Replacement Rudder Cable Advice

[MicHughV]

I have used the 7x19 s/s cable and cable clamps for years and years without a single problem. I keep them greased though at the quadrant end, but not sure if this is a help or hindrance.

Edson recommends to oil the chain inside the pedestal every year or so, and this oil will drip down to the cable also " lubricating" it.

Interestingly enough, I've had the chain break, but not the cable. This was prior to me learning to lube the chain.

[akopac]

Mine broke and it was the same cable in sheath system you had. I got it shipped from Edson to Papeete Tahiti and installed it in 1 day. I did have a problem sourcing the super lube silicon lubricant they specified but did find it eventually.

[coopec43]

Originally Posted by Peter Hunt

There is basically no conduit, not sure where that came from, and my run seems perfect, I do not have any chafing spots, etc. The boat design was great, although the pulley size is a little small, about 5"

I did a lot of research when I was designing the steering for Helen

It doesn't matter whether you are installing an overhead crane or your yacht steering the rules for sheave diameter /cable diameter are the same.

There are lots of tables online but the recommendations are always the same. Here is one which recommends a sheave diameter of 7.5 inch for a 5/16 cable.

https://strandcore.com/resources/technical-resources/pulley-sheave-radius-guides/

[wholybee]

Originally Posted by Peter Hunt

There is basically no conduit, not sure where that came from, and my run seems perfect, I do not have any chafing spots, etc. The boat design was great, although the pulley size is a little small, about 5"



I will check with the experts as well, but I am fairly sure I can solve this one, was just wondering about the cable options. Just have to find a flexible SS or dyneema cable.


It does go through the boat vertically, at the helm, for about 1 inch, but does not seem to touch there at all, lands right on the sheaves, and turn directly to the rudder quadrant. So the run is clean and short.

Some other poster brought up the conduit and confused things for a bit.

100% go with dyneema. Many boats were originally outfited with 4" or 5" sheaves, and there isn't enough space or there will be alignment problems if you change sizes to 8". So you are probably stuck with sheaves too small for cable, and that will lead to premature failure. That is one reason why I feel dynemma is better, it works with the smaller sheave.

Use a splice on the chain end. Dyneema splices are super easy, just look up Brummel Eye Splice on youtube.

On the radial end, I used a round turn and 2 (really 3) half hitches. Splices are not adjustable, and you need some adjustability here. It'll probably take a few adjustments to get it right. Good to know Edson thinks the clamps are ok, but the knot is still easier.

The only place I see a problem after 10,000 miles is the sharp turn in the radial (if you have the same type as me) to the eye bolt. I have chafe in the dyneema at that corner. I cut some scrap leather to soften that corner, and I think that will resolve that issue.

I had to adjust the eye bolts A LOT during the first 1000 miles. Probably 2" each side. So make sure your initial setup allows for that much adjustment, or use a better dyneema than I did. I used Amsteel Blue, which is not heat set, so has some initial construction stretch.

[coopec43]

Warren
I'm sure that is excellent advice as Peter's sheaves a small diameter and to replace each sheave at around $A300 ea. would be too costly to go down that track,

People swear by Dyneema and at last check many production yacht manufacturers had swung over to using it. Cheers.

[abarrow]

Originally Posted by JoeRobertJr

Warren,
Using Dyneema is an intriguing option, even if just an emergency repair. I am wondering how the synthetic line would handle the rubbing inside the wire conduits. My first impression is that the steel cable would withstand that better than Dyneema.

Unfortunately, my steering cable installation has conduit making turns that violate the specs from Edson. It worries me. I haven't yet worked out how to place sheaves to avoid these conduit turns. It's on my list.

I was on a 53 ft trimaran a few years ago on a delivery from Sardinia to St. Lucia. Not far into the delivery, the rudder cable broke. We purchased what we thought was the right cable, but that broke after only a few days. So, we replaced both cables with Dyneema. It worked great, and as far as I know, it's still in service on the boat. Just be careful of two things: wear points and stretch. Dyneema, unless it has been pre-stretched, will initially stretch about 10%. However you attach it, just be sure you have a way of taking the stretch out after a few days or weeks of use. The other thing is just be sure that where the cable goes into things like conduit, you have something there to lead it smoothly - don't make it go around edges. This may seem obvious, but the original stainless cable went past some areas that would've shredded Dyneema. On the ends where you can't do a good Brummel lock on the loops, make sure you stitch them well so they don't slip out.

[sinnerman]

Originally Posted by GordMay

Type 316 SS, 7 x 19* construction [as used for wire halyards], is usually used for pulley type steering cables.
Though it has about 10% less strength than 304 stainless steel, it's much more corrosion resistant.
* 19 individual wires, within 7 strands
Your lifeline was probably 1 x 19 construction.

Ditto to above.

lifeline cable, 3/16" dia, 316 stainless.

Available pretty much anywhere..(Edson will charge you an arm and a leg, however....)

