A question for precision machinists

[zoidberg]

Thanks. I'll look at providing further support by means of a guide bearing as suggested by MikeGunn in #38. The firm who provided the featured spherical bearing, IGUS, should be able to provide me with a solution.

Dispensing with the original wide slot is a primary objective. It is a 'downflooding hazard', and breaches my First Principle - 'Keep the ocean on the outside'.
It is VIP to eliminate all possible sources of friction in the operation of any windvane gear, most especially in light airs. Concertina bellows in the transom would multiply line-friction and admit unwanted seawater to the inside.
The geometry of the 'lead' of the tiller controlling lines is important. The original arrangement would have the lines pulling the tiller UP as well as sideways, causing it to scrape on the upper arch of the slot i.e. friction The new arrangement has the tiller raised to the optimum height so that the lines come horizontally.
The tiller, restrained in that slot, traps the manual helmsman's legs in place if/when the rudder is forced fully over when going astern.
When picking up a mooring buoy, I like to stand on the cockpit seats to keep sight of the 'target' as it disappears below the bow. That involves a lifting tiller.

We're getting there....

 

[penfold]

You could fit another bearing, but it's not going to be easy to align or mount sturdily enough to resist the loads.

Your current proposal

Will need a bearing to resist cantilever load, in red

Alternatively avoid the cantilever load by getting rid of the cantilever

 

[Poignard]

Is this a Cutlass 27?

 

[Gary Fox]

Is this a Cutlass 27?
View attachment 113379

This, I reckon, is what the OP has, you can see the concealed rudder stock. Thanks to Yachtsnet where there is more info on this design.

 

[penfold]

You're both right; the photo is of a Cutlass modified(listed by a zillion online brokerages) more or less as the OP wishes to achieve.

 

[Poignard]

You're both right; the photo is of a Cutlass modified(listed by a zillion online brokerages) more or less as the OP wishes to achieve.

It would be useful to know how that modification has been done in other boats.

 

[penfold]

An intrepid YBW correspondent from Dunoon and environs is needed to blag a viewing and photograph the doings, as the photos in the listing do not feature the cockpit at all, never mind what's hiding in the lazarette.

 

[Tamar]

If the idea is to get rid of the tiller when using the self steering? Just a thought, could the original set be retained and maybe a hinge on the tiller to get it out of the way when using the autopilot? Or even a fitting that can remove the tiller all together?

 

[LadyInBed]

If the idea is to get rid of the tiller when using the self steering? Just a thought, could the original set be retained and maybe a hinge on the tiller to get it out of the way when using the autopilot? Or even a fitting that can remove the tiller all together?

See #41

Dispensing with the original wide slot is a primary objective. It is a 'downflooding hazard', and breaches my First Principle - 'Keep the ocean on the outside'.

 

[Tamar]

See #41

Ah, of course thanks

 

[zoidberg]

Is this a Cutlass 27?

Yes, Poignard ( and Gary Fox )... Your pic illustrates 'zackly what I'm trying to achieve.

I've dug out this arrangement drawing from another owner..

He has arranged a support-structure for a pair of support bearings, at 'A'. That looks like steel.
He's also suggesting a fabricated 'cage' of sorts at 'B' to carry the loads between the lower rudder post and the upper tiller input, missing out the threaded stud which reverts to its original purpose.
I have, in the meantime, come up with this, using some 'pretty damn solid' Cutty Sark teak, from wwww.igus.co.uk....

I reckon I could fabricate a robust support for another lower bearing, much as indicated in Penfold's #42, in red.
I have enough 'milspec' 12mm grp sheeting and enough Wessex resin 'n tape for a battleship's bulkhead.... and the weather is warming up!

Edit: I've ordered a second of these bearings, and will mount them both to provide support broadly as indicated in #42 above. They accommodate an angular movement range of -+ 28 degrees. That should take care of most alignment problems.

 

[Poignard]

Yes, Poignard ( and Gary Fox )... Your pic illustrates 'zackly what I'm trying to achieve.

I've dug out this arrangement drawing from another owner..

He has arranged a support-structure for a pair of support bearings, at 'A'. That looks like steel.
He's also suggesting a fabricated 'cage' of sorts at 'B' to carry the loads between the lower rudder post and the upper tiller input, missing out the threaded stud which reverts to its original purpose.
I have, in the meantime, come up with this, using some 'pretty damn solid' Cutty Sark teak, from wwww.igus.co.uk....

I reckon I could fabricate a robust support for another lower bearing, much as indicated in Penfold's #42, in red.
I have enough 'milspec' 12mm grp sheeting and enough Wessex resin 'n tape for a battleship's bulkhead.... and the weather is warming up!

You're enjoying yourself doing this. That's the main thing.

Another way (you have probably considered it) would be to extent the rudder stock in a straight line out through the transom and , where it emerges, have a teak chock with a suitable bearing mounted on it. The tiller could then be attached to the stock with a fabricated bracket that allowed you to lift the tiller. Obviously the tiller would have to be extended, or a new one made.

Also you would have to replace your single backstay with twins, or an inverted 'Y'.




Incidentally, the bearing support 'A' in your drawing could be made of GRP. Like this:

 

[Avocet]

Sorry guys. I'm late to the party on this, having missed this thread, but there's quite an active Cutlass 27 group on Facebook where someone has done this exact same modification quite recently, if the OP hasn't already come across it?

Also, there was a magazine article some years ago, where someone had gone down the alternative route of just continuing the straight line through the transom and putting a "blister" on the back to cover it.



I don't think it's pretty, but the existing backstay chainplate arrangement isn't particularly stiff on the Cutlass and it could probably be usefully reinforced by such a mod. The owner of the boat in the article doesn't seem to have gone down that route though, but has gone for twin backstays instead.