self steering

[bill broome]

any one got pics or drawings of wind-vane self steerer suitable for a 7 metre cat?

lo-tech, hand-made, rugged, or at least pretty would be good.

[TeddyDiver]

Other thread.. http://www.boatdesign.net/forums/boat-building/self-steering-24799.html

[bill broome]

most of those guys have a metal fabrication shop, and spend too much time in it.

i like the bungy cord and jib sheet style, but it doesn't work off the wind.

so i'll build my own. if i get something that works, it'll be in living color here. may take a while though- very hard to get 'rugged' and 'sensitive' in the same 'rustic/primitive' implement...

meanwhile, if you see something with plywood, cords and miniblocks-

[TeddyDiver]

A flap attached to stern rudder (just like in aeroplanes), small (pref aerofoiled) wing in a vertrical axel controlling the flap. Adjustment knob to turn the wing to desired position.. :D

[bill broome]

td, i have come across references to this technique, in high tech devices.

not certain why it works, as the aim is to correct the angle between the wind and the hull. i can imagine the hull pulling the rudder towards centerline through boatspeed, and thereby causing the vane to induce a turning impulse on the fin, so on the rudder. very indirect and maybe unresponsive, especially if you lose speed quickly.

on the other hand, fewer moving parts, not much friction- i'll try it out.

[oldsailor7]

Having fiddled with all kinds of so called self steering devices over the years-----I only have one piece of advice.

Get an Auto Helm. :cool:

[TeddyDiver]

Bill, changed wind direction turns the wing turning the flap to the same direction, which turns the rudder to opposite direction...

In shorthanded cruising it's more convenient to have both a windvane and an autohelm. They actually aren't compareble, other steering relatively to wind and other to a heading. Sometimes depending on the circumstances it's a huge difference

[oldsailor7]

Thats a very good point, and it just depends on what you want to do. :cool:

For instance we sailed from Sydney to Lord Howe island on auto pilot the whole way.

The pilot held us to the most direct route. We adjusted the sails to suit as we went along.

As the wind backed we hardened up the sails. As the wind rose we reefed.

We ended up with a triple reefed main alone on a very close reach, with never an anxious moment. Average speed for the whole trip was 10.2 kts.

We were sailing a Spindrift 45 Catamaran, with three crew.

[bill broome]

i am willing to believe a passive, wooden, device won't work as well as a well-fed 1st mate, but i can't feed a 1st mate so will have to aim for 'better than nothing.'

regards, bb

[rayaldridge]

Bill, find a copy of John Letcher's book, Self-Steering for Sailing Craft. He devotes a lot of the book to home-made windvanes, and even shows sheet-to-tiller setups for sailing off the wind.

Whether or not such approaches will work for you is partly determined by how fast your boat is. Fast multihulls are generally not considered good candidates for windvanes, because the apparent wind can change so much in a puff.


Ray

http://slidercat.com/blog/wordpress

[catsketcher]

Hello Bill

For a 7 metre cat you would be far better served getting a small tiller pilot secondhand. Less money, less work and it will actually drive a multi.

cheers

Phil Thompson

[dialdan]

Hi Bill
How about installing a trim tab on your rudder and then using a tiller pilot to drive the trim tab , they say it works a treat .
You can even use a morse cable to connect them ,which helps to keep the tiller pilot out of the weather
Al

[Landlubber]

it does work to a certain degree in normal weather, it is when the going gets \rough that the full rudder is required, then the trim tabs units do bugger all, and it is then that you actually want it to work well, an extra pair of hands that does not fall asleep

[garydierking]

The Jim Brown designed Searunner series of trimarans included the design for a self steering wind vane. During six years and 20,000 miles of Pacific cruising it performed beyond anything imaginable. Anything from 4 knots of wind with huge swells to surfing at 22 knots was never a problem. I never touched the wheel during all that time except to enter and leave a harbor.
I'm not sure what the key factor in its design was.
The large stern hung rudder (with a skeg under the hull) would respond instantly to the slightest movement of the trim tab. It never failed to fascinate me and I'd spend hours just watching it work. It was certainly the most valuable member of the crew.

http://homepages.paradise.net.nz/garyd/SearunnerSteering1.jpg

[farjoe]

the hinges at the bottom of the rudder and the tab must sure create a lot turbulence in that area.

Would such a system function for a semibalanced rudder with no skeg and the tab attached, perhaps more rigidly, to the back top of rudder and above only?

Would you need 2 tabs for the 2 rudders of a cat?

