Rudder cup

[Orakal]

Hi, im in the middle of having the boat welded watertight and, since we have had the boat the steering has had alot of play leading to abnormal amounts of vibration so while shes out ive looked into it.

 

There is a fair amount of play caused by the 5mm gap between cup and rudder as shown in the pics.

 

 

 

So my question is what would you do.

I need to know what tolerance is usually given to this arrangement before i go further as i dont want it too tight.

 

Then im thinking i have 3 reasonable options,

 

1,Replace the cup completely with a more suitable one.

2,Try to get a sleeve made to reduce the play.

3,Try and get a bearing fitted to make a nice smooth motion.

 

I can see the bearing being an issue down to corrosion and i know of another who did it and ruined the bearing when hitting something with their rudder.

My other problem lies in the fact these are not off the shelf pieces so im trying to find somewhere that can turn me either piece i decide to use.

 

So if you have a workshop and can make me the piece and ship it im happy to pay or if your local enough collect said item.

Or if you can point me in the direction of a place that can make it me im happy to go along and sort it out, im in wolverhampton and the boats near penkridge stafford so anywhere within 10-20 miles of either is great.

 

Thanks for your help.

[matty40s]

I thought this was a golf thread...

[dave moore]

Norton Canes Boatbuilders, not far away, could easily fabricate a new cup for you, whether they would remove the old one and refit I'm not sure. Phone number is 01543 374888, ask for Tony Bate or Glynn Lewis. Tony is away until next week, Glynn has lunch at one-ish so would answer the phone. PM me if I can help further, I'm a loose part of the team!

 

Cheers

 

Dave

[springy]

Hi

 

I would suggest a bit more measuring before actually doing anything - the position you are measuring maybe

showing the worst wear - if both the cup and rudder post are a bit oval then the 5.4 mm gap (2.7 mm each side)

in the ahead position may rapidly shrink as the rudder is swung to the side.

 

cheers

 

springy

[Neil Smith]

Yes I would think it would wear oval as it is mostly in the ahead position, it would need replacing ie a simple welding job that most boat yards could do.

 

Neil

[Timleech]

Yes I would think it would wear oval as it is mostly in the ahead position, it would need replacing ie a simple welding job that most boat yards could do.

 

Neil

 

Yes they always wear oval, so any bush needs enough clearance to allow for that.

If the cup is a good solid piece and not just a bit of water pipe, probably worth fitting a bush. I've had success with plastics bushes, either Vesconite (a proprietary material for underwater bearings) and Acetal (Delrin) for the cheap & cheerful model. Don't bother with your option 3, if that means a ball or roller bearing, it won't last five minutes underwater before it seriously deteriorates.

 

Tim

[Orakal]

Norton Canes Boatbuilders, not far away, could easily fabricate a new cup for you, whether they would remove the old one and refit I'm not sure. Phone number is 01543 374888, ask for Tony Bate or Glynn Lewis. Tony is away until next week, Glynn has lunch at one-ish so would answer the phone. PM me if I can help further, I'm a loose part of the team!

 

Cheers

 

Dave

Thanks ill certainly keep them in mind, kinda thing im looking for and my welder can put it on no prob after i take the other off.

I do concede that i will have to take more measurements after cleaning it all up more so i can see the true wear to see if as you all suggest its oval and if so replace the cup completely but can anyone tell me what an acceptable tolerance is around the rudder to the cup?, as i know 5mm is huge and very poor so what gap do i leave?

 

If the diameter of the base of the rudder is 33.2mm for example, what size bore do i fit it into, 35mm...is that to small and abrasive?

[ditchcrawler]

Thanks ill certainly keep them in mind, kinda thing im looking for and my welder can put it on no prob after i take the other off.

I do concede that i will have to take more measurements after cleaning it all up more so i can see the true wear to see if as you all suggest its oval and if so replace the cup completely but can anyone tell me what an acceptable tolerance is around the rudder to the cup?, as i know 5mm is huge and very poor so what gap do i leave?

 

If the diameter of the base of the rudder is 33.2mm for example, what size bore do i fit it into, 35mm...is that to small and abrasive?

Is the bottom of the rudder post still round or is that oval as well?

[Orakal]

Is the bottom of the rudder post still round or is that oval as well?

It all looks round to be honest, theres no visual signs of oval wear and with how long its had that much play it may well have worn round itself...might have been on for 38 years for all i know.Ill take more measurements to make sure.

[bizzard]

What might work although I've never tried it is to clean out all loose rust from cup and stock end and then wrap the end of the rudder stock with polythene and then mount it in the the cup centrally and then pour in some GRP resin to make a bearing this should key itself well into the internal roughness of the cup so won't rotate with the stock. Resin will not stick to polythene so it can be removed from the stock after the resin has cured. Depending on how smooth you can get the stock end will determine the wear rate of the resin, but It should last at least between docking for blacking when the bodge could be performed again. Nice and cheap.

