Hydraulic system

May 2024 update

Now working perfectly!

The hydraulic system on the 435 consists of a pump which incorporates raise/lower valves controlling a circuit each for the the cylinders which operate the centreboard and rudder.  It has a reservoir for fluid,  (ethylene or proylene glycol)  and uses plastic hoses.      While the hydraulic system works well, it is prone to corrosion, particularly the rudder cylinder's shaft, especially if the rudder is left down and not cycled for extended periods.    More recent models use a mechanical system instead of hydraulics.

Hydraulic Cylinders

I've had an interesting experience with cylinders.    (Bear in mind:  The boat in the Caribbean, and I am in Toronto.)

I purchased the boat knowing the rudder cylinder had failed.   It was leaking and had a badly corroded shaft. I brought it to Toronto knowing I could easily find a hydraulics shop for a rebuild.  The shop I selected told me that the internal clearances were too tight, so (without checking with me) they machined the piston slightly smaller and rebuilt it (including a new shaft) for a reasonable sum.   It looked perfect and worked smoothly.   In Oct 2023 I installed it and it leaked.  More delay.  I ended up ordering one from Hydroem (via Alubat) to install in May 2024, and it did not fit into the upper section of the rudder housing.   The unit sent had raised welds whereas the original had been ground and polished.  Fortunately I had the tools and materials aboard to grind these myself.  The rudder, with its new bushings, pins, axles and cylinder is now working flawlessly. 

The centreboard cylinder was working and in better shape.     Nonetheless, I removed it and had it inspected at Hydrostore in Curacao. Erik told me that the clearances were too tight, but begrudgingly replaced the seals, warning that it was still too stiff/tight. (note - this was the second competent professonal specialist that noted this)   I reinstalled it and ordered a replacement from Alubat rather than risk a later problem.   The replacement arrived and did not fit as the flat section on the shaft was not ground adequately to clear the flanges where it engages the centreboard. Apparently there are two versions, and the wrong one was sent.  As the rebuilt cylinder worked fine, I left it in use, and will grind the appropriate clearance on the other when I get a chance. 
So I now have a spare unused centreboard cylinder and will investigate rebuilding the improperly rebuilt rudder cylinder.
There appears to be something dimensionally different about the tolerances in these cylinders vs those commonly used in industry.  Until this is understood I would only order from Alubat/Hydroem unless the boat, owner, and hydraulics shop are all local.  Why are they different, and what is the specification?

Pump

Once freed up, the clever combination pump functioned properly though there was some play/wobble/wear in the handle mechanism.  I elected to inspect and correct this.   It is best to remove the mounting bolts to get at the screw that forms the lower pivot of the pump linkage, as it is awkwardly located in a counterbored recess in the back of the left side of the pump.  Upon disassembly it was found that a cut-down M5 hex head screw had been used for one of the pivots.  It was simply sitting in place, not secured.   As a result it was bent and worn, and jammed in place.  ultimately, it was extracted and a correct replacement cut.  Fortunately the threads in the pump housing weren't damaged.   This M5 SS screw must be cut to the correct length and possess the correct 10mm threaded and 25mm unthreaded dimensions for it to fit and function as intended. 

The use of the damaged screw led to some wear in the stainless steel link.  See below for dimensions.

 The handles and screws will be secured with blue loctite.   I will add English labels for operation by guests.

Pump Fuses 

‘Pastille’ in French, referred to as a ‘fuse’ in English, this sacrificial disc is located in the pump and ruptures in the event of a locked centreboard (or rudder) encountering an Orca or other  submerged object, hopefully prevcnting damage.  (To the hydraulic system, while still discouraging the orca) 

Many have suggested that DIY fuses are fine in this application, some are more cautious.   Thought I’d investigate….

The beer can is made of .007" aluminum, punch is 1/2” in diameter. 

Here are the factory-supplied parts - .006" thick copper, 12.4 mm diameter

I doubt the DIY approach would be a problem.

Bleeding the system.

In order for a hydraulic system to develop its full pressure and function correctly, it must be free of air.   Hydroem publishes instructions for this.  

I had to install and remove the centreboard and rudder cylinders several times, and found the bleeding process to be simple and intuitive. (I didn't refer to Hydroem's instructions, which I had read and forgotten.)   By installing one hose, extending (or contracting) the cylinder by pumping, then installing the other hose, then cycling the system, most if not all of the air can be purged.   You can see the bubbles suspended in the fluid and hear as it enters the reservoir under pressure.  Any remaining air can be eliminated by a few reailse/lower cycles, with some time between to allow the bubbles to rise and escape in the reservoir,  and the fluid will appear clear and the pump can develop and holds the necessary pressure.   Easy.

Original Posts

Update - April 2023

As noted below, I was able to free up and disassemble the rudder cylinder.  Though I was prepared to replace with new, I figured I’d bring it to a local hydraulics shop for assessment.   It needs a new shaft and seals of course - estimate is C$300-500.  Much better than €1300 plus shipping, taxes etc.    normally such things go the other way. 

The pump was stiff, and the rudder cylinder nearly seized. The centreboard would raise but  not lower with hydraulic pressure.     Definitely not hardware store items, and clearly suffering from age and neglect.  I’ll offend other owners if  I call it an OVNI weak point, but it’s definitely a talking point for most.  

Hydroem 2-section Pump

Here’s a link to my January 2023 attempt to operate the pump.  

https://m.youtube.com/watch?v=gES-mjiD7vU

When I returned in March I lubricated the pump and it began to work freely.  I inspected the copper ‘pastilles’ and they were intact, so the centreboard issue lies elsewhere.  

Hydroem Rudder Cylinder

On my initial inspection, the  rudder would not operate with pump pressure and would only budge (slightly)  if the rudder were moved by hand.  With some cycling, it eventually ended up gushing hydraulic fluid from around a corroded cylinder shaft.  

 In my return in March I commenced work on the rudder (documented elsewhere) and managed to excavate and remove the cylinder.

  It was quickly condemned by a very helpful Erik at hydrostore in Curacao as it could barely be moved and not disassembled.  I brought it home with me.

Hydroem, the manufacturer in La Rochelle France, quoted €1300 for a replacement.  

Somewhat curious,  I sprayed a liberal amount of PB blaster inside, and let it sit for two days.  (Old engine trick…)

Though stiff, it could now be moved more easily, and with some crisp hammer taps I managed to slowly get it extended, then apart.  Much to surprise, while the shaft is destroyed, the rest looks pretty good. 

Perhaps it can be rebuilt with a new shaft and seals?

https://ovni-owners.org.uk/forums/topic/easing-stiff-ovni-centreplate/

From

https://ovni-owners.org.uk/forums/topic/hydraulic-hoses-for-lifting-keel-and-rudder-ovni-435/

 The exact hose that i have in Nella (2006 – 435) is Synflex 3031-02 1/8″ . It was made by Saint Gobain in 2003.

Saint Gobain was taken over by Eaton (USA) in 2006 which is also owns the Danfoss brand–its still being made and its measured in inches.
The internal diameter is nominally 1/8″ but more accurately 0.130 inch
External diameter is 0.340 inch
Hose is available from Eurohydraulics (https://www.eurohydraulicsscotland.com/) –they are super responsive and friendly and expect a shipment of 3031-02 to arrive in about 6 weeks

Its also available from the Hydrasun (https://hydralink.hydrasun.com/PublicCatalogue/Page.aspx?i=11001) catalog. But at present they don’t have any in stock and its going to take “about 6 weeks” if ordered.