Hydraulic Steering Issue - Rudders Don't Keep Alignment on Cat

[Capt Phil]

Had a similar problem aboard a 65 foot Sea Ranger inside the Avalon Harbor years ago.
I was following one of smaller tie up vessels into our berth when the Sea Ranger took an abrupt turn to Starboard and we almost collided with a ferry that was moored to a ball right beside the ferry terminal.
I had lost all steering ability at both helms, threw both engines into reverse and came to a stop about 2 feet from the moored ferry!
Turns out this loss of steering was caused by air in the steering hydraulic system which I trouble shot on our return trip to San Diego. Autopilot would not hold a course no the way back to San Diego. Boat just wandered around. Steered by engines on way home.
Used an air compressor the void the hydraulic system of fluids then refilled the hydraulic system very SLOWLY from the top resevoir
Problem solved!
Phil.

[deblen]

Is it even possible to keep 2 rudders & rams syncronised by hydraulics alone?
Do you need a "tie rod" between tillers to maintain alignment? / Len


https://www.google.com/search?q=twin...GfAY-046eG13M:




https://www.sbmar.com/articles/marin...ering-systems/

[stinkpots]

Manual hydraulic systems have bypass valves. If for example you turn the helm over to the stops and keep turning the wheel the hydraulic bypass valves will operate. If you marked a Centre point on the steering wheel you will now find it is no longer Centred. Depending on how your twin rudder steering has been set up this could be something to consider.

[InsuredApple]

I've rebuild the entire 3D model of our hydraulic system...

[InsuredApple]

Originally Posted by RaymondR

Do the hydraulic lines actually come out the side of the cylinders as you have drawn them?

Yup, that's out setup.

Originally Posted by smac999

Can you not put a mech tie bar on? The cat I was on last week had one behind the back deck.

Is this how most cats are? Seems they would all be miss aligning over time.

Nah, not really possible. I mean... it's probably possible somehow, but would require major fiberglass work, moving the generator somehow...

Most of our friends have small catamarans with mechanical steering.

Originally Posted by 44'cruisingcat

Probably the majority of cats have some mechanical connection between the rudders.

But hydraulically linked systems can work well. My rudders basically never get out of alignment.

I wish our rudders would stay in alignment for more than 3 hours. It's frustrating.

Originally Posted by Dave852

You show the valves between the liquid tie bar and and the line going back to the helm. On my boat I also had pressure relief valves installed there. Basically a spring loaded ball bearing that I had cleaned the gunk out and looked fine. But in the end removing them solved my alignment problem. Newer helm pumps have the bypass built in to the pump so any bypass does not affect alignment.

Ah interesting. I've heard of equalization valves as well... I'm a bit surprised that too "highly rated" companies haven't been able to figure this out.

Originally Posted by MIRELOS

Had a similar problem on my FP60, was not a hydraulic problem but an auto pilot problem, spent countless hrs. with Furuno tech support, they are great and still things did not work, finally got a marine electrician I know to look at it, reprogrammed the auto pilot commuter from scratch. If you have made any repairs (changing any part of the system) you need to have the main computer to recognize it by reprogramming. It took me a year to get it right...thanks Tony T in NY for your knowledge

Amazing, I bet you were happy when you finally cracked that nut.

I don't believe our rudder alignment issue is related to the autopilot -- the alignment issues happen even when we don't use the autopilot.

Originally Posted by deblen

Are you sure that the actual rudders are out of line?
Could it be that one of the rudder angle meters or it's sender are the problem? / Len

Oh, they get out of alignment It gets so bad they... ya.

[deblen]

What are the bypass valves between the yellow & P/S lines for? Your A/P pump appears to be plumbed correctly,though I recommend shutoff vaves @ the tees,in case you need to remove it or it leaks,etc.


By "power steering" the A/P pump from hard over to hard over several times,you can remove the air from the system without bleeding. / L


Edit: We were posting at same time. Your post #20 answered this.


But I still question whether you can keep rudders aligned without ty bar or feedback of some kind.

[Cadence]

Originally Posted by InsuredApple

This is a rough diagram that I quickly whipped up... just to show our hydraulic system, the bypass valves (green), the liquid tie bar (blue)...

I would expect the system to have a pressurized reservoir?

[44'cruisingcat]

Originally Posted by deblen

Is it even possible to keep 2 rudders & rams syncronised by hydraulics alone?
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Yes. My rudders don't go out of alignment.

Most hydraulically steered boat's rudders stay aligned.

If rudders are going out of alignment it's because there is a fault.

[DeepFrz]

Are they always out of alignment in the same way? If so I think you might have a leaky valve in one of your shutoff valves.

[DeepFrz]

Do you have mechanical stops on your rudder tiller arms? Hopefully you do and they are all adjusted properly. Just one more thing to check.

In my above post it probably wouldn't matter if they always failed with the same rudder pointing off center. I think it could be either valve leaking.

[belizesailor]

Originally Posted by deblen

Is it even possible to keep 2 rudders & rams syncronised by hydraulics alone?
Do you need a "tie rod" between tillers to maintain alignment? / Len


https://www.google.com/search?q=twin...GfAY-046eG13M:




https://www.sbmar.com/articles/marin...ering-systems/

Yes, it is. Some boats have a hydraulic tie bar...which works properly.

[BruceS]

A big majority of houseboats on the River Murray in Australia have twin outboards that are connected via hydraulics. Some even have a second steering on the top deck.
Most or many use the locally made Hydrive units.
https://hydrive.com.au/admiral-series/
I never hear of the OP's problems if bled properly on setup.

[InsuredApple]

Originally Posted by DeepFrz

Do you have mechanical stops on your rudder tiller arms? Hopefully you do and they are all adjusted properly. Just one more thing to check.

In my above post it probably wouldn't matter if they always failed with the same rudder pointing off center. I think it could be either valve leaking.

What are mechanical stops? Are they essentially strong pegs that prevent the tiller arm from moving beyond a certain angle? If so, then no, we don't have anything like that...

What an annoyance. I just found a leak on the 3rd time rebuilt hydraulic ram. We should have just purchased new rams, but I was told that rebuilding them and machining them would be cheaper and just as good as new rams.

[DeepFrz]

Originally Posted by InsuredApple

What are mechanical stops? Are they essentially strong pegs that prevent the tiller arm from moving beyond a certain angle? If so, then no, we don't have anything like that...

Yes, they stop the rudder, usually at a 35 deg. angle so that the hydraulic rams don't bottom out. Actually in checking this out it seems that rudder stops are not necessary although it may be a requirement of some ram manufacturers.

[44'cruisingcat]

Originally Posted by InsuredApple

What an annoyance. I just found a leak on the 3rd time rebuilt hydraulic ram. We should have just purchased new rams, but I was told that rebuilding them and machining them would be cheaper and just as good as new rams.

Is it leaking from the shaft seal?

The reason I ask is that I initially had problems with leaking shaft seals on my steering. (Ultraflex) If the leak was on the hydraulic link side, the rudders would go out of alignment.

One day I was complaining to a guy at a hydraulic steering stand at a boat show, saying what an easy life the seals on steering have, compared to say, the rear damper on a motocross bike, with dirt, dust and extreme pressures, and yet they hardly ever leak.

The guy made an interesting point. In many cases the pressures in hydraulic steering systems may be too LOW to make the seals work properly. Most seals have a C shape cross section, and use the hydraulic pressure to force them against the shaft. With low pressures they can leak.

So I looked for the same sized seals, but with a solid cross section. Once I found and fitted them, problem solved. About 8 years now, and not a drop leaked. Rudders stay aligned.