Acera vs Dyneema & Jordan Series Drogues

[NevisDog]

Why not just use a reeving splice on halyards?

[thinwater]

There is a negative to nylon that is often overlooked: rebound.

In the case of a sea anchor, it is unavoidable. You need the stretch and so you live with being pulled forward when the wave passes.

In the case of a drogue, JSD or other, there are two additional negatives:

1. The drag is delayed by the stretch, as much as 20-40 feet. That allows the boat to build momentum down the wave face.
2. If a drogue is pulled from the face of a wave, recoil allows it to spring forward. Some have reported a drogue being "thrown forward" by a wave, but that is not what they are actually seeing. They are seeing the effect of recoil and wind. No stretch, no recoil.

Since drogues, including the JSD, can absorb impact by tearing through the water, not much stretch is needed. Whether the light weight or handling problems of Amsteel is more important is a different matter. I really hate handling Amsteel, but others feel differently. Personally, I would suggest plying with a drogue or anchor with Amsteel before you make the call. I reached my opinion after playing with Amsteel rodes.

[Seaworthy Lass]

Originally Posted by thinwater

There is a negative to nylon that is often overlooked: rebound.

In the case of a sea anchor, it is unavoidable. You need the stretch and so you live with being pulled forward when the wave passes.

In the case of a drogue, JSD or other, there are two additional negatives:

1. The drag is delayed by the stretch, as much as 20-40 feet. That allows the boat to build momentum down the wave face.
2. If a drogue is pulled from the face of a wave, recoil allows it to spring forward. Some have reported a drogue being "thrown forward" by a wave, but that is not what they are actually seeing. They are seeing the effect of recoil and wind. No stretch, no recoil.

Since drogues, including the JSD, can absorb impact by tearing through the water, not much stretch is needed. Whether the light weight or handling problems of Amsteel is more important is a different matter. I really hate handling Amsteel, but others feel differently. Personally, I would suggest plying with a drogue or anchor with Amsteel before you make the call. I reached my opinion after playing with Amsteel rodes.

Thanks for the feedback.

I have no opportunity to test out a series drogue made with UHMWPE before making one and I imagine the same applies to most cruisers, so I need to rely on what others report. Yours is the first really negative report on handling issues.

I guess for me if retrieval is slow, at least it is not likely to be unsafe, as it will be occuring when conditions have calmed. I am of slight build and not very strong and I think deployment of a 50+ kg drogue in survival conditions would be more of a problem for me.

SWL

[malbert73]

Yeah- overall a good outcome if you are actually discussing retrieval if a drogue, eh?

[Seaworthy Lass]

Originally Posted by malbert73

Yeah- overall a good outcome if you are actually discussing retrieval if a drogue, eh?

LOL, that's for sure!

[Seaworthy Lass]

I emailed Wilhelmsen in Norway today regarding splicing Acera and received a prompt reply with a detailed pdf attached. I will try and work out later how to attach it here.

A brummel lock was not suggested, instead the base of the eye should be stitched with Acera. Interestingly, unlike dyneema, the insertion of the needle needs to be through strands rather than between them.

I smiled looking at the diameters of Acera it covered: from 6mm to a whopping 96 mm.

SWL

[thinwater]

Originally Posted by Seaworthy Lass

Thanks for the feedback.

I have no opportunity to test out a series drogue made with UHMWPE before making one and I imagine the same applies to most cruisers, so I need to rely on what others report. Yours is the first really negative report on handling issues.

I guess for me if retrieval is slow, at least it is not likely to be unsafe, as it will be occuring when conditions have calmed. I am of slight build and not very strong and I think deployment of a 50+ kg drogue in survival conditions would be more of a problem for me.

SWL

Actually, I wrote and meant to practice with ANY drogue or anchor under load (no fair using the engine). Try breaking out an anchor without using the windlass. In a nutshell, it is very difficult and potentially dangerous to do anything where you actually have to handle moving Amsteel under load, because there is no grip. It will take twice% as many turns on a winch or cleat to hold. line grabs won't work.


Just buy enough for a bridle leg or some such and try it as an anchor leader for a few weeks. This is a minor investment in research. Tell us if you like it. I have my suspicions your opinion may change. You can always cut the test piece up for soft shackles, which we do like.

