Can any one tell me the diameter of the wire strop passing through deck sheave between shroud tensioning purchases and main shroud, I was using 3mm stainless steel (same as shrouds), but that just snapped in a force 5. Caused a spectacular 3 sail capsize and imminent rescue by the SCYC launch!

Thanks in advance

Suspect fatigue rather than weakness Stainless Stell wire rope fatigue and as it doesn't rust it doesn't show, the old advice was to use galvanised where it ran over sheaves and replace when it showed rust. Also A flexible wire such as 7X19X19X19 (lift cable) is better than the usual 7X19 (Not flexible at all.) or the other constructions that are supposed to be.

I'm sure that it is at least 5mm wire that is fitted to our boat, as originally rigged by Guy Winder.

Thanks

Popped to local chandlers - all he had [flexible) was 4mm [7x19 I presume]. So two strops now made up! No more mast thinking its on a Finn!

Further to this, has anyone (successfully) replaced the aforementioned flexible bit of wire with a dynnema / high tech line spliced rope? I think this is a bit easier on the side decks when towing - wire strops & varnish is not pretty. Can also change the length easily at home, rather than having to visit a riggers. 4mm should be strong enough.

What is the wisdom of the mighty Merlin Forum?

yes i did on my plastic boat, and when the wire starts fraying on storm cloud i'll do the same.

Needs to be vectran though, not dyneema.

Vectran - still 4mm though? Cool.

I'm pretty sure it was 4mm. I just rang P&B and said "Make me some strops" and they did!

Top Tip, if you are going to get them made them up in large diameter (whatever is supplied on a winder, probably 5mm) wire, take the sheave out and have it made up through the sheave, as you will not be able to get the eyes through once the strop is made up

I carry a table of relative breaking strains on the van. It's based on a. n. other wire and Marlow D12 and V12. The vectran is a much better all round alternative than dyneema to wire BUT is is slightly weaker overall for the smaller sizes. I'm not sure how other makes of dyneema (or vectran) compare to MArlow but as long as it's the same quality (SK75 for dyneema) then I guess it would be about the same...
Breaking strains in Kgs
      3mm    4mm     5mm
1x19  720    1280    2000
7x19  510     970    1420
D12   995    2056    2395
V12   993    1678    2405

Just measured mine and they are 4mm 7x19...

Regards

Tony

Re "Top Tip" 
I've taken the sheaves out of the side-decks (for re-varnishing) - these actually open up so that you don't need to thread the wire through before having the eye splice made. Maybe there are different sheave boxes...

Methinks there is something iffy with the Marlow loading tables - V12 at 4mm being weaker than D12 at same diameter!