Farr 3.7 lowers...

[daryl_wilkinson]

All the 30knt sailing has taken it's toll on my Farr's 3mm wire lowers. These are bonded on to the mast.

Those with experience of SK75 / wire rope of different types. What would best replace this. Also when bonding onto carbon have you taken any chaff precautions around the area where the rope exits from under the layer of cloth? Like shrink wrap plastic / tube over the rope?

[Will_Lee]

Can you send a picture?

[daryl_wilkinson]

Umm...well I would if they would show up?




http://www.flickr.com/photos/16146533@N08/6673403581/in/photostream
http://www.flickr.com/photos/16146533@N08/6673404567/in/photostream

[phil_kirk]

A novel way of attaching wire to carbon!.
On E-Numbers we used SK78 for the lowers spliced in loops around the mast.  I made 2 brackets with a mast shaped curved plate with a small peice of carbon tube bonded and laminated on to it. The plates were bonded onto the mast. each lower was lead through the carbon tube bit and around the mast. The plate also acted as additional mast thickness and anti chaffe to protect the mast.  The SK78 is easy to inspect and can be changed quite easily.  I have so far seen no chaffe. An idea i borrowed from an int 14.

Your issue is that you can't lead a line around the mast where your lowers are attached unless you cut a small section on mast track out. A simple speed bump on the mast would also probably be sufficient to stop a lower from sliding down the mast.

I wouldn't directly epoxy SK75 or 78 to the mast because you will see chaffe where the flexible bit of rope meets the epoxied bit.  It may work if you lead the wire through electrical wire insulation tubing.  Eg used for earth wire when wiring a socket. This can be bought in B&Q.

[daryl_wilkinson]

thanks Phil... in your experience what diameter rope replicates the same strength / stretch of 3mm wire?

I would like to bond on the same way as the pic, as it is a rotating rig, but I'm aware of the chafe problem. That's why I was thinking of a shrink tube covering. SK78 over any other?

[Will_Lee]

For SK78, the 3mm is stronger than 3mm 1x19 ss wire, but it is much less stiff. We had some 5mm SK78 which was stiffer than 3mm wire.

If you can get 4mm (we couldn't), I'd probably recommend that. Its about as stiff as 3mm wire but lighter and much stronger.

People say you can get the same behaviour from 3mm SK78 as you get from wire if you pull on more tension. I am not convinced about this. Hooke's law says you get the same % increase in length per unit extra force whatever the tension, so I would not expect more tension to give you less yielding behaviour in use (which is what you don't want from D2s). Unless SK78 is not a straightforward elastic material of course.

[Stuberry]

SK90 has a higher breaking load than 75 or 78 and is stiffer. But it suffers more from creep, so is less suitable standing rigging.

[daryl_wilkinson]

Stu, Ross,

have you made any movement forward on you Farr 3.7 build? I ask as I have a couple of other people interested in doubling up on materials etc on there builds.

[Stuberry]

Nope, we're looking for somewhere to do it at the moment.

We will probably source our wood seperately and not really in a position to 'double up'.