July 26, 2016

Wet feet in the aft end

 THE COCKPIT of a sailboat is where most of the action takes place, but why is it called the cockpit? The dictionary tells us that a cockpit is a hole in the ground where cockfights take place, but I have noticed that cockfighting does not take place much on sailboats any more. So the question remains.

During the times I have spent in nautical cockpits my mind has been most concerned with what would happen if a big wave came flooding over the stern and filled the cockpit. At times like this, in the middle of a dark night, I try to calculate mentally how quickly the water would drain away through the patently inadequate drains provided by most boat builders. I never succeed in this calculation. Even if I remember that pi are squared and pressure is equal to something to do with height, minus friction in the drain pipes, I can never come up with a figure that is reassuring. It always takes too long for the cockpit to empty itself.

With a cockpit full of water, the boat will be trimmed way down by the stern, and succeeding waves will find it easier to roll on board and find their way down below, even if you have a nice strong bridge deck and sturdy companionway washboards.

I find myself wondering if the bilge pumps can cope with this sudden rush of water into the bilges, and trying to remember when last I cleaned the strainers. And so the watch passes in nervous contemplation until, at last, I am free to hand over the helm, take a large suck at the rum bottle and throw myself upon a warm bunk.

You might well ask why the cockpit is situated so far aft, in the position most vulnerable to large following swells. Well, it’s because that’s the place from which the person at the helm can get the best view of the sails. This is especially true for small boats, although some bigger boats can accommodate center cockpits that are less likely to be flooded.

One of the great authorities on ocean cruising, Eric Hiscock, said it was debatable whether the cockpit should be made self-draining. I would have thought this a no-brainer, but I have learned to be cautious about gainsaying the old-timers, and I’ve noticed that several well-known designs, such as the Nordic Folkboat, have cockpits that drain directly into the bilges. Their later fiberglass version, the International Folkboat, does have a self-draining cockpit, however.

Hiscock’s observation was that a self-draining cockpit in a small yacht would have to be so shallow, to keep it above normal water level, that the crew might washed out by a boarding wave.  Obviously, the more freeboard your boat has, the deeper a self-draining cockpit can be, and the better the protection for the crew.

My own observation is that the cockpit drains are never big enough, and the seat-locker lids are never waterproof enough. Furthermore, luckily, the instances of sailboats being pooped are reassuringly rare.

Some people say that most of the water in a flooded cockpit would be flung out quickly by the violent motion of the boat. Hiscock was one of them. But I have my doubts. In any case, I don’t want to try it. I might get flung out with the bathwater.

Finally, I’d like to share something it took me many years to figure out, and that’s why the drains in most cockpits are situated at the forward end of the cockpit sole, not aft where it would seem to make more sense.  It’s because when a boat sails at speed she raises a quarter-wave that rises aft, sometimes almost up to deck level.  With the water level outside so high, the normal gravity drains would never work; in fact they might back-flood water into the cockpit. So yacht designers place the drains close to the forward edge of the cockpit where the water level outside is lower.

For various reasons, some boats never manage to empty the cockpit completely when they’re under way and heeled. Often, you’ll find them equipped with teak gratings to keep their owners’ tootsies dry, but if your boat doesn’t boast this deluxe feature I’d recommend a pair of rubber boots. As nautical couture goes, it’s not very haute, but it’s a lot cheaper than a teak grating.

Today’s Thought
In smooth water God help me; in rough water I will help myself.
— George Herbert, Jacula Prudentum

“This here plant belongs to the fuchsia family.”
“Uh-huh. You just looking after it while they’re away?”

(Drop by every Monday, Wednesday, Friday, for a new Mainly about Boats column.) 


Anonymous said...

Hi John,
Why don't small cruising boats have large drains back through the transom like seen on small Wayfarer 16 dinghy? I was looking at an old Pearson Triton and was thinking a 2inch high by 5inch wide tunnel from the aft of the cockpit to the lower edge of the transom which would have a piece of stiff rubber as a flapper valve would work nicely to keep big water out. Those two little drains forward don't look very high flow.

John Vigor said...

Anon, there are quite a few boats that drain the cockpit the way you describe, including racing boats that have no transom whatsoever, in which the water runs out as fast as it runs in. But if you have a "normal" stern and transom, you need a fair amount of freeboard to accommodate a cockpit whose floor is both high enough above water level, and low enough to provide decent protection for the crew.
John V.

Anonymous said...

Hi John, in your opinion how fast should a swamped cockpit drain at sea? Looking at that early Triton a lot of work will be needed to make it an "ocean" cockpit. With all the openings, shifter slot, vertical lazarette opening, etc, it seems more gallons would be in the bilge vs returning to the ocean:)

John Vigor said...

Hi Anon: The simple answer is: before the next big swell comes along. But quite frankly I wouldn't worry about it too much unless you had an extra-large cockpit and no bridge-deck to stop the contents of the cockpit from flooding down below through the companionway hatch.
There are two makeshift answers to the problem if it really worries you. One is to fill part of the cockpit with a block(s) of polystyrene before you set sail. It should be shaped to fit and well fastened down. The other answer, which I prefer, is to fill the cockpit with bags of sails. They, too, should be well lashed down or held in place by strong lines over the top of the bags. Those lines should be fastened to clips screwed into the cockpit walls at a height you find suitable -- it's always a good plan to have those clips in place for emergencies.
The sailbags are nice and soft, but they will make the cockpit shallower, less protective, and more difficult to move around in. You must also make sure that they don't block the cockpit drains. But they will stop an awful of water from gathering in the cockpit and they are quite a comfort if you find yourself safely down below while you're lying ahull in a gale.
John V.

57 Degrees North said...

We are not terribly big on couture around here no matter how you slice it, but rubber boots are most definitely de-rigeur. In fact they are common enough to be considered appropriate footwear for any occasion... Top Siders (and related fashionable togs) by comparison, are almost guaranteed to generate levity and unkind comments from local bystanders.

So when plotting a course Northwards, leave the haute couture behind and flaunt those brown rubber boots, secure in the knowledge of warm and toasty feet regardless of what type of cockpit sole you have.

Oh, and speaking from experience, if the motion of your vessel is violent enough to "fling out" the water from a flooded cockpit, you probably have other, far more pressing issues to deal with... In any case, I have always been amazed at how much can be accomplished with a five gallon bucket when one is well and truly motivated.

Anonymous said...

Several years ago (in 1980's or so) two Swedish boaters converted their boat (somewhat Colin Archer lookalike) so that they removed the footwell in the cockpit - IIRC they had some coamings left in place but in practice the cockpit was part of deck. I think they claimed that it was structurally a lot stronger and they circumanvigated the globe successfully. Also they said that they got a lot more storage room under the removed footwell and in the book jacket they were sitting in the 'cockpit' feet straight and smiling happily... perhaps with good harness arrangements etc would give enough security in such a solution...