Taming the boom

It was an overnight race down Australia’s rugged east coast from Bateman’s Bay to Montague Island. We had rounded the island in increasingly light airs and were now sailing north in about two knots in the dying breeze. We were all a little apprehensive. The night air was balmy, but one of the south coast’s notorious summer “southerly busters” was due. We could expect winds of anything from 25 to 40 knots and a deep temperature drop.

With a good crew there is usually time to pull in one or two reefs once the first cool puffs are felt, so we still had the full main up trying to coax the last bit of push from the fading nor’easter. But the southerly wind socked in much more quickly than anyone expected and in minutes we were surging north at more than six knots with a 25-knot breeze coming over the stern.

The forecast was for 25 to 30 knots. Saraband our long-keeled 30-foot Clansman, could carry its smallish full main comfortably in 25 knots downwind; 30 knots was okay with care. Since we were racing we couldn’t pull in reefs without rounding up and losing precious time. With the seas fairly flat, I decided to take a risk. The southerlies often blow themselves out in a matter of hours.

We rolled the first reef into the headsail, rigged a preventer, and braced ourselves for an exciting ride. For the first hour things were fine; then, as the seas began to build, the wind speed climbed to 25 to 30 knots, gusting to 35. We came close to gybing several times as Saraband gyrated its way downwind. It was time to reef.

The near-disaster happened as I was leaving the cockpit to go to the mast to prepare to tuck in the first reef. The helmsman reacted a second too late to an extra-strong gust, and the boat’s stern yawed though the wind. We crash-gybed. The preventer line, which had clearly passed its use-by date, snapped, and the boom scythed across the cockpit. I ducked my head just in time, but the boom thumped into my shoulders, knocking me completely cold — and nearly overboard.

I recovered with nothing worse than Technicolor bruises, but a couple of weeks later, just a few miles from our home port of Bateman’s Bay, the owner of a beautiful Kiwi yawl was knocked down by the boom in an accidental gybe. He fell, hitting his head on the primary winch, and was killed.

Shortly afterwards I bought a boom brake. What are boom brakes?

Boom brakes are simple, but quite expensive, devices that can act both as preventers and gybe-tamers. They can even function as vangs. They slow the speed at which the boom moves across, even in accidental gybesproviding they have been set up properly. They will also hold the boom steady in very light airs and sloppy seas.

The principle on which all the brakes work is simple enough. The brake unit is hung from the boom just aft of the vang. A strong line runs from a padeye on the gunwale up to the brake and then down to a block on the other gunwale from where it is taken back to a tensioning deviceusually a spinnaker winch. (The Kiwi-designed and built Servobrake works on a slightly different principle.)

The system works on the same principle as a winch: the more turns around the winch/brake, and the more tension on the line, the greater the friction. As the boom moves across in a gybe the friction that is generated in the brake slows its speed. The spinnaker (or other) winch is used to set different tensions for different wind speeds. There is less risk of the line snapping with a brake than with a preventer because the latter is fixed, while the brake, if properly set up, will slip under pressure. Even the strongest preventer line can break if a wild broach puts the boom and mainsail into the water when the boat is moving fast.

For me, the best demonstration of the value of boom brakes came some years after the Montague Island race incident during a singlehanded crossing of Bass Strait. I was sailing in near-gale conditions and very big seas under just a triple-reefed main with my boom brake set up and tensioned quite firmly.

The boat was being steered by an overworked and underpowered autopilot, and we were yawing a lot. Every half hour or so a big gust or wave would cause the boat to push its stern through the wind, just enough to gybe. The boom, slowed by the brake, would swing quite gently across with only a quiet “thunk” indicating that a gybe had taken place. It would usually gybe back again within minutes. There was no drama, and, most important, I could move around the deck and cockpit without the constant worry of being knocked over by a viciously swinging boom. But

while boom brakes are a godsend for short-handed sailorsespecially sailing off the wind under self-steering in heavy weatherthere are a few things about them that you should be aware of. The downside

