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Old 13-01-2008, 15:41   #1
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hydraulic steering and rudder?

hello everyone,
We have a sail boat with hydraulic steering. The boat is hauled out for the winter in CT. We have noticed that the rudders been moving. We align it so that it is centered and sometimes( not always) we noticed that when we go back to the boat the rudder is hard over. Is it possible that because of the weather the hydraulic fluid is expanding and pushing on the rudder? Has anyone else noticed this?
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Old 13-01-2008, 17:25   #2
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Hydraulic steering is subject to some internal leaking. It is why hydraulically steered boats cannot have a windvane attached to the wheel, the position tends to drift.

I would not worry about it as long as the rudder is responsive to the wheel and you have no fluid loss.
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Old 13-01-2008, 18:24   #3
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Not normal

A good hydraulic system does not creep or leak significantly internally. There are a lot of crappy systems and installations out there that have added to the myth that all hydraulic systems creep or leak significantly. If this were true in general hydraulic backstay adjusters, for example, would not be used successfully and all hydraulic jacks would slowly collapse. As you probably know, this is not true except for lousy products.

If your system did not do this initially there are two places to examine: overpressure valves, which may be integral with a hydraulic autopilot, or the internal seals of the ram. The most suspicious area is the internal seals of the ram. If you do not have overpressure valves the test is simple for the ram: put the wheel hardover both port and stbd and lean hard on the wheel. If the seals are bad the wheel will keep turning very slowly. It is less likely that the helm pump is leaking internally yet is possible.

If you are handy you can replace the ram seals with generic ones obtained from bearing supply houses. Look at the number on each seal and buy replacements. Cost should be in the order of twenty five bucks or less.
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Old 13-01-2008, 18:29   #4
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thanks for the quick replies.

1. we have zero fluid loss.
2. this is the first boat and first time out of the water so we don't know if its normail or not
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Old 13-01-2008, 22:35   #5
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The internal seals will not leak fluid externaly. Rick is spot on. and I shall also add, a small spec of dirt stuck under the check valves will do the same thing. It could be worth doing a flush of the system with clean oil. Oh and ensure the oil is the correct weight and type. This will make the system harder to turn. The wrong type can damage seals. You will usually have the choice between an ATF or a 10W hydraulic oil.
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Old 13-01-2008, 22:58   #6
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look at "Hydrive" "Hynautica""Wagner""Kobelt" some of the more common steering systems. As a general rule they will all say there is no creep unless you have a problem. The fluid expansion due to a change in temperature should "relief" in the top of the steering pump or a separate expansion vessel
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Old 13-01-2008, 23:02   #7
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You have an internal seal that is leaking. It's that simple.
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Old 13-01-2008, 23:16   #8
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What I don't quite get is why is it naturally going to one side. Is the boat on a heel???
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Old 14-01-2008, 09:56   #9
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If you are handy you can replace the ram seals with generic ones obtained from bearing supply houses
be careful if you attempt this, not all "O" rings are compatible with all hydraulic fluids. Make sure the rings you use are for the type of fluid that you are using or you may end up that mythical creek. If you can, get "viaton" O rings. They are good and are compatible with almost any type of fluid, even synthetic ones.
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Old 14-01-2008, 11:42   #10
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If your system is over 5 years old you may just want to replace all the o-rings.

Your problem sounds like a check valve leaking, maybe just in your pump. Most have a ball check and a speck of dirt or metal chip can allow it to stay open just enough to force it one direction during temperature changes.

Thats one of the reasons I've installed directional pressure gauges. On hot days, while sitting on the hard, I can actually see the pressure climb up to 150 psi on both sides/directions of the system. If one were 0 on one side and the other climbing, then my rudder would turn on it's own.

If it's in the water you will not see this because the rudder is being worked by wave action.

Depending on the manufacture of your system you maybe able to just pull the directional valve off the back of your pump and clean & reseal it. Or take it to someone that does hydraulics.

How old is your system???
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Old 14-01-2008, 11:51   #11
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The check valve is just a small ball bearing with a spring behind it. Beware of that when you unscrew the little sealing cap. You will find a block on the back of the helm pump. On each side will be that little cap. Easy to take out and allow a small flow of fluid, this will flush any foreign object and then screw the set back home again.
One other thought that Del prompted me with his comment of pressure rising. Most commonly found are balanced rams on the rudders. But in some not so common installations, Non-balanced rams were used. This is compensated for in the system, but if you get a pressure diferential, it will move the ram one way more than the other. However...in saying all that, even 150PSI pressure build up will not swing the rudder hard over. That requires the half the entire volume of oil in the system to flow to one side. Once again, I can not understand how the rudder would move that far if the boat is sitting verticle on the hard. You sure some kid isn't playing with the wheel after everyone goes home??
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Old 14-01-2008, 11:56   #12
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What I don't quite get is why is it naturally going to one side. Is the boat on a heel???
Wind?

Steve B.
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Old 14-01-2008, 12:01   #13
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Wind?
The check valves should stop the wind from moving the rudder. Otherwise in certain sea states, you would have the helm wheel fly around on you. That is the one major advantage with hydraulic. Not matter the load on the rudder, the wheel should stay where put. Although some don't like that feel, or lack of it.
Besides, it would take one mighty gust of wind.
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Old 14-01-2008, 16:23   #14
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i will certainly look deeper into all your suggestions when I go over to the boat next weekend.

i don't think a kid is playing on it. it's pretty hard to climb up there the way we are situated. I am defiantly sure it's not the wind becuase I can't even move it by hand. The boat does not look like its heeled to one side, but it is something to consider.
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Old 16-01-2008, 22:13   #15
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What I don't quite get is why is it naturally going to one side. Is the boat on a heel???
Many hydraulic steering systems are pressurized. If there is a pressure differential somewhere, it could make sense. The one on my boat I have pumped up to 30 PSI according to the manufacturers specs.
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