Looking for an Auto-helm self-steering vane

[CactusWren]

The boat that I bought last June once had an Auto-helm on it and the mounting bolts, backing plate and mast base are still on the boat. I would like to find a used unit to install. Any leads would be appreciated.

[Steersman]

An 'auto-helm' is an electrical device. Is this what you are looking for?

Remember, this is s wandvane forum

I think you need to post some pictures.

[jan alkema]

There is also an "auto-helm" windvane system, manufactured by Scanmar. It consists of a windvane which turns a trim tab on an auxiliary rudder. The windvane has a horizontal axis and there is no feedback in the "linkage" between vane and trim tab.

Jan

[BoatBits]

The Auto-Helm is an excellent gear and while it does not provide feedback as such it did get us across the Atlantic twice. You might want to check o Sarara at Sea's download page for pretty clear info on how to make a similar self steering gear. http://www.sailsarana.com/selfsteering.htm

Bob

http://boatbits.blogspot.com/
http://fishingundersail.blogspot.com/
http://islandgourmand.blogspot.com/

[jan alkema]

With a horizontal vane axis and no feedback between the vane and the auxiliary rudder the system has a tendency to oversteer. I am wondering how the system will behave on downwind courses.

Jan

[BoatBits]

Hi Jan

Having a couple Atlantic crossings with an Auto-Helm vane and another with an RVG all I can say is that they seem to work as well as most vane systems. Maybe the downside is that balance is a little more important but at the same time, since you can use your boats rudder to help balance, maybe it works out equal. M experience with both gears is that they work downwind very well but that said I still prefer the wind on my quarter whatever the gear!

Right now I am in the process of working up a new auxiliary vane (getting rid of my Atoms clone) and trying to sort out whether it is worth my while to sort out a pendulum rather than a trim tab... So far the jury is still out.

Bob

http://boatbits.blogspot.com/
http://fishingundersail.blogspot.com/
http://islandgourmand.blogspot.com/

[peter foerthmann]

Good afternoon,

just some more considerations:

while the lenghten of a trim-tab-operated steering rudder - disregarding if main- oder auxiliary rudder - is just as long as the trim-tab-axis is being situated behind the main - or auxiliary rudder shaft - so about max 50cm, the lenghten of the power lever on a pendulum rudder is being substancially longer, roughly between 130 - 190 cm. Thus the power output is huge compared with the - excuse me: a bit outdated trim-tab systems. Which is why so many of the previous manufacturers have ceised production since decades. Scanmar marine certainly is the last soldier to offer them.

Trim-Tab units have been one step amongst many steps in developments of windsteering systems during now about 50 years. In particular on long keeled boats this kind of gear have been popular and useful, while the todays boats designs certainly will not be the very best friends of these units with some particulars in terms of prevention of oversteering.

Importantly: yachtsmen being capable to make their boats obbey even under motor in reverse - might soon realize that a trim-tab, that cannot get centred and locked during maneouver under engine backwards - will at least causing some additional grey hair on skipper head - because the boat will not always do want what the skipper want it to do.

Life is a compromise - yachtsmen should at least know which one they will be accepting....

kind regards

Peter Foerthmann
http://www.windpilot.com

[jan alkema]

I don't think that the power arm of a trim tab is here a problem. The auxiliary rudder can be balanced so no big steering power for the auxiliary rudder is needed. May be the steering power for the auxiliary rudder should be reduced to prevent oversteering, as there is no feedback for this system.
The horizontal vane axis tilt angle can give a tendency for oversteering when the boat is not heeled, so on down wind courses.
I like to show a recording (around 1977) on a small yacht with a big windvane, with an adjustable vane tilt angle, directly working on the rudder. There is no feedback from rudder to vane. The coarse was a broad reach and the boat was heeled a bit. The left part of the recording was taken with the vane axis = 0. The boat started zig zagging, indicating oversteering. The right part I adjusted the vane axis to 10 degrees aftwards. See that immediately the zig zagging stops and a normal coarse control is shown. A tilted vane axis helps to reduce oversteering.

Jan

[attachment=0]effect vane axis angle_NEW.jpg[/attachment]