Dalliance
Well-Known Member
I need ot replace my main halyard which is a 10mm B-on-B at the moment and I'm thinking of changing to Dyneema to reduce friction in the system. Could I go as low as 6mm in Dyneema or will I need 8mm?
What size Dyneema to replace a 10mm braid-on-braid?
- Thread starter Dalliance
- Start date
cliff
Well-Known Member
Strength is not the issue rather sheeve size and comfort when handling the rope would be of more importance. I would stay with the 10mm - saves changing the sheeves and rope clutches etc.
I certainly would not like to be plling on a 6mm rope or even 8mm - 10mm is the smallest I would go.
BTW: if you have high friction going round all the deck organisers and sheeves changing rope will not help - you need to free off the sheeves and lubricate the spindles.
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I certainly would not like to be plling on a 6mm rope or even 8mm - 10mm is the smallest I would go.
BTW: if you have high friction going round all the deck organisers and sheeves changing rope will not help - you need to free off the sheeves and lubricate the spindles.
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jeremyshaw
Well-Known Member
You should be able to go down to 6mm if you really want a rope that thin. But one "braid on braid" is not the same as another. If you visit marlowropes.com you can see the breaking strains for each of their ropes.
lw395
Well-Known Member
I think the marlow website has some guidance based on the size of sail and boat, so maybe start from there rather than what was fitted before. Also Harken site is worth a look for guidance.
If rope size is the cause of friction it is worth going down a size if possible, but as others have said you need to ensure all the leads are fair and the sheaves free too.
It may be your masthead sheave was intended for wire, which is a cheaper option for low stretch.
If 10mm rope runs at all, then 8mm shouldn't cause much friction on the sides of the sheave boxes, so little benefit in going down to 6 other than cost.
If rope size is the cause of friction it is worth going down a size if possible, but as others have said you need to ensure all the leads are fair and the sheaves free too.
It may be your masthead sheave was intended for wire, which is a cheaper option for low stretch.
If 10mm rope runs at all, then 8mm shouldn't cause much friction on the sides of the sheave boxes, so little benefit in going down to 6 other than cost.
savageseadog
Well-Known Member
8mm will be OK as long as your clutches hold it.
Ceirwan
Well-Known Member
But as has been said, your going to be pulling it so you don't want it to harsh on the hands...
8mm is fine on a smaller boat, but if yours has 10, i'd stick with it.
8mm is fine on a smaller boat, but if yours has 10, i'd stick with it.
Dalliance
Well-Known Member
I've cleaned and lubricated all of the sheaves/organisers and blocks but the 10mm B-on-B is actually too large for the organisers and the clutch and that is where the greatest friction occurs. 8mm will solve all of these "size" problems - I think the halyard was increased from 8mm to 10mm when the sail was changed to a FB main in order to cover the increased weight.
I'll replace with 8mm Dyneema this w/e.
Thanks for the advice
I'll replace with 8mm Dyneema this w/e.
Thanks for the advice
mikejames
Well-Known Member
I have 8mm and 10mm spectra/dyneema halyards on Forethought..
The clutches are rated from 8mm to 10 mm and the 8mm jib halyard flattens and slips more than polyester would and so I have to back it up with a turn or two on the halyard winch and the original Westerly cleat.
Although 6mm looks like it would fit, the different (to polyester) splicing method of spectra/dyneema goes much easier with new thicker rope.
So I would replace 10mm with 10mm and enjoy the reduced stretch (smiling sweetly as you part with several pounds per metre , my halyards on a GK24 with a 11 metre mast were £200 each a few years back) - but watch out because shock loads will yank harder on fittings along the way , and these then fall off or break .
I pulled out a mast foot turning block using a size 8 winch , a 12 inch handle and a good heave with all my body weight ....
The clutches are rated from 8mm to 10 mm and the 8mm jib halyard flattens and slips more than polyester would and so I have to back it up with a turn or two on the halyard winch and the original Westerly cleat.
Although 6mm looks like it would fit, the different (to polyester) splicing method of spectra/dyneema goes much easier with new thicker rope.
So I would replace 10mm with 10mm and enjoy the reduced stretch (smiling sweetly as you part with several pounds per metre , my halyards on a GK24 with a 11 metre mast were £200 each a few years back) - but watch out because shock loads will yank harder on fittings along the way , and these then fall off or break .
I pulled out a mast foot turning block using a size 8 winch , a 12 inch handle and a good heave with all my body weight ....