Dyneema backstay with integral SSB antenna

[poiu]

Originally Posted by estarzinger

...............
btw sorry to distract your thread with that detour above, was not my intention.

No distraction for me. I can tune out the noise.

Very helpful info. Thanks. It had not occurred to me the way 12 strand intertwines that each strand would possibly get damaged at some point.

I wonder if the explanation for why there is such a large variance in the life of 10 year old samples may have something to do with that issue. With some samples the strands will be consistently buried and sheltered from UV and with others due to a random movement in the braiding process at production they will come to the surface and sit in a position where they are vulnerable to being UV damaged. The samples with sheltered strands having higher strength.

A corollary of this is if it wouldn't be best to cover the rope?

I probably can pull test my own rope. I have access to heavy hydraulic equipment. A cylinder of the right size at the right pressure will apply a pretty predictable force. At what point does the constructional stretch stop? I would have thought a pull to 75% yield limit might be a good target. What do you think? 30tons+ is a pretty daunting load though. Will the constructional stretch not reset once the load is removed?

[poiu]

Originally Posted by Jesse

You have an interesting project. The only problem that I can see is the possibility of snapping the copper core if the antenna is attached to the masthead. due to the creep of the Dyneema. A loop or coil in the antenna wire once it exits the back stay core might handle that but loops and coils detract from an antenna's performance. You've a great idea here please keep us posted.

Copper pvc coated wire is really stretchy. It will easily cope. There will be no attachment at the masthead as the wire is to be buried in the backstay.

I'm sure no loop is needed. The wire will just elongate inside the backstay. It won't pull through anyway as it will be too tightly held.

[estarzinger]

Originally Posted by poiu

I wonder if the explanation for why there is such a large variance in the life of 10 year old samples may have something to do with that issue.

The braiding is clearly a variable, but there are a bunch of others (there is also a difference in the actual filament sizes and in the initial coatings on the rope, and there appears to be a difference in the flutter the ropes experienced). I'm trying to do a statistical analysis to unravel it all - I hope I have enough samples to get significant results.

A corollary of this is if it wouldn't be best to cover the rope? Yes, but the trick cover is not rope/braid, but a wrapping or sleeve with something thin/solid like the UV resistant version of Tedlar® - you can look at what the high end guys do to cover PBO stays as a best practice.

I probably can pull test my own rope. I have access to heavy hydraulic equipment.

Ah, nice . . . . a 50% pull will pretty much do it,
leave it on 50% for a couple hours (have to pump it up periodically as it stretches). It will mostly stay out, unless you disrupt it by coiling tightly - do a big diameter loose coil after you have pulled it.

............

[poiu]

Originally Posted by estarzinger

............

Excellent. Thanks.

[maxlynn]

I'm not well informed regarding the exact materials or termination mechanics, but I and many other racing boats have fitted synthetic backstays covered with a plastic coating. On larger racers (e.g., 70 ft) the antenna wire is buried within the assembly. On my boat, a 40 ft'er, the antenna wire (a #14 insulated stranded wire) the wire is simply taped to the backstay assembly. As was stated previously, it eliminates potentially problematic insulators and in my experience, performs at least as well. Durability has been excellent; mine has been in place for 12 years at shows vitually no deterioration. The only downside I've experienced is with the termination durability where the antenna wire is attached to the hi-voltage lead. There has to be a coil or slack to allow for the adjustment range of the backstay. That creates an issue of fatigue wear at that point. I'm sure that most rigging companies can fabricate such a backstay that will satisfy your needs.

[Boatguy30]

I have made several SSB antennas with 8 or 10 gauge wire inside a Dacron cover hung between the stern and a slight extension off the masthead crane.

I would recommend you run the wire up the outside of the dyneema and either heat shrink a cover on it or cover it with a Dacron cover. I would be happy to make it for you and ship it over.

On a side note, a rigging company recently pull tested a backstay made for a tartan 10 sailboat out if dyneema double braid. A 5 year old backstay in Chicago only had 50% strength. I was pretty shocked by that. I have yet to confirm if the mast was up the entire time or the mast was unstepped in the winter. Still maybe 1/2 the UV or less in Chicago vs the tropics.

[model 10]

My Amsteel lifelines failed after only 8 years. I had a barber hauler lashed to one of them , and it broke. UV damage.

