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Old 14-01-2014, 02:38   #1
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Self-steering auxiliary rudder

I have a self steering device with an auxiliary rudder. Because this limits manoeuvrability in the marina I thought I might link it to my main rudder when entering and leaving the marina so they work in tandem. The ship's rudder is a skeg-hung rudder and the auxiliary rudder for the windvane hangs from the rear of the transom, directly behind the main rudder. Do you think this will have the desired effect, i.e. improved manoeuvrability as opposed to leaving the auxiliary rudder to swing freely while steering with the ship's rudder? This pertains to reversing s well as when going forward.

Thank you,
jimthom
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Old 14-01-2014, 05:29   #2
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Re: Self-steering auxiliary rudder

Can you lift the auxiliary rudder out of the water?

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Old 14-01-2014, 05:50   #3
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Re: Self-steering auxiliary rudder

Thanks Kevin84, but it is too heavy and dangerous to try to move unless tied up at the dock.
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Old 14-01-2014, 06:00   #4
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Re: Self-steering auxiliary rudder

Quote:
Originally Posted by jimthom View Post
I have a self steering device with an auxiliary rudder. Because this limits manoeuvrability in the marina I thought I might link it to my main rudder when entering and leaving the marina so they work in tandem. The ship's rudder is a skeg-hung rudder and the auxiliary rudder for the windvane hangs from the rear of the transom, directly behind the main rudder. Do you think this will have the desired effect, i.e. improved manoeuvrability as opposed to leaving the auxiliary rudder to swing freely while steering with the ship's rudder? This pertains to reversing s well as when going forward.

Thank you,
jimthom

I have been experimenting with this recently after reading how an aux rudder could help with long keel boats with skeg hung rudders when manoeuvring in pens. My setup was pretty crude so take the following with a grain of salt.

Our boat has a skeg hung rudder set well forward of the stern. A small aux rudder set close to the stern with an area approx one quarter of the main rudder, but with almost the same length of leading edge, appeared to be almost twice as effective at controlling the boat in reverse, once there was significant boat speed, say one knot or so..(That is twice as effective as not very effective at all so still not that great). In forward it was ok if moving at at least a knot but did not benefit from engine power as well as the main rudder being far from the prop wash so no help at all really at manoeuvring speeds where I find a generous prod on the throttle can really spin our boat nicely despite its weight.

My conclusion, when thinking about just the issue you describe, was that I would go to great pains to ensure my windvane rudder can be easily removed from the water. The forces involved were nasty in reverse (remember a balanced rudder when reversed is over balanced and can be surprisingly difficult to center).

It's probably not much help to say it, but if I were investing the time and effort to engineer such a coupling between wheel and aux rudder I would see if a similar effort could make the blade either easy to remove or swung out of the water.

Maybe a photo of your setup would give some here an opportunity to suggest a solution?

Matt
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Old 14-01-2014, 06:02   #5
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Re: Self-steering auxiliary rudder

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Originally Posted by jimthom View Post
Thanks Kevin84, but it is too heavy and dangerous to try to move unless tied up at the dock.
jimthom

Sounds like a monster. Which brand is it?
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Old 14-01-2014, 17:04   #6
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Re: Self-steering auxiliary rudder

My auxiliary rudder is not mounted in the photo, but it fits into the vertical tube that houses the bearings via a 6" spigot that is an extension of the rudder shaft. Very strong.

When deploying, the rudder is lifted with little blocks so the spigot is inserted into the rudder tube and then locked in place with wing nuts on either side of the horizontal stub that's on the right side of the attachment photo (you can see the threaded hole), and a pin through the fitting on the left side of the attachment photo.

The hinges that allow the rudder to swing up and down are stainless 3/8" loops held in place with the wing nuts.

If I'm in the marina channel I have to leave the helm (I usually solo), crawl out on the swim platform reach down to the water line to remove the pin and loosen the wing nuts, and swing the rudder up.

I think this is too hard. If I leave the auxiliary rudder deployed, I have four choices.

Lock the main rudder and steer with the auxiliary rudder.

Lock the auxiliary rudder and steer with the main rudder.

Leave the auxiliary rudder free and steer with the main rudder (might be okay going forward).

Set up a parallelogram so the rudders works in tandem (might be okay going forward.

My rudder placements are similar to yours Matt.

Thank you,
jimthom
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Old 14-01-2014, 17:35   #7
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Re: Self-steering auxiliary rudder

OK, my imagination is not quite good enough to fill in the blanks, but I will credit you with the nouse to understand the practicalities of getting the darn thing out of the water and the difficulty involved, and you reckon that's a no go, that's good enough for me.

In that case, addressing your original question from my own limitied experience, I would opt for locking the rudder in the straight ahead postion based on the following logic.

1. Locked straight ahead avoids the chaotic nature of an overbalanced unsecured rudder in reverse causing problems by having a 50:50 chance of flipping to the wrong direction when reversing.

2. Locked straight ahead is at least predictable in its behaviour (and as some have remarked in other threads, goes some way to resisting prop walk, which might be a a good or bad thing in your case)

3. I am a HUGE subscriber to the KISS principle (as is evident by the fact that our boat now rides a good four inches higher in the water than when we bought it a year ago) and the idea of slaving the aux to the main rudder feels like an invitation to technical dramas and anything that risks steering problems to me is an unacceptable risk.