[RLWP]

A very long time ago, faced with the same situation as you, I turned up a bush to fit into the cup - an open sleeve.

 

When I fitted it, firstly the apparently round spigot on the rudder stock wasn't any more and I hadn't measured the right part, so I had to file material out of the bush. That meant the bush would fit, so I fitted it.

 

Next problem was that the rudder had become incredibly stiff, which I cured by filing a load more material out of the bush. The stiffness was because the rudder shaft was bent from a previous cilling (ex-hire boat), as was the skeg. In the end, after a lot of filing and swearing, I had a very thin walled bush sitting in the cup.

 

The last time I looked, the sleeve had worn through and disappeared - I haven't bothered to replace it

 

Richard

 

MORE: Oh yes, the vibration is caused by the prop, not the rudder

Edited October 3, 2014 by RLWP

[Orakal]

A very long time ago, faced with the same situation as you, I turned up a bush to fit into the cup - an open sleeve.

 

When I fitted it, firstly the apparently round spigot on the rudder stock wasn't any more and I hadn't measured the right part, so I had to file material out of the bush. That meant the bush would fit, so I fitted it.

 

Next problem was that the rudder had become incredibly stiff, which I cured by filing a load more material out of the bush. The stiffness was because the rudder shaft was bent from a previous cilling (ex-hire boat), as was the skeg. In the end, after a lot of filing and swearing, I had a very thin walled bush sitting in the cup.

 

The last time I looked, the sleeve had worn through and disappeared - I haven't bothered to replace it

 

Richard

 

MORE: Oh yes, the vibration is caused by the prop, not the rudder

 

The vibration when cruising is coming from the stated problem.

There is so much play the rudder is actually banging in the cup and the swan neck visibly vibrates with a huge movement and as more water is pushed over rudder it becomes unpleasent at more than 50% power and with a lister sr3 thats not alot of power.

I think a new cup is the way to go, just need someone to make it.

What might work although I've never tried it is to clean out all loose rust from cup and stock end and then wrap the end of the rudder stock with polythene and then mount it in the the cup centrally and then pour in some GRP resin to make a bearing this should key itself well into the internal roughness of the cup so won't rotate with the stock. Resin will not stick to polythene so it can be removed from the stock after the resin has cured. Depending on how smooth you can get the stock end will determine the wear rate of the resin, but It should last at least between docking for blacking when the bodge could be performed again. Nice and cheap.

Thats an idea i have toyed with myself as it will make a tightish self fitting bearing as such, im trying to get a long term solution though but if all else fails this seems viable.

[RLWP]

OK - the sleeve idea is a non starter. You have 5mm of diametral clearance, I wouldn't try to end up with less than 2mm diametral clearance otherwise you'll find relocating an unshipped rudder nearly impossible. That gives 3mm diametral clearance, or a sleeve with a wall thickness of 1.5mm

 

You could easily bend such a sleeve up from metal strip, machining one would be very tricky.

 

And, once more - the vibration is caused by the distance between the propeller and the rudder, not by the rudder itself. It may be easier to shift the propeller shaft in the coupling to give a bigger gap between the prop and the rudder

 

Richard

Edited October 3, 2014 by RLWP

[Timleech]

OK - the sleeve idea is a non starter. You have 5mm of diametral clearance, I wouldn't try to end up with less than 2mm diametral clearance otherwise you'll find relocating an unshipped rudder nearly impossible. That gives 3mm diametral clearance, or a sleeve with a wall thickness of 1.5mm

 

You could easily bend such a sleeve up from metal strip, machining one would be very tricky.

 

And, once more - the vibration is caused by the distance between the propeller and the rudder, not by the rudder itself. It may be easier to shift the propeller shaft in the coupling to give a bigger gap between the prop and the rudder

 

Richard

 

 

That does rather depend on the rudder arrangements. If it's the typical arrangement used by Liverpool Boats and others, where the rudder post passes through a tube in the rudder blade and where unshipping the rudder is impossible without bending the skeg down, then that particular issue shouldn't arise.

I just yesterday machined up an acetal bush with under 1.5mm wall thickness, no trouble at all.

Agree though that the *source* of the vibration will be the prop and its wash, but reducing the freedom for the rudder to vibrate can help a lot. Best way is a really heavy, solid rudder assembly as used on working boats

 

Tim

[RLWP]

I too can machine thin walled sleeves - much easier to slip in a brass strip in this case to test the idea

 

I can't remember seeing an SR3 in a Liverpool shell

 

Richard

[Timleech]

I too can machine thin walled sleeves - much easier to slip in a brass strip in this case to test the idea

 

I can't remember seeing an SR3 in a Liverpool shell

 

Richard

 

We'll have to disagree on that one, I reckon (given a lathe) machining a plastics bush is easy, doesn't take long and makes a better job.

