Dynex Dux pull test- preliminary results

Discussion in 'Sailboats' started by Gashmore, Nov 16, 2008.

  1. Gashmore
    Joined: Feb 2008
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    Gashmore Junior Member

    Finally got everything together to start testing the Dynex Dux as standing rigging. It has been a learning experience. I was set up for testing metals and concrete and while the principle is the same the instruments required for testing rope is considerably different. The first thing I realized is you can't glue a strain gauge to a rope. :) Second steel is a homogeneous material so measurements can be taken on a very short section and applied to the whole. Braided rope must be measured over a long distance to eliminate the effect of local variations.

    I followed the Cordage Institute's specification CI1500-2 as closely as possible but tried to include some additions related specifically to standing rigging. It took some time to assemble the equipment needed to produce reasonably reliable results without spending a ton of money.

    John at Colligo Marine provided a sample of new 9mm Dynex Dux terminated with Brummel splices around deadeyes. At my request the sample was left in “as spliced" condition without pulling out any splice set. Pin to pin finished length at a reference tension of 10lb was 82.125”. Gauge length on the undisturbed section was 24”.

    My normal test rig can only handle 24” so I welded up a framework of 2” heavy wall steel tube 12’ high and mounted the 4"x8” hydraulic cylinder from my tube bender in the base. The pump was geared down to get a piston rate of 1” per minute.

    Gross pin to pin measurements were done with a digital readout borrowed from my milling machine interfaced to my laptop. The undisturbed section was measured with a 1" range LVDT position sensor (Macro Sensor GHSD 750) with a resolution of .000026". Tension was measured with a 10,000lb Dillon dynamometer and secondarily was recorded to the laptop through a pressure transducer (Hydac HDA3774) on the hydraulic cylinder calibrated to the dynamometer. Sensor output voltages were fed through a National Instruments A/D interface to the laptop and monitored with two digital multimeters.

    The pin to pin data was used for the first pull to get an idea of the splicing set. Pulled to 6,000 lb (25% of MBL) the initial overall elongation was 6.65" including .125" in the undisturbed section. Relaxed to 1,000lb and left for 30 minutes .62" was recovered pin to pin. (I am sure this will vary with the diameter of the line and skill of the splicer.) On subsequent pulls it was used to estimate the elongation of the test unit as a whole. In the undisturbed section all but .010” of the .125” was recovered when the tension was reduced to the reference 10lb tension indicating very little construction stretch.

    After the first pull the rope was cycled 50 times to 20% of MBL then twenty pulls were done with dry rope at 68F. The average elongation of the undisturbed section was .00076 in/in/1000lb. This number varied from a maximum of .00079 to a minimum of .00075 trending lower as the testing progressed. This was somewhat better than what I had estimated (.00084 in/in/1000lb.) by interpolating from the Strong test on 13mm. This is probably because the orientation of the fiber is slightly closer to the load direction as the line gets thinner. Estimating from the new chart on the Colligo web site I see we are pretty close to what Hampdijan is saying. (1.7" over 600" at 4,000lb works out to .00071 in/in/1000lb)

    To get an idea if exposure to rain typical of standing rigging has any effect I am going to soak the line in fresh water for 24 hours and repeat the test next weekend and will report back.

    From these preliminary results 9mm Dynex Dux exceeds the specification of 5/16 1x19 but creep is going to be the controlling factor. Still working on a control to maintain a stable hydraulic pressure over several months for the creep test but should have that solved in the next week or so.

    To be continued...

    Glenn Ashmore
     
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  2. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Nice work!
     
  3. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Some promising results, Glenn. Looking forward to hearing more as you continue this series of tests.
     
  4. Bertil
    Joined: Feb 2006
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    Location: Sweden

    Bertil Junior Member

    I have a 40-footer (ONE 40) and I have used those lines from Hampidjan as standing rigging for two season and is very satisfied with the weight safed aloft and by the handling compared to rod as we dismast every season here in Sweden. My boat weighs 5400 kg is very wide 4,5m and have water balast of 700 kg on each side, so it is rather stiff.
    The only thing I had to do the first season was to shorten them a bit because the splices get packed. It is an easy job to move the splices a bit.
    The weight saved a loft is over 20 kg, and the price if you do the splices yourself is aboat the same as a rod-rig.
    Greetings
     
  5. Gashmore
    Joined: Feb 2008
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    Gashmore Junior Member

    Creep test update

    Well, this is about as exciting as watching paint dry. I have had this 9mm Dynex Dux under 2,000 lb tension (8% MBL) for 60 days now at a constant 80F and have seen only .01" of creep over the 24" gauge length. I am going to up the load to 4,000 lb for another 30 days and see what happens.
     