Example alternate supplier:
https://www.d21ent.com/product-p/d21-92.htm

cheers

[captchetco]

It is a good idea to occasionally lubricate steering cable with a cable lube, available at some chandleries. but always at industrial supply stores. The wires wear internally as the cable rounds a curve (inside wires go a shorter distance than outer, which makes the wires rub against each other as they shift).There are lots of different cables available, pulley. I used the aircraft type 316 7x19. Lubing the pulley shafts and cable before embarking it will last 20 years, variable by the direction change at pulleys.

[Icarus]

7x19 by 5mm diameter... SS or galvernised steel wire cable.
SS tends to work harden over time..

Nothing wrong with flex gal...

[coopec43]

Originally Posted by Icarus

7x19 by 5mm diameter... SS or galvernised steel wire cable.
SS tends to work harden over time..

Nothing wrong with flex gal...

That size cable would be OK for an 18ft run-a-bout!

On my 43ft yacht the steering cable is SS 7/19 10mm (3/8 in)

[wholybee]

Originally Posted by coopec43

That size cable would be OK for an 18ft run-a-bout!

On my 43ft yacht the steering cable is SS 7/19 10mm (3/8 in)

3/16" was standard on many boats in the 35-40 foot range equipped with Edson steering. It's plenty strong, the issue is wear around the sheeves, which is worse with larger cable sizes.

It doesn't matter with Dyneema though. That is what it should be replaced with.

[coopec43]

Originally Posted by wholybee

3/16" was standard on many boats in the 35-40 foot range equipped with Edson steering. It's plenty strong,

When you say "boat" do you mean "yacht" or "boat"?

How can you say a 3/16 in cable is OK when you don't know the design of the yacht(?) or boat?

[wholybee]

Originally Posted by coopec43

When you say "boat" do you mean "yacht" or "boat"?

How can you say a 3/16 in cable is OK when you don't know the design of the yacht(?) or boat?

Yacht or boat? Are you just trying to argue?

I never said it was "ok", I said that many boats in the 35' to 40' range came with 3/16" standard. My 18,000 lbs. 38' foot Morgan came with 3/16" cable from the factory and lasted nearly 40 years. Dyneema is still better.

[coopec43]

Originally Posted by wholybee

Yacht or boat? Are you just trying to argue?

I never said it was "ok", I said that many boats in the 35' to 40' range came with 3/16" standard. My 18,000 lbs. 38' foot Morgan came with 3/16" cable from the factory and lasted nearly 40 years. Dyneema is still better.

When I was considering installing a Coursemaster Autopilot the company's expert needed to know what steering loads the unit had to be able to handle. Once he had the design specifications of the Roberts Mauritius 43 ketch he was able to work out the loads and decide the appropriate sized model.

Looking at the design of the Morgan 382 tells me a lot about the loads on the steering cable

The yacht doesn't have a balanced rudder which would lessen the load on the steering cable

Obviously the size/shape of the rudder would affect the loads - height/width

Rudder angle. Loads increase with rudder angle

Speed of yacht. Loads increase with speed

As far as the steering cable is concerned on the Morgan 38 the steering pedestal is virtually over the top of the rudder quadrant. Therefore the cable is probably one meter long - it is not going to stretch (or break) much in one meter!

Contrast that with my center cockpit Mauritius 43 the steering cable is around 4,5M - plenty of room for stretch and breakage. (That is why I have 10mm diameter cable)

If you want to know what loads there are on any steering cable there is a formula please see below. (I'm sure you will find it helpful)

When the torque necessary to manoeuvre a boat is not specified by naval architect nor
by the shipbuilders yard, it can be calculated as follows:-
It must be known that the torque necessary to manoeuvre a boat depends on:
• the speed of the water flowing on the surface of the rudder at a certain angle;
• the rudder size;
• the total sweep of rudder (& a part of the boat) when rudder shaft is not perpendicular;
• the compensating surface;
Torque calculation for a maximum speed about 25 knots:
T = S x [(0.4a) -b ] x V
2
x k
T = Torque in kgm
S = Total surface space of the rudder in m
2
(h x a)
h = Height of the rudder in m
a = Width of rudder in m
b = The value of the compensation in m
V = Speed of the boat in knots
k = Coefficient according to the total angle of rudder
- Port to starboard 50° k = 10.84
- Port to starboard 60° k = 13.01
- Port to starboard 70° k = 15.89
- Port to starboard 80° k = 17.80
- Port to starboard 90° k = 19.52
Straightening according type of boats:
- For boats equipped with jet engine T x 1.3
- For power boats with two engines and one rudder T x 0.5
- For sailboats T x 0.5
- For twin rudders T x 2
Example: Assume a rudder with a height of 0.5m(h), an overall width of 0.35m(a) and a
balance of 0.10(b). Maximum boat speed = 22 Knots. Port to starboard = 70°.
The maximum torque on the rudder blade is given by:
T = S x (0.4a-b) x V
2
x 15.89
T = (0.5 x 0.35) x ((0.4 x 0.35) - 0.10) x 22
2
x 15.89
T = 0.175 x 0.04 x 484 x 15.89
T = 53.9 Kgm Assuming twin rudders maximum steering torque = 107.8Kg

[Icarus]

Originally Posted by coopec43

That size cable would be OK for an 18ft run-a-bout!

On my 43ft yacht the steering cable is SS 7/19 10mm (3/8 in)

Was ment to type 5/16