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Ensign
Join Date: Dec 2009
Posts: 39
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Hi all,
Being new to your forum, I have noticed that the common theme of why are self steering or autopilots either not satisfactory or burned out/failed. I thought it might be a good theme for what makes these work, or what have people found that works, especially as the weather picks up as they are nearly all satisfactory in light airs and smooth conditions that we usually try out this stuff ....
I have a few observations from 50 years of sailing that I would like to share, from 28' van de stadt trintella ( a full keel cruiser ) singlehanded to hawaii and back from victoria bc when I was a kid to 86' maxi boats, and lots in between with trips trans pacific, round the world, etc....using from primitive bungee to tiller vs jibsheet to aires and hydrovanes, a variety of electric and electronic autopilots.
The first consideration is how well balanced the boat is. Autopilots and vanes tend to fail as the breeze comes up and the chop builds on the swell. Not checking how 'hard' the helm is, is very common. We drive our present boat with the three finger rule. If there is more weather helm than can be held with three fingers, we adjust sails and almost always slow down the boat.
If going upwind, most boats balance pretty well, usually being over on your ear is the hint that all is not as it should be....off the wind, the prevailing long cruise prevailing condition of choice, several factors come into play:
1. the wind pressure is measurable, roughly 0.25 pounds per sq ft at 8 knots, 1.8 at 18, 3 at 30 etc.
2. as the wind speed goes up, the main is the biggest lever on the boat, trying to round the boat into the wind
3. as the swell builds, all boats try to surf to some degree, and just as the wind load goes up, the hydro loads on rudder and steering also go up dramatically with speed
4. wind strength vs load varies dramatically with temperature. a 40 knot squall in the 89 degree tropics is easy to ride out for 15 minutes compared to the increased loads of a 40 knot gale at 55 south with air temps in the 20's I will not bore anyone with the charts or calculations, but you can look up same...
Off the wind, the relative wind seems much less, (wind speed - boat speed) looking forward with the wind at your back instead of throwing spray in your face going to weather, so sitting under the dodger standing watch is comfy, the boat is not heeling much and until the autopilot makes expensive noises, or the vane fails to keep the surf/round-up rig and sails thrashing, the loads and wear and tear are really huge.
If you don't take action soon enough, when you do is never any fun...
Item 1 take off the big lever first. We reef early, we do not even have a first reef in our cruising main. We put a flattening reef in at 12-14 knots with our Navtec hydraulic system. Takes 20 seconds and making the main flat really decreases the rounding up load. Moving the draft is really important, outhaul and halyard tension is key to no ugly belly in the main.
To reef, we bring the boat to a beam reach. The relative wind is lower than if you round up, the motion is a good as it gets with the boat going nearly parallel to the swells, the main does not hang up in the spreaders even with the boom let out all the way. If the boat is going fast we roll up some jib and/or put the staysail up while in the dead air behind the main, and modulate speed by how much fore triangle we leave up.
If the weather or darkness looks unsettled, we then go to our 2nd reef or 3rd reef or even take the main off entirely. The loads on the steering reduce dramatically when the boat is just being pulled by the staysail and or jib, and you are back to three finger steering. So far this has made our Neco autopilot sail around the world nearly twice without doing anything but changing the oil in the gearbox and religiously using motorcycle chain lube on the chain in the binnacle and on the steering cables every passage or 3000nm or so.
We added a totally independent B&G hydraulic ACP2 system, complete with rate gyro, remote vision wireless control. This was done because it allows the watchstander all the data on the bus, plus the ability to tack the boat if you fall overboard, which with one button push would tack the boat and make her heave to, and wake up your partner to bring you a towel before you are out of sight over the horizon....The pilot needed a lot of tuning to the boat, but does steer way better in the only conditions that count, when the breeze is up, big chop and swell and the boat is surfing. The dynamic gain changes the response so when surfing at 18 knots the rudder response is miniscule, and as the boat slows down and then uses more rudder at lower speeds. Finally, even though it took some real effort to make everything fit, but it allows steering the boat without using the wheel, quadrant, steering cables or emergency tiller, etc.
The same methodology works just fine with a simrad tp-10 tiller pilot on the little J27 we race, as if you keep things balanced, even surfing at 14-15 knots with the code 0 or big VMG kite and only 2 people on a jack and Jill race, the little tiller pilot will keep up if you are aware of the boat balance and helm loads, even where you walk as the weight shift steers the boat. Fortunately most of the boats we cruise on are not as sensitive as a windsurfer, where there is no rudder at all but the balance of where the sail area is in relation to the center of hydrodynamic resistance...
OK, I promised I would not allow any of my math or engineering geek get out...any others have any comments on what works for them, or those illuminating 'wow, we sure don't need to do that again' comments?
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