Jib boom performance improvement

[Jonathan Stuart]

All,

Not sure if this has been discussed before so apologies if I am repeating something.

What I know has been discussed is that the self tacking jib can be ineffective downwind. That is for a number of reasons but I felt that the jib pivoting on rope loops is not ideal. That restricts movement and the resistance will grow as required jib swing increases.

So as an experiment I replaced the twisted shackle (that attaches jib boom to stem head) with a swivel shackle, an 8mm one of these - https://www.seascrew.com/browse.cfm?STAINLESS-STEEL-316-SWIVELS-JAW-JAW&l=0000000469

The jib now swings more freely. I have only sailed with this a couple of times - so there may be issues for me to discover - but on the first sail I went on a dead run and the jib boom happily swung out to just under 90 degrees to the boat and stayed there - rock solid without falling back or flapping about once.

Jonathan

[Rob Waller]

The new furling arrangement seems to make the jib completely ineffective downwind - it wasn't too bad with the original rig. So this sounds like a great solution. Thanks.

[Jonathan Stuart]

The new jib furling shouldn't affect downwind performance as long as (1) the furling line has plenty of slack so it doesn't pull on the jib boom and (2) the forward block on the unfurling line is attached to the jib boom's pivot axis.

As an aside, I have also replaced that forward block with a swivel block because at some angles of jib boom swing the line didn't run nicely through the block. I made that change mainly out of perfectionism but it could potentially affect the jib boom's swing.

Picture attached that shows both changes.

[Peter Cockerton]

Jonathon

Nice idea, will implement this one myself, i guess in light conditions and on a run the twist created in the strop when the jib is at 90 degrees will try and pull the jib back.

One comment though from your photograph it appears that you have the strop splice bent around the shackle, i would think this is best to avoid and put the splice in a straight pull area.

Peter

[Jonathan Stuart]

Peter,

Thanks for pointing that out and I have now moved the splice. The swivel has certainly worked well for me so far. The jaws on mine are a little narrow so it pulls the strop slightly tighter and the reduced slack means the boom doesn't sit as well when the jib boom isn't supported by the jib (or topping lift). I have a topping lift and have changed the way I position the boom when the boat is de-rigged and that works for me.

Jonathan