Wire rope for Lifting Keel

[Amp1ng]

This wire runs from the keel head through 180 degrees around a two inch sheave and onto an electric winch with 2 inch drum diameter! What material should I use?

 

[ccscott49]

Depends on how heavy the keel is! But I would say 4mm 7 x 19, stainless wire or galvanised wire, or even 4mm kevlar rope. IMHO Thats if its a relatively light or well balanced keel. Bigger diameter wire, isnt really going to be happy bending around 2" wheels.

 

[Amp1ng]

Keel weighs approx 950 lb. The original was 6 mm diameter, for me the question is more one of what meterial should it be made of given the sheave and drum diameter?

 

[ccscott49]

OK, go for 6mm, 7x19 stainless wire rope. The 7x19 is much more flexible than rigging wire 1x19, which means it has seven wires in each of 19 cores, making up the wire, where as most rigging wire, (stiff) is one wire in each of 19 cores. If that makes sense, there are other compositions, but those are the most common and most popular.

 

[Amp1ng]

What about the brittleness of stainless and the work hardening charachteristics when twisted around sheaves and the winch? What would make you choose stainless instead of Galvanised?

 

[ccscott49]

The only reason I would use stainless instead of galvanised, would be superior corrosion resistance, I use it on my davits and havent had any problem with my cables work hardening, due to twisting around a small drum and over a small sheave and block. Most wire davits have stainless wire. As I said, why dont you consider kevlar rope instead of either?

 

[Amp1ng]

Thanks for the input, I had thought of using Spectra but was a little nervous about its abrasion resistance and whether or not it would suffer damage if the sheave edges had sharp burs, I guess the answer would be to renew the sheave perhaps with aluminium to safeguard the rope.

Thanks for your help

 

[mainmarine]

my Cornish Crabber had 4mm 7 x 19 stainless over smaller sheaves, recommended replacement every 5 years depending on use,
with regular checking for broken strands.

 

[charles_reed]

You'd be well advised to look at one of the 3 high-tensile textile ropes. I'd avoid Kevlar, my experience it work-hardens (Ie fatigue fails) worse than stainless wire. Vectran has less stretch than Dyneema/Spectra.

I've used both the latter, successfully, for guard rails over the last 10 years. Both my Kevlar halyards failed, suddenly by fatigue - it's also very uv susceptible.

 

[spiney]

I have the same problem on my Westerly Nimrod 18’ It has a winch operated lifting keel. The problem is if you take weight of the winch often caused by touching the bottom the steel cable can jump off the winch and jam or worse still form a ’bird’s nest’ on the spool.

Could I use a nylon strap as some people use on a trailer winch.

Could I dispense with the winch altogether and just fit a rope & cleat? Or would I find it impossible to get the keel up if I where hard aground?

 

[Bill1]

Yes you can use a nylon tape, the keel wire on my nimrod snapped about 2 years ago and I replaced it temporarily with a about 1.5m of tape that I used to use for a sling when climbing. Its still in place and working well! As its protected from sunlight most of the time ie in the cabin it should last a long time.
I think you will find the keel too heavy to lift without the winch.