Rudder hydraulics

[MichaelRoberts]

As discussed in previous threads, we are building a sixty foot catamaran, actually more like a 54 footer with long narrow bows.

Anyway I need help with the hydraulic steering system please.

The system comprises starboard and port helm pumps, auto pilot pump and two rams - port and starboard. It is all plumbed in with 1/2 inch copper tube, flared fittings and no hoses except short ones to the rams.

It took ten litres (two and a half US gallons) of expensive hydraulic oil to fill and bleed. Just the copper tube - about 45 metres of it - took about 5 litres.

Needless to say it took quite a few weeks.

And now it doesn't work very well. The rudders can move freely but when the rams are attached and I turn the wheel the movement is stiff and jerky.

OK I know it's air bubbles. How best to get rid of the remaining air and will the rams ever move smoothly?

Thanks
Michael
ARCHIMEDES

 

[fallguy]

There is a fellow named Tyler Holland with a small company in the US who I purchased my catamaran bleeder kit from. He is exceptionally friendly and his product is reasonably priced.

Just looking at your drawing and from an amateur's perspective, I wonder whether he would recommend an additional reservoir for each of the helm pumps. The helm pumps are a source of a lot of change, for lack of a better word. I had some trouble with my system when I thought I could run too small a reservoir. The reservoir on the other pump might simply be a clear line if he think you need it.

The product is called bubble purge. Call him. Ask if you need a second reservoir and get the bleeder kit. It'll run you about $200 to recover your sanity. Dan

Oh, and despite the fact he is an outboard guy, pretty sure he can still build you a bleeder kit.

About us – Outboard Specialty Tools https://outboardst.com/about/

 

[fallguy]

Here is how I store the kit. Garage service door sure is dirty!

 

[fallguy]

Here is what I bought. Tyler can probably help you. You might need to do some configuration if the bleeders don't fit the tubing for non-Seastar etc.

Make sure and tell him all your dimensions so the hoses are all long enough.

 

[kapnD]

One reservoir should work, if placed on the highest helm, but if the two helms are on the same level (catamaran opposite hulls), the one without the reservoir should not be vented.

 

[MichaelRoberts]

You guys are so helpful, thank you for your comments.

You are right kapnD, I did put a vented plug in the port helm pump (following the instruction book) and next day there was a puddle underneath, so I sealed tight. But now seems like good idea to have a second reservoir, one on each helm pump.

Thanks for your bucket picture of the bleed kit Fallguy, It has inspired me that the best way to move bubbles back up to the helm pumps might be to feed oil into the bleed nipples down on the rams. This could be done with a long plastic tube from the rams back up to an oil filled bottle temporarily mounted higher that the helm pumps.

Stupid problem, so much work has gone into it, hope it will work in the end
Thanks again
Michael

 

[kapnD]

Bleeding air takes patience, especially if there’s long tubing runs with dips along the way.
The air will all come out at the cylinder and the high point eventually, I like to bleed all it will give initially, let it sit overnight and bleed it again until there are no more bubbles.
The kit makes it more visual, and is cleaner, but it’s not altogether necessary.

 

[comfisherman]

I like a small detached reservoir, and a crossover valve on each ram. I'll try and find a Pic of a setup as I'm home from the boatyard at the moment. Crossover let's you pump lots of bubbles clean through the system, and the detached reservoir allows the bubbles to escape the helm mechanism without being re introduced to the system.

I've installed some long systems in crows nests for guys who like wheels over remote jog levers, bubbles have a shocking ability to get trapped in long runs.

 

[MichaelRoberts]

Good advice comfisherman - the fluid link from the bum end of each ram is about 6 metres long (20 feet)
It goes up from the port ram, over the bridge deck and down again to stb ram
It's a bubble trap
Feeling more optimistic now with all the encouragement of you all
Monday morning, double shot coffee, here I go