Mizzen sail self steering

  • 02 Feb 2022 16:07
    Reply # 12540327 on 10940457

    David P.,
    Howard kindly sent me a copy of your sketches.  Looks like you have the concept figured out.  I noticed that you used 4 extra blocks to lead the steering lines down to deck level.  I assume to help get them out of the way in the cockpit.  That's fine if it works, but watch the friction!  Every block adds up.

    Good luck and keep us posted.

  • 02 Feb 2022 01:43
    Reply # 12516148 on 10940457

    David, I look forward to hearing how your self steering experiments go.  Meanwhile I'm having trouble opening your sketches, so will have to figure that out.  

    Our mizzen self steering system will hopefully be getting a thorough test in April.  We plan to launch Minimus II from southern California in late March, then sail down the west coast of Baja.  If we feel good about her performance and self steering at that point, we'll hang a right and head for Hawaii.  Otherwise, we'll head into the Sea of Cortez.  In either case, should be a good test.   

  • 02 Feb 2022 00:10
    Reply # 12513493 on 10940457

    A few years ago I played round with the Letcher (Self-steering for Sailing Craft) methods. I found his jib to tiller scheme worked well on a broad reach but I  his mainsheet to tiller, with elastic encouraging the boat to luff up, was less effective. 

    My alternative is to take a line from the mainsheet, or the mainsheet traveller, to the lee side of the tiller and rigged it so its tension encourages the yacht to luff up. I then used a weight to  the windward side of the tiller to oppose the luff. I used the weight in preference to rubber tubing as it gives a constant restoring force. I prefer to use a connection to the mainsheet traveller as it allowed me to adjust the mainsheet without altering the self steering. After adjusting the the position of the connections of the lines to the tiller to alter the leverages, I found it to work well from on the wind to a beam reach, or a bit further off the wind.  An increase in wind strength causes a tendency to luff, which is good helm  technique. On one occasion, a lull caused  a jibe. But as the wind had died, it did not cause any harm.

    I was experimenting with a dedicated mizzen, a secondhand Heron jib held flat by a sprit boom, when COVID came and stopped my sailing. With changes of placing of the deck end of the sheeting, it had the advantage of steering the yacht on any point to the wind, including directly into the wind while the other sails were hoisted or reefed. But it took some fiddling and I think I will use the mainsheet traveller to tiller system instead. I commend the use of a similar system to readers

  • 01 Feb 2022 19:32
    Reply # 12505412 on 10940457

    Hi David, i am up in the Vancouver area of BC, Canada.  I am borrowing your idea for the windvane self steering for my Macgregor 25 sailboat, which I am planning on re-rigging as an Origami Junk Rig, as per Paul McKay.  I am making a small version as a dinghy sailer currently, I will be posting stuff on it on another post.  I was so excited when I saw your blog and videos about it that I designed some changes that occurred to me to cut down on some of the stringy bits that go across  the stern of the boat.  It's just me, I just have to mess with any design I see, to tweak it for my own amuzement and entertainment.  Hopefully, if it works out as planned, it will relieve me from the tyrrany of the tiller. 

    I have already installed a system years ago that will hold the boat on course for a few minutes at a time, and allows me to steer the boat from anywhere from bow to stern (useful in sail raising and anchoring!  I singlehand almost always).  On the bow pulpit, I have attached a 60cm bungie on each side, with a 1/8" low stretch line going through small sheaves tied to the life line stantions, back to the cockpit, and with a loop tied to the cockpit ends of the lines after they go through one more turning block and loop around the tiller tied as to put a bit of tension on the front bungies.  I have another long piece of bulk bungie chord that is tied across the cockpit, and that with a quick twist, goes over the tiller and holds the two loops of line from sliding off the tiller, and offering some resistance to the tiller turning.  I can steer it from anywhere on the boat, including down below, with the pop top up, as I often sail in protected waters. With a quick reach to one line or another, I can correct the course.  The bungie across helps trim the rudder for weather helm, of which the current rig has more than I like when things pipe up!  I am so done with reefing a pointy top rig that I am bent on junk rigging her.  I only want to do one drastic change at a time, so I am experimenting with the Origami Split Junk Rig on the two folding inflatable dinghies I am currently building.  Wheew!  What a mouthful!  I spend way too much time on this, but in the days of Omicron, what is a sailor to do?