[rayaldridge]

Gary-- thanks for the post and diagram--

What's the little hemispherical bump at the bottom of the skeg?

[garydierking]

I think it's a zinc anode to prevent electrolysis in the stainless fittings. Note the wire shown connecting the fittings.
I didn't have one fitted and after a few years I found that stainless eating worms had been busy on the bolts.

Gary

[bill broome]

gary d: thx for the pic. i had figured out the basic mechanics, but this gets me a better start on relative size of fin and vane. i also realized while looking at it, that the vane has to be well balanced on it's axle to prevent 'inertia' steering as the hull rolls over a wave.

farjoe, i will try to mount the device on the back of the rudder, with fin and vane on the same axis. this will eliminate most of the connecting link complexity. what remains is just the two selector disks that set the relative angle between tab and vane. it might not work due to the vane having a direct effect on the rudder through weight and windage. then, plan 'b'. and 'c'...

will need devices on both rudders, or at least a quick and easy way to move one to windward rudder. i'm going to try to put pivots above the waterline, initially. make it easier to mount and service at sea. but this might not be a good idea in a really fast boat. i'm going to be a slowish boat, for comfort.

[dialdan]

Hi Bill
How about you lock off the two main rudders and then use your homebuilt windvane with it,s own rudder centrally mounted on your rear beam? Hydrovane and Auto - Helm are two commercially available units that do this quite successfully I believe. Google Hydrovane and look in the photo section.
Al

[bill broome]

i've sketched a preliminary design on my boat blog:

www.sailtherapy.blogspot.com.au

[bill broome]

hmmm, link has been miswritten, no .au.

www. sailtherapy.blogspot.com

[bill broome]

www.sailtherapy.blogspot.com

bound to get it right soon...

[farjoe]

Bill

your sketch is a bit too small for us (or at least me) to understand principle. Can you post a bigger picture?

[dialdan]

Hi Bill
This could be worth a look . www.sailsarana.com/selfsteering.htm

Al

[Chris Bretter]

Wharram have a windvane system that is all wood and seems to work well
James Wharram Designs 40 pounds for the plans

[bill broome]

thx chris. i'll pay for plans as quick as i'll pay for sex: never that desperate. there's no hurry, i'm a hobbyist who enjoys mucking about in the shed as much as sailing. more when it rains.

[bill broome]

farjoe: i haven't figured out how to insert a large pic in this thread, but i have put the sketch in the 'gallery' under multihull self steerer,with some notes.

[Chris Bretter]

I think if you get a look at it you will be able to fabricate one its all wood and very adjustable and cheap:D :D

[farjoe]

farjoe: i haven't figured out how to insert a large pic in this thread, but i have put the sketch in the 'gallery' under multihull self steerer,with some notes.

thanks i will have a look

[sandy daugherty]

I don't understand why wind vanes are successful on a tri, and universally useless on catamarans.

[bill broome]

don't like the sound of that 'universally', grasshopper.

one possibility: lee rudder does most of the steering, lee vane might be occluded by windward hull.

might have to go with tiller control if that turns out to be the case.

[rayaldridge]

Bill, it can be done, apparently. Here's an old thread about self-steering on Wharrams:

http://www.wharram.eu/cgi-bin/yabb2/YaBB.pl?num=1114909465

[bill broome]

ray, thx for wharram link, although it's a bit discouraging.

now your 'slider', that's worth a smile! narrow dory is my choice too, on a fun per dollar basis.

[rayaldridge]

Bill, thanks for the kind words. I was pretty much forced to use that hull form, in order to get enough displacement for two and a camping outfit in a cat under 16 feet.

While poking around looking for self-steering info for cats, I came across a story about Cooking Fat, the Tiki 21 sailed around the world, mostly solo. The boat was equipped with a home-made vane, but it wasn't used for short tacking, as it had to be moved to the windward transom to work well. Fine for long passages, of course, but might be a clue as to why cats seems to be less amenable to self-steering.

[popperspop]

Bill......Some of us are currently hooked on the travel blog of a canadian by the name of Tony Bigras. His sixteen foot catamaran "Miss Cindy" has self steered down most of the length of Baha California due to having a " Bi Plane " sail arrangement. He even has some video footage of the tiller while self steering.
No wind vane or mechanism, just two parallel main sails. You could e-mail him with a question on self steering. His Blog :

http://www.ideaintegrator.com/boats/tmc/default.html

Dwight

[bill broome]

thx pop= will take a peek