Dyneema running rigging

[lw395]

+1

Stretch in jib sheets is very bad! Assuming you have a jib which can be trimmed flat at all -- many of them can't.

But a flat over-trimmed jib is not going to make you go fast, just lean over and go sideways.
I suppose it stops the over-powered main from making the boat round up if you're sailing it really badly.

But how much are your polyester sheets going to move from say a steady 12 knot true wind to say and 18 knot gust? 1%? How many inches is that? On the boat I race, it would be about one if we're cross-sheeted and a one inch ease isn't much. On the dinghy we're deliberately easing more than that as a small gust hits.

It's also worth noting that some 'cruising dyneema' hasn't got much dyneema in it, so if you go down one size, the stretch can be pretty similar to polyester.

 

[Dockhead]

But a flat over-trimmed jib is not going to make you go fast, just lean over and go sideways.
I suppose it stops the over-powered main from making the boat round up if you're sailing it really badly.

But how much are your polyester sheets going to move from say a steady 12 knot true wind to say and 18 knot gust? 1%? How many inches is that? On the boat I race, it would be about one if we're cross-sheeted and a one inch ease isn't much. On the dinghy we're deliberately easing more than that as a small gust hits.

It's also worth noting that some 'cruising dyneema' hasn't got much dyneema in it, so if you go down one size, the stretch can be pretty similar to polyester.

That's kind of a non-sequitur -- no one advocated overtrimming the jib!

But if you are hard on the wind in strong wind, with the jib trimmed flat, even a very small amount of stretch can mess you up. YMMV, but on my boat, behavior in gusts was very noticeably improved with the dyneema sheets.


As to cruising dyneema -- I completely agree with you, and I don't touch the stuff. If you want double braid dyneema with a polyester cover, you should go for the good stuff. One size down doesn't make a big difference in cost to "cruising" dyneema.

 

[thinwater]

Leaving the jib pinned in, it will stall during the gust. Easing the sheet a little allows the top to twist off slightly, opening the slot.
Easing the traveller and keeping the jib in will close the slot if there's any overlap on the jib....

Jib. I can see your point. That depends very much on the clew angle of the sail; some twist and some get full. I've had both. You are right, the amount of stretch would be hard to measure.

The amount of stretch I'm taking about with a nylon traveler line is on the order of an inch. nothing noticeable re. trim. When it is noticeable is during a jibe, where it takes the smack out of a mistake. I once replaced my traveler with a bit of free Spectra I was given. It was like jibing against a brick, even in light air. I then switched to climbing rope and it was MUCH better. Even in the harshest gusts, however, the traveler only moves a fraction of an inch, because it is a multi-part purchase.