Question regarding covered Dyneema and Jammers

[Jordan]

I want to move to covered dyneema reefing lines, like warp speed, etc.

My reefing lines are in-boom, and I have a spacecraft gooseneck with integrated cams/jammers.

If all the strength is in the core, and dyneema is very slippery, do jammers/cam-cletes work at all?

Seems like it would just jam the cover and the Dyneema would still slide in the middle, so you'd load the cover and not the core.

Thanks!!!

[thinwater]

Originally Posted by Jordan

I want to move to covered dyneema reefing lines, like warp speed, etc.

My reefing lines are in-boom, and I have a spacecraft gooseneck with integrated cams/jammers.

If all the strength is in the core, and dyneema is very slippery, do jammers/cam-cletes work at all?

Seems like it would just jam the cover and the Dyneema would still slide in the middle, so you'd load the cover and not the core.

Thanks!!!

This is a problem, and the core can slip inside the cover. The most common failure mode is for the cover to tear off the core.You can reduce core slippage by ...

• Good fit in the jammer
• Coating the line section in the jammer with Yale Maxijacket diluted about 30%. This increased friction between the cover and core and firms the line slightly, which helps in jammers.

Or you can just stay with polyester. The failure will be due to cover wear, you can't down size without the jammers slipping and core slippage issues, and stretch is less critical than a halyard, for example (2:1 purchase and shorter length).

[s/v Jedi]

You can do better for these reefing lines by using two lines and a low friction ring.

First line is Amsteel Blue single braid. One end tied around the boom, then up and through the reef cringle, then down and through the aft sheave in the boom.

Normally, this line continues through the boom and comes out through the sheave and jammer at the gooseneck. Not now, you only go forward a couple inches, through a low friction ring and then back to an anchoring point. Some booms already have something for that, or you mount a pad eye on the inside of the boom.

Now you take a double braid polyester line that is compatible with the jammers and you splice it around that low friction ring. While reefing, you pull the reefing line into the boom as a loop.

[two-rocks]

Originally Posted by s/v Jedi

You can do better for these reefing lines by using two lines and a low friction ring.

Now you take a double braid polyester line that is compatible with the jammers and you splice it around that low friction ring. While reefing, you pull the reefing line into the boom as a loop.

Unrelated question from the OP, but doesn't that create a 1:2 adding friction? (minus the friction of dyneema of course)

[Jordan]

Originally Posted by thinwater

• Coating the line section in the jammer with Yale Maxijacket diluted about 30%. This increased friction between the cover and core and firms the line slightly, which helps in jammers.

Or you can just stay with polyester. The failure will be due to cover wear, you can't down size without the jammers slipping and core slippage issues, and stretch is less critical than a halyard, for example (2:1 purchase and shorter length).

For Maxijacket - I'd pull the cover back to expose the core and apply the coating?


On my last big trip I broke my 12mm 2nd and 3rd polyester reef lines on different occasions - it was the radius of the reefing blocks on the sail combined with high load in extended gales. I don't really want to go to 1/2" since thats a lot of weight to hang up there... my 3rd reef line is 34m long. Thus the 10mm covered dyneema.


What about binding the cover to the core for a few meters around where it gets jammed with dyneema whipping twine? Is that a thing?


I think I could even fit the rope in my walking foot sewing machine.

[TheOffice]

Binding the cover should work. sort of like 12 strand with a cover added where it engages the clutch.

[thinwater]

Originally Posted by Jordan

For Maxijacket - I'd pull the cover back to expose the core and apply the coating? No, if properly diluted to a watery consistency it soaks through very, very quickly. The line must be dry. I have done this a number of times.

On my last big trip I broke my 12mm 2nd and 3rd polyester reef lines on different occasions - it was the radius of the reefing blocks on the sail combined with high load in extended gales. I don't really want to go to 1/2" since thats a lot of weight to hang up there... my 3rd reef line is 34m long. Thus the 10mm covered dyneema. For extended bad weather, no matter the reefing line material, it is good practice to place a lashing to take the clew load.


What about binding the cover to the core for a few meters around where it gets jammed with Dyneema whipping twine? Is that a thing? Not that I have heard.

I think I could even fit the rope in my walking foot sewing machine. I am 100% certain this would be better done by hand with waxed whipping twine. The pressure tight stitching will distort the line too much and the cover will want to tear where the stitching starts. Locking stitches are not tensioned tightly.

See above. I think the Maxijacket is all you need. Thin it so it soaks in deep. For maximum chafe protection, for example dock lines, you leave it full thickness. But even thinned it protects from chafe ~ 3-5 times.

[s/v Jedi]

Originally Posted by two-rocks

Unrelated question from the OP, but doesn't that create a 1:2 adding friction? (minus the friction of dyneema of course)

Yes, but you also have a 2:1 at the reef cringle and these cancel each other out. Of course you also have that when using a single line, but here the added benefit is that you only pull half the length of line for reefing plus when not reefed, this part of the line sits inside the boom, protected against UV.

The OP would only need 1/4” Amsteel Blue (would create a 6 ton breaking strength reef) which greatly improves friction at the reef cringles (I think he has blocks) and of course you need a winch for reefing anyway. Even if you need to turn the slow side when it gets tight, you only have to winch in half the length so that’s okay.

You hope the boom is long enough to do this for the 2nd reef as well instead of going 1:3

[s/v Jedi]

Originally Posted by Jordan

For Maxijacket - I'd pull the cover back to expose the core and apply the coating?


On my last big trip I broke my 12mm 2nd and 3rd polyester reef lines on different occasions - it was the radius of the reefing blocks on the sail combined with high load in extended gales. I don't really want to go to 1/2" since thats a lot of weight to hang up there... my 3rd reef line is 34m long. Thus the 10mm covered dyneema.

What about binding the cover to the core for a few meters around where it gets jammed with dyneema whipping twine? Is that a thing?

I think I could even fit the rope in my walking foot sewing machine.

Yes, so you need to go down in rope diameter. You can strip WarpSpeed because the core is Amsteel Blue so it has UV protected coating. You can go down to 3/8” 9mm WarpSpeed II and strip to the 1/4” 6mm Amsteel Blue core for the part that runs outside the aft end of the boom.

I would recommend the setup I described above instead. I did not test core slip in these jammers but these lines work great in Lewmar and Spinlock clutches because that’s how my halyards have been for many years now.

[ggray]

Originally Posted by thinwater

[*] Coating the line section in the jammer with Yale Maxijacket diluted about 30%.

What do you dilute with?