or a screen can be attached.)
The movable part of the hatch is where it all happens. In the top rim of the lid are machined slots that admit air and, of course, water (rainwater, spray, waves, etc.). The slots lead to a channel in the aluminum extrusion. As shown in the photo, the inner gasket and flange on the base permit the separation of water and air. The water runs out through vents in the external gasket or where the gasket is omitted entirely (on the hinge edge of the hatch). The air passes through to the inside of the boat. In essence, it’s a miniature but very long Dorade.
The dogs engage one of two positions. The first snugs the hatch down but leaves the air channel open, a situation that would prevail most of the time. The second position, much tighter, squeezes the lid down tight, compressing both the external and the inner gaskets against the hatch base. This would be needed only in very heavy weather or perhaps in extremely prolonged heavy rain, when the water might accumulate in the channel faster than it could run out.
Following our original assessment of hatches in 1994, Earl Hinz, a veteran sailor and author, pointed out in a letter that for offshore service, a hatch must have more than flexible seals. Hinz said that because solid water can squirt through such gaskets, the force of solid water must be broken by structural lips.
Because Bomar’s new Seabreeze has two such lips (one overhanging flange on the lid and a double-baffled hook on the base) it shouldn’t leak in the ventilating position and certainly not when clamped down in the second position.
The volume of air admitted probably won’t equal that of a couple of big conventional Dorade boxes, but Kyle is quite sure that the circulation will surprise boat owners.
He said that wind tunnel tests showed that if the wind is but 3 mph, the 18" x 18" Seabreeze will move more than 400 cubic feet of air an hour. A 6-mph breeze would run 875 cubic feet of air through the boat. The figures compare favorably with non-powered ventilators from Nicro, Beckson or Vetus. (West Marine advises that the average 30' sailboat contains about 800 cubic feet of air and that ideally the air should be changed no less than once an hour.)
The long-range effectiveness of the new Bomar hatches is probably dependent on the elasticity and “memory” of the gasket material. If the external gasket fails to retain its original shape, the hatch might eventually start to leak a bit in heavy weather. The good news is that it’s the easiest gasket to replace. The important inner gasket, not exposed to the sun, should last forever…especially if the hatch is dogged tightly only when necessary.
The new hatches, with 180° opening, also have clever locking handles and spring-loaded hinges adjusted with an Allen wrench (no “riser” arms are needed). The hinges are even designed to provide increased tension as the lid is opened to 180°. The tension prevents the lid from banging down on the deck.
Because they’re made of extruded aluminum, the Seabreeze hatches cost almost a third less than Bomar’s top-flight cast aluminum hatches. For instance, a 19" x 19" cast Bomar lists for $605 and discounts for $400. The same size in a Seabreeze lists for $435 and discounts for $290.
It’s a good question whether any hatch made of extruded aluminum can be as good as a cast hatch, most of which are made of the highly regarded aluminum-magnesium alloy called Almag. The complicated shape of the Seabreeze’s extrusions suggests rigidity that should equal that of the cast types. As robust? Hard to say. Unlike the one-piece bases and frames of cast hatches, an extruded hatch must have seams, either at a butt or around the let-in hinges. Such seams usually are weak points, the site of potential leaks.
For those determined never to flinch from anything the ocean can serve up, a heavy cast hatch remains preferable. All others, and particularly those who need better ventilation, might consider the Seabreeze.
Available in many sizes, with 3/8" or 1/2" acrylic or Lexan lens, the Sea Breeze hatches enjoy full US and European approvals
Contact- Bomar, P.O. Box W, Charlestown, NH 03603, 603/826-5791.