    I will post more when I get further into the wind vane project.  I seem to run numerous projects simultaneously, not good for project completion, but what fun!  I find if I take positive action immediately when I see an idea I like, which you can imagine leads me down some interesting paths....  Anyway, here are a few sketches I have done so far.

    I thought that if I attach the control lines for the steering sail to a cross T that is firmly bolted to the rotating 2" (50mm) PVC pipe suspended from the 1-5/8" x 1/16" aluminum mast tube, and carry that down to just above the top  of the cockpit.  This de-couples the sail from the aluminum tube, as the control lines for the sail are fixed to a 2' cross piece, which in turn is attached to the 2" PVC pipe.  I can have an adjustment mechanism whereby there are two discs of material, HDPE or some such; the bottom one has a hole through it to fit the pipe, followed by a cap drilled out to 1-3/4" for clearance, to center the 2" pipe.   The aluminum tube runs up to the top inside the PVC pipe and down to the bottom of the second piece of PVC 2" pipe, about 8', as the aluminum tubes I can cheeply procure are about $33 CDN each are of that length. On top of the lower disc, there will be another one with a strut sticking out 16-20" (experimentation to be done to determine how long the lever arm needs to be).  The lever arm will be attached to two lines that run from the lever arm to turning blocks, one on each side with geometry to maximise  the leverage from 0* to 45*.  This way the lever arm is designed to stay in alignment with the rudder and the sail can be aimed in alignment with the wind direction, coupled by the two discs at cockpit level via locator pin.  From the lever arm to a crossbar with a block at each extremity, that is attached to the aluminum inner mast. From there, back across the cockpit and then to the tiller through another turning block mounted on the lower pushpit. This utilizes the 2" PVC pipe as a transmitter of torque from the sail turning to the lower lever arm.  There will be an index hole in the top disc and a series of holes all around the lower disc in alignment with the hole in the upper disc to get the sail/rudder alignment right.

    The bottom pipe will be fastened to the stern, cap on the botom, drilled cap on top with the 1-5/8" aluminum tube running from there up to the mast head where the haliard and the lazy jacks will be attached. The aluminum inner mast will have a way of indexing it so it always stays in the same orientation, a pin that is clamped to the aluminum mast with an indexing pin, like on David's rig.  I am planning on attaching the 2 blocks that go to the lower lever arm to the aluminum inner mast, thus keeping the whole rig easily removable for trailing. (it is a trailer sailer). Wheew!  Marathon derscription.  hopefully the drawings, more like doodlings, will elucidate my points.   Now, ...to work!  I will. post pics as I progress.  Next job is getting some welding done on the trailer.  Rust never sleeps!   The drawings are dated and sequencial, showing the thinking that went into the changes I planned. 

    I have the mast and the pvc pipe, loads of polytarp and low stretch poly line, 1/4" grommet system from Sailrite, and other buildy bits like aluminum bar stock and HDPE cutting board.  I have drilled the caps, but that is it so far, not much to show. As they say, the devil is in the details.  Friction is my constant companion, may it's highs and lows be of use to me in the functions of the system.

     Anyway, I despise politics;  I have been riveted by the Canadian Truck Ralley in Ottawa, waiting for our 'leader' to show tomorrow on Ground Hog Day, and see if he will see the shaddow of a convoy parked outside parliment and scurry back into his hole for another 6 weeks!  You lot over in Britain have just chucked all the controls away already, let us hope Canada does too so we can try these scoundrels for treason!  It will be a day to remember in Canada when our Covid 1984 wall goes down!  Unlike our government, I HAVE been following the science...  Maybe we can get back to actually treating illness now.