[Seaworthy Lass]

Originally Posted by thinwater

Actually, I wrote and meant to practice with ANY drogue or anchor under load (no fair using the engine). Try breaking out an anchor without using the windlass. In a nutshell, it is very difficult and potentially dangerous to do anything where you actually have to handle moving Amsteel under load, because there is no grip. It will take twice% as many turns on a winch or cleat to hold. line grabs won't work.


Just buy enough for a bridle leg or some such and try it as an anchor leader for a few weeks. This is a minor investment in research. Tell us if you like it. I have my suspicions your opinion may change. You can always cut the test piece up for soft shackles, which we do like.

Thanks for the input. It is very appreciated. This is such a new area that discussion is very helpful.

I need to preface my comments by saying that I have no personal experience with the series drogue. I am only going by experiences reported by other cruisers.

Firstly, I agree Amsteel alone can't be winched under high load. From the reports I have read though, the retrieval loads are not high if you are not sailing/motoring. Also, having the cones attached to the line provides grip otherwise not present. The line needs to be tailed, but retrieval is not difficult once you have the cones around the winch.

The key is apparently to have a line from the end of the bridle to the boat so that the bridle can be winched up and the line with the cones attached can be looped around the winch.

I think simply trying to winch bare Amsteel line under high load does not simulate the same scenario.

SWL

[N1774]

SWL Why did you go for the tapering sizes rather then the whole length at 12mm or 10, or whatever is needed?

[Seaworthy Lass]

Originally Posted by N1774

SWL Why did you go for the tapering sizes rather then the whole length at 12mm or 10, or whatever is needed?

Cost .

[thinwater]

Originally Posted by N1774

SWL Why did you go for the tapering sizes rather then the whole length at 12mm or 10, or whatever is needed?

Also because "what is needed" varies with the position on the drogue. The design has always assumed a tapered rode.

[N1774]

Originally Posted by thinwater

The design has always assumed a tapered rode.

Can anyone point me in the direction of the original design documents? I don't see any explanation for a tapered rode in the USCG report, there is info about the design & attachment loads that is linked to regularly. I assumed that the taped rode is cost saving - rather then structural.

N

[NevisDog]

Originally Posted by N1774

... I assumed that the taped rode is cost saving - rather then structural.

Reducing the diameter of the tail saves unnecessary cost and weight, but extra weight-saving seems insignificant with dyneema/acera (not so with nylon) - so yes, cost-saving seems all that is left.

[kmacdonald]

It's obvious that the load increases as the number of cones increases. Using only the minimum strength rode required reduces cost, weight, and stored size of the drogue. It will therefore make it easier to deploy. The more sections you have with varying diameter rodes, the more splices you have so that needs to be factored in. IMHO dyneema is the way to go for weight and size savings. It's abrasion resistance and lower internal heat build up under load is also a huge plus.

[Korvessa]

Originally Posted by Pauls

The advantages of dyneema type rope for bulk and weight savings are significant. However, if you read Jordan's write up on the development and final design of his drogue, the primary target for the drogue is to prevent the boat being accelerated to a speed high enough to allow pitchpoling while keeping the stern to the waves. In other words it is designed for heavy wave impact. He used nylon rope for a reason which he describes clearly - to give enough spring to allow the boat to initially give to the wave impact before slowing its forward speed. This reduces the impact loads on the boat.

In his charts he includes one for additional rode strength required for less springy lines. If you choose to use a line as stiff as dyneema it would be a very good idea to apply that data. Under conditions of a heavy wave impact the loads on the rode will be significantly higher and the rode should be sized accordingly.

Also, and this is really important, the hull attachments will also need to be designed for these increased loads. Hull attachments built to Jordans original specs for nylon line will be understrength when using dyneema.

I'd suggest that a rode with some length closest to the boat made of nylon - perhaps 1/4 of the length, and the balance made of dyneema might be an ideal design. Loads on the rode diminish further from the boat because there are less cones pulling. The springiness of the nylon therefore becomes less and less important towards the tail.

I like the idea of reducing the bulk by using high-tech line, but the above concerns are concerns I share. Stretch is, I believe, part of what makes the JSD work well. If you remove stretch, you could end up with shock-loads that could be much higher than expected. While it may not break the high-tech line, it's hard to predict how the sudden forces would affect the boat compared to the more gentle, and elastic forces of nylon or polyester.