[UNCIVILIZED]

Originally Posted by poiu

Thanks for this. I have spoken to John in the past and he was helpful, but he couldn't help with a full re-rig. Dyneema rigging can't do the discontinuous rigs in big sizes. I don't understand why. I put it down to not enough market to justify the risk in developing it, but I don't know.

Perhaps this is due to the availabilty, or rather, lack there of, of fittings for synthetic rigging which work with tip cup hardware? I'm very definitely curious to know more if you've more information.

Frankly, discontinuous rigging is a pain in the ass. Too many components to check or replace when rebuilding a rig. Exotic metals. Unique, & or unobtainable fittings, sometimes no longer in production. Many, many types of fitting designs, a lot of which aren't compatible with one another. And now that Navtec's gone, & I think, much of Lewmar (rigging) these issues will get yet more problematic.

Besides which, one almost literally needs a PhD to design, build, & or work on many such rigs. Including FEA software, etc.
Give me Compacted strand, & mechanical terminals any day over this: Please!

I'm not sure I can reduce the windage though anywhere without removing the bimini and going for a roll up dinghy instead of one on davits, compromises I'm not ready to make.

If you post some pics of your boat, plenty of us can take a look at cutting down on her parasitic drag. And a thread on such things would be very, very informative to many members. Plus I'd enjoy it as well. Given that like this one, it would be a good source of learning & information. Thus keeping the brain cells vital, alive, & growing.

[Viking Sailor]

Or you can go with a grounded backstay antenna:

http://www.cruisersforum.com/forums/...nna-41908.html

[jfranta]

take a look at any line. if there is airspace, or even less dense areas in the line then you will get some amount of constructional elongation as the strands tend to go parallel to each other under load. Dyneema SK75 is not heat stretched at the fiber level, like the newer chemistries beyond SK78, and therefore nests together better when heat stretched, cut a 7 mm piece of Dux with a sharp knife and you will see what looks like a single with 12 cells in it, it is that compact. This also contributes to some amount of elastic stretch. When the rope makers measure their line for stretch, they naturally cycle the line and even leave it at load for some time before they record their numbers, to set the braid. These issues become problematic when using the line for standing rigging, as you can imagine. We have tested most of the new stuff including DM20 from English braids, years ago now, but it even has more elastic stretch then SK75, in braided form. If you have too much constructional elongation it usually means you will eventually have to resplice with turnbuckles or use lashings and adjust them until the braid settles in. You can pre-stretch before you put it on the boat but then when you roll up the line to get it to the boat it will loosen again. SK75 Heat stretched is still the best in our book.

The 2x12 strands are smaller so they nest together better than the larger strands.

The Saga's are very tender boats and both owners of these boats have been ecstatic about the performance difference. 5 degrees seems large to me also, but we took over 40 lbs off the rig just on the uppers and intermediates.

We stand firmly behind our published numbers as we have rigged over 750 boats now successfully. Stretch is the number 1 design parameter. If you get that wrong it shoes up immediately.

Our stretch numbers are all generated in house on the Dux. The steel, carbon, aramid numbers, are mostly provided, although we have some PBO numbers from in house testing.

Originally Posted by poiu

That's good information, thanks. I can't see my heel angle being reduced much. That Saga 43 must be an unfeasibly tender boat if it reduces heel by 5 deg unless it is measured at extreme heel angles, but I suspect you don't believe it either in a practical sense.

When looking through the Gleistein catalogue they give the stretch at .3% at 10% load for all of their SK78 and DM20 Heat Set products and using that figure it can be easily calculated against the Navtec catalogue what the equivalent stretch is in rope to steel, yet in your website's stretch matching guide it gives equal stretch of steel rigging to ropes that correspond to much lower thickness than I calculate with. Dux is heat set and pre-stretched like SK78/DM20 and of higher stretch in fibre. Can you explain all that?

I looked at Gottifredi Maffioli's catalogue and they give a lower stretch for a given rope diameter the higher the grade of dyneema, so an SK75 being more stretchy than SK 78 or SK90. I don't understand why you say your SK75 has a lower stretch?

SK75 should also have a much lower creep than the other grades. Is that not an attractive attribute?

Why do the finer fibres of the 2 x 12 improve the constructional stretch?

