Cat-Ketches and Self Steering

[Howard]

This relates to the topic of self steering. For day sails and short trips, steering the boat is part of the fun...if not the whole point..... of the activity. On longer trips......it gets old. When you are out of sight of land and have several hours of open water to cross, some sort of self steering is handy. Most of my sailing is short trips, but I also have an interest in cruising, and have been known to trailer my boat 1,000 miles to the Chesapeake for trips of a week or more. Out of curiosity and in anticipation of a bigger boat, I built a self-steering windvane just to see what would happen. The third iteration worked very well and could actually steer better than I can. But (and this is for Jeff), the way I built and mounted it required I remove my swim ladder off the stern to use the existing bolt holes. Yes it worked, but I found I needed a swim ladder more than a wind vane so it came off and the ladder is back on. Experiment over.

A better alternative for small boats is sheet to tiller self steering. I have John Letcher's book and have waded into that again to research sheet to tiller methods. What I missed the first time was his reference to boats and rigs that have inherent self steering capability. Conventional wisdom is that it's a full keel boat boat for tracking, coupled with a trimmed head sail and slack main that basically "wallows" to weather. Off the wind, they used twin head sails and "wallowed" downwind. The other type of boat.....and here is where it gets good.....that self steers is a split rig...the farther the sails are  apart from the center of gravity of the boat, the better. Even better is if the boat is "stiff"...meaning resists heeling...to begin with. All of a sudden, it hits me that a sharpie style boat with a cat-ketch rig is very near to what he is talking about. That sounds to me like just about all the B&B boats with cat-ketch rigs.

Several of you have mentioned the ability to trim the main and mizzen so she self steers. I'm wondering how well it works (how much "wallow" is present), and if this can be improved upon by the use of sheet to tiller methods.

If you haven't read the book, the method on a sloop is basically to balance the power of a sheet....main on the wind or jib off the wind.....with a piece of elastic (a spring). The sheet attaches to the tiller from the weather side and the elastic attaches to the tiller and is to lee. Although much more complicated that this, the effect is that when it is set and sails trimmed, a boat turning to weather loads the sheet of the sail, it pulls the tiller to weather and corrects the course. If the boat falls off, the load on the sheet drops, the elastic pulls the tiller to lee and the boat turns back on course. If you watch these in action, there is a constant set of "corrections" going on and it steers a very tight course.

My guess is that there is enough load in the sheets of a cat-ketch rigged boat...even with a sprit rig....to supply enough power make this system work. When the loads are heavy....you use a block to divide the load. If the loads are light, you can reverse the block power it up.

Anyone ever messed with this to see how well it works? I suspect it will (both on and off the wind), I'm just not sure on a cat-ketch which sail would work the best. If like on a sloop, you would use the mizzen going to weather and anything from a beam reach down to a run, the main. If the mizzen blankets the main off the wind so that the tension on the mainsheet drops, it's a perfect setup for sheet to tiller steering off the wind.

Or if these boats steer a tight course when trimmed, and if you need it at all.

[Charlie Jones]

Take a look at this video. This is Tehani sailing some 25 miles out in the gulf, under sheet to tiller steering- she shore ain't "wallowing" along ;D

http://sailfar.net/video/gulfofmexico2.wmv

We used sheet to tiller for almost 3 days offshore, part of the time with a reefed main and reefed jib, until the wind got way aft and I hadn't set up for that, so we had to steer. But sheet to tiller works very well on sloops.

What design vane did you build? I'm currently working on one for us. We've also added a tiller pilot. Laura claims if she ever had another child, she'd name it Navico  ;D One of those should work quite well on a cat ketch also.. No reason for it not to.

[Howard]

Charlie:

The point was sheet to tiller does work....what wallows is a boat without it.....a trimmed jib and slack main...with each alternately filling and pulling.

Off the wind, you move to the jib sheet, but it's the same process. On a boat the size of yours, the jib sheet may have too much power, so you throttle it back with a block somewhere in the system.

On the vane gear, a couple of photographs...before it was painted. Yes it worked very well, but notice the complexity. Just moving something like the position of the sliding block on the servo oar tiller arm...half an inch....made it work or not work. I just built it. Was designed by engineers who have studied these for years. For smaller boats, best to stick with Sheet to Tiller if you can!

On autopilots, they work best under motor power and I'd insist on having one for a cruising boat for those days when you have to motor for hours. With sails, if the wind shifts direction on you.....trouble. And you gotta have a lot of battery juice to keep them working under sail.

[Charlie Jones]

lol- yeah- I KNOW about using the jib- just hadn't set things up yet and it was dark We'd been on the wind for 2 days, then at sundown it shifted. Plus we were crossing the Galveston Channel fairway at the time and had about 4 ships around us. 23 miles out and still ship traffic!!

But yeah- sheet to tiller works VERY well. Once you understand it it's simple to set up and adjust also. In that video you can see the power pick-off using the dead end part of the main sheet. A couple of small blocks lashed to stanchions to lead the line forward and some surgical tubing is all that's needed.

For those of you aren't familiar and want to try it, DON'T try using bungee- it doesn't have the linearity that surgical tubing does and won't work nearly as well.

And while on the subject, here's an EXCELLENT website about the gear and setting it up-

http://www.jsward.com/steering/index.shtml

Sailing on the outside, the tiller pilot works pretty well under sail- you just have to adjust the sails once in a while, or blip the course setting. Need to be on watch anyway, so that's not a huge task. Sailing in narrow channels, not so well- the oscillations from slight wind shifts makes it a tad scary then particularly if you are sharing the channel with commercial stuff- under power is fine.

And the auto tack feature SURE is nice, making handling the jib a snap,  even for Laura . Of course, she can tack the boat by herself without it, but it does make it nice.

The setup I'm playing with on the vane is a horizontal actuated vane, coupled directly to the tiller. Doesn't use an oar in the water. Got the design from Belcher's book on wind vanes ( I have Letcher's also) Tehani is so easily steered- one finger even with the rail down- that that design SHOULD work on her. If it doesn't I'm only out some time because I'm using scrap from the boat building shop to make it with- no cost.

[JeffM]

I'm going to have to look into this again.  Thanks, Howard and Charlie!  Sometimes my boat will self-steer with wind before the beam for varying periods with just a little sail balancing.  Other times no.  I can't yet always predict whether it will work under any given set of conditions.  It would be nice to have a reliable method for the longest stretches.  I'm going to study Charlie's link.