Help! Where in the world to find a 39mm rudderstock!

[teneicm]

Hey all-

So we've had to rebuild our rudder and after a good start of pulling it apart, we've stalled because we can't find a supplier of 39mm diameter solid rod 316L. Why Privilege boatbuilders chose to use 39mm back in 1992 is anyone's guess, but apparently they had a source then... now, not so much.

Anyone have any ideas? Is someone's Google-power stronger than mine?

We are considering going up to 40mm if we cannot find the 39mm, but that will involve removing epoxied in rudder bearings as well as enlarging the "tube" / groove left in the rudderblade (which means the rudderstock won't sit perfectly centered and might lead to balance issue). Long story short, finding a 2.4 meter long 39mm rod will be better on multiple fronts.

Cheers- Matt

[Orion Jim]

A machinist can remove 1mm from your 40mm stock on a lathe.

[model 10]

Get somebody with a lathe to turn down the 2 areas? The area in the rudder does not need to be that nice, so it could be done quickly.

[teneicm]

We've enquired about having a larger shaft machined down. Most of the local engineering shops here (Malaysia, Singapore, Thailand) can't handle the 2.4 meter length for some reason. Some can, but they're asking a crazy amount of money to do it and then warning about not being able to meet some pretty basic tolerances (like saying they can only do it +/- 1mm tolerance). Seems pretty sloppy to me.

I haven't asked some of the engineering shops back in the States if they can do it... perhaps I'll try that tack.

[coopec43]

QUOTE: We are considering going up to 40mm if we cannot find the 39mm, but that will involve removing epoxied in rudder bearings as well as enlarging the "tube" / groove left in the rudderblade (which means the rudderstock won't sit perfectly centered and might lead to balance issue).

I wonder just how critical rudder bearing tolerances are when I read

"A small amount of wear, maybe around 1mm at the bearing, is acceptable, but if there’s significantly more than this further investigation will be needed."
https://uk.boats.com/how-to/how-to-replace-rudder-bearings/


Could you very carefully sand the bearing with about 320 grit abrasive to take a 40mm shaft? Maybe get a 37½ mm PVC tube with abrasive (320) contact cemented to the tube and then sand the bearing internally?

[steamgoat]

Well 1.5” is 38.1mm, a loose fit? Available ,I think, from Onlinemetals.

[Chotu]

Originally Posted by teneicm

We've enquired about having a larger shaft machined down. Most of the local engineering shops here (Malaysia, Singapore, Thailand) can't handle the 2.4 meter length for some reason. Some can, but they're asking a crazy amount of money to do it and then warning about not being able to meet some pretty basic tolerances (like saying they can only do it +/- 1mm tolerance). Seems pretty sloppy to me.

I haven't asked some of the engineering shops back in the States if they can do it... perhaps I'll try that tack.

This can definitely be done in the States.

But also, you don't need to turn the entire thing. Just the part that sits in the bearings/bushings. The part in the rudder can be a different size by a milimeter. This might open up more possibilities in the area you are in. They could use the lathe on a smaller section instead of the whole thing.

Have you verified the exact measurement inside the bushings or bearings? Wear takes place over the years and you may be able to slip a 40mm section in anyway.

[coopec43]

Matt


I wonder if OP realize a Privilege 482 is a catamaran and therefore would be a spade rudder?

[Steel sails]

You need to ask around for a machine shop with a “centerless grinder”
They can hold tolerance of 1/1000” if needed but you don’t need that accuracy.
No length restrictions on centerless machines.

If you are really stuck I can do it here in Houston for you but the shipping to your part of the world would cost more than the piece is worth.

Budget price for the piece centerless ground to size about 500$ ex Houston
316L material
You would have to have someone collect from us and arrange the shipping.
Pm me if you need more help


Regards
Paul

[teneicm]

Originally Posted by Chotu

But also, you don't need to turn the entire thing. Just the part that sits in the bearings/bushings. The part in the rudder can be a different size by a milimeter.

The part that goes in past the first bearing in the hull (which is basically the entire exposed part of the rudder shaft) is almost 1.7 m long. Also, the issue with not having the entire shaft at 39mm is that we'd need to alter the "imprint" left by the old 39mm shaft on the internal part of the rudder. This could lead to an imperfect alignment and balance issues (which is important in a spade rudder).

[teneicm]

Originally Posted by coopec43

Matt


I wonder if OP realize a Privilege 482 is a catamaran and therefore would be a spade rudder?

Do you mean me (Matt, also the OP)) or someone else? But yes, the boat is a cat with spade rudders. With a huge long rudderstock as the ruddertube actually extends to be above the waterline (elimnates the need for seals or gaskets).

[teneicm]

Originally Posted by Steel sails

You need to ask around for a machine shop with a “centerless grinder”

If you are really stuck I can do it here in Houston for you but the shipping to your part of the world would cost more than the piece is worth.

Thanks. I'll ask around for the centerless grinder. May also take you up on your offer if we still strike out. $500 plus shipping may be worth it to know that it's actually done properly....

[cyan]

In the States? metricmetals.com in Ohio
(Australia might be cheaper to send.)
Thailand... maybe.

[RaymondR]

Since it's only 1mm it would probably be easier to make a boring bar out of a piece of tube so that you could ream the existing bearings out the 1 mm and use of the shelf material for the ruddeer stocks. Make it long enough to go down through both top and bottom bearings and the holes will stay aligned.

[Alan Mighty]

Originally Posted by teneicm

We've enquired about having a larger shaft machined down. Most of the local engineering shops here (Malaysia, Singapore, Thailand) can't handle the 2.4 meter length for some reason. Some can, but they're asking a crazy amount of money to do it and then warning about not being able to meet some pretty basic tolerances (like saying they can only do it +/- 1mm tolerance).

I can understand that shaft length might be a limiting factor.

If for example you're in Penang, Malaysia, you should be able to find someone to do the job.

For example, here is a list of fabrication/manufacturing companies with centreless grinding gear: https://www.mfg.com/discover/en/Cent...A/Pulau+Pinang

And they're not the only ones. For example: https://www.zyprecision.com/