Also what is meant by constructional stretch? I would have thought that the constructional stretch is virtually eliminated after pre-tensioning and heat setting and that nearly all that is left is the fibre/material stretch. Is that not so?

[jfranta]

Originally Posted by Guy

My Amsteel lifelines failed after only 8 years. I had a barber hauler lashed to one of them , and it broke. UV damage.

What size, what material, and how did they fail?

[Benz]

John Franta, while you're paying attention to this thread, may I turn aside to ask what you make of Marlow's MAX? It claims to be the same as Dynice Dux and NER's HSR. Have you played with it at all?
Thanks
Ben
Zartmancruising dot com

[model 10]

Originally Posted by jfranta

What size, what material, and how did they fail?

1/4" red Amsteel The line failed right at the end of a bury There was a lashing of 1/16" Samson string holding up a sheet block near there, flogging sail etc.

[jfranta]

Evans, sorry that you spent so much money to prove that you don't have to be as conservative with designs as we are. We have designed standing rigging for over 750 boats now over the last 10 years with no failures, so we might know what we are doing. Boats to 100 feet in length. Before we did this most thought Dyneema creeps too much, many still think this. Then the stretch paradigm that we have had to change. Yes, there have been learning opportunites with my company as always with the introduction of any new technology, but our large factors of safety have helped with the unforseen.

As I have said before I commend and value the work you have done. It has certainly been complimentary to the industry. You do not have to knock all that come before you and it makes you unprofessional at best. It really detracts from your work and it is a shame that you don't feel you can just stand on your own merits. Brion Toss has written several books on Rigging and to say that he has no technical knowledge is obsurd and says more about you than him.

Because of my experience, I don't agree with all you say and I do think that you advocate some dangerous paradigms, like a spliced eye with a whipping for standing rigging, when you can use a Brummel that is much more conservative and it will never shake out. Would you use a swage fitting on wire that relied on a whipping to hold it together for standing rigging? Have you ever seen a leeward shroud get shaken around? In this thread, you said Rod rigging has an almost infinite life? I bet that would make the Navtec (now Hayn) guys cringe!

Having said all this you are entitled to your opinion but you also have some legal obligations with what you say.

Originally Posted by estarzinger

It's just the truth John, which I hope is helpful for fellow sailors to understand.

My comment about you above was (I thought) balanced - I did say the guy would (probably) not lose his mast following your lead, which he might do DIYing it. If someone is looking for practical knowledge and experience with dyneema rigging you are one of the short list I recommend, but if someone is looking for engineering or technical analysis you are not (and neither is Brion - while he is absolutely terrific at many other aspects of rigging and ropework).

Brion has since accepted what I said and we have moved on, and worked on things together since. (the backstory here is that years ago Brion was asked by a magazine to tech edit an article I wrote. He said to the editor that I was all wrong and that they should not publish it. I said back to the editor they should get a qualified engineer to tech edit it, and we agreed on a Harken engineer, who after a review said I was exactly right and the magazine published it. That was long ago, and we have done good work together on for example soft shackle development since - where his button is the one I recommend most).

I guess you never have, despite my going to significant personal effort (and expense) to test the issue in question in depth and to help you better understand it. (the back story here is that John challenged a best practice paper I wrote for US Sailing on dyneema lifelines. However John was wrong in his criticism; as he had, and continued for a long time, to miss-interpret or miss-understand bend radius strength loss in loops.)

I have moved on, am only doing rope work development for the heavy lifting industry now, where there is more activity and the consequences are higher, and thus professional standards are somewhat higher than in 'yachting'.

[conachair]

Originally Posted by Benz

John Franta, while you're paying attention to this thread, may I turn aside to ask what you make of Marlow's MAX? It claims to be the same as Dynice Dux and NER's HSR. Have you played with it at all?
Thanks
Ben
Zartmancruising dot com

I've played around with marlow d12 max SK99, quite amazing stuff. Made a few small strops up which were attached to mooring warps in a very bouncy marina for a few months in winter in SW UK, went through the fairleads and one against a steel bracket on a spring. After a few months having a hard life with a 10t steel boat getting thrown about every time a storm came through they held up very well indeed for chafe, some threads chafed but only a little. Can't comment about UV, just says UV resistant on the web site. There was also some tech 12 technora which melted a bit, but still far from parting.