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Old 21-01-2019, 12:58   #1
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Hydraulic steering excessive turns

Hi, could those of you with hydraulic steering please advise how many turns of the wheel you have lock to lock?
I am converting my Prout Snowgoose 35 to Vetus hydraulic steering and having given the supplier the rudder dimensions (same as a standard Snowgoose 37 I believe) they have done the calculations and come back with a system that gives 8 turns lock to lock - seems a bit excessive.
I questioned it and they said that due to the rudder size and being transom hung (i.e. no balancing portion of the rudder) the potential forces in a following sea could be very high so have specified their largest cylinder, the MTC17510. They said this is often used for commercial workboats so seems a tad excessive for a 35 ft sailing catamaran but they rechecked the calculations and stood by it. What do you guys and girls think?
Thanks
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Old 21-01-2019, 13:12   #2
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Re: Hydraulic steering excessive turns

Sounds like they keep the cylinder power up by having the pump low volume per turn. Bigger pump volume per turn = faster turning. But it's kinda like gears on a bicycle... for high speed you have to use more power per turn. Sounds excessive to me though. I can't remember for sure but I think my last hydraulic steering boat was like 3.5 turns lock to lock...?
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Old 21-01-2019, 15:07   #3
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Re: Hydraulic steering excessive turns

8 turns lock to lock would be awful.

They're likely overspecifying the ram to cover themselves. I went through this with Hydrive.

To get reasonable turns lock to lock you need to match the pump size with the ram capacity.

Ie, if its a 1000cc ram, you need a 330 cc per turn pump to get 3 turns lock to lock
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Old 21-01-2019, 15:45   #4
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Re: Hydraulic steering excessive turns

8 turns l/l??? good grief, I can't imagine trying to control a boat with such a setup, nor can I imagine such a poorly designed boat t hat would require that much mechanical advantage.

What is the standard steering set up on that design? There should not be a need for greater mechanical advantage in a hydraulic system.

For reference, our cable system is 1 1/2 turns l/l, and we have a slightly balanced skeg rudder (not much balance area)... and the effort is quite modest. Obviously, things are different on different boats!

Good luck in the job.

Jim
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Old 21-01-2019, 15:53   #5
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Re: Hydraulic steering excessive turns

My last boat (a 1977 42' Californian) was 5 turns stop-to-stop.
My present boat has an adjustable pump. It was adjusted to 6 turns stop-to-stop when I bought it and 5 turns now.
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Old 22-01-2019, 03:20   #6
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Re: Hydraulic steering excessive turns

Thanks all of you, 3 1/2 turns or so seems to be about average so 8 is way to much. Does anyone happen to know the make/model of their system and even better would be the cubic capacity of the helm pump and ram?

The cylinder they have specced is a vetus MTC17510 that has 356 cc volume and max torque of 175kg (the biggest they do) and the helm pump is also the biggest they do , the vetus HTP4210R, and that only pumps 42 cc per wheel revolution, hence the issue -

356/42 = 8.5 turns lock to lock.

I have asked this question on the Prout owners group and 3 1/2 turns seems to be about average on Prouts from 31 ft Quests right up to 50 Quazars so im assuming I just need a much smaller cylinder. Prout built boats for serious weather so cant believe they would be under specifying such things but I have run the calculations myself now and it agrees with what the supplier says so what am I missing?
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Old 22-01-2019, 04:57   #7
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Re: Hydraulic steering excessive turns

I'd say you're right. 3 1/2 turns lock to lock gives you the same mechanical advantage whether it's hydraulic, cable or mechanical.

So you'd be looking at around 150 cc for the ram.

If you're worried that that might be too small a ram, maybe look at other brands to see if bigger capacity pumps are available.
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Old 22-01-2019, 05:09   #8
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Re: Hydraulic steering excessive turns

Ultraflex has a 68cc helm pump:

https://uflexusa.ultraflexgroup.com/...elm-pumps.html
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Old 22-01-2019, 05:11   #9
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Re: Hydraulic steering excessive turns

We have a 50' Outremer with slightly balanced rudders that runs 3 1/2 turns l/l.

