Ventilation Aboard Seal
by Kate and Hamish Laird

• The Lairds are staying in the UK for the winter, and are looking forward to getting the sails back on the boat. The summer's schedule includes Ireland, Scotland, and the Faroes, before heading off for South America in August.

One night in the Southern Ocean on a BT Challenge boat, we were slogging to windward (as ever) with the wind averaging 50 knots. We were all well used to the motion and the shuddering stops as the boat came down hard off the waves. Before leaving Australia, we had removed all the dorade cowls and replaced them with aluminum disks, which we siliconed down and tightened with the clamping ring.

Our cabin had a butterfly vent at the base of one of these dorades, well inboard on the coachroof. With a huge lurch, the boat took a wave, and a wall of water came in through our vent. My cabinmate Ligia was directly under it, but lucky enough to have a Gore-Tex bivy sack over her sleeping bag. There was nothing to do about the leak now. She pulled the bivy sack over her head and said to me, "If I'm dead in the morning, sue Gore-Tex; we'll know it's not breathable." She went on to have a good night's sleep – it's amazing what you can sleep through if you're tired enough.

The problem with ventilation is if the air can get in, so can the sea.

Dorades

This picture was vivid in my mind when we build Seal. We do have dorades on board, but they are all high on the combing around the raised saloon, and when we sail offshore in high latitudes, we take them off completely and replace them with aluminum caps, siliconed on and bolted down with six machine screws each.

Seal underway from Greenland to Scotland in September. Dorades are completely removed (and storm covers are on the windows.)

We do have a secret "dorade" though, to provide ventilation when we're offshore. In the center of Seal's deck is the keel box, which provides a well protected spot for ventilation. At the aft end we have three pipes coming off it – one for engine room ventilation, one for the raised saloon, and a third for the heater fresh air intake. Eight feet farther forward at the other end of the keel case are a series of ventilation holes drilled in the cover. This acts as a huge dorade box to keep positive pressure on the vents (particularly the heater intake) without the risk of a wave filling them up – the waves run down into the keel case and back into the sea.

Hatches

On Seal, the raised saloon serves to lift its hatches well above the deck. The portlights on the aft end of the raised saloon can be open in nearly all weather, and the ones on top can be open long after the ones on deck need to be closed. The galley hatch is the last one to close: most of any incoming water will land on the galley counter and drain straight down the sink; the rest will soak the raised saloon sole, but the two access hatches into the engine room are well sealed (and guttered just in case) to keep water (or stray bits of soup) off the engine.

We had an incident on our way from Greenland to Scotland last summer when two of our guests felt their cabin was a bit rank after a week without opening the hatch. We'd been in a gale for a few days, and now the wind was light. We had some leftover seas slapping about, so Hamish said don't open the hatches. They did anyway. Sure enough, after an hour or so, a wave dove down into the hatch, soaking their bunks, sleeping bags, gear, everything. When we arrived in port after a week's passage, with several gale force days, it took us less than two hours to clean the rest of the boat. It took them (we're very grateful they volunteered for the job) two full days to wash the mattresses, bedding, and sleeping bags, and to oil all the tools that live under the bunk in that particular cabin.

But what about at anchor? Clearly, a hatch that opens forward will catch the wind better and bring it down below if you are swinging to one anchor, but almost all ocean-going boats have aft-opening hatches. We discussed this with Ed Joy at Chuck Paine's design office. Common wisdom is wrong, he told us. The hatch dogs are actually the strong point, and can be easily tensioned, whereas the hinge end is a fixed tension, and more likely to leak. Aha. So all Seal's hatches open forwards to catch the air at anchor.

Fans

Where we cruise, keeping cool at anchor is usually not a problem – keeping warm is much more of an issue. We did spend a month in Belize last year, however, and it was hot – unbearably hot, really, when you weren't under water. Twice when we stopped in Belize City, the thermometer reached 108. There wasn't a breath of air to circulate around, and we don't have air conditioning. We didn't do much except swim and scuba dive, and tried to move the boat only in early morning or late evening.

Hella Fans are very good – we have to turn all seven on to get them to register on the amp meter. (We have the 24-volt model.) One thing we did learn while installing them is there is no standard between the black wire and the black with white fleck wire...three or four of ours ran backwards and had to be rewired. Test each one before wiring! Our fans are all at the foot of the bunks – someone pointed out to us that if your feet were cool, the rest of you felt okay, and that foot fans were much less annoying than head fans.

Another thing we learned in the heat was it's not all about ventilation. Avoiding heat build up in the first place is almost more important. Most of the following tricks were not originally planned for keeping the boat cool, but they did help enormously in Belize.

Insulation

We have three to four inches of blown foam insulation everywhere above the waterline. We did this for the Arctic and Antarctic, but it is as good as keeping heat out as in.

