Posts Tagged ‘seaworthiness’

How to buy a boat

4 November 2009

The first step to a cruising life is to choose and buy your boat. Or maybe build it, but even if you’re planning to do that, you have to choose the design first too. Many sailors already have a boat, and so the advice for them is to look at it afresh and decide if it really is the one for you, and your companions, and for the lifestyle you have in mind.

The two main differences between local day sailing or day racing, and cruising is that you  spend many more hours on board, both sailing and anchored or tied up, and you may end up sailing in weather or sea conditions that you did not specifically choose.

Starting with the hull, the most important thing is that it is a seaworthy shape. Seaworthy is not the same as fast.

Plan form

If you look down on a yacht and it looks like the front half of a much bigger boat, then what you have may well be fast, it may even plane in a calm sea with a huge spinnaker up. The trouble is that when it heels, it will tilt bow-down. It will be a real handful in a blow, needing a skilled and alert hand on the helm. That wide aft-section has a huge buoyancy and when following seas come up under it, it will be picked up and swept to the side, again needing quick, agile and accurate actions from the helm to prevent broaching.

When you look down on a sea-kindly yacht it looks like a boat, tapering in nicely at both ends with the widest beam around midships.

It should not be too beamy either. I have seen a diagram that shows a normal ocean swell passing under three different boats from the on the beam. One is an old-fashioned design called a lead-mine, which was very narrow with a heavy lead keel very deep below (hence the name). Due to the circulation of water within every wave, this design actually leaned into the oncoming wave as it approached and then tilted its mast after it as it departed. A flat-bottomed racing, planing design sits flat on the water and is tilted in the opposite way by the approaching water bulge – away from the approaching wave, then away from it the other way as it departs. The third boat, nicely proportioned in a classical, boaty kind of way, just goes up and down vertically without leaning either way.

Now, real waves are not the exact right size or shape for any boat and if there is such a beam wave that does not make Rusalka roll at all, there are enough of them that do that I’ve never noticed one in a rough sea. None the less, I’m sure there is some truth in that diagram, and that beamy boats  feel much worse when wallowing in a big sea.

‘Wallowing in a big sea’, you say? Well, don’t sit there wallowing, get some sail up and get moving! When she’s planing along with a white wake behind, you won’t be wallowing, you’ll be skimming over the top of it all as she was designed to do. Well that’s thinking like a racer again. What about when there’s no wind for three days, just a big swell on the beam? What about when you’re cooking and eating, or when you and your partner are both tired and no one  wants to hand-steer? What about if one of you has just fallen down the companionway, or burnt your hand while cooking and first aid is required? When you’re cruising, you can’t just retire and head back to the clubhouse when something goes wrong, or radio the safety boat to come and take a crew member off. You need a boat that will look after itself and all on board all the time, no matter what happens. You need a seaworthy boat, and that’s one that’s boat-shaped.


There is no doubt that the best lift to drag ratios come from high aspect ratio foils. That means that a long, narrow wing is more efficient on an aircraft and that a deep, narrow keel and a similar rudder are more efficient underneath a racing yacht. This underwater layout is also very handy in a crowded marina – the boat will be instantly responsive to the helm and you will be able to turn sharply into any tucked-away berth. This design also goes with the beamy, bummy plan form described above. When she gets twitchy in a blow with the unbalanced hull causing you to veer off course with every wave or gust, then the highly efficient steering will allow the highly alert helmsman instantly to correct every twitch and veer.

Yeah.  Well you can see where this is going, can’t you?  What about when the helm is exhausted, or when the self-steering is not at its best? Do you just accept broaches and rounding up as par for the course? Of course not. You need a boat that has inherent directional stability. Stability is an interesting subject. A coin on a table is ‘stable’ no matter whether is sitting on its side or balanced on its edge, but it is much more stable lying on it’s side. Fighter jets with anhedralled wings (sloping down as they leave the fuselage) are inherently so unstable that a human cannot fly them straight and level without the aid of the fly-by-wire computer. On the other hand they can twist and turn in flight so sharply that they hope to out-manoeuver any adversary.

A long-keeled yacht has a large tendency to want to keep going in the same direction, for the same reasons as the flights on the back of a dart or an arrow keep it predictable in flight. This can be a nuisance in a crowded marina, but can be a life-saver in a storm with exhausted or injured crew, with no one on deck for hours at a time, in a big following sea, under electronic or windvane self steering, etc, etc. In short, when cruising.

