Acera / Dyneema

[Pete7]

We have received a couple of questions on the construction of a Jordans Series Drogue (JSD) from Dockhead. It's quite a technical question involving construction and since he is in the Arctic only has a limited range of materials on board including a selection of Acera which if you haven't heard of is this stuff, similar to Dyneema but a looser weave and much cheaper.

ACERAâ„¢ Amundsen | TIMM

The two questions:

1. We are making our Jordan drogue using Acera cordage -- a fantastic Dyneema substitute discovered by Seaworthylass. It looks and feels and splices exactly like good single braid Dyneema -- I mean, the kind that is coated to prevent the frizzing which otherwise occurs when doing ropework with Dyneema.

But here is the problem -- the method for attaching the cones doesn't seem to be applicable to the relatively loosely woven Acera cordage. I am not confident that stopper knots will hold the tapes when there is no load on the drogue. So we thought to wrap the tapes back around and tie off with constrictor knots or tie them together with reef knots, holding the main rope together in the process. Anyone build a drogue out of Dyneema or comparable single braid, and have any tips?


2. I have done a lot of splicing with Dyneema over the last few years, and I always followed Brian Toss' method in my copy of his book (First Edition "Rigger's Apprentice" dated 1998), page 100, "Mobius Brummel", which instructs burying 48x the diameter of the line. I have now heard from SWL that Brian Toss now recommends a 72x bury. The question is whether I need to do the splices over again. I have used a lot of Dyneema spliced at 48x under sometimes huge loads and never had a problem, but I wouldn't want to take any risk with something like this. Anyone have any insight?

[BigBeakie]

Re his first question about the figure 8 stopper knots pulling through, I'm doing a JSD using same Amundsen Acera, and if you pass through the Acera twice with the webbing instead of once, I could not shake it loose or pull it out no matter how I tried. And the JSD would always be under load when used anyway, pulling the Acera bundles tightly together and locking in the cones, so even less likely to lose a cone, I would think.

SWL has made her JSD, she may have a view on this.


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[Pete7]

Thanks, I will pass your idea on to Dockhead this evening.

Pete

[Seaworthy Lass]

Originally Posted by BigBeakie

Re his first question about the figure 8 stopper knots pulling through, I'm doing a JSD using same Amundsen Acera, and if you pass through the Acera twice with the webbing instead of once, I could not shake it loose or pull it out no matter how I tried. And the JSD would always be under load when used anyway, pulling the Acera bundles tightly together and locking in the cones, so even less likely to lose a cone, I would think.

SWL has made her JSD, she may have a view on this.

Hi BigBeakie
Thanks for the comments regarding how you secured the tape.

I didn’t have a chance to make up the drogue before we left the NL and planned to do so at anchor during the summer. I am ashamed to say I have been super lazy and I have not done so yet .

I have been corresponding with Dockhead and sent him summaries of all the general information I could find on JSD construction and the few snippets I could find specific to dyneema. There has been very little information online regarding what to do with HMPE ropes.

Regarding bury lengths for dyneema, Dockhead’s query came up after I said I would make the bury length 72x diameter, as per Brion Toss’s recommendation in the second edition of his book. Loads may be high and they will be cyclical, so I prefer to take no chances. Evans Starzinger’s early advice was that 63x was the minimum needed (Samson Ropes also specify 63x), although lately Starzinger has suggested there is no benefit using greater then 48x. Dockhead has already made up a few splices for the drogue using 48x and was hoping someone would confirm 48x was OK so he would not need to remake these.

SWL

[BigBeakie]

Hi SWL,

I've been impressed with the tech data sheets on the Amundsen, it looks to me like a credible equivalent to SK98. Do you agree? Thinking of using 12mm for staysail & jib halyard on the Antal halyard tensioners. Would appreciate your thoughts about that.

How are yours tensioners going, have you retensioned since launching your dream boat?


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[Seaworthy Lass]

Originally Posted by BigBeakie

Hi SWL,

I've been impressed with the tech data sheets on the Amundsen, it looks to me like a credible equivalent to SK98. Do you agree? Thinking of using 12mm for staysail & jib halyard on the Antal halyard tensioners. Would appreciate your thoughts about that.

How are yours tensioners going, have you retensioned since launching your dream boat?

I think breaking strain is similar to SK75/SK78 (figures vary a bit between different manufacturers). SK99 is about 20% higher than this.

I haven’t seen any specifications for creep for Acera Amundsen (SK78 is similar to SK99, SK75 is similar to SK90). Have you found any data on this?

% elongation at break seems low at 2-3% for Acera (a bit lower than dyneema).

Regarding halyard diameter, I had a look at what is suggested for a 50’ cat and found 14mm double braid polyester or 12mm dyneema is recommended. Not sure how they arrive at these figures - the latter has a breaking strain of about 3x the former.

Our dyneema headsail halyards are 10mm. We haven’t retensioned them since delivery, though this may have been done by the rigger post launch. Sail shape still looks good .

SWL

[BigBeakie]

Sorry, I meant SK78, not SK98😳

I have a few graphs, but away from my computer so not sure any of them show creep. I'll check when I get back in a few days.

When sizing our halyards, it was the resistance to creep ( bigger is less creep) that determined the 12 mm choice rather than break strength, which is way more than required. Good to here the halyards have been stable on the tensioners.

Have you had a look at some of their other cordage yet? I'm getting some of their new 48 braid poly covered Amunsen core with a bind layer, for sheets etc. If it's as good as what I've seen so far, things might get interesting.....👍



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[jdazey]

Following.

[Seaworthy Lass]

Originally Posted by BigBeakie

Have you had a look at some of their other cordage yet? I'm getting some of their new 48 braid poly covered Amunsen core with a bind layer, for sheets etc. If it's as good as what I've seen so far, things might get interesting.....👍

Dagama? Amundsen is the only Acera I have seen in the flesh, but I have had a good look at Wihelmsen’s catalogue. I will be very interested in how the Dagama handles and performs generally.

Where are you sourcing it?

I have been very happy with the Amundsen. I have made soft shackles with it and also used it for the section of the snubber that goes over the bow roller (Brummel eye splices each end, 70x line diameter bury with 1/3 tapered).

SWL

[CGirvan]

Is Acera available in the States/Canada?

[BigBeakie]

Thanks SWL,

The DaGama is really stiff, and when I say stiff I mean you have to push to bend it. I got some 20mm thinking it might be good for an Abbott drogue, but the storage would be terrible. The core fibres are glued together.

However their other lines seem very nice. Am currently investigating and testing, so will let you know the results.



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