Under Hull Rudder - problems to look out for

dylanwinter

dylanwinter

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www.keepturningleft.co.uk
I have only ever had transom hung rudders

assuming a 26 foot twin keel boat of around 26 feet and three tonnes displacement has an underhull rudder joined to the tiller by a short length of metal running in a tube through the hull

How do I tell if the thing needs any attention and might cause me problems over the coming 18 months

bent bits of metal?

clonked rudders?

Leaky tubes?

any experience based advice gratefullly received

Dylan
 
You are not thinking about a Westerly Centaur by any chance, are you?

Suggest you look first on the WOA website.

Nothing magic about that type of rudder. no real difference from transom hung rudders except that the bearings are not so visible. The early Centaur one is a bit crude as it is a simple spade plate rudder with a rather inadequate 1" shaft, so can bend if banged hard enough. Later one has a skeg so has a bearing lower down to support the rudder better.

Very simple to check for obvious signs of wear in the bearings by waggling the rudder from the bottom.

Even worn bearings are not life threatening. Unlikely anything will fall off and some folks just put up with the clonking and perhaps a bit of loss in precision.
 
Tranona said:
You are not thinking about a Westerly Centaur by any chance, are you?

Suggest you look first on the WOA website.

Nothing magic about that type of rudder. no real difference from transom hung rudders except that the bearings are not so visible. The early Centaur one is a bit crude as it is a simple spade plate rudder with a rather inadequate 1" shaft, so can bend if banged hard enough. Later one has a skeg so has a bearing lower down to support the rudder better.

Very simple to check for obvious signs of wear in the bearings by waggling the rudder from the bottom.

Even worn bearings are not life threatening. Unlikely anything will fall off and some folks just put up with the clonking and perhaps a bit of loss in precision.
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Perfecto

just what I wanted to hear
 
This is a Westerly rudder. Mid 1970s Berwick but I guess the later Centaur might be similar.

It is as deep as the keels and has been bent slightly several times . Looks like its been bent again since the last time I did it!

It is not supported by the partial skeg in the way Tranona says... he might be right about the Centaur one though ... he is not known for being wrong!.

When drying out .... its always been on a drying mooring .. one has to be careful to set the rudder straight so that that it lines up with the little fin above it. That way it cannot bend.


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Dylan

I gotta an idea.

Since you are chucking the inboard, and building a well for the outboard, why not cut off the "under-hull" rudder at the same time, and re-attach it to the the transom ?

Or, as the Irish joke goes: Well Sir, to get to Dublin, I wouldn't start from here to begin with.
 
The rudder bearings on our w31 sometimes used to swell up after the boat was launched if she had been out of the water for the winter. This only happened when they got worn which is counter intuitive. Had to replace them twice in 20 years of ownership. I would suggest you replace yours when in the slings prior to launch. Not too expensive from Trafalgar and reasonably easy to install. I would also check for osmosis in the rudder itself. Ours had it yet the hull was OK. Also look for bad rust stains - theoretically the tangs which are connected to the rudder stock could be rusty and the nightmare would be for them to detach !
 
VicS said:
It is not supported by the partial skeg in the way Tranona says... he might be right about the Centaur one though ... he is not known for being wrong!.
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Believe they changed in 1976 from the crude plate to the partial skeg and moulded rudder like the one in your photo. Suspect the change was because of the old unsupported one bending. Assume the later type is moulded in two parts with tangs on the shaft, so probably worth checking for delamination.
 
Tranona said:
Believe they changed in 1976 from the crude plate to the partial skeg and moulded rudder like the one in your photo. Suspect the change was because of the old unsupported one bending. Assume the later type is moulded in two parts with tangs on the shaft, so probably worth checking for delamination.
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I am thinking a spade rudder will be simpler

D
 
dylanwinter said:
I am thinking a spade rudder will be simpler

D
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Really would not get worked up about it. Crude plate spade rudders were common in the early days of GRP boats with flat bottoms because they were....well, crude and cheap. Although some say simplicity is good, they do bend because the stock is only 1" diameter and unsupported outside the hull. Partial skegs were developed to give better support to the shaft and a much better shape to the rudder. That type was pretty universal on cruising boats for the next 30 years or so and many still consider it a good design feature.
 
Tranona said:
Really would not get worked up about it. Crude plate spade rudders were common in the early days of GRP boats with flat bottoms because they were....well, crude and cheap. Although some say simplicity is good, they do bend because the stock is only 1" diameter and unsupported outside the hull. Partial skegs were developed to give better support to the shaft and a much better shape to the rudder. That type was pretty universal on cruising boats for the next 30 years or so and many still consider it a good design feature.
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the spade gives me a bigger flat area under the hull for my new hole

simpler cutting

and possibly a cheaper boat

D
 
The skegs on the W31's are just a simple fairing attached by self tappers. They add no strength whatsoever, but they do look nicer when the tides out & you can see them.

You'd have to be pretty unlucky, or damned careless to bend a rudder post, but I'm sure it can be done if you try hard enough.
 
Jolly good

Searush said:
The skegs on the W31's are just a simple fairing attached by self tappers. They add no strength whatsoever, but they do look nicer when the tides out & you can see them.

You'd have to be pretty unlucky, or damned careless to bend a rudder post, but I'm sure it can be done if you try hard enough.
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Jolly good stuff

it sounds as though I can put rudder concerns behind me

D
 
Hi everybody,

I was wondering if an all moving blade with improved section would help also getting a better performance on a First 35 of 1985???Any suggestions?Say a blade from a mumm 30 which is longer and better designed.
Thanks
 
One possible fault that hasn't been mentioned is crevice corrosion on the shaft. I suggest you drop the rudder down about a foot and check the shaft for pitting, especially in way of the lower bearing and where the blade meets the shaft. Any pits would indicate that the shaft and possibly the internal structure is not reliable.

I have sawn through a pitted shaft only to find the solid rod shaft to corroded down the length internally. I wish I still had the photos .....
 
Also, no one has expressed any concern about the tube itself.

Macwesters (26', but probably more models) used a piece of scaff tube which after 30/40 years half full of seawater could be delicate.

I liked my Seawych transom hung rudder and now the same on my Mirage 2700
 
NickRobinson said:
Also, no one has expressed any concern about the tube itself.

Macwesters (26', but probably more models) used a piece of scaff tube which after 30/40 years half full of seawater could be delicate.

I liked my Seawych transom hung rudder and now the same on my Mirage 2700
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Na, its stainless but prone to leaking where it attaches the hull, simple to fix though....

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Roger
 
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