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  • 23 Aug 2021 19:31
    Reply # 10950904 on 10940457
    Anonymous member (Administrator)

    Is there any evidence of the Thames barges could be brought too self-steer?
    My armchair guess is that the way the mizzen was sheeted to their rudder had little to do with self-steering. However, the mizzen sheet force would at least offload the tiller a little, and one did away with the boomkin.

  • 23 Aug 2021 16:35
    Reply # 10950480 on 10949341
    Anonymous wrote:

    Many of the Thames Barges on England's East coast had a similar system with the mizzen sheet attached to the top of the rudder blade.

    Powell's and the Thames Barge method are interesting variations on mizzen self steering.  If I understand the latter correctly, with mizzen sheet connected directly to rudder blade, it wouldn't allow for much adjustment in power vs  leverage.  That brings up a question I have about the version I'm using, which is how significant the placement is of the steering lines on the tiller.  That is, closer to the rudder head for more power, or toward the end of the tiller for more leverage.  This is something I haven't experimented with so far, so it may or may not have a significant effect.

    Another area I'm curious about is how well the system scales up.  My data set is pretty small, having only used it on a 5.5m monohull with a 1.4 sq m mizzen sail and a 7.3m catamaran with a 1.8 sq m sail.  


  • 23 Aug 2021 15:09
    Reply # 10950350 on 10949341
    Deleted user
    Anonymous wrote:

    Many of the Thames Barges on England's East coast had a similar system with the mizzen sheet attached to the top of the rudder blade.

     What's nice about this would seem to be the lack of the need to reverse the direction of pull with blocks........ far less  hardware, and elimination of the rats nest of lines and blocks in the cockpit... Everything is aft of the transom.......But that's a mixed blessing...
  • 23 Aug 2021 04:41
    Reply # 10949341 on 10940457

    Many of the Thames Barges on England's East coast had a similar system with the mizzen sheet attached to the top of the rudder blade.

  • 22 Aug 2021 22:48
    Reply # 10948730 on 10948577
    Anonymous member (Administrator)
     it could only serve for balance and self steering and for a riding sail....... an air rudder on a boat.    I searched the net for accounts of a yawl mizzen being used this way, and the only account I ever found before this was on a sailing dinghy somewhere in New England.  It was not connected to the rudder in that account

    I don’t have the technical knowledge to make my own contribution  to this interesting discussion but I have come across a diagram of a 19th century Chinese lug sail yawl with a boomkin for the mizzen that is an extension of the tiller - the diagram was from a chap called Baden Powell, founder of the sea scouts and brother of the founder of the Boy Scouts.  I’ll try to attach the diagram here, and the textual description of how it worked, but it and the relevant article were also published by our editor in one of the recent magazines.  Could this be the solution to getting stuck in irons?

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    Last modified: 23 Aug 2021 01:04 | Anonymous
  • 22 Aug 2021 22:16
    Reply # 10948672 on 10940457
    Anonymous member (Administrator)

    The mizzen of a classic yawl rig is dimensioned to keep the boat on course when sheeted to a smaller alpha than the mainsail  (The mizzen of these yawls were not connected to the rudder). If the boat is forced a little off the course, downwind, the rise in the mizzen’s drive will be much higher than that of the main, causing the vessel to head up again until the balance is re-gained. If forced off course upwind, the mizzen will lose all its drive much before the main, and the boat will fall back on its course. This works as long as the apparent wind is forward of the beam.

    In other words, the mizzen of a yawl works in a similar way as the stabilizer of a classic aeroplane (say, a Cessna 172)  -  except that the plane’s stabilizer is acting in the vertical plane (pitch)...


       " ...there is nothing - absolutely nothing - half so much worth doing as simply messing about in junk-rigged boats" 
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