Pumps are Vetus MTP5310R with 53 cm3/rev. I'd have to dig to get the cylinder #, but obviously somewhat smaller since we run ~200cm3 lock-to-lock. Have never felt underpowered at the helm and we've been in some pretty serious weather and some really 'dynamic' sailing conditions.
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Old 22-01-2019, 10:20   #10
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Re: Hydraulic steering excessive turns

Pugcat,

Is there a reason you are going with Vetus for your hydaraulics? The original Hydraulics on a Prout are (often?) Hynautic which is now SeaStar. We have replaced much of the original hydraulics on our Snowgoose 37' and are happy with the Seastar helm with the original (rebuilt) hynautic ram. We are nowhere near 8 turns lock to lock. I think it's probably about 3-1/2...

FYI our system :
- HF6007 Helm
- 3/8" Copper tubing
- Rubber hose to Ram (Similar to HF5508)
- K-19 Ram
- Raymarine Type 2 Pump (Autopilot)
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Old 22-01-2019, 10:59   #11
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Re: Hydraulic steering excessive turns

This is John Mardall for Vetus Maxwell headquarters office. The number of turns, hard over to hard over is essentially the ratio between the capacity of the pump (volume of oil pumped in one full rotation) and the volume of the cylinder (volume of oil displaced when ram moves from one end of its travel to the other end). Of course, I'm not going to interfere in the business of one of our dealers, but if you'd like to contact me direct at jmardall@comcast.net, with the details of the quote, I'll check the calculations, speak to the dealer and then recommend a solution. We do supply large capacity pumps, which are most often used in commercial applications, but will solve your problem, if it still exists after I've checked the calculations.


All the best
John Mardall
Vetus Maxwell Boat Equipment
email: jmardall@comcast.net
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Old 22-01-2019, 11:47   #12
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Re: Hydraulic steering excessive turns

We have two helms on our hydraulic steering circuit. Both are individually adjustable for flow volume [within limits...]

I have them both set at just under 4 turns stop-to-stop. We can dial them down to about 3 turns, and up to about 7, depending upon the needs.

With a new system, you will also want to properly size the hydraulic pump that the autopilot will be driving.

I mention this assuming your new system will have comperable features, and if not, to let you know they exist.

Cheers! Bill
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Old 22-01-2019, 15:24   #13
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Re: Hydraulic steering excessive turns

That sounds a bit on the high side, but it may be air in the system, or did they deliberately make it as low-geared as that for a hydraulic autopilot such as a TMQ or similar quality unit?
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Old 22-01-2019, 20:53   #14
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Re: Hydraulic steering excessive turns

With that many turns the autopilot pump is going to have to work very fast and long. May not be able to keep up with the course corrections in following seas. Check with Sea Star (Hynautics/Capilano). JMHO
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Old 22-01-2019, 21:26   #15
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Thumbs up Re: Hydraulic steering excessive turns

Quote:
Originally Posted by Pugcat View Post
Hi, could those of you with hydraulic steering please advise how many turns of the wheel you have lock to lock?
I am converting my Prout Snowgoose 35 to Vetus hydraulic steering and having given the supplier the rudder dimensions (same as a standard Snowgoose 37 I believe) they have done the calculations and come back with a system that gives 8 turns lock to lock - seems a bit excessive.
What do you guys and girls think?
Thanks

I agree with everyone else on those wheel turns. Eight is entirely too much.

I had the cable steering in the pilothouse wheel station replaced with manual hydraulic steering on my Tayana 37. It is 4 turns lock to lock. I don't have the specs on the ram to share with you, but the decision was to go one size larger than the optimal. With all sails down, motoring at max rpm in > 40 k of wind into 10' standing waves was a good test. I could definitely feel the resistance on the rudder, but I have no complaints.
The pump needs to be matched to a ram that can easily stand up to as much force as the rudder can deliver in the worst of conditions. Don't skimp.
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