Hydraulic steering sizing

[Larry aberg]

I I need help on figuring out how to improve the hydraulic steering system on my 55 ft powerboat.

The issue is during conditions when we are running with waves and surfing down the waves the forces on the steering wheel are more than the system can exert. The wheel is solid no matter what force you apply to the wheel

We generally pull the power back to slow down or end up doing lots of S turns down the coast.

It doesnt take much of a swell to put us in the scenario.

The boat is heavy displacement meaning full of fuel and water 52,000 lbs semi planing hull.

The hydraulic system is a 1.7L helm pump and 1.7 cu inch ram. It looks like thermoplastic hydraulic lines with copper fittings and compression fittings.

There is a auto pilot pump installed with a course computer and goes to max during the conditions above unable to keep a course.

The system works fine in calm waters.

I’m assuming the hydraulic steering system was not designed for this size boat?

What size Ram and helm pump should i be looking at?

Recommendations?

Topic

[Clark Leighs]

Glad to hear it is working out properly now.

[Larry aberg]

Update with PA35

I installed the updated hydraulic system new ram, helm pump, 3/8″ hydraulic hoses and Accusteer PA35.The PA 35 is a nice power assist pump albeit not cheap. Doubling for the auto pilot pump also. The adjustment pots are very sensitive and you can dial in how much assist you desire very easy to adjust. Very quiet unit when operating. I have the gain on the unit set at 52% presently.  This gives the feel of the BOAT in power assist mode similiar to the un-assisted mode without any force needed to move the wheel.  Really helps steering when up on step and big water conditions. The rest of the story has to do with the manufacture lack of attention to detail during assembly of the steering system.   I pulled the boat out of the water this past summer and removed the rudder tie bar. I found out that the starboard rudder did not move even when trying to leg press it. Port rudder moved easily. The starboard rudder upper bearing was 1/4″ out of plumb and the assembler forced the 1.5″ rudder shaft to fit the bearing causing it to bind.  It was an easy fix to ream out the aluminum channel .25″ and free up the rudder.  Took me 30 mins. Over the years the bearing was scarred and required replacement along with straightening the rudder shaft.   Works great now      

[Clark Leighs]

HOw are you doing?

[Larry aberg]

accusteer PA 35 hydraulic pump

Still working on fixing my steering system, back on it shortened rudder connecting bar 3″ to straighten out rudder geometry. existing cylinder ram is weeping fluid now so replacement is imminent. Here are some questions I have:

I like the Accusteer PA 35 power assist and auto pilot pump. Do you have experience with this pump?

The output flow rate spec says 3.5cu in/s

recommended cylinder capacity 35-60 cu in

I am looking at the HC 200B7 or HC 200B9 16 cu in and 20.5 cu in displacement cylinders to suit my torque requirements. Do I need to increase the size of this to satisfy the PA 35 requirements?

They are smaller than the recommended cylinder capacity size of the PA35.

the cylinder output flow rate is adjustable as a percentage of overall flow rate, I believe, on the PA 35.

what would your recommendation be for cylinder ram with the PA 35 I need approximately 1200ft lbs prefer 7″ stroke. Installed 3/8″ ID Parker MSH-6 hose rated 1000psi no elbows only straight fittings.

1.7 cu in helm pump existing. 15″ wheel existing.

Thanks for help, trying to avoid making a large mistake with this upgrade.

Larry

[Tony Athens]

That would be a start.. Set then up straight with a +/- 1/2″ adjustment, but when doing that plan out the entire redo as the tie bar is just part of the system..I.E.–PLAN AHEAD………………… If you don’t have the access to do it right, redo what is needed so you can make it right . Why do another “builder install” ?

Tony

[Larry aberg]

Where to start

Very poor installation. I am assuming both rudders should be straight no toe in toe out?

I will need to shorten the tie bar to get rid of the 12 degree offset.

Once this is done, might be difficult to remove the bar without floor removal i can take a look at what I have.

I will also start installation of new hydraulic lines

[Tony Athens]

Larry,

If your measurements as to rudder angle P&S are accurate, your builder is blowing smoke to make up for very poor engineering as to how they set up your steering..

In so many words, who ever engineered / installed the steering system was not qualified to do it…

Your initial post proved that confirmed that without any doubt..

Basically, you need to start with a clean slate

Tony

[Larry aberg]

Rudder geometry dimension

6-9/16″ center line of rudder shaft to centeriine of ram attachment.

Re-measured rudder angles with a bitmore accuracy. When full port 45 degrees on port rudder. Starboard rudder at 33 degrees.

Manufacturer says that is close to their setup th he inside rudder has a tighter turning radius than outside rudder.

Sorry for the late response.

[Larry aberg]

Rudder geometry

I will get those center line dimensions this weekend.

When hard to port, the port rudder is 45 + degrees but the starboard rudder is 29 +/- degrees.

Hard to starboard the dimensions flop port rudder is 29 +/- and starboard rudder 45.

The tie bar adjustments are max in the shortest dimension. Looks like the bar might be too long? I

[Tony Athens]

Steering Geometry

Larry,

Let’s 1st determine some basics..

1) Look at the attached pics–This is what correct steering geometry would look like hard-over to hard-over with 45 degree rudder.

2) You “speed square” kinda suggests you have a 45 degree rudder. Odd for a twin engine vessel

3) Give me 2 distances– C/L of rudder shaft to ram attachment length & C/L of rudder shaft to tie rod attachment length

I know it’s hard to see how things are as the deck is over much of it, but would you say that hard over in both direction looks the same but mirrored as to all angles? Many sets-up in the retracted more are close to a “toggle over” effect.

