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Old 05-09-2014, 22:46   #1
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Unhappy Windvane self steering with trim tab

I own a Gary Mull Chico 30, they have a transom mounted rudder, which lends itself to using a trim tab for self steering,. Has anyone experience of using a rudder trailing trim tab linked to a transom mounted windvane for self steering?

Have read Bill Belchers book, and Bill Morris's on the subject but would like to hear from somebody who can confirm it works ok.

Bit nervous, as nearing the point when I have to start modifying the rudder !
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Old 06-09-2014, 01:21   #2
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Re: Windvane self steering with trim tab

There is a discussion here Placement of Windvane Steering System. with photos of my kit at 25/31/35. The principles should be just as applicable on a transom hung rudder as on my aux rudder.

Boat is currently at Gulf Harbour, if you are near there you could come and have a look but PM first as I am out and about a bit.
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Old 06-09-2014, 05:10   #3
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Re: Windvane self steering with trim tab

Hi chips. Great boats, those chico 30's. I did a auckland to gisboune race on chubasco (a wooden chico 30) when I was 15, and the delivery up from napier. It was a great trip with a good crew that I will never forget.

Anyway, ive used trim tab windvanes on three boats. They work fine for open water offshore but tended to oversteer downwind, and arent quite as precise as a servo pendulum in shifty conditions. I would be slightly worried about oversteering on the fin keeled chico. Two of the boats I sailed on where long keeled, and the other had an auxilary rudder system exactly the same as pinguino's (also made by Ini). So all had better natural damping than you will have.

Dont let this completely put you off, but I wouldnt modify the rudder too much initially. Look at something like the quartermaster trim tab system which is all above water and just clamps onto the top of the rudder. If you make the trim tab hinge up it would be easy to lift out of the water for motoring. This stops any vibration and heavy steering that the trim tab can cause, and also stops weed growing on it when leaving the boat.

Some tricks are to use bungy to help limit the rudder oversteer downwind, and make the feedback adjustable so you can desensitise it for downwind.

Have you thought about just building a belcher OGT. With only the horizontal windvane direct to the tiller. Simple and no underwater parts. It would be easy to modify into a wind unit for a trim tab, or servo pendulum if you decided you needed more power down the track. I recall the chico rudder being very nicely balanced so it would be perfect for this system.

Cheers Ben


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Old 06-09-2014, 06:26   #4
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Re: Windvane self steering with trim tab

I have an Alan Pape design Ebbtide 33 cutter with a transom mounted rudder. When I bought the boat she had a custom trim tab self steering system(Clearway I believe) which the previous owner had made several trans-Atlantic crossings with. It was very temperamental and required endless and constant adjustments as well as requiring the boat to be in absolute perfect trim so taking advantage of brisk conditions for power sailing was not possible. I replaced it with a Hydrovane and fabricated a robust mounting bracket which can be seen along with many others on their website. The power and control are amazing and it will steer the vessel in any conditions from zephyrs to gales, downwind, upwind, with the added advantage of being a back up rudder. You can trim your main rudder to balance as well and take advantage of power conditions. When motoring you can install a cheap tiller autopilot to the auxiliary tiller handle and do away with expensive and energy draining larger systems as the balance rudder can be controlled with your finger!
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Old 06-09-2014, 07:16   #5
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Re: Windvane self steering with trim tab

The tab is said to work best if removed from the rudder.

I watched a trim tab steered boat the other day and she seemed to wander about quite some.

I would do a thorough research up first. Maybe some model building, prototyping, etc. before a 100% commitment to a particular solution.

Have fun building, then sailing.

Cheers,
b.
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Old 06-09-2014, 08:59   #6
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Re: Windvane self steering with trim tab

I used a Quartermaster for about 9K miles and loved it. It just clamped on the rudderhead, with the engagement line running to the tiller. The shock cord trimming lines were what kept it from over steering. About 2/3 of the way forward on the tiller was a large round head screw that stuck up, and a resin phenelic (sp?) board with 10 or 12 holes in it, that was connected on both sides with shock cord. The routine was to get the boat on course, drop the latch to engage, and then put the trim board into whatever hole you thought would trim it right. Watch how it handles for a while and maybe move the trim board by a few holes for fine trim. It took a while to get used to it. The first few times I tried it, I thought it was hopeless. Your boat will be much faster than my Contessa, so you will have more trouble downwind with OUT RUNNING THE WIND. Any windvane needs enough wind over the deck to work right. If your boat starts surfing, all bets are off. Good Luck. ______Grant.
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Old 06-09-2014, 09:37   #7
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Re: Windvane self steering with trim tab

Sailed a Bristol Channel Cutter with trim tab self-steering. Worked really slick.
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Old 06-09-2014, 13:58   #8
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Re: Windvane self steering with trim tab

Quote:
Originally Posted by gjordan View Post
The shock cord trimming lines were what kept it from over steering.
I use 'ordinary' line to limit the movement of the rudder ( or the aux rudder in my case) to a few degrees. Otherwise..yes - she will oversteer and you will be all over the ocean. Just like hand steering, everything has to be in balance, and you should only be applying a fee degrees of helm at most.
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Old 08-09-2014, 18:52   #9
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Re: Windvane self steering with trim tab

[QUOTE=chips;1621977]I own a Gary Mull Chico 30, they have a transom mounted rudder, which lends itself to using a trim tab for self steering,. Has anyone experience of using a rudder trailing trim tab linked to a transom mounted windvane for self steering?

In 1980 I purchased a second hand fin keel/spade rudder Chance 33 in Chicago & sailed it to the West Indies. Along the way, in Annapolis I found a used J 24 rudder & the "brain" of an old -then- British built Hydrovane. I bolted fittings on the Chance 33 transom for the J 24 rudder & had a stainless steel bracket built for a trim tab mounted on the trailing edge of the J 24 rudder. The Hydrovane activated the trim tab which, in turn, turned the J 24 rudder one way or another. The main rudder was set amid-ship. It worked beautifully, even in heavy seas! With a transom mounted main rudder, you can have the trim tab mounted directly on the main rudder, the tricky part is the wind-vane aerial & the mechanism that send the impulses to the trim-tab... Good luck ! PS: I apologize for my English... I'm French but it's not my fault... I was born that way
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