450: Dyneema Steering Cables

[arsenelupiga]

Originally Posted by robert sailor

I'd be too worried about chafe in the longer term but what do I know...I've seen stainless wire last over 40 years on some boats. Maybe I'm too conservative but I can't imagine rope lasting for long periods in this type of use.

true, but is much easier to inspect dyneema. And if there is no chafe, no issues. I have been told wire is still fine, 1 month before failed. The other still working side had 70 % of wires faulty after I did some destructive testing. Meaning that from 2.5 T of pull, breaking strength was only 750 kg or so. It was occasional sea spray that caused this as another turn further inside boat wire was spotless.

[UNCIVILIZED]

Originally Posted by robert sailor

I'd be too worried about chafe in the longer term but what do I know...I've seen stainless wire last over 40 years on some boats. Maybe I'm too conservative but I can't imagine rope lasting for long periods in this type of use.

Chafing on what exactly? And how often does one replace say a Spectra mainsheet due to wear? Which, the line sees an incredible amount of cyclical loadings & friction in such applications. This even when docked. Since it gets cinched down fairly firmly in port, so the resulting wave induced movement in the sheet gets fielded by only a few inches of line.

[robert sailor]

Originally Posted by UNCIVILIZED

Chafing on what exactly? And how often does one replace say a Spectra mainsheet due to wear? Which, the line sees an incredible amount of cyclical loadings & friction in such applications. This even when docked. Since it gets cinched down fairly firmly in port, so the resulting wave induced movement in the sheet gets fielded by only a few inches of line.

To be honest I don't know exactly how the steering is set up but I assume it's through a series of pulleys and in my experience that's where wire breaks down. I also know that high tech line is not that tough when it comes to wear through chafe. That said, I really don't have that many facts to support my opinion. I was on a fellows boat that used it on rigging and he was having more than his share of trouble with chafe and wants to go back to stainless. Unlike most uses on a boat line is usually set and doesn't get that much action but steering is something that is constantly moving. Anyways just my thoughts

[UNCIVILIZED]

I'm thinking that metal steering cables break down due to the tens of thousands of flex cycles they see, where they pass over the pulleys that route them from the quadrant to the helm. Not so much from friction causing them to chafe.

[blackswan]

We use 38mm HMPE to tie up our five hundred tonne tugs. During spring tides the range is about four to five metres and the boats are always moving with surge from sea and swell, sometimes a lot of surge when a cyclone passes by.
Yes the lines chafe but it's pretty slow and we seem to get at least a year or so out of a set of breast lines.
Having seen this I'd have to say that HMPE chafes but so does wire rope. It is amazingly chafe resistant and I'd be happy to put it on my yachts steering cables and may do so soon as part of our next refit.

[robert sailor]

Originally Posted by UNCIVILIZED

I'm thinking that metal steering cables break down due to the tens of thousands of flex cycles they see, where they pass over the pulleys that route them from the quadrant to the helm. Not so much from friction causing them to chafe.

Yes of course your right, metal doesn't really chafe it simply breaks down due to continual flexing. In my experience line will last almost forever if it's just loaded and unloaded but introduce just the slightest rub over and over and it will chafe through in no time. When we are crossing oceans I always adjust the spinaker halyard every day or two because I've seen the halyard chafe through by just rubbing the same spot on the mast head block over and over. Years ago on my last boat I used Spectra lines on the windvane and it's a series of pulleys that are constantly moving and I only get one crossing before the chafe is so bad they can't be trusted. So I may be out to lunch on this but it's these experiences that cause me to think the way I do. When I hear that sailors are getting years and years of safe use out of high tech line in their steering systems then I'll change my mind.

[StuM]

Originally Posted by robert sailor

When I hear that sailors are getting years and years of safe use out of high tech line in their steering systems then I'll change my mind.

My 2002 Belize still has (what I believe is) the original high tech line in its steering system and a recent inspection shows no appreciable wear. I have no intention of replacing it at present.

[Jim Cate]

robert, one of the factors that lead me to investigate Dyneema in yachting use was seeing that trawlers were replacing wire rope with it in their gear. Hard to imagine a more chafe prone usage than that, and they were reporting that the Dyneema outlasted wire.

Anecdotal for sure, but it impressed me! We've gone to sk75 for runners, baby stay and backstay on our boat as well as lifelines, and have had no chafe issues at all... in about 7 years.

In a cable steering system, there are few inherent chafe points. Wire breaks down from flex cycles... like where it is bent going over the small sheaves at the base of the pedestal. Dyneema does not suffer from that failure, so it may well outlast wire.