4. The benefits of moving the aux rudder I observed in manouvering with my own (very kludgy) test rig were not great enough to warrant the added complication. (Back to KISS again)

But, I do caveat all that I have said by remarking that our boat is very heavy, with horrid freeboard and is a total nightmare to get in and out of the pen, and that the system I was using was undersized for our boat, probably significantly so. Therefore, the benefits on a more slinky and pleasantly mannered boat might justify the added complexity of a slaved system.

If you do slave it please report back on the results, I for one will be very interested in what you discover. Being about 6 months away from putting my windvane together you might influence my final design (which currently has a blade that swings up out of the water in much the same way a trailer boat rudder does.)

Matt
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Old 14-01-2014, 19:28   #8
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Re: Self-steering auxiliary rudder

G'Day JT,

On our previous boat (an old IOR one tonner) I built an aux rudder vane which steered her for many thousands of miles. I too worried about reversing, and fooled around with using the aux for augmenting the steering. Frankly, it never seemed to do much good. However, if allowed to flop fully to the wrong side, it sure as hell did some harm! After some disgruntled experimenting, I resorted to securing it amidships and steering with the main rudder whilst reversing. That boat backed up in reasonable control either with or without the aux rudder. With it locked amidships, it did increase the turning circle in both forward and reverse. Sometimes when I anticipated having to make a sharp turn into a marina berth I would free it up. Woe was us if I screwed up and had to reverse back out for a second try!! Oh... that boat was a fin keel and partial skeg main rudder, with the rudder well aft.

I'm curious how you would make the connection between the two rudders? I'd guess that you would want to disconnect whilst using the vane to steer the boat... I'll be interested to hear what you end up doing (as will Matt, above).

Cheers,

Jim
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Old 14-01-2014, 19:29   #9
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Re: Self-steering auxiliary rudder

I've got a WindPilot Pacific Plus on my full keel severely rudder challenged boat. Had serious issues maneuvering in the marina getting into my slip with the vane steering rudder locked on center. Tried leaving it free to rotate and stream into the water flow past it but that didn't help. Even made maneuverirng worse. After more than a couple of embarassments in the marina came up with a brilliant idea, use the self steering to help steer the boat in close quarters. Rigged a line on each side through a couple of fair leads and tied them to the wind vane weight. Now I just pull on one or the other line to fool the self steering rudder into thinking it's the wind telling it to steer. Night and day difference in maneuvering. No more embarassment. Still use the boat's rudder in conjunction with the self steering rudder but it's the SS rudder that does most of the work.

The WPP vane uses a pendulum servo rudder to turn the vane steering rudder. Have to have some boat speed for the Pendulum Servo Rudder to give input to the steering rudder. Fortunately, the WPP vane is so sensitive that it's not been a problem even when the boat is barely moving.

Unfortunately, it doesn't work backing up. Still at the mercy of the boat's whim where it's going in reverse.
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Old 14-01-2014, 19:32   #10
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Re: Self-steering auxiliary rudder

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...on my full keel severely rudder challenged boat....

....Still at the mercy of the boat's whim where it's going in reverse.
Sometimes it just helps to know one is not alone in one's marina manouver suffering.
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Old 14-01-2014, 19:37   #11
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Re: Self-steering auxiliary rudder

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.....Therefore, the benefits on a more slinky and pleasantly mannered boat might justify the added complexity of a slaved system.
I suspect Jim's previous boat fits the category of more slinky and pleasant mannered for the sake of my caveat.

Jim, why didn't I just ask you instead of stuffing around with plywood mockups and nearly falling overboard when my top rope "hinge" failed and the contra force on the top of the aux rudder shaft nearly threw me over the stern...? Sigh.
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Old 14-01-2014, 21:37   #12
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Re: Self-steering auxiliary rudder

I always keep mine heavily damped ( photos in a few days when I am back on the boat) even when sailing so that maximum rudder that can be applied is about 5*. If you need more rudder than that your sailplan is unbalanced. Coming into a pen I let fly one or other damping line depending on whether I am wanting to turn to port or starboard so that the aux rudder can follow along.... but only in one direction.
In Patagonia where a lot of backing up was required on a daily basis I never bothered shipping it ... I just lashed the entire beast on deck.

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Old 14-01-2014, 21:40   #13
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Re: Self-steering auxiliary rudder

Another thought... what would be good would be a means of locking the trim tab at midships in relation to the Aux rudder.... then you wouldn't have the main rudder going to port, the aux rudder to stbd and the tab going wherever it felt like on a totally random basis..
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Old 15-01-2014, 14:02   #14
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Re: Self-steering auxiliary rudder

Thank you everyone for your ideas and relating your experiences. I'm working on the linkage and will report back. With some setups a couple of blocks and lines would work, but with mine I think I need solid push/pull rods as there is too much stuff in the way.

Cheers, Jim
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Old 16-01-2014, 05:31   #15
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Re: Self-steering auxiliary rudder

I have a Hydrovane self steering gear, which is excellent. It does widen the turning circle of the boat. I have had no problem if the rudder is locked in fore and aft position and then allow for the circle. I have more trouble with windage on the cutaway forefoot of the Ohlson 38.

Currently I am in a very congested marina and day-sailing in among the shoals off Felixstowe Harwich. I have not much opportunity to use the vane so I have taken the rudder off to assist turning. I use the Autohelm 4000 for short distances when motoring.
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