Tony

[Larry aberg]

Ram selection

The existing ram has 7″ stroke and is half the torque I need. On the sbmar website a 1200 ft lb 7″ stroke seafirst ram doesnt exist. The closest one has a 9″ stroke.

Do they make a 1200 ft lb 7″ stroke ram? If not what options do I have?

Add second ram on the starboard rudder or use a 9 ” version.

[Tony Athens]

I would upgrade your steering in steps

1) New ram

2) New 3/8″ ID steering lines/ non-restrictive fittings stern to helm area

3) No on the Kobelt helm pump-Played with a few and do not like them at all.

4) With a small diameter steering wheel like you have, you want to stay with a helm pump in the 1.7-2.5 cu-in range.The larger you go, the less turns but the rim force will increase noticeably, plus fluid friction increases.

5) Street $$ for your equipment–Use GOOGLE for that.If you are not comfortable with after sales support, we can help that way.

Tony

[Larry aberg]

Thanks Tony,

The existing helm pump is 21 years old, i would feel better to upgrade it also since everything else is
going to be new.

Would you stay with the same manufacturer say Kobelt for the helm pump and cylinder or use a seastar with a accusteer PA35 power assist/auto pilot pump.

If we go with a new helm pump what size would be ideal?

I will check on the rudder shaft dimension next time at the boat.

Whats the ballpark pricing on the PA 35 accusteer pump.

Larry

[Tony Athens]

That is a lot of rudder for a 1.5″ shaft.. If this is a slow boat, like 10K’s or so , you are ok..

Your rudder shape/design & balance is fine..

You just need at least 50% more disp. in Ram size and one that can operate up to 1000 PSI without flexing/binding..

Adding a “power pack” or electrical power assist which is what I really think you mean, would be nice.. Accursteer ( Owned by Kobelt now) makes one that also replaces you autopilot pump ( all in one)–A very high end unit but well worth the cost…It cut the steering effort by 50% +++.

http://kobelt.com/products/accusteer/list/product-detail/pa35-accu-steer-power-assist-steering-unit/power-assist-steering-units

If you stay with your current helm pump ( which is OK) replace the steering lines with 3/8 ID Parker Steering hose and use SAE#6 flare fitting for all.

https://ph.parker.com/us/17573/en/marine-steering-fast-response-hose-msh/msh-6

Tony

[Larry aberg]

Attached is the layout of the rudder assembly from Carver.

Should give you a good idea of what we are working on.

When I take my phone camera down there they all come out out of focus too close for the lens.

I’ll work on getting a different camera.

[Larry aberg]

Rudder drawing

I have attached the rudder dimensions and my rudder torque calculation.
It looks like with twin rudders I can get up to approx 14,000 in lbs.

IHow would the helm pump sizing change if wewere to use a hydraulic DC pack?

The routing of new lines might be interesting. I’m assuming you want me to use the copper lines since they do not expand during pressure. It might be difficult or impossible to installl copper tubing w/o kinking.

I’ll get the pics of the ram and rudders this weekend.

[Rob Schepis]

Larry aberg wrote:

The auto pilot pump has no tags on iit. Picture provided.

It’s a Ray pump, couldn’t tell if it’s a Type 1, 2, 3…. figuring probably a Type 2 but then I downloaded your pic and zoomed in on it and can see the “2” hiding behind the center fitting so it does appear to be the Type 2 size.

[Larry aberg]

Hi Tony,

Yes I know its undersized, now we need to come up with a system plan helm pump, ram, hoses. Auto pilot pump and fittings that will work long term.

The helm diameter can be increased quite a bit. What kind of diameter are you thinking about?

I will get some better pictures of the ram setup. Its in the aft cabin and not a whole lot of room.

How about power assist electro/hydraulic pumps? I saw some of these on the seastar home page?

I will also take a look at how the factory routed the hydraulic lines.

[Tony Athens]

Undersized Steering System

Larry,

Your system size would be something I’d put in a single engine 18-20Kts cruise 22- 26ft boat with a 18-19″ Deep rudder, a 16-17 span and a 25% balance.. .

As Rob said, totally under sized in all respects……………………….If you want to get this right, then post this :

1) a good pic of your helm station so I can “see” what you have for room.

2) Send me your rudder blade dimensions and a simple drawing that goes with it.. Depth, span and balance or leading edge dimension and the shaft diameter.

3) Some really good picture(s) of the rudder log, support bearings , and pics of the current ram as installed with the tie bar etc.. Put my eyes in your lazarette.

One note————Unless you can increase the steering wheel diameter, increasing helm displacement is not necessarily mandatory to get the “steering power” you need to overcome the forces you are experiencing.. Steering power is a function of the ram displacement and the pressure fed to it mixed in with the proper ram to tiller arm geometry.. It is not a function of helm displacement.

Marine Hydraulic Steering Systems

Tony

[Larry aberg]

Ram specs

Finally was abke to get some of the i fo sorry for the lag time.

The wheel is 15″ diameter, the hydraulic lines are 3/8″ O.D. the rram is a SeastarHC5314 7″ stroke, 10.2 cu. In. Torque at 1000psi @35degrees is 7117in/lbs.

The helm pump is 1.7cu in. Seastatar.

The auto pilot pump has no tags on iit. Picture provided.

[Author]

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