Modern Rudder Bearings on Racing Yachts. How do they Work Please

[savageseadog]

How do modern rudder bearings work. I viewed a steering system that had a large aluminium stock c75mm passing through a round block which I assume is a bearing seemingly attached to the hull. The bearing had a rubber gaiter round it fixed with at least one jubilee clip. The upper part of the gaiter was just open which didn't really look right. I looked at another yacht of the same type and the gaiter was of a different type but tapered down from the bearing to the rudder stock and clipped at both ends.

So:

I assume the bearing has its own seal against water, how is it done?

What is the reliability of the bearings and how easy are they to change and approx cost?

What function does the gaiter perform?

The Aluminium sock doesn't strike me as a great idea what's the opinion here please?

 

[oldsaltoz]

Aluminium rudder stocks are used to reduce weight.

I suspect the rubber boots you saw were placed to prevent marine growth, hard shells will cut aluminium over time if a structure is close enough for them to cling to.

As for what the bearings are made, almost positive they are much the same as we all use, but may be contained by carbon fibre for added strength and less weight.

Let's hope someone will correct me.

Avagoodweekend......

 

[savageseadog]

[ QUOTE ]
Aluminium rudder stocks are used to reduce weight.

I suspect the rubber boots you saw were placed to prevent marine growth, hard shells will cut aluminium over time if a structure is close enough for them to cling to............................

[/ QUOTE ] The gaiter/boot was inside the hull. A picture is worth a thousand words but I didn't have a camera.

 

[oldsaltoz]

[ QUOTE ]
[ QUOTE ]
The gaiter/boot was inside the hull. A picture is worth a thousand words but I didn't have a camera.

[/ QUOTE ]

Then it may have been a seal fixed to the hull and upper section a seal fixed to the shaft, much the same as a prop shaft, again this reduces the total weight.
No external tube required = less weight.

Avagoodweekend......

 

[DavidMcMullan]

Try looking at the Jefa Rudder systems site http://www.jefa.com/rudder.htm , as they have a number of examples shown.
Usually the gaiter is fastened at both ends.

 

[savageseadog]

[ QUOTE ]
Try looking at the Jefa Rudder systems site http://www.jefa.com/rudder.htm , as they have a number of examples shown.
Usually the gaiter is fastened at both ends.

[/ QUOTE ]Never heard of them but looks the business thanks

 

[PeterGibbs]

quote:

Then it may have been a seal fixed to the hull and upper section a seal fixed to the shaft, much the same as a prop shaft, again this reduces the total weight.
No external tube required = less weight.
_______________________________________

This is common and logical too. The stock, secured at its top and where it passes through the hull, only requires a means of preventing water from flooding the boat. So a gaiter attached to the hull, inside, and extending up the stock well beyond the heeling line of the boat will keep all water out. The gaiter doesn't need to clamp the stock at any point. That's the way it is on many Bavarias, basic and simple.

PWG

 

[Adamastor]

IIRC, 'dog, JEFA make the bearings you were looking at, if they were on a Bav or the likes. If you were looking at a European yacht, the likelihood is great that it was a JEFA bearing- look at the JEFA website and look at the different solutions they offer- raceboat steering is actually quite an interesting game!
The gaiter is a clever, simple way of fixing the trouble with PUR seals. JEFA have solved some problems with bearing technology by going back to first principles- they use the smallest number of components to achieve their solutions, so that, for instance, their roller-bearing races are actually machined inside the sphere which makes their bearings self-aligning.
JEFA's material science is quite interesting, too. They use ali alloys which have peculiar properties in terms of elastic flexibility and sigidity, and they also use stainless steels with strange formulations too. Weight is an issue, yes, but cost is of far greater importance, especially in semi-production boats.
I rather suspect that the ali stock you were seeing was specified as a substitute for an exotic stainless tube. I'm sure that the real secret police of racing wouldn't be seen dead with anything as agricultural as an ali stock- they'd rather use a square c-fibre one! For bearing-shells and structural components, JEFA usually use hard-anodised ali, and the roller-bearings are usually Torlon or something similar, while the ball-bearings are most often Delrin and the likes, and they usually pot their bearings inside either ali or mandrel-wound fibre tubes if they require gaiters.