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

[InsuredApple]

Originally Posted by DeepFrz

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.

Aha, interesting. Let's hope we don't have to get those put in... we're sitting at a marina here in Fort Lauderdale waiting for the hydraulics company to show up and get the job done we hired them for.

Originally Posted by 44'cruisingcat

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.

That's really interesting. I'll bring this up... when (hopefully) the hydraulics guys show up at the boat tomorrow. Arg.

[B-Baysailer]

Has anyone checked the bypass valves .if there the way you have in the diagram if one has a leak the cylinders will get out of sync.

[B-Baysailer]

That would be a internal leak

[skipperpete]

Originally Posted by DeepFrz

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.

DeepFrz
Thinking of the rudder stops is fantastic trouble shooting, if one ram hits the stop before the other it could cause the other ram to continue to travel ...via even the minutest of internal leaks. Your mention of the rams bottoming out would have the same effect because the ram at full stroke and stationary allows pressure to keep trying to move the other ram with the possible consequence of putting that rudder out of synchronization.
If this is correct it will always be the same rudder to the same angle each time.... but my guess is that it still requires an internal leak (tiny leak) to do it. The cure could simply be adjusting the rams so they both bottom out at the same time.

[InsuredApple]

Originally Posted by B-Baysailer

Has anyone checked the bypass valves .if there the way you have in the diagram if one has a leak the cylinders will get out of sync.

That makes a whole lot of sense. If one of those valves does not isolate the two circuits, then there would be an alignment issue.

I wish there were some gauges or sensors that could be installed to keep an eye on things. This guessing is frustrating.

[MIRELOS]

I didn't think so either, but they haven't gone out of alignment since I fixed the AP, worth checking it out

[captlloyd]

I maintain that if it leaks fluid, it’s leaking air also. Fix one and you fix them both. Leaks fixed and air bled the distance between rudder arms can’t change.

[Fantazia55]

I am having the same problem with my Switch 55 catamaran. There are only manual bypasses, so the only way for the connecting hydraulic line to get out of sync seems to be the rams failing to seal. The prior owner replaced the rams, one of them twice. Each time it seemed to fix the problem until next time they hit rough weather. Once it starts to occur, it gets gradually worse with use. I suppose replacing the rams may fix it for a little while, but something is causing the rams to fail. Is it possible the rams are too small? To make matters more confusing for me I have two pilot drives, one on the starboard quadrant and one between the lines coming out of the steering pump. Flip a couple of switches to select your choice. I wasn't aware of this setup until I started chasing all the lines to look for leaks. No signs of leaks, just gradual toe in of the rudders, and accompanying loss of steering. This loss of steering causes the autopilot to fail after a bit of time. The rudder angle indicator and the autopilot drive are on different rudders, which must confuse the autopilot pretty well. The rudders are easily re-aligned by opening the bypass valve and moving the rudder manually to align with the other. This however involves opening the engine hatches on the stern transom steps, not desirable in rough seas. As a new catamaran owner, docking without rudders is not very desirable, though the engines worked so far. Anyone think of anything else to do?

[InsuredApple]

Originally Posted by Fantazia55

I am having the same problem with my Switch 55 catamaran. There are only manual bypasses, so the only way for the connecting hydraulic line to get out of sync seems to be the rams failing to seal. The prior owner replaced the rams, one of them twice. Each time it seemed to fix the problem until next time they hit rough weather. Once it starts to occur, it gets gradually worse with use. I suppose replacing the rams may fix it for a little while, but something is causing the rams to fail. Is it possible the rams are too small? To make matters more confusing for me I have two pilot drives, one on the starboard quadrant and one between the lines coming out of the steering pump. Flip a couple of switches to select your choice. I wasn't aware of this setup until I started chasing all the lines to look for leaks. No signs of leaks, just gradual toe in of the rudders, and accompanying loss of steering. This loss of steering causes the autopilot to fail after a bit of time. The rudder angle indicator and the autopilot drive are on different rudders, which must confuse the autopilot pretty well. The rudders are easily re-aligned by opening the bypass valve and moving the rudder manually to align with the other. This however involves opening the engine hatches on the stern transom steps, not desirable in rough seas. As a new catamaran owner, docking without rudders is not very desirable, though the engines worked so far. Anyone think of anything else to do?

Hey. We are working with High Seas at LMC on our hydraulic issues. The company we initially hired to do the job... we had to move on, after 2 attempts to fix leaking hydraulics.

Bruce at High Ses came by our boat to look at everything. They removed the rams, tested the rams (that were rebuilt by others before), and found internal leaks. The fluid was bypassing the internal seals.

Now we are waiting for new rams to come from France.

I'd recommend that you get the rams tested -- this is easier than said if you don't have easy access to a place that can test the rams.

[Cadence]

A SWAG is that the rams are undersized.

[Fantazia55]

I just talked to a local hydraulic shop, who recommended taking them off and bringing them in for a checkup. Guess I should know their condition before too long.

[InsuredApple]

Happy 2020!

Quick update. After paying MutliTech around $3,000 to fix the issue, then hiring Fort Lauderdale Hydraulics (Craig) to fix the botched MultiTech work and paying him also around $3,000... we ended up hiring High Seas.

They came by the boat, removed the cylinders, tested them, and found an internal leak on both cylinders. They suggested that replacing the cylinders would be the best option -- so we ordered new cylinders, waited 4 weeks or so, and High Seas installed them.

The funny thing is that initially, everything looked fine, so we departed Fort Lauderdale to the Bahamas. But we then found a not-insignificant hydraulic leak coming from a fitting. I emailed High Seas... 48 hours later, Bruce from High Seas was on the boat in Nassau and replaced a fitting. A fitting that that Fort Lauderdale Hydraulics had installed (it looked cross-threaded).

Since then, we've had MINOR alignment issues and NO leaks.

Very impressed with Chris and Bruce at High Seas.