If I was to need to replace my steering cable, I'd be going to Dyneema Dux or something similar.

Jim

[RaymondR]

I prefer the geared and pushrod types of steering but have wondered if toothed belt and webbing strap would not be a better way to design and implement quadrant style steering. The toothed timing belt on my car does an awful lot of passing over small sheaves in the 100,000 K life recommended by the manufacturer.

[robert sailor]

Originally Posted by Jim Cate

robert, one of the factors that lead me to investigate Dyneema in yachting use was seeing that trawlers were replacing wire rope with it in their gear. Hard to imagine a more chafe prone usage than that, and they were reporting that the Dyneema outlasted wire.

Anecdotal for sure, but it impressed me! We've gone to sk75 for runners, baby stay and backstay on our boat as well as lifelines, and have had no chafe issues at all... in about 7 years.

In a cable steering system, there are few inherent chafe points. Wire breaks down from flex cycles... like where it is bent going over the small sheaves at the base of the pedestal. Dyneema does not suffer from that failure, so it may well outlast wire.

If I was to need to replace my steering cable, I'd be going to Dyneema Dux or something similar.

Jim

Thanks Jim, I guess I've been away from this stuff for too long. I used it on runners myself but never on stays, what's your opinion on using it to re rig?

[Stumble]

Originally Posted by robert sailor

Thanks Jim, I guess I've been away from this stuff for too long. I used it on runners myself but never on stays, what's your opinion on using it to re rig?

At this point its a pretty proven system. Much lighter than wire, about the same price, tested lifespan for the line is 7-8 years minimum, probably 10 maximum in the tropics.

Building it can be DIY, designing it really isn't. The line needs to be sized for creep not strength so it's a bit different than wire. Typically the rope ends up 50-100% stronger than the wire it replaces, but it just depends on your rig.

[Dockhead]

Originally Posted by robert sailor

I'd be too worried about chafe in the longer term but what do I know...I've seen stainless wire last over 40 years on some boats. Maybe I'm too conservative but I can't imagine rope lasting for long periods in this type of use.

Steering by manila ropes has a long tradition of course -- that's how the steering on the old square-riggers was done. But I really wouldn't even try dyneema, or any other kind of cordage, for steering, on my own boat -- exactly because of chafe.

I saw a massively strong dyneema sheet destroyed in 10 minutes when it touched an untaped cotter pin.

I love dyneema and use tons of it on my boat -- actually the boat was delivered new with a lot of dyneema on her (running backs, staysail sheet, outhaul). But dyneema like all cordage is vulnerable to chafing, and you can't even see the steering cables, to see whether or not they have touched something which could destroy one made of cordage. In my opinion, this is really a job for steel cable, not cordage of any kind. All you need is for something to shift in the bilges in rough weather and fall over onto the steering line, and you could be without steering in a few minutes. I shudder to contemplate this.

[robert sailor]

Originally Posted by Dockhead

Steering by manila ropes has a long tradition of course -- that's how the steering on the old square-riggers was done. But I really wouldn't even try dyneema, or any other kind of cordage, for steering, on my own boat -- exactly because of chafe.

I saw a massively strong dyneema sheet destroyed in 10 minutes when it touched an untaped cotter pin.

I love dyneema and use tons of it on my boat -- actually the boat was d elivered new with a lot of dyneema on her (running backs, staysail sheet, outhaul). But dyneema like all cordage is vulnerable to chafing, and you can't even see the steering cables, to see whether or not they have touched something which could destroy one made of cordage. In my opinion, this is really a job for steel cable, not cordage of any kind. All you need is for something to shift in the bilges in rough weather and fall over onto the steering line, and you could be without steering in a few minutes. I shudder to contemplate this.

Mmmm! Thats been my mindset to date but I've been getting the opposite feedback from others here. More thought needed.

[patha]

Good discussion - If I were to buy 6mm Dyneema as a back up emergency steering cable, how much line should I have on hand?

[UNCIVILIZED]

Originally Posted by patha

Good discussion - If I were to buy 6mm Dyneema as a back up emergency steering cable, how much line should I have on hand?

At $1/ft, & even at twice that, I keep 100' of 6-8mm Amsteel Blue in my seabag. The one for delivering & racing other folks boats. And just a week ago I picked up a spool of 10mm for $0.25/ft. It's one of those items that you shop for more by budget, or for a job, than per fixed length. As what boat can't use a good length of cordage onboard that can be used as a spare for any of it's running rigging, or in a pinch, as a stay or shroud. And in the smaller sizes you can use it to secure literally anything, in lieu of shackles, bolts, or metal bails. Handy for strops & pendants too.