Is it OK to tie knots in dyneema jib sheets?

[Lucky Duck]

Looking at replacing the sheets that came with the boat and 'cruising' dyneema piqued my interest, would it still be possible to attach the sheets - and retain sufficient strength - with a knot or would a spliced shackle be required?

 

[knuterikt]

Looking at replacing the sheets the came with the boat and 'cruising' dyneema piqued my interest, would it still be possible to attach the sheets - and retain sufficient strength - with a knot or would a spliced shackle be required?

You are opening a can of worms now

YM did a test April 2012 (i think)

4 different knots to attach a rope was tested
-Bowline
-Flemish loop
-Anchor bend
-Double fisherman's loop

For Dyneema all of these reduced the breaking strength to 35% - 39% of the original breaking strength.
All of these knots broke in the same way - the cover broke at the knot and the Dyneema core slipped out of he rope.

 

[onesea]

Do you really need cruising Dynema sheets?

When the sail is flogging it will shock load the winch more, only marginally but its there. When the sail is tight in the stretch will hardly be noticeable on a regular sheet, the loads do not change that much on a jib-sheet once its set IMHO.

Either way spliced eye in the end of your sheets and a soft shackle to secure to the jib...

 

[Rossynant]

You are opening a can of worms now

Rather Pandora box...
What's wrong with a bit more sensible rope, like braided or plated polyester? Heard that knots still have some 50% strength on it, some less breaking the rope, like flemish (figure 8) even 70%.

 

[boaterbaz]

I would recommend Polyester braid on braid for sheets. The stretch is immateriall, possibley advantageous. You should be trimming the sail continiously as you bimble along. Softer on the hands as well.

 

[dunedin]

Unless the deck-gear is designed for it, modern no stretch ropes can put extra shock loads on fittings, and sometimes more slippery for cams/jammers

Great for replacing wire halyards, kicking straps etc - but I would wonder about the pros and cons for genny sheets

 

[William_H]

As said use a braided polyester rope for jib sheets. Unless it is a big boat strength is secondary to size big enough for comfortable handling. Stretch is not a real concern for jib sheets. Yes use a knot and occasionally retie with the knot in a different position to move the points of high wear so prolonging the life of the rope. good luck olewill

 

[Lucky Duck]

Thanks for the responses,

Just looked up the predicted loadings on the harken website which gives the a predicted loading (30m2 @ 20 knots) of around 250kg so dyneema looks to be somewhat unecessary.

 

[alant]

Looking at replacing the sheets that came with the boat and 'cruising' dyneema piqued my interest, would it still be possible to attach the sheets - and retain sufficient strength - with a knot or would a spliced shackle be required?

How kind is Dyneema to your hands & can you easily grip it?

 

[prv]

How kind is Dyneema to your hands & can you easily grip it?

The stuff itself, not very. But the "cruising dyneema" the OP was considering is a dyneema core with a conventional polyester braid on the outside, for this very reason.

Pete