Yawl rig and self steering ?

[PeterSibley]

I suppose the question is is it possible ? By self steering I'm refering to wind vane steering. I have a strong interest in the yawl rig( gaff ), mainly as a method of reducing sail area while maintaining a decent main, I also like some of the handling characteristics of a yawl for inshore work. I suppose the asthetics of the rig are an attraction also.

I haven't been able post drawings of my design yet, but in short ,she is medium heavy displacement , plumb stem,short counter .30'wl, 35' oa...drawings of some kind, probably rough copys of too faint lines etc will follow some day!

Any advice and opinion will be most welcome!

[Ian McColgin]

The yawl was originally evolved as a sort of rule-beater, but as it rig it can work rather well - as a marconi rig. The gaff yawl is . . . well, I've seen a few and the boats and owners appeared unhappy.

It's hard enough to stay the mizzen with a triadic, but you can't get that with a gaff main. It's hard to get enough horsepower in the mizzen to even counter the extra windage of the spar and rig, but when you add the clutter of a gaff that can't even be vanged and a rig really too low for a nice mizzen staysail off the with, one wonders at the point.

All that aside, the happiest self-steering rigs I've seen (and the kind I'll eventually fashion for Granna) for boats with big overhanging booms is to have two, one on each side on a tube over the upper mizzen shroud on each side. Use the weather vane. This takes a bit of extra clutching and often takes a smaller vane. One solution is to get away from the servo-pendulum approach and work a trim tab onto your rudder. While that's easiest with an outboard rudder, it can be done with any rudder if you use pull/pull sheathed cables coming in to a turn along the rudder and then running free for a few inches up along and ahead of the rudder stock so even as the rudder turns the tab adjustment is not altered.

The trim tab has essentially two different controls: One on the helm that can be locked in relation to the wheel; and the second where either of the two vanes is clutched in.

G'luck

[DerekW]

This is a subject I've been pondering too. Inverted vane just forward of the mizzen is my current best guess...

If you have not yet run across it, Walt Murray has a lot of interesting information on his pages dealing with DIY windvanes (http://www.mindspring.com/~waltmur/Self-Steering/) .

On the first page there is also a link to a related discussion forum.

Good Luck
Derek

[Aramas]

The yawl was originally evolved as a sort of rule-beater... Yawls were around long before there were rules and their owners seemed to be quite fond of them for the most part.

Peter, is your rudder inboard or outboard?

One approach is to have 2 vanes, one in each quarter, but that's ungainly (see Robin Knox-Johnson's ketch Suahili) . My favourite setup is to have the vane mounted on the top of the mizzen with a shaft down the mast (either inside or on the front). I think there's a sketch in Skene's. You just have to be careful to allow for mast bend when designing the bearings and shaft.

Then you have the options of having the shaft operate a rudder trim tab or an aries style pendulum with lines to the tiller. Trim tabs on inboard rudders are do-able but fiddly and awkward to repair and maintain. Pendula are rather too Heath-Robinson for my tastes.

[ 04-02-2004, 11:29 PM: Message edited by: Aramas ]

[Gerald]

I kicked the idea around to hang an inverted vane from the mizzen mast. I have used stainless bicycle cable and hard plastic tube for several projects and had that in mind for power transfer. I planned to hang the oar on a shaft that went thru the transom. Using Walt's setup for oar control all cables would be run to a point inside the hull. The setup would change a great deal if you have a rudder hung on the transom. In that case you can design without running cables to the tiller
As for the mizzen ...... it is great for keeping the boat into the wind at anchor and great when you heave too. As for powering the boat .......... it sort of helps.
Gerald

[Zane Lewis]

I do a lot of sailing on a Yawl, 28LWL,34LOD
44LOA, 10'4B, 5D, 7.5 ton.
So a not dissimilar boat. But leg of Mutton rig with a cutter setup on the main.
On the Mizzen we have fore and aft stays so no triatic is needed. Approx sail areas are Miz 95, main 380, staysail 120, outer 120, Yankee genoa on Furler 360, Mizzen staysail 200, Asyemetric crusing MPS. http://www.woodenboat.net.nz/Boats/boatmischief/boatmischief2.html

Before you spend too much money and time on the self steering gear I would suggest that you wait until your new boat is in the water. We can self steer from on the wind to about a broad reach (130deg) by using sail balance. When the wind goes too far aft combinded with a following sea we need to steer except for short spells while making sail ajustment. The long keel gives you some time to go forward and make changes and get back before she viars to far off course.