 

I know nothing of the OP's boat, just answering what I thought was a general point about rudder clearances

 

Tim

[bizzard]

Depending on the diameter of the stock, a 155g Glenryck pilchards tin, the ones in tomato (about 65p) has an ID of 2'' precisely with a 6 thou wall thickness including the label which is of a pleasant red colour and worth leaving on. If the top is removed with a tin opener that cuts below the rim instead of on top it will leave the tin with a smooth and flush entry to insert the stock. The cheap cost of a tin of this rich in protein and Omega 3 pilchards could allow you to leave the pilchards in it which would afford extra rudder stock lubrication. When you next dock the boat the pilchards should be all nicely mashed up, ideal for making a sandwich or a nice pate.

[RLWP]

 

We'll have to disagree on that one, I reckon (given a lathe) machining a plastics bush is easy, doesn't take long and makes a better job.

 

I know nothing of the OP's boat, just answering what I thought was a general point about rudder clearances

 

Tim

 

What clearance would you be aiming for Tim?

 

Richard

[John V]

Looking at Tim's post mentioning acetal bush....I went and tried to find my way round the RS components on line catalogue (without success...I'm much happier with the old fashioned type)

I believe they do various types of self lubricating plastic stock ideal for turning up bearings...I think I remember a molybdenum loaded plastic.

[pophops]

I had the same problem with a worn top bearing and rudder cup recently. The inner sleeve of the old bearing was used as a new cup, being the same inside diameter as the rudder stock. The old cup was cut off the skeg and the new one welded on in its place. A new top bearing was fitted and all the rattles and vibration have gone.

[Orakal]

The boat is a 1976 Harborough Marine with a grp top....Ive unbolted the 4 bolts around the bottom of the swan neck allowing me to lift the rudder out the cup but it wont drop any further than its sitting now.

Relocating it will be easy as i can lift it without much effort so no matter what i use its not a problem.

I have never took any photos detailing the arrangement but the ones i have might help i dont know.

 

 

 

I was under the illusion if i had a brass sleeve it wouldnt stay the course given the thin sleeve needed if i need a diametral clearance of 2mm.... If i used either brass or a hard plastic could it not be tighter and allowed to find its own seating or is this not a viable option?

 

This boat has had this bad steering vibration since we had it so im wondering if a bush had been fitted prior and wore away and just never tended too.

Im either going to have to go with a slip or a new cup, neither is an issue as the welder still has to return.

Im looking to buy either piece from someone who can manufacture it for me obviously after i have taken more comprehensive measurements to ensure the bottom of the rudder isnt oval.

So lets say i want a new rudder cup save worrying about the bushes wearing/fitting which i think is the proper way to go who can make and ship one to me in Wolverhampton.

Can you provide me with a rough cost only please as well as everything has to be finalised.

The skeg isnt bent and everything is straight and true

[Timleech]

 

What clearance would you be aiming for Tim?

 

Richard

 

Basically, whatever will turn reasonably freely

Given that shaft and bore will be both oval, it tends to be a guess it/suck it and see process.

One thing to remember, if you're turning up a bush, is that the bore in the cup will almost certainly be wider at the top than the bottom, so you need to be able to measure the minimum bore at the bottom unless you have your lathe handy for the job and can try the fit before the job is finished.

Also, as you point out, if the rudder can be lifted out of the skeg it'll need possibly a bit more clearance, but certainly a bit of a 'lead' at the top of the bush to aid entry.

 

 

Looking at Tim's post mentioning acetal bush....I went and tried to find my way round the RS components on line catalogue (without success...I'm much happier with the old fashioned type)

I believe they do various types of self lubricating plastic stock ideal for turning up bearings...I think I remember a molybdenum loaded plastic.

 

For plastics underwater, watch the potential for water absorbtion, which will cause the bush to swell. Acetal absorbs very little water, Nylon (for example) can absorb quite a lot.

A really thin walled bush won't swell very much anyway.

 

Tim

Edited October 3, 2014 by Timleech

[David Mack]

Given that shaft and bore will be both oval,

It wouldn't be that big a job to file the bottom of the shaft back to something close to round.

[Timleech]

It wouldn't be that big a job to file the bottom of the shaft back to something close to round.

 

I've done that quite a few times. Easy enough if you have the rudder in a vice or similar, a bit of a pain if it's dangling on the back of the boat.

 

Tim

[bizzard]

I also once owned a 1970's H. Marine boat and the rudder blade was sandwiched into a slot in the stock at the top and secured with two nuts and bolts. The bottom had a short piece of stock which was also was slotted and sandwiched the rudder blade and secured with two nuts and bolts with the bottom of it sitting in the cup. This was H. marines standard for doing it. If yours is the same you could get a new lower short bit of stock stub machined up with a rudder slot and new cup to match welded on. The drilling of the new short stub would be done when all is erected on the boat and aligned up truly.