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Member Since 03 Dec 2005
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Topics I've Started

bend radius with larger diameter dyneema

11 February 2016 - 04:30 PM

Hi all,


I see there was a thread about dyneema and bend radius recently.  We put that issue completely to bed for 6mm and smaller lines back last fall (because the loop is twice strength, a bend ratio of slightly better than 1:1 is full strength).  But John F continues to insist there is some sort of scale effect that changes/reduces it in larger diameters.  The industry does not agree with him, but it has been an 'unresolved' question. 


So, to put it all finally to bed, I am (just organized today) hiring an independent test lab to break 15 samples at different bend rations and throat ratios with 12mm heat set line.  They need to build a jig to easily change the bend ratios, and I need to order the line and splice up the samples, so it will probably be about 5 weeks before I get results back.


BUT . . . the head of this testing lab is a true rope/line expert -  the technical director of the Cordage Institute in addition to doing state of the art industrial cordage (they are working on NASA parachute lines today) since 1974.  


I was talking with his son, who has been with him since 1978.  When I explained why I was doing the testing he said in passing: 

"Not sure who your “expert” (which is how I referred to John F when I explained the situation) is on Dyneema, we fabricate large diameter dyneema lines everyday that are used in the Overhead Lifting industry and based on our and Cortland’s extensive testing we have no problem in recommending a 1:1 D/d  configuration in the eye.  We generally have not seen any significant reduction in strength going as low as 1:1."  


In any case, I will report back on results when we get them.





'new' product idea for sailing - Molle gear

05 February 2016 - 11:43 PM

I have been playing with outdoor/shooting gear recently, and it has mostly all converted to the Molle approach - which for those of you who have not used it is a modular load carrying system adapted/specified by the military (officially in 1997, but really not rolled out until after the 2001 wars). 


It is lightweight and completely non-corrosive/non-rusting/non-magnetic - so pretty much perfectly designed for sailing.


It allows you to completely customize how and where you can carry gear (from knives to flashlights to plbs/pAis).  It would make total sense of PFD's, harnesses, foul weather gear, fanny bags, and gear bags.  A huge assortment of different sorts of pockets and holsters (flashlights, phones, knives, etc) are already available (although the sailing brands might want to sell their own at 'marine' price premiums), so what the sailing brands need to do is build the Molle base webbing pattern onto their gear.


Given all the various gear we are told we should carry for 'safety' it makes total sense.


Taking it to the logical extreme, which the military has, Ideally I could see a base harness/mesh vest with molle system, which could the mount any of several optional PFD systems and any of the other other safety gear in whatever location you prefer.  But you could usefully 'start' just by adding the molle bases to existing gear.


As an aside, while talking about this gear, it is also interesting to look at military "rigger's" belts, as a really simplified 'harness' for tethering yourself to the boat.  There is some neat 'high strength, quick release' buckle technology that's been developed. 


Seems to me that the sailing gear is now about 20 years behind the military developments in load carrying gear.