TECHNIQUE Sailing on autopilot: here’s how not to strain it

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autopilot
You are sailing, alone or with a small crew, on autopilot. Gait by gait, let’s see how you will have to adjust the sails as best you can to lighten the pilot
decreasing the risk of strains, ruptures and all that goes with it. (opening photo taken from https://swellvoyage.com)

ADJUST THE SAILS TO LIGHTEN THE PILOT

Upwind wide
At this gait it is generally possible to strike a balance between the mainsail tending to heel and the genoa tending to bear down (lean). This balance will allow the autopilot to require minimal effort, or even to disengage it and lock the tiller. In practice, to proceed with the tiller locked in, one operates in two stages: first, with the pilot installed or by hand steering, one chooses a windward course a little narrower than desired and adjusts the sails to it. Then, second step, you lock the tiller by putting the pilot on “standby” or by securing the tiller with a matafion (a hemp braid); then you lightly let go of the mainsail sheet.

The boat, leaning slightly, will then be on the desired course and at a steady gait: if it tends to lean, caulk a bit of the mainsail so that it will bear down to resume the previous course; if it tends to bear down, take power off the mainsail and then make the boat lean (the genoa has a less important role in the adjustment mechanism: it is the engine and not the flywheel, so it provides propulsion). If you do not get a good balance on the first try and the boat tends to heel, it means you are leaning too much on the mainsail: too much thrust in the back than in the front. It is then necessary to open the mainsail a little more. Of course, you will have to repeat the operation and readjust the sails if the wind changes speed or direction. Balance is generally easy to find as long as the heeling does not exceed 15 degrees.

Otherwise, the genoa will push, like the mainsail, to heel, because heel increases and there is no more adjustment. It is then a matter of reducing the heeling by decreasing the power of the sail: one will have to retract the genoa sheet point to close it at the top or, if that is not enough, take a hand of reefing and above all begin to furl the genoa. One may well proceed, upwind wide, with the tiller stuck in the middle or, when the wind strengthens a bit, with a reefed mainsail and a reduced genoa, at least as long as the heeling blows are not too violent.

At load-bearing gaits
At carrying gaits, the sails work under thrust and no longer in finesse; the sail force thus undergoes little change as the boat’s course changes: there is no longer the adjusting effect that, upwind wide, allowed the tiller to lock. In addition, at carrying gaits, the wave causes counter-heeling and not just heeling: the tiller will have to have different reactions (upwind, the boat may have too much heeling, or not enough, but it is always on the same side and the wave interferes less on course keeping). At carrying gaits, therefore, it is impossible to find a stable balance and lock the tiller. The pilot cannot be dispensed with, and the skidding or counter-skidding that happens suddenly, without any premonitory signs, will impose considerable efforts on him (just as it would on the crew member who is at the helm in the case of manned navigation).

In order to limit the pilot’s workload as much as possible at this gait it will be necessary:
1. Avoid overpowering and, in windy conditions, lower the mainsail to continue under jib only, so that the boat is more docile to the tiller and therefore easier for the pilot; in this case it is as if the boat is pulled from the bow.
2. Depending on the wind, wave, and sailing destination, look for the course that will keep the boat flat and the tiller as neutral as possible; often 10 degrees more or less changes everything.

In the crosswind
At this gait, one is in an intermediate situation: it is possible to achieve a stable balance that allows one to do without the pilot, with a wide wind and flat sea. But more often, modern drift boats fail to proceed with the tiller locked in: they either put the wind back up and stop with the sails spinning, or they lean more and more until they gybe. However, as with carrying gaits, you will be able to lighten the work of the autopilot by using only the genoa.

In any case, avoid overpowering your boat.
The boat is said to be overpowered when an increase in sail thrust no longer increases the speed. Under these conditions,
there is excessive heeling and the boat responds poorly to the tiller: whether maneuvered by hand or by the pilot, the tiller is no longer sufficient to rest the boat (the mainsheet will need to be let go). For the pilot to work well, whether you are at carrying, traverse or upwind gaits, overpowering must be avoided at all costs. The sail must be adjusted so that the boat responds easily to any command given by the tiller.

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