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Old 17-03-2017, 10:35   #31
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Dyneema Steering Cables

Good discussion points here guys. This has gone a long way into my replacement plan.

Im convinced that I'll be going to dyneema (heated, Amstel blue if i can find it) and will put in a 8-10mm line rather than 6mm to cater for any long term wear/abrasion ( I have inspected the turning sheaves for smoothness, burrs,etc.). I will maintain the original turn screws on the rudder bar to adjust for any initial stretch and the dyneema will be tied to the turn screw eye that will allow for any gross adjustments and easy replacement if needed later. I'll also be making up 2 spares. The job will be completed late next week when we arrive in Papeete.

Steve
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Old 17-03-2017, 11:15   #32
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Re: Dyneema Steering Cables

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Originally Posted by UNCIVILIZED View Post
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.
I do the same thing, ideally I have a length of 6-8mm dyneema long enough to replace anything onthe boat, whatever the longest line is. In realit i buy a half spool (300') at a time (about 1/2 the price of retail for a half spool) and just carry it around with me, when it gets too short I buy another one.
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Old 17-03-2017, 11:18   #33
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Re: Dyneema Steering Cables

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Originally Posted by Emerald Sea View Post
Good discussion points here guys. This has gone a long way into my replacement plan.

Im convinced that I'll be going to dyneema (heated, Amstel blue if i can find it) and will put in a 8-10mm line rather than 6mm to cater for any long term wear/abrasion ( I have inspected the turning sheaves for smoothness, burrs,etc.). I will maintain the original turn screws on the rudder bar to adjust for any initial stretch and the dyneema will be tied to the turn screw eye that will allow for any gross adjustments and easy replacement if needed later. I'll also be making up 2 spares. The job will be completed late next week when we arrive in Papeete.

Steve
Look for NER-HSR, but I wouldn't size it any larger than whatyou removed. The line could be too large for the blocks, wire sheaves are very particular about line sizing. 6mm HSR has a mbl of >12,000lbs. It should be more than strong enough.

If you have 7x19 stainless wire it's mbl is ~4,600lbs by comparison.
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Old 17-03-2017, 13:30   #34
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Re: Dyneema Steering Cables

I'd be cautious about dyneema in an area you cannot inspect easily.

My experience with this is that I set up the control lines from our Monitor wind vane to the steering using 3/16" dyneema. Each line is approx 4 m long (we have wheel steering in a center cockpit). The lines ran through several blocks and are above deck. So, this is like a "steering" application.

The Monitor helped us sail from Seattle to Glacier Bay, and then most recently from Seattle to Hawaii where it got a **lot** of use.

Chafe was what killed our Monitor on our passage to Hawaii. The chafe occurred where the line went around a block making a 90 degree turn. The block had a sheave with a radius of 1 inch, so about 5 times the line diameter. Bear in mind that the tension on the lines is really quite small (tens of pounds, not hundreds). But the constant back and forth of the lines caused the same area to bend and unbend thousands of times. It became very fuzzy but still looked like most of the line was still good, and I must confess I could not believe it parted when it did.

I am considering switching to coated stainless steel wires! We had a lot of problems with stretch - the Monitor is very sensitive to line tension and with 4 meters of line, a small % change made a big difference. Even the difference between a wet line and a dry line was very noticeable. My hope is s/s will not have this problem. Replacing it periodically would be easy.
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Old 17-03-2017, 14:43   #35
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Re: Dyneema Steering Cables

It's definitely worth pre-stretching Dyneema, once it's been spliced to spec' for the application. And depending on where it's being used, adding a couple of coats of Maxi Jacket II, or RP25 for added wear & UV resistance. This is probably true for steering cables, but why not call NER & ask. As they'll likely have some other good tips as well.
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Old 17-03-2017, 15:13   #36
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Re: Dyneema Steering Cables

more details for better application. Sorry paper is a bit 'used' as I was using it quite a bit to ensure minimal loss of strength. Dyneema is superior to steel, minus fire & chafe. Material on turning wheel is important also. I inspected after first ride sorted out chafe points and then in prolonging intervals. And still do as it should be anyway because steering to important to fail.
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Old 17-03-2017, 16:47   #37
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Re: Dyneema Steering Cables

I thought about changing my steering cables to Dyneema. I didn't because they run through the engine room above my engine. I was worried about the heat.
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Old 17-03-2017, 18:21   #38
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Re: Dyneema Steering Cables

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Originally Posted by Training Wheels View Post
I thought about changing my steering cables to Dyneema. I didn't because they run through the engine room above my engine. I was worried about the heat.
Dyneema is basically a plastic weave. It would have to rub against the exhaust to do any damage. The heat might make it more elastic so the stretch factor may go up a bit.
Although the melting point is pretty low at 290į+ F. All you need to know about Dyneema > http://www.pelicanrope.com/pdfs/Dyne...Tech_Sheet.pdf
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Old 17-03-2017, 20:09   #39
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Re: Dyneema Steering Cables

Dyneema looses massive amounts of strength if it is exposed to temperatures in excess of 220F (just above boiling water). So well ventilated engine rooms are ok, but could be risky, badly ventilated ones would be a disaster.
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Old 18-03-2017, 01:03   #40
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Re: Dyneema Steering Cables

I don't want to hijack the thread but how do you get access to the steering cable?
I can only see the portion between the engines.
How do you check the rest of it? Is it one continuous piece?
How do you remove it?

Thanks in advance.

P.S. Every time I have access to Internet and read this forum my to-do list gets longer and longer... I guess that's a good thing?
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Old 18-03-2017, 11:52   #41
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Dyneema Steering Cables

Access to the steering lines and sheaves on the 450 is thru a few areas. Yes, between the engines but you have to be quite thin to crawl up to these 2 horizontal sheave location for inspection. There is another cable access via the lazerette. The vertical sheaves are accessed via the storage cabinet next to the outside fridge (assuming you haven't the icemaker) by removing the inside liner. There is access to the chain via the upper stbd side salon cabinet by removing the access board. And finally there is access to the top of the steering sprocket/chain when your remove the compass.

Port and stbd cables are independent and join at the swaged fitting at the chain below the sprocket. Cables are differing lengths as there is an offset from center of your helm.

Referring to arsenelupiga's paper above, both 7mm and 9mm dyneema (HTS, Amsteel, etc) easily conform to the bending radius and sheave groove radius. Ive rechecked this against Samson's application rqmts. The 450 sheaves are D=110mm (inside) and Dgroove=11mm resulting in acceptable results.

I have not yet removed the steering lines except to make the one temporary replacement with dyneema. But I suspect I will run messenger lines, open the sheaves (from their cheek plates), lift and lower the chain from its helm sprocket to the lower access point where the vertical sheaves are, and start the measurements, cutting and reinstalling of each line. In a nutshell.

Creep with these dyneema lines is negligible. Elongation is approx 3.5% at breaking. Critical temp before degradation occurs is approx 329C but not an issue as there is no excessive heat exposure. U/V is not an issue as there is no exposure. No chemical exposure either. The turning sheaves are U shaped and not V shaped as recommended. The sheaves are free of burrs, dings, etc.

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