PS I may be a little biased against self steering gear as I believe in maintaining a steering watch. After all a ship can be on you 15-20 minutes after comming into view. (My only offshore experiance was in a Multi hull where you never left the helm alone and we had to VHF a ship to avoid us.)

Have you considered the electroic gear that would also self steer in the light or when motoring as vane gear has a minimum wind speed it will work in.
Good Luck Zane

[Gerald]

Zane
My boat can also be steered by balancing the sails. However, it only works for me if there is a very stiff breeze. Lighter winds and the boat just won't hold course.
As for vanegear having a minimum wind speed:
As you know the power to steer the boat is not generated by wind power but hydraulic power. I am sure there would be a minimum wind but it would probably be a pretty darn light breeze.
Gerald

[Zane Lewis]

Hi Gerald,
I was thinking of wind required to overcome the fiction etc in the wind vane. In the Light stuff (5 knots) we can still self steer as long as the wind is on or forward of the beam. Any less and we would normarly motor.
However we aren't crossing oceans, Typically our longest trips are 120 NM between between stops.
Zane

[Ian McColgin]

There really are only two systems that work. Direct vane to rudder does not have the power. Some vane to narrow auxillary rudder sort of work but for the mainstream:

Servo-pendulum is the way to go. The rudder like thing over the stern is a balanced blade easily angled by the vane. It's on a horizontal fore and aft pin so the whole blade can glide in an upward arc when turned a little. This water power is the force that powers the steering control. These systems are well tested in the past forty years and there's a couple of brands out there.

A trim tab on the rudder is also nifty, but you need a straight trailing edge for the rudder and getting the control back into the boat if not an outboard rudder is a bit of a challenge.

If you ever steer with a trim tab, you'll wonder why anyone ever makes anything else. I sailed a Bolger unit with a trim tab mounted as a mini-tiller and locking screw at the hand end of the regular tiller. You could dial in just enough trim to make the rudder effortlessly cock a little weather helm - very nice as the right little weather helm gives the boat a more efficient foil in the water. Unlocking it enabled one to actually steer with just the trim tab so long as there was way on the boat. It's really a gas.

For your use, maybe you should just go with an electric powered hydrolic ram on the tiller arm or disc with a choise of compass or masthead wind vane control. You could spend a whole lot of money making something rather agricultural looking that does not work too well anyway.

G'luck

[PeterSibley]

Thank you all for the replies. Sorry I haven't responded ...Ive been offline for a while with computer problems.I'll read the above and digest,
Peter Sibley

[PeterSibley]

Zane...thanks for posting Mischief's page ...a beautiful boat! Very well done !

[Zane Lewis]

Thanks Peter,
Mostly/all my Dad's work.
I have posted about her a few times now so I try to keep it down a bit now.
Cheer's Zane
ps did you read part 1 of the story with the pic's of the wrecked strip plank hull. A very good sell for strip plank, edge nailed and riveted to ribs.

[PeterSibley]

No...I missed it ,whereabouts do I look ?
Peter

[Zane Lewis]

Try here
http://www.woodenboat.net.nz/Boats/boatmischief/boatmischief.html
Thanks Zane
Do you have an pics of Plans of your Yawl we can look at?

[PeterSibley]

Zane, I'd like to but the only copy I have is rather large and unfortunately fairly faint, probably too faint to copy well .She is a heavy displacement hull so far, no rig drawn....thus the discussion.I had originally assumed she would be a gaff cutter ...rather British, but with a more kicked up bowsprit.The Yawl idea is to decrease sail areas and generally generate a rig that my not very strong wife could get home with in extremus.That is a good idea I think but the vane steering side of things creates a problem.

Re the design drawings, if you have a copy of Classic Boat, November 2001, there is a drawing of "Lizzie May", a 42'er built by Luke Powell of Working Sail. I have to admit that my design bears a remarkable similarity...not the same but very similar , except that she is 35' rather than 42' and with a different stern treatment.

Peter