Hydraulic steering for an old Moody Halberdier ?

[STILL AFLOAT]

Hi All !
I am currently renovating an old Moody Halberdier.
I thought changing the worn out steering, would be a simple task.
I contacted Vetus, & gave them the approximate size of the rudder, and told them which boat it was, I put the overall weight to 12 tons, due to extended fuel & water tanks etc.
Their reply was as follows ..
We would need to know the rudder dimensions, including the balance point which is the pivot point from the leading edge. And the max boat speed, then we can work out the force acting on the rudder and recommend a suitable system.

So, to answer their questions, I went to the Moody website, for information.
The Moody site, is somewhat lacking...
In as much, as when I went to the site, it says : Click here ! if you want to buy the 45 ft DS.
Click here.. If you want to buy other Moody Boats.....

All I am trying to do, is find out what Vetus steering system I need for the Halberdier.
I am out of the UK, and just need the correct numbers, for their steering pump & ram, for my boat, so I do not end up with an either undersized or oversized steering system.

Its OK putting a catalog together with pump 1 or 2 or 3, but then at least they could add suitable for " Whatever " boat size & weight ?

Any hint or info , will be greatly appreciated.
Thanks.

 

[Sticky Fingers]

I'd suggest you register as a member of the Moody Owners, they have an excellent technical section with loads of factory manuals and drawings, available FOC to members, only £20 a year, bargain. Also many members with extensive technical knowledge on their boats.

http://moodyowners.org/

 

[STILL AFLOAT]

Thanks For That !
Will Do !
Merry Christmass

 

[Sticky Fingers]

You too, thanks

 

[scottie]

Glad to see that Vetus would not supply without dimensions.

 

[Bodach na mara]

I did that job many years ago on a Westerly Renown. Like you, I was asked for information about the rudder and boat speed. I made a sketch to scale of the rudder which is not hard to do, as you can simplify it to the basic quadrilateral shape (or in my case a quadrilateral with a bit cut out of the top edge as it is semi-balanced) and put dimensions on it. They need to know where the rudder stock is within the rudder and be able to work out the centre of effort. a photo accompanied with sketch and dimensions should do. The speed is important (7 or 8 knots at a guess) but displacement is not. The forces are dependent only on speed and rudder configuration.

After fitting, the pros and cons are :-

Pro: finger light and easy to install

Con: the mid-point drifts in use and the Vetus system used not to have a reservoir of fluid, so it overflowed in hot weather as the fluid expanded.

Hope this helps.

 

[Cardo]

I did that job many years ago on a Westerly Renown. Like you, I was asked for information about the rudder and boat speed. I made a sketch to scale of the rudder which is not hard to do, as you can simplify it to the basic quadrilateral shape (or in my case a quadrilateral with a bit cut out of the top edge as it is semi-balanced) and put dimensions on it. They need to know where the rudder stock is within the rudder and be able to work out the centre of effort. a photo accompanied with sketch and dimensions should do. The speed is important (7 or 8 knots at a guess) but displacement is not. The forces are dependent only on speed and rudder configuration.

After fitting, the pros and cons are :-

Pro: finger light and easy to install

Con: the mid-point drifts in use and the Vetus system used not to have a reservoir of fluid, so it overflowed in hot weather as the fluid expanded.

Hope this helps.

+1

I revamped my old Southerly's steering with a Vetus hydraulic system. Again, I had to calculate the maximum force exerted on the rudders in order to establish which hydraulic ram was required, which in turn dictated which hydraulic helms were suitable.
My system has a reservoir, which is definitely required if going anywhere hot or if any of the system goes near the engine bay.

All hydraulic steering systems will suffer from mid-point drifts, I use my autopilot's rudder sensor to see what the rudders are up to.

 

[maxi77]

Vetus are quite right, you need to be able to calculate the forces acting on the rudder to size a steering gear properly. To do this properly you do need the rudder blade dimensions and the position of the stock on the blade. They do also need the likely maximum speeds ahead and astern. After all there is little point in having a steering system that will not move the rudder when the proverbial hits the fan. Whilst an as built drawing should be OK it may be worth checking that the rudder has not been modified.
;

 

[STILL AFLOAT]

I think some people are missing the point.
Vetus have been in buisiness long enough to be able to categorise their units.
So , rather than just be faced with all the Drums & a load of numbers, they could easily group the units.
Then , at least , when looking for a unit , suitable for a long keeled 36 ft , 12 tonner, I would not have to waste time looking at systems suitable for the Queen Mary.
After all, they manage to give the HP rating, for their engines .

