Steering Pulleys (Sheaves)

[stormalong]

Why such heavy cable? My 44' boat uses 1/4 inch and it is plenty strong. Going so large on the cable makes your whole design larger and much more expensive.

Why not ask Edson to design a system for you. You don't have to buy it, just use their size recommendations.

[coopec43]

I asked the same question "Why such a heavy cable?" and the answer is in the design of our yachts.




My yacht is center cockpit.

Your steering cable is probably one meter whereas my steering cable is nearer 5 meters. If my steering cable stretches ¼ inch that translate to about 4 inches play at the wheel. Obviously 10 mm cable will stretch a lot less than 6 mm cable and therefore the steering will be much more precise with 10 mm.

Of course with your yacht, with such short steering cables there would be virtually no stretch.


PS I like your yacht!

[stormalong]

Originally Posted by coopec43

I asked the same question "Why such a heavy cable?" and the answer is in the design of our yachts.

My yacht is center cockpit.

Your steering cable is probably one meter whereas my steering cable is nearer 5 meters. If my steering cable stretches ¼ inch that translate to about 4 inches play at the wheel. Obviously 10 mm cable will stretch a lot less than 6 mm cable and therefore the steering will be much more precise with 10 mm.

Of course with your yacht, with such short steering cables there would be virtually no stretch.

PS I like your yacht!

Thank you, I like my yacht too!

There have to be far more Roberts Mauritius 43s around than my Nordic 44 (they only built 39). Is there an owners group where you can get advice?

[RaymondR]

Originally Posted by coopec43

A 10mm 7/19 stainless steel cable should not be used on anything less than a 7 inch pulley otherwise it will tend to fray. I therefore need about a 9 inch diameter pulley which are very expensive if you buy Lewmar, Harken, Ronstan or Edson. Roller bearings could be a consideration although brass bearings are very reliable.

That's about an 18 to 1 sheave to rope diameter which is probably what is being quoted for an acceptable ratio however for long life you need about 30 to 1.

Having about forty years of professional experience with wire and sheave systems consequently when I built my last boat I was fairly determined to avoid them and settled on a pure mechanical system without cables. I ended up with a Whitlock system and found it excellent from a durability and reliability viewpoints.

I realize that a centre cockpit boat presents design challenges for a mechanical steering system but with better than thirty years of sailing experience behind me now would certainly make the effort.

[coopec43]

Some amateur builders used truck steering boxes and then rods and levers to the rudder. I think if that was done well it would be a good system.

[transmitterdan]

I suggest you might want to have a relook at Dynema. You should be able to terminate at the quadrant with an eye splice about the same as the wire is terminated. How is the wire terminated now? Picture?

Or in the alternative, splice a long run of Dynema to a short run of wire that terminates on the quadrant.

For sure Dynema is the “optimal” solution. If some of the turns are very low angle you might also consider using low friction rings instead of pulleys. Less expense and maintenance free.

[coopec43]

Originally Posted by stormalong

Thank you, I like my yacht too!

There have to be far more Roberts Mauritius 43s around than my Nordic 44 (they only built 39). Is there an owners group where you can get advice?

Having seen some Roberts Mauritius yachts (including the one I helped build) I have not been impressed. I am very happy with mine so far. This is my yacht album.

https://www.flickr.com/photos/440710...57631756633356

[Bycrick]

At the risk of hijacking the thread, maybe hydraulic steering would be an answer?

[Lepke]

Originally Posted by Bycrick

At the risk of hijacking the thread, maybe hydraulic steering would be an answer?

Exactly. Pulley systems wear and break. I was running solo on a 55' fishing boat when a not-to-old cable decided to break. It was a bitch getting in. Hydraulics can be powered or unpowered. They last a very long time, essentially forever with a minimum of care. My current boat has a 45 year old system. All of it simple to rebuild. Most autopilots requires a pump, but if you add a remote the rudder can be controlled anywhere on the boat.

[stormalong]

Originally Posted by coopec43

Having seen some Roberts Mauritius yachts (including the one I helped build) I have not been impressed. I am very happy with mine so far. This is my yacht album.

https://www.flickr.com/photos/440710...57631756633356

WOW, that is beautiful. Well done.

[coopec43]

Originally Posted by Bycrick

At the risk of hijacking the thread, maybe hydraulic steering would be an answer?

Yes, I won't argue with that. I did consider the pros and cons of hydraulic steering but rightly or wrongly I went for the chain/cable. Maybe I'll regret my choice......

[Ambler]

Originally Posted by coopec43

Yes, I won't argue with that. I did consider the pros and cons of hydraulic steering but rightly or wrongly I went for the chain/cable. Maybe I'll regret my choice......

Well I had cable and didnt like the big holes in the bulkhead between the engine room and aft cabin so I converted to hydraulic steering. That enabled me to design and build a 200 litre diesel tank where the cables ran. Also I then increased my water capacity by 180 litres by converting the leaky, stinky, fibreglass diesel tank in the main cabin to freshwater.

So now after 15 years of suffering the lack of feel, creep etc, I wanted to go back to cable and also fit a Fleming windvane for the upcoming bluewater adventures.

The ovious route to take was to fit a new wheel and shaft (Lewmar) to the aft bulkhead of the cockpit. The control lines from the fleming to the new wheel location also don't cut the cockpit in half. The binacle will stay as a hand hold by the way.

I bolted a cleat to the quadrant to take up the slack in the middle of the one length (about 6 metres )of dynex. The two ends have Brummel splices to turnbuckles which are also attached to the chain which fits onto the sprocket of the wheel shaft. The turn buckles are easy to get at and flush with the forward aft cabin bulkhead.

Job done, works well and I have a spare dynex cable just in case.

Hope that info helps anyone following

[coopec43]

Ambler


I think lack of feel was the main reason I didn't go hydraulic.


I don't know why you had huge holes in the bulkhead for cables. My cable will be 10 mm so I would certainly expect the holes would be around 15mm and there would be only two of them.


As far as water capacity is concerned I hope to have an el cheapo desalinator installed (but that should be the subject of another thread)

[coopec43]

I am progressing with the chain and cable steering for the yacht.

The "V" belt pulleys cost $50 and the roller races $3 but then there is the machining. Fortunately my Son has just bought a lathe and while he is inexperienced he is doing a great job. (I can't guess what a Fitter and Turner would charge per pulley)

I've shown the pulleys to the professional yacht rigger who examined them carefully and he can see nothing wrong with them.

The cost of an Edson 8 inch pulley (with needle roller bearing) is $285