Having the aft end of the long keel attached to the bottom of the rudder not only makes the rudder much stronger, but also helps keep ropes and other debris out of the propeller, and stops floating things getting between the keel and the rudder to ruin your day that way too.

Berths and accommodation

The first thing you’ll lose without that big back-end is the stately aft cabin. It’s useful when all your family or friends want to come and stay in a marina, but it’s no use at sea and quickly becomes a junk storage area when living aboard for any time. When people came to visit us in distant places we booked them in a local hotel and took them for day sails around the bay. Sea berths are easy to get in and out of, are narrow and they have lee cloths or lee boards to keep you in place whatever the boat does. Double bunks are nice in harbour. Design a liveaboard boat for the people who are going to live aboard, under way and at rest. Liveaboard yachts are not holiday clubs or floating hotels – booking a hotel room ashore helps the local economy and gives both you and your guests space to relax and enjoy the visit.

Big, open spaces in a boat at sea are dangerous spaces. The narrower the walkway, the less far there is to fall. Falling into a something a foot away hurts, falling against something that is two or three meters away can easily break a bone, and a broken bone 800 miles from land can be a serious problem.

Other considerations

Apart from the main items discussed above, most of the rest a boat can be altered and adapted if they’re not quite right already. It’s worth thinking about a few points, though. If too much needs altering or adapting, it may alter the price you would like to pay for a given boat.

You’re going to want a big anchor, lots of heavy chain (or nylon rode) and a windlass to pull it all up with. Make sure that if these are not fitted already, there’s plenty of room for them, and not too fiddly to access and operate.
Guard rails
Nowhere is it written in stone that a yacht must have wire guard rails, but a power boat can have welded steel rails. I had a local stainless steel fabricator weld two 1″ tubes coming up off the top of the pushpit curving along beside the cockpit another 9 inches above the top wire and then curving down to replace the first stanchion, just ahead of the cockpit. These make the whole cockpit much more safe and secure, give me something to hold when standing staring out to sea, and gave me a place to mount a couple of solar panels, like solid dodgers.
The cooker must be on gimbals, so that it can be used at sea. There must be a bolt to stop it swinging around, for example when opening oven door, in port.
Windows and hatches
There is a story of one of the early ocean yachtsmen taking a hammer to the boatyard and smashing all the windows in his newly built yacht to prove to the builders that they weren’t strong enough. That’s probably over the top, but there is also a story here in Jersey of a powerboat coming back from France getting caught in overfalls where the tidal flow, the wind and the uneven seabed combine to cause large standing waves. It had the whole cabin top ripped off and sank in no time, losing all on board. I have seen yachts with very silly patio doors or french windows that didn’t look like they would stand the first boarding sea. Think in terms of wheelbarrow-fulls of water travelling at flying-through-the-air speeds. It certainly sounds like a hammer-blow when you are below.
Also think about securable hatch covers on the companionway and on all internal and cockpit lockers. You must not lose a companionway board in a storm and you do not want your woodwork tools all over the place inside after the first knockdown. I knew someone who cut 10-inch round holes on their cockpit coamings to fit big, weatherproof loudspeakers out there for the stereo. I don’t think those speaker cones are wheelbarrow-proof, and once ripped away, those 10-inch holes will sink the boat in a few hours. I hope he’s still OK.
You do not need a fridge on a boat. If you have one, providing it with power will come to dominate your life. Poor people living in hot countries – and that is a very large proportion of the whole human population – do not have fridges. Learn to shop and eat like they do. In the Caribbean we ended up going ashore about every other day. When ashore we treated ourselves to visits to cafes and bars. When shopping we had to discipline ourselves only to buy enough for the rest of today and for tomorrow. Anything fresh would be going off after that. We are used to milk in tea, but we soon got introduced to the joys of a kind of chai – tea bags, cinnamon bark and sugar all in a teapot and left to stew. Most meat we ate was in local eateries; afloat we made vegetable curries, lentil stews, ate fruit, and enjoyed the odd slices of ham or local cheese. It really wasn’t a hardship by any means. We have a fridge, but switching it on is a luxury, not a routine necessity.

In the end…

All of the above is not to say that perfectly successful long-distance cruises can’t take place in fast boats, or that people cannot live aboard boats with no guard rails or with huge aft cabins. These are just thoughts about the kind of things that may not be obvious, but that individually or collectively may make life a little more comfortable or a little safer in some circumstances.