 

[scottie]

The torque calculation for a maximum speed of about 25 knotts:
T = Torque in kgm
k = Coefficient according to the total angle of the rudder
T = S x [(0.4a)-b] x V2 x k
S = Total surface area of the rudder in M2 (h x a) h = Height of the rudder in M
a = Width of the rudder in M
b = The value of the compensation in M
Port to Starboard 50o Port to Starboard 60o Port to Starboard 70o Port to Starboard 80o Port to Starboard 90o
V = Speed of the boat in knots
Straightening according to type of boat:
- For boats equipped with jet engines
- For power boats with two engines and one rudder T x 0.5
- For sailboats
T x 1.3 T x 0.5
Whilst this refers up to 25 knots it works at the speed that you would expect your boat to achieve note that V is squared so the difference between 5 and 8 knots is significant and the centre of pressure is vital throw in the loads sailing and you will see how difficult it is to get it right without all the information

 

[maxi77]

I think some people are missing the point.
Vetus have been in buisiness long enough to be able to categorise their units.
So , rather than just be faced with all the Drums & a load of numbers, they could easily group the units.
Then , at least , when looking for a unit , suitable for a long keeled 36 ft , 12 tonner, I would not have to waste time looking at systems suitable for the Queen Mary.
After all, they manage to give the HP rating, for their engines .

If you want the steering gear to work as you require it has to be sized properly, different 36 ft 12 tonners will require different gear because it is not the boat size that matters but the power required to turn the rudder and that is controlled by the size and shape of the rudder and whether it is balanced or not and if it is balanced by how much it is balanced. It is just because they have been in business for so long that they know to ask these questions. I spent 3 years designing and selling hydraulic steering systems.

 

[maxi77]

The torque calculation for a maximum speed of about 25 knotts:
T = Torque in kgm
k = Coefficient according to the total angle of the rudder
T = S x [(0.4a)-b] x V2 x k
S = Total surface area of the rudder in M2 (h x a) h = Height of the rudder in M
a = Width of the rudder in M
b = The value of the compensation in M
Port to Starboard 50o Port to Starboard 60o Port to Starboard 70o Port to Starboard 80o Port to Starboard 90o
V = Speed of the boat in knots
Straightening according to type of boat:
- For boats equipped with jet engines
- For power boats with two engines and one rudder T x 0.5
- For sailboats
T x 1.3 T x 0.5
Whilst this refers up to 25 knots it works at the speed that you would expect your boat to achieve note that V is squared so the difference between 5 and 8 knots is significant and the centre of pressure is vital throw in the loads sailing and you will see how difficult it is to get it right without all the information

Not forgetting of course that the torque requirement is usually greater astern than ahead

 

[STILL AFLOAT]

Hmmm..
Thanks for the detailed responses.
Obviously more complicated , than I expected.

 

[Adamastor]

Maxi77 will confirm that when they spec a system for speed "x", there is a presumption that the owner won't be doing all their navigation in reverse! I'm not a hydraulic super-geek, but I've also been round the block enough to say that sizing a system isn't hit-and-miss. Do the homework and you'll be styling with your new steering!
The other considerations are the size of your wheel, as well as your personal choice for sensitivity. Vetus is a very good resource: the same range of cylinder coupled with different helm pumps can mean the difference between a few turns to steer and a wheel that feels like a stripped thread!

 

[STILL AFLOAT]

Well, in the end, an old mate came out to help me , who had been a Naval Articifer.
So he more or less took over. On top of that, we found a company called Gopar on the El Sebadal industrial estate above Las Palmas. They looked at the 1971 3/4 inch ram & said , Yes we can fix this.
They dismantled the ram and turned new seals, replaced them, then re assembled the whole thing, all on the same day .
Incredible Service !
Then my mate did the bleeding as I topped up the steering drum, now, its all back together & working.
Thanks for all your help & responses.