Flotation for the Dinghy
by, 06-18-2014 at 01:10 PM (414 Views)
A good dinghy needs to serve many masters. I have no inflatable or outboard. No emergency life raft, either. So my 60-pound mahogany plywood Eastport pram needs to be a jack of all trades--sailboat, tender and one-man lifeboat. I wouldn't give it up, but the little pram does have limitations. Despite sealed compartments under bow and stern seats, when swamped it doesn't support enough of my weight to bail it out. It sails wonderfully, but for kids, a training boat needs to float high if capsized, which is why Sabots and Optimists have those lashed-in buoyancy bags. And then there is the ultimate function as last boat still afloat when bad turns worst.
The dink rides securely lashed upsidedown on the foredeck. To make it sit flush, with no wobble, I trimmed the transom to conform to the crown of the deck. A hard dink on deck has unexpected good consequences. It doesn't interfere at all with the genoa or with passage to the bow. The skeg makes for a grand first grab when going forward in a seaway, and the next handhold is an insert in the inverted daggerboard box (rightside-up, the insert closes off the trunk for towing). The most treacherous journey on most sailboats in heavy seas is from mast to bow pulpit. No more, on my boat.
So, am I making a case for light wooden dinghies on deck? Sure. But I can only carry two other people, and the water needs to be pretty flat. Rowing them is no fun, although alone you go like a surfboard. Forget a half-mile ride ashore with five guests in blazers drinking Prosecco, that's what an outboard-powered inflatable does so well. However, I don't miss dragging a wet mass of whale blubber out of a too-small compartment, pumping it up, and then praying over a British Seagull for an hour. Do they still make British Seagulls? Cute as a kitten and pass the spark plug wrench.
Anyway, how many dinghies can you have? One must serve.
As a solo lifeboat, an Eastport pram will make you smile. After all, an emergency life raft can be had for under $1,500. A standard inflatable, if pumped up in advance of disaster, does as well or better. I suppose you could have all three, and tow them in a fourth.
More flotation was definitely needed for the lifeboat role. It came in two cans--as two-part, 2-ounce expanding foam from U.S. Composites, at about $85 the gallon.
Although the chemical reaction causes heat, it's not all that much. So I just lined the forward well of the dink with cardboard, taped black plastic trash bags to contain the expansion in the necessary shape, mixed the components for the recommended 15 seconds, poured like it was nitroglycerine and ran behind the blast wall.
For the foam to rise the ambient temperature needs to be 70F, and 80F is better. Every ten degrees below 80 means 20 percent less expansion. I did the fill in three pours, since it is difficult to calculate the result. Urged by a heat gun, the foam rose in minutes and was hard and smooth in half an hour. When done in close sequence, each new layer adheres to the old. In three hours out popped a perfectly sized plug of foam that looks like it will support 200 or 300 pounds. Great fun.
I screwed a piece of 3/8 inch plywood over it to hold it firmly down. Added weight, about 8 pounds. Some lines looped around the gunnels give a lifeboat-like appearance and place to clip on a safety harness.
Are you crazy, going offshore with a wooden dink instead of an eight-man emergency raft? Well, maybe not, if singlehanding. During several gales at sea I've considered what it would be like to inflate and board a life raft in 50 knots, and concluded that a good result was not assured. At 80 knots, as in the Fastnet race, success seemed quite improbable. At best under gale conditions you can expect to clip your harness and EPIRB onto the survival vessel and manage to remain attached to it while departing the wreck in an uncontrolled way. When it's all hell in a handbasket, anything that floats is what you need and you'll be in the water with it, not inside it. Later you can bail and climb aboard and wait for rescue.
I conclude that, in 2014, there will not be much waiting. With a GPS EPIRB, AIS, and a Satphone, to survive abandoning ship in a storm likely means rescue within days. If you are run down without warning by a containership, well, your raft is probably not as important as your luck. If your boat is sinking after being holed by a telephone pole or an angry swordfish, or otherwise flooding beyond the capacity of the pumps, then if you have managed to communicate your position or at least turned on the EPIRB, you will probably bob off when the time comes with a dry shirt as she sinks out from under your feet. And this you can do in a pram as easily as with $6000 kit that must be inspected every three years for $900.
Risk assessment is a personal thing. My calculation, made while warm and dry and feeling clever, is based on the premise that satellites have changed everything. The likelihood of 60 days in a raft holding your hat upsidedown in rain squalls has been decreased by the swarm of observant grandmas in geosynchronous orbit overhead. What is all-important now is your GPS position and clean underwear. Fail to inform the satellites and the odds of rescue, even today, drop sharply, as the recent lost-keel event illustrated. If you do get off a call for help, as perhaps when your child develops a dangerous rash, no expense will be spared in coming to your aid. It is a little-acknowledged fact that, there being no world war, the navies of the world have nothing better to do than speed toward your plywood dinghy with its bleating EPIRB. The whole world is listening and wants nothing more than for you to shut up and appear for penance on the evening news. A lost yachtsman becomes a training exercise. That's good, and better than the old Navy Survival Manual for Lifeboats, which told how to make a fishhook out of a penknife and advised not to drink urine. Or anyway, what settles for good when disaster strikes.
I hope not to demonstrate any of this, or defend the thesis against a jury of sharks. But it does help justify adding eight pounds to what used to be a very light dinghy.