  6. jmolan
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    Location: Mexico/Oregon/Alaska

    jmolan Junior Member

  7. jmolan
    Joined: Dec 2008
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    Location: Mexico/Oregon/Alaska

    jmolan Junior Member

    Hey Lighten Up!

    Gashmore, just in case you have not built your chainplates and deck fittings yet. ...take a look....I am working on this sort of thing. After the gains and fun I am having with the rig up above, I am on a mission to tacklle the deck also. So far so good. "Softie" hanks and shackles, chainplates and deck tangs coming. The weight is just coming off and the boat feels so much better motion and speed wise....:) Get your Dux in a row!

    http://www.equiplite.com/2009/Frames/equipliteproducts4.html

    Updated photos at: http://s30.photobucket.com/albums/c305/jmolan/Alaska stuff/Synthetic Searunner/?start=all
     
  8. Gashmore
    Joined: Feb 2008
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    Gashmore Junior Member

    To late for the chain plates. They are carbon composite integrated into the topsides and deck. I didn't want to worry about leaks.
     
  9. mxsailor
    Joined: Oct 2006
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    mxsailor Junior Member

    chainplates

    Wow. Show me! Have pictures?
     
  10. jmolan
    Joined: Dec 2008
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    jmolan Junior Member

    MX sailor, I am in San Carlos also, give me a call. 226-0968, I have all kinds of synthetic rigging already up and running, just returned from 6 weeks on the baja side......:)
     
  11. jmolan
    Joined: Dec 2008
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    jmolan Junior Member

    Been some good happenings all over the world with Dux rigging. Check out this link.

    Will be a fully rigged Dynex Dux Westsail at the Annapolis show if any one is interested.

    Check out Nigel Calders write up in Sail magazine recently. Fiber rigging is coming of age...!

    Hey Gashomore, any more news on the testing?

    http://www.colligomarine.com/
    http://www.strongrope.com/news.htm
     
  12. tspeer
    Joined: Feb 2002
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    tspeer Senior Member

    I went with Dynex Dux for my shrouds at my last haulout. I'm pretty happy with them, except that the rigger didn't allow for enough creep. The cap shroud terminals are right down on top of the chain plates and have no more takeup. In chop, I can feel the rig jerking as either the leeward shroud or the forestay goes slightly slack. I need to get the shrouds shortened up a bit.
     
  13. jmolan
    Joined: Dec 2008
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    jmolan Junior Member

    That is no good...:-(

    I suspect (without knowing for sure) that you are suffering from "constructional stretch".

    A 12 braid will relax from handling. We have found you need to make up the first splice, then pre-stretch it to realign the fibers, before you take your next measurement for the second splice. If you do not do this, you will get up to two inches of constructional stretch after you mount the rope and put the tension on it.

    I have a couple questions if I may:

    What size and length did you use. What kind of attachments did you use. what kind of boat and rig? Are you using turnbuckles or dead eye set ups?

    It is not difficult to re-splice Dux, I have done it a number of times.
     
  14. Gashmore
    Joined: Feb 2008
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    Gashmore Junior Member

    Sorry for the delay

    I got so bored waiting for this d*#ned stuff to creep that I lost interest back in May. :D I hear the hydraulic pump kick off for a second or two every now and then so it is still holding and the data loggers are still running. I will download them this weekend and let you know what I find. Should show something because it has been 90F+ in the shop for most of the Summer.

    I think you must be right about Tom's stretch. Even though Dux is pre-stretched there is still a little construction stretch left in it if just from handling and splicing. If you don't get out that stretch before settling on a finished length you can exceed the available room for adjustment as the fiber sets in.
     

  15. jmolan
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    jmolan Junior Member

    Gashmore, hope the boat building is creeping along better than the Dux test. I look fwd. to the data you have compiled....should be interesting

    I am currently doing a complete rig for a 34' Trimaran using all 7mm. I will be sure to put a load on the ropes before I make the 2nd splice in each. I did not do this on my own rig, and ended up taking up maybe 2" over the next few months. It has stopped now and is "rock hard".....:)
     
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