Which hydraulic steering should I choose?

[Maika]

My catamaran, a 40ft one-off, is steered by Ultraflex cabels, which I find really bad. The only reasonably prized option is hydraulics. (It is not possible to have a physical tie-rod beetween the rudders.)
I contacted Vetus, but their solution will give me a 7 turn lock-to-lock, which I find way to much.
I have also contacted HyDrive, which claim their Fluid-Link is excelent when not having a tie-rod, but have so far got no response from their Norwegian partner.
My next try will be LECOMBLE & SCHMITT, but are there other manufacturers I should have a look at?

[Cheechako]

Not sure in Europe. In the US probably Teleflex Seastar. You need a higher output pump to reduce your number of turns. 7 turns is huge. A lot of bigger powerboats use hydraulic, maybe check out what is used on them over there.
Take a look on Ebay just to se all the brands under "hydraulic helm steering"

[senormechanico]

There's gotta be a better solution. Can you possibly use cables?
My Dragonfly has 2.5 turns lock to lock and it's just perfect.
A neighbor's power boat has 5 turns and it's dreadfully unresponsive and boring to drive at all speeds.

[multihullsailor6]

Maika,

Vetus also produces other steering pumps which you should be able to incorporate: the HTP30 (R) with 4.9 turns and the HTP42 (R) with 3.5 turns when using the MTC72 ram. My 11m cat has the MTC72 ram and two HTP30 pumps which I'm happy with.

[Maika]

Today I have the T72FC - 38868K - dual cable steering helm
T71FC and T72FC Rotary steering systems
modified so that each cable go in from each side, since the rudder pole arms are pointing towards each other.
The slack(?) on the wheel is a half turn, which is pretty anoying, and I have not managed to figure out why. Also, I can not attach a proper stering wheel, since the cone only fits small motor boat wheels.
I know both Teleflex and Ultraflex provide hydraulic steering, but are these for sailboats?

[Maika]

Originally Posted by multihullsailor6

Maika,

Vetus also produces other steering pumps which you should be able to incorporate: the HTP30 (R) with 4.9 turns and the HTP42 (R) with 3.5 turns when using the MTC72 ram. My 11m cat has the MTC72 ram and two HTP30 pumps which I'm happy with.

Hi,
The guy from Vetus told me that since I need two pumps (because i do not have a mechanical tie-rod), the lock-to-lock will double, giving a 7 turn with the HTP42.

Edit: but you write that you have two pumps, so is this not correct?

[44'cruisingcat]

Geez, the guy from Vetus sounds like a dimwit.


You Don't need two pumps unless you want two helms.


Even if you have two pumps, the lock to lock number won't change (provided the helm pumps are equipped with anti-backflow valves, and if they aren't the steering won't work at all.)


You don't use a mechanical tie rod, instead you need a hydraulic one. The two steering cylinders are mounted in series, as it were. This also doesn't affect the turns lock to lock.

[Maika]

Sorry, I meant he told me that two cylinders (not pumps) doubled the lock numbers. If this is not correct, then I am happy

[Maika]

This is what he told me:

It is possible to put an "hydraulic tie-rod" between the two cylinders - please see attached schematic. The drawback is that two cylinders doubles the number of turns at the wheel for any given pump: e.g. 1 x HTP30 plus 1 x MTC72 gives 4.9 turns hard-over to hard-over, WITH 1 x HTP30 plus 2 x MTC72 gives 9.8 turns hard-over to hard-over. The several valves allow for the synchronisation of the cylinders. 1 x HTP30 plus 2 x MTC72 gives 9.8 turns hard-over to hard-over.

(I also attached the schematic.)

[44'cruisingcat]

I found hydraulic steering manufacturers/salespeople incredibly hard to deal with. Most of them wouldn't know if their arses were on fire. Some are so busy trying to cover their arses they try to sell you ridiculously oversized systems.


Hydrive make good gear, but they insisted I needed cylinders that could deliver 750 kg of thrust. To each rudder! And they simply refused to sell me a smaller system.


I bought Ultraflex hydraulic, with cylinders that deliver 100 kg, and that is plenty. But I can't recommend Ultraflex either, because the cylinders had the wrong type of seals fitted! Now I have fitted the right seals it's pretty good.


All I can suggest is that you need to educate yourself in hydraulics a little. You can't rely on manufacturers or salesmen to know what they're on about.


Work out how much thrust and stroke length your cylinders will need.


Consider how much load a tiller 1 metre long attached to only ONE rudder would have. On a cat, it's not much. Maybe 5 kg max? Then look at what length tiller your hydraulic cylinders will be working on.


Say it's 100mm - then you'd need 50 kg thrust from each cylinder. But because your cylinders will be mounted in series, you need to double that number.

So you then look for suitable cylinders with plenty of thrust and a stroke length that will give you the right range of movement - 45 degrees each way is more than enough.


Having worked out what cylinders will suit, look at their full stroke displacement. Since the cylinders are in series, you only need to consider the volume of one cylinder.


Say it's 300 cc. Then you look for a pump that will pump 300cc in the desired number of turns. ie if you want 3 turns, you need a 100 cc pump.

[undercutter]

We have a hynautics system on our monhull but not sure if this is still around.

The pump is a Wagner built in British Columbia, Canada.

The only critical part is the pump who's flow will determine the number of turns on the wheel to produce sufficient flow to move the cylinders (sized appropriately) for the power to move the rudders under load. i.e. the bigger the cylinders the more flow required for the same movement.

The system should be based on these requirements and not just purchased off the shelf. Some determining factors will be boat displacement (weight), rudder size and potential installation of auto pilot as you will need to know whether you will have to install a continuous running pump for this or not. With 2 cylinders I would assume that a CR would be required. Octopus makes a good one and they are also in BC and service the shipping industry as well.

Good Luck

[44'cruisingcat]

Originally Posted by Maika

Sorry, I meant he told me that two cylinders (not pumps) doubled the lock numbers. If this is not correct, then I am happy

Be happy! Because he's wrong. The cylinders are mounted in series, so basically what happens is that as one cylinder moves, it displaces oil into the next one, and moves it too.

The full stroke displacement of two in series is that same as one on it's own.

The downside of that is that at a given fluid pressure, each cylinder only develops half the thrust.

[44'cruisingcat]

If you already have cable steering, there are some boats here with pull pull cable steering which the owners are really happy with, and certainly seem to offer better feel and quicker response than hydraulic.

[2Hulls]

Originally Posted by 44'cruisingcat

If you already have cable steering, there are some boats here with pull pull cable steering which the owners are really happy with, and certainly seem to offer better feel and quicker response than hydraulic.

I couldn't agree more. Perhaps re-engineering your cable system is a smarter way to go. Likely way cheaper and for sure more enjoyable steering.

Dave

[Rowy]

We have hydrive steering that is just under 2 turns lock to lock. Works really well. The hydrive guys can get you pretty much water ever turns to lock you want with a combination of different pumps and rams.

When I queried the ram sizing was told it is dictated by when the boat is going backwards, even if only momentarily. A balanced rudder is just the opposite when going backwards. You can feel this for yourself through the helm if backing up at speed.

The design load isn't considering when you back out of your pen in a hurry, but when the boat is momentarily knocked back by a wave. Be it in breaking seas or crossing a breaking bar, neither is a good time for rudder failure. Rare event that won't ever happen to most boats, but thats what design loads are there to cover, not the average nice day.

There is a good article of an Alpha 42 cat that did just that on a delivery voyage in the atlantic in oct 2014 Yachting World.