Replacing 12mm Reefing Lines with 10mm Dyneema Mix

nigelmercier

nigelmercier

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I am considering replacing my 12mm reefing lines with 10mm, but have been advised by Selden that I need to upgrade the specification of the 10mm. My supplier has said this:

A normal 12mm polyester braid on braid has a breaking load of 2500 kilos. I can offer you a 10mm line, which has the cover in polyester and the core with Dyneema (80% of Dyneema + 20% Polypropilene). This rope, on 10mm, has a breaking load of 3500 kilos.

The Dyneema mix is almost twice the price of polyester BoB, so I need to know:

Is it really worth reducing the line diameter?
Can a soft-eye be made in this Dyneema mix using Selden fids?
Should I be concerned that it contains Polypropylene?
 
I think I'd be concerned about stretch as well as break strain.
Dyneema is great but is it needed?
Can you put some numbers to the loads and work out what the stretch will be?
 
Went from 10mm polyester to 8mm dyneema this winter on Ariam, and very happy with the results. The cover is just there for grip and is not dyneema; I assumed it was polyester but perhaps it's something else. Feels quite hard, like an abseiling rope, which means it's nice and slippery through the blocks and sheaves. The clutches have no problem, 8mm is within their spec (find the model number for yours and check them). It certainly can be spliced, but the technique is different. There are videos online.

I haven't spliced mine though - the connection to the sliders inside the boom is stitched, whipped, and heatshrink-ed just like the original. The clew pendants are attached to the boom with a bowline (line goes round the boom then a small bowline onto itself) and the tack pendants are currently attached with a bowline through the spectacle ring and the tail of the bowline half-hitched round the standing part for a little extra security. The originals were fastened to a small shackle with a Selden halyard knot; I did intend to splice the new ones to a shackle in a similar way, but the "just for today" bowlines are still there four months later and I don't really see much reason to change.

I was wary of the knots slipping, as we are warned about with dyneema, but the conventional cover means you can treat this stuff more like the rope you're used to. I haven't see any signs of slippage.

Pete
 
nigelmercier said:
Is it really worth reducing the line diameter?
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If you find your single-line reefs harder to handle than you'd like them to be, then this is the number one way to reduce friction and improve handling (excepting anything being broken/worn out in the system).

We went from 10mm polyester braid to 6mm dyneema on a 30ft boat and never looked back. As it happens I have just bought two new reef lines (due to unexpected chafe occuring when the reefs are set, not when the lines are running) and the 6mm Liros dyneema I have got from Jimmy Green (polyester cover on dyneema core) has a breaking strain of 2200kgs, not far off what you've been quoted for your existing 12mm polyester. I would be very tempted to consider 8mm dyneema, but it all depends on how happy you are with the friction in the setup as it is.

If the boat is not single-line then the above may not apply.

We had no problem going down to such thin line with our spinlock clutches but they are probably smaller than whatever you have if your reef lines are 12mm as it is. I am sure you will be fine hardware-wise in going to 10mm.
 
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bitbaltic said:
excepting anything being broken/worn out in the system
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And this is well worth checking. Get the end casting off the boom, pull the guts out (mousing as required) and have a good look at it all. Ariam's boom wasn't obviously damaged when we bought her, and things worked adequately for two seasons, but in taking it apart to fit the new reefing lines I found that half of the little plastic wheels on the sliders were missing or worn away, the axle for all the clew sheaves was bent, and the main outhaul sheave had disintegrated (the resulting stiffness no doubt triggering gorilla antics from charterers and hence the bent axle). The clew casting itself was also slightly broken, but Selden no longer offer it as a spare so we're living with it.

Pete
 
I've just replaced a 12mm braid on braid halyard with 10mm Marlow D2 Competition which is their 'cruising' version. 30m cost £185 from Jimmy Green which included them splicing on a Gibb shackle I posted to them. They turned the order around in a couple of days which was impressive.

Although I haven't tried the D2 yet, it is much lighter and far less bulky than the 12mm.
 
Some clarification:

The cover is polyester and the core is a mix of 80% Dyneema + 20% Polypropylene.

Boat is 47 feet, sail area 46.40m2

David Barden at AllSpars said "... you can go down to 10mm diameter line however will need to upgrade to a cruising Dyneema or full Dyneema product to get the strength back up ..."

Reefing is Single Line.
 
prv said:
And this is well worth checking. Get the end casting off the boom, pull the guts out (mousing as required) and have a good look at it all. Ariam's boom wasn't obviously damaged when we bought her, and things worked adequately for two seasons, but in taking it apart to fit the new reefing lines I found that half of the little plastic wheels on the sliders were missing or worn away, the axle for all the clew sheaves was bent, and the main outhaul sheave had disintegrated (the resulting stiffness no doubt triggering gorilla antics from charterers and hence the bent axle). The clew casting itself was also slightly broken, but Selden no longer offer it as a spare so we're living with it.

Pete
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Which is reason why having blocks etc inside the boom is pointless.
they only add to friction & cannot be sorted easily.
On my boat the single line reefing does not have this & although my boat is only 31 Ft ( self tacking jib so big main) I just have a single line through the boom for each reef system
 
Daydream believer said:
Which is reason why having blocks etc inside the boom is pointless.
they only add to friction & cannot be sorted easily.
On my boat the single line reefing does not have this & although my boat is only 31 Ft ( self tacking jib so big main) I just have a single line through the boom for each reef system
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Sure, so maybe if starting from scratch one wouldn't fit a Selden system. But if one already has it, then it makes sense to give it some TLC from time to time.

Also note that most of the damage to mine was nothing to do with the reefing, it was the outhaul tackle and pendant.

Pete
 
Well, I've started the job. I decided to go against previous advice I'd read and stripped out all the furling lines from the boom, rather than using them to pull through with; I've kept the battens from my old mainsail to use for rodding. There was a lot of gunk in the boom that I wanted to wash out, and the lines were in the way.

The only snag I can see up the boom is the block for the outhaul, but if I clamp at the end of the boom and keep it tight it should stay out of the way.

I was surprised to find that both the 1st and 2nd reef lines from the car to the luff are the same length, I was expecting them to be just the height of their respective cringle.
 
vyv_cox said:
I changed from 12 to 10 mm. The reduction in friction was well worth the money.
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I'll second that. I had single line reefing on a yacht that was almost unusable until I reduced the line size and used a dynema core. It was solely the friction on the small blocks that was the problem. The absence of stretch was an added bonus, especially for single line reefing. By the way, this system had moving blocks in the boom and it all worked really well with smaller lines. 1st and 2nd reefs were the single line system, the third reef was the traditional system for slab reefing.
 
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I changed from 12mm braid on braid to 10mm dyneema on a Selden boom last winter. I also changed the SS sliders with plastic wheels for new all plastic ones.
The dyneema I used was standard stuff, not a blend in the core, but if the breaking strains are as you quote in the OP, then the blend should be OK.
There is a noticeable reduction in friction in the system, making reefing and shacking out very much easier.
There is also a very noticeable reduction in the stretch in the reefing lines, which means I can keep the luff of the main tight when the sail is reefed, which was always a problem with the 12mm braid on braid.
The boat is 46ft and the main about 51 squ m.
 
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