Should I use Dynex Dux?

[Gashmore]

Until about a week ago I was sold on going to Dynex Dux standing rigging for my 45' monohull but I have had three different riggers trying to talk me out of it. From what I have found so far I think if the pre-load is kept under about 7-8% and the line is sized so it never sees more than 20% I won't really have a problem with creep but these guys have looked at the Hanjidan site and say they don't like what they see.

I have to admit that the available technical information is a bit sparse. Even allowing creep not to be a big problem stretch under load makes a big difference. I asked someone at Hanjidan Canada about an elongation (Young's) modulus so I could get some idea of dynamic stretch and all they could say was it stretches about 3%. But 3% at what load? Surely not at 20%. 3% on a 60' cap shroud is almost 22". How do you compare an N/tex of 120GPa of Dynex Dux to an E of 107GPa for 1x19? If I knew the denier of each line size I think I could figure it out but nobody can tell me.

I guess I am just a congenital engineer. I like hard data more than sales talk.

[Brian Duff]

What kind of boat and what rig ? I don't recall an earlier mention of it. Have any of those three riggers set up a boat with Dux yet?

Look forward,

[Gashmore]

It is a 45' x 14' masthead sloop. Intended as a live aboard Caribbean island hopper with good performance. Non-overlapping jib I =58.75' P=53.85" J=17.25' E=20.27 RM30 = 60,000

These guys are experienced riggers working primarily in rod and 1x19. I don't think they have been exposed to any fiber rigging other than maybe one replacing a set of PBO. They seem to be equating Dynex Dux to Dynema/Spectra.

[Brian Duff]

My feeling is that, given the design or your rig (you mentioned triple spreader in an earlier post) and the fittings that are likely on it, you should stay with Rod or wire rigging.

While the dynex works fine, and creep is not a real problem on simple rigs, your mast requires a much more percise tune. It would be easy , given the lack of information available, to use the wrong size of dynex for, say, the intermediates and end up with the upper creeping way out causing the indtermediates to bear too much load ... this is just speculation though, I have only fit dux to single spreader rigs , where it works fine.

What type of mast do you have (trying to figure your end terminations and spreader design).

There certainly is merit to the DUX, especially in the Caribbean where stainless has such a short life !

[Gashmore]

Sorry for the delay. The mast has not been ordered yet. I want to make a final decision on the standing rigging before I commit so other than the composite chainplates (2 for V1 &V2 and 1 for D1) I am not limited. I don't believe I am locked into tripple spreaders either if doubles would be easier to work with. OTOH, the additional weight of a stiffer mast might use up all the weight savings of the Dynex.

BTW, I have done some deductive analysis on the stretch factor which I will put in a separate post.

[Brian Duff]

Gashmore ,

You have listed a beam and RM for your boat, along with rig dimensions, but I would like to know what type and model of boat you have. Are the chainplates all the way outboard?
Why does it have no spar now ?
Where is the boat in the Caribbean ?

How will the boat be used ?

with that RM and the beam and the I you listed, we could do a good Dynex rig I think. You should consider actually hiring a rigger to help you with this design and planning, as well as the construction and rigging of the boat. The fittings available for Dynex will not work with standard mast parts.

Are you coming to Annapolis for the show ?

[Gashmore]

The hull is cedar strip/composite. Designed by John Fox and based on a de-tuned Nelson Marek 46. Builder is yours truly and currently in my backyard here in Georgia. Expected launch date Summer 2008. Web site is www.rutuonline.com. I have not had time to update it is some time but it will give you an idea of the project.

Composite chainplates are laminated into the topsides, The boat will be used for Caribbean island hopping 6 to 8 months a year and Florida/Georgia coastal during the hurricane season. I am talking to Selden and Charleston Spar about providing the bare spars and spreaders but I need to settle on the standing rigging method before I commit.

Being a numbers oriented engineering type I have built a spreadsheet based on Larsson & Eliasson but lack credible stretch figures for Dux. I did find a figure of .0012 mm/mm/1000Kg on Strong Rope's site and extrapolated figures for 9 and 13mm based on rope weight but not knowing exactly where Strong's number comes from I can't really trust it. I have asked Colligo for a sample of 9mm to pull and try to get some independent results. I am amazed that Hampidjan doesn't seem to have any stretch figures.

I am a hard core DIYer but will definitely seek professional help for the rigging. Waited to late to get a hotel room south of BWI so I will be flying up for VIP day at o'dark thirty. What booth are you in?

[Brian Duff]

Interesting Project.

I wish there was more rig detail on you website. I am interested in discussing what your doing, even if you don't need to hire someone to build it for you!

Do you have more detailed drawings on the rig plan from your designer? I hope so