I remember sailing on a black steel-hulled boat in the tropics – I could give a good weather forecast without getting out of bed, just by putting my hand on the ceiling. With Seal's unpainted aluminum hull and the insulation, there's no heat coming in at all through the sides.

Light Bulbs

We avoided Halogen lights because of the bulb heat – we didn't want that kind of heat near our foam insulation - and so we opted for surface mount incandescents and a few sets of Hella LED lights where the brightness wasn't so critical. (All our night lighting is red Hella LEDs as well). Instead of a florescent tube in the galley, we put in a row of six 12-volt white LED lights (with each pair wired in series to get 24 volts). Again, we had other reasons for doing this (once you've carried a 24-volt florescent tube in your luggage, you will never do it again), but the effect was much cooler lighting on unbearably hot nights.

Keep the Sun out

We have full blackout shades for all the hatches and windows. The hatches are to help us sleep in the land of the midnight sun (we had a month without sunset in Greenland last summer) and the saloon window shades are to keep light off the deck at night and for privacy alongside.

Anna's third birthday, with the full light-blocking shades on the forward windows.

Whenever we had to lock up the boat in Belize, we made sure to draw all the blackout shades on the hatches and hang them on all the windows. We forgot once, and it made an unbelievable difference to the temperature inside the boat.

While on board, we used the blackout shades on the slanting forward saloon windows and Phifertex Mesh screens on the vertical windows (none of these windows open). The Phifertex Mesh cuts 70% of the sunlight, yet gives a fairly good look at the outside world. (Be warned, the Phifertex doesn't do a thing for privacy at night.) We had these made specifically for the tropics, and we were very pleased with how they worked.

The Phifertex Mesh sun screens at work (with the dorades behind).

Keep the Bugs out

Rumor has it that in some parts of the world, you can keep your hatches open without worrying about mosquitoes, no-see-ums, and the like. I started sailing in Maine, and rate good mosquito screens right up there with things like the deck.

On most of our hatches we have an Oceanair "surface sky screen" – this is a clever design with a mosquito screen on one side and a blackout shade on the other. You can pull out mosquito, blackout or have nothing over the hatch. These worked very well (British design, notes Hamish), and have the great advantage that you can slide the screen back and close the hatch when it starts to rain without really waking up. For a new build they were reasonably economical because we used them in place of headlining trim. The mesh is also very fine; one of our hatches wouldn't fit an OceanAir cartridge, so I made an old standard Velcro and mesh job on the sewing machine, but a handful of Belize no-see-ums managed to make their way through. It is on the remake list when we get to Scotland – apparently they have the finest anti-midge screening around.

The back of the raised saloon is covered by a massive screen that runs on an awning track and covers the main door and the four port lights on the aft end of the saloon, as well as giving a mini screened-in porch.

Wind Scoops and Awnings

We sometimes string bed sheets up as wind scoops over hatches, but we don't spend enough time in hot weather to bother with especially-built ones. Same with the awning: I brought enough fabric to the south to make an awning over the cockpit, but I never built it. It was too hot to work! We didn't accomplish anything but the most crucial work while we were in the tropics. (I did sew the last few mosquito screens without much prompting, though.) If we ever go back to the tropics to cruise, I will make some rain covers for the hatches (really, Hamish, I promise) before we go, so that we can leave the hatches wide open when it's raining. Another thing that was "tropic-ed" off my job list.

Engine Room

With our sealed engine room, it became apparent that 4 x 4-inch dorade vents were not enough ventilation in the tropics. Engines don't like the heat, nor do the batteries. We improved matters by installing an exhaust blower in one of the dorade pipes. (It is important to have an exhaust fan, not an inlet fan, so as not to pressurize the engine room, which could cause the fumes to come into the boat rather than out.) We didn't buy a continuous service blower (we should have), but the off-the-shelf Jabsco Marine Blower has worked beautifully. We even soaked it once, but it is designed to keep the motor clear of incoming waves. (This, if we needed it, was another proof of concept of getting rid of the dorades completely for high latitude offshore sailing: we had the dorades fully closed in the position the manufacturer describes as "closed off entirely." Not entirely enough.)

And if that Doesn't Work...

When a friend of mine went to college in Alaska many years ago, she was surprised to see a quarter-sized plug in the wall, tied on with a piece of string. "What's that for?" she asked. "Fresh air," said her roommate.

I don't like sailing where it's quite that cold (the thermometer stalled at minus 70 F that winter) - but give me some good thermals, better foul weather gear, and a Refleks heater, and I think the tiny portlight in the bulkhead over the galley sink is about enough ventilation for a sailing boat.

We're heading down to Antarctica for next February to support a climate change research project. That will be just the right temperature. But between now and then is a long passage through the tropics, where no boat has enough ventilation...and we will no doubt go back to the bucket-of-saltwater-over-the-head technique.

You can learn more about the Lairds and Seal at their website www.expeditionsail.com.