Let me start with saying again that I like the idea of synthetic rigging a lot, incl. going back to deadwoods. I am one of those who replaces shackles with spectra lashings, I have vectran halyards, spectra lifelines
and so on and I do everything myself.
We replaced all the rigging in 2005 with Jonas from Trinidad Rigging and I was his apprentice during that time; swaging my fittings and putting on my Norseman fittings etc. Jonas told me what books
to get about rig tuning and we tuned our rig together. I think I now know all there is to know about the rig on Jedi, which is more advanced than most cruisers.
We selected Samson Amsteel Blue 1/2" for our runners, which aren't really runners because they go all the way up to the masthead. They are used for trim (mast bending) and for high wind
running as we don't have backstays on either mast
. I love the new runners; all the problems we had before, like a retracted one wrapping around an upper spreader or slapping the spreaders cutting into the aluminium, are gone.
Now about Dynex Dux (I'll call it DD). What I write here is not to attack you; it is to explain why I think your website shows the wrong information. If you have better information, you should put that on your site instead of what's there now, not tell me to ask a quote to get the right information. I will ask a quote when I am interested in buying very soon, which I am not, so don't use your commercial
skills on me, use your rigging knowledge.
Since your boat has extremely high static loads, your limiting parameter will be Creep.
Why do you write that? (I assume you are a rigger because you post like you know everything about this) You know that this is the normal on every boat with a fractional rig or aft-swept spreaders, there is nothing extreme about it! The pre-tension should be 20% of breaking load
. It can even be increased up to 25%
if the forestay still sags at 20%. For masthead rigged boats, which is most of the cruising boats, it is a little less: 15%
. I am well willing to exactly explain why this pre-tension is needed (absorb shock loading, reduce masthead movement to leeward by 50%) but you know all that.
So, my Bridon 12mm Dyform has a minimum breaking load of 31,746 lbs so my pre-tension is 6,350 lbs. Every boat with 12mm Dyform capshrouds has at least 15% = 4,762 lbs pre-tension.
We are a bigger boat than most, so let's look at something smaller: 3/8" capshrouds of regular 1x19 with a conventional masthead rig. The pre-tension should be 2,171 lbs. If it's a fractional rig, it will be 2,895 lbs.
Now we get to the question which DD we must select for that. We should select for stretch and creep you write, so let's do that. Stretch is similar according to your data so we have to look at creep. Now, what is reasonable? 1/2" per year? I can live with that.
So let's look at the graph for creep. to keep under 1/2" creep on a 50' section you get the following static loading:
7mm: 750 lbs (5% of breaking strength)
9mm: 1,500 lbs (6.25% of breaking strength)
11mm: 2,450 lbs (6.65% of breaking strength)
13mm: 3,500 lbs (7.14% of breaking strength)
So, for a masthead rigged cruiser with 50' long 3/8" capshrouds, 11mm DD is good and for a fractional rigged cruiser with 50' long 3/8" capshrouds you need 13mm DD.
If the masthead rigged cruiser has capshrouds 70' long it needs 13mm DD and if the fractional rigged cruiser has 70' capshrouds it needs more than 13mm but all data above 13mm is missing.
The masthead rigged cruiser increases shroud
diameter by 15.49% and saves 75% weight (your site states DD weighs 1/6th the weight of wire so which wire is compared to which DD for that?! For rigging it is 1/4th in this case). The fractional rigged cruiser increases shroud
diameter by 36.48% and the weight savings are unknown because the weight of DD is missing from the pages.
As the Colligo page is now, you need a boat with capshrouds of max. 3/8" (or may be 10mm) that are less than 70' long or there is no data for you.
So, who told me that creep is okay when staying under 20% of breaking load? Ah yes, JMolan: I hope you selected well under 10% for yourself or you will be tensioning weekly and re-splicing after a couple of years!
What do I want to see on the Colligo page: The following specs for DD:
breaking strength. That is 15% less than the current values I guess? (American specs are often 15% higher because they don't specify minimum breaking strength but some average or something which is utterly useless for rigging)
- stretch diagram up to SWL plus a 2nd one up to breaking load
- creep diagram up to SWL plus a 2nd one up to breaking load
- weight per 100' or whatever.
And this should be listed for sizes up to 16mm, or so that at least boats with 1/2" and 14mm shrouds can find the info they need without asking for a quote.
Ah, I almost forgot: about the stretch diagram. Read the small print, the graph is based on assumptions. You will need to put every size DD on a test bench, and measure the whole thing, not a single
strand. That is the data you must publish. At the same time you can test the "set" or constructional stretch and publish that too.