Part of the price of enhanced safety is inconvenience. Even though I know exactly where the control lines are on our boat, I still manage to trip over them regularly. Plus, taking the control line out to the gunwales means that you have to unclip and re-clip your safety harness as you go forward clipped to the jackstays.Second, getting the tension on the brake line just right, so that the boom neither refuses to gybe nor gybes too quickly, is very fiddly, and somewhat nerve-wracking in strong winds. Set the tension too low and you could do some damage in a gybe. Set it too high and the boom won’t swing across at all. The latter problem isn’t too seriousjust take a little pressure off the winched line and the boom will swing across easily. In principle, you could set the tensioning line for each wind speed, note the speed, and then mark the line accordingly. But I found after a while that I could guess how much tension to apply at different wind strengths pretty accurately by whacking the tensioned line with a winch handle and listening to the sound it made.

Third, it is difficult to get the boom to swing right out when running before the wind because the brake lines tend to want to center it. A preventer is superior in this respect since it tends to pull the boom toward the bow. Being able to tension the brake line from both sides can help here, but this adds the expense of another turning block. It also makes marking lines for different wind strengths just about impossible.

Some brake manufacturers advertise boom brakes as a replacement for a vang, while others state that the vang and brake complement each other. Personally, I would never get rid of our solid vang. To begin with it stops the boom from dropping when reefing or lowering the sails. This is something that no boom brake can do. Second, when short-tacking you want the boom to move across quickly. A vang can help control sail shape without slowing the lateral movement of the boom; a boom brake cannot. And if you are harbor racing or cruising in moderate conditions with a good crew, a boom brake isn’t necessary.Our Dutchman Boom Brake can be tensioned by a block and tackle taken forward to the base of the mast, but bringing the brake line back to a winch in the cockpit via turning blocks on the gunwale and at the stern is more convenient and provides more precise tension control. On our boat the brake is tensioned and cleated off on the starboard spinnaker winch. If you don’t have spare winches you will have to use the primary winch that is not in use to tension the brake line. But you can’t cleat the brake line off on that winch and leave it since will be needed if you gybe. The solution is obvious: fit a stopper between the turning block on the gunwale and the turning block at the stern. But, like so many boat solutions, this involves more expense.

While all the brakes work on the same principle, they do so differently. The Heinson brake is essentially a drum with alloy cheeks around which turns of line are made, just like a winch. This is similar to the original, and expensive, French Le Walder brake that was used by Philippe Jeantot on Credit Agricole in the 1980s BOC races. Some users on the sailing bulletin boards have reported problems with the arms on the Walder breaking or deforming.The precision-made Dutchman takes a different tack, so to speak. Here the line goes around three sheaves, two fixed and one free to rotate. The sheaves, all in the same plane, are sandwiched between black alloy plates. The rotating sheave can have friction added by a large knob on the outside of the brake. On our boat I don’t bother with this adjustment, except to ensure that it is completely released in very light airs.

The simple and inexpensive New Zealand Servobrake system works rather differently. Here the brake line is fixed at each gunwale and is tensioned by a travelerbasically two pulley blocks, one on either side of the Servobrake and connected by a separate line. Pulling on the traveler line tensions the brake line by pulling the two blocks closer together.

In the U.K., Scott Design produces the Boomlock that, as its name suggests, locks rather than brakes the boom. It works as a preventer rather than a gybe-tamer. The Scott Boomlock costs a hefty 346 pounds U.K.

The cost of boom brakes varies considerably. For our Sadler 34, a new Dutchman Boom Brake would cost $249.00 U.S. from the U.S. mail-order firm West Marine. But add at least another $150 for the turning block, padeye and line. The Heinson brake costs $199.99 U.S.; turning block, padeye, and line would involve similar costs to the Dutchman system. By far the least expensive is the ingenious New Zealand Servobrake that costs approximately U.S. $80 ($160 N.Z.). But the two blocks and line would more than double this cost.

Boom brakes are more expensive than traditional preventers, they are more demanding to set up properly for different wind strengths, and their lines get in the way going forward. But the security they give when running in rough weather more than makes up for these drawbacks. Today I would not dream of heading offshore, especially short-handed, without one.

By Ocean Navigator