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Rope/knot/splice load testing


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#1601 allen

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Posted 06 August 2014 - 08:20 PM

^^ you probably know but you have to get an IR gun pretty close to read the temp of what you want.  The one I have is not very good and has an 8:1 spot size meaning if you want to measure a 1/4  inch spot, you can be 2 inches away.  I saw a guy on Youtube try and show that the tip of a knife heated with a belt sander didn't get hot with the same IR gun I have about a foot away.  I repeated the experiment and basically melted the metal on the knife red hot.



#1602 Estar

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Posted 06 August 2014 - 08:48 PM

^^ yes, thanks, I knew it needed to be close but have never seen any specs on how close (its one of the better fluke guns) - I also have 'measured' the temp of the pieces by simply pinching the piece with my finger, and gotten 'results' at least roughly consistent with my IR gun. I have also closely/microscopically inspected the slip surface after the tests and not seen any obvious signs of melting.

 

In my above post I was really trying to say that (1) I had measured tried to measure temps, (2) my measurements were very very crude, (3) I don't think I am getting much of the piece very hot (not near melting point) but I don't know (and cannot know with my equipment) about temps right at the slip surface.



#1603 allen

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Posted 06 August 2014 - 08:54 PM

^^ I never tried to measure the temperature but I did get smoke and where there is smoke...



#1604 NHRC

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Posted 06 August 2014 - 09:31 PM

I have done a lot of break testing for super yacht running rigging. Up to 46mm sk90 cores. We noticed huge temperature differences thoughout the line at load points and around the ends of tapers.

As you say the surface physically feels warm, but we noticed that the inner core had heat damage/melting, so we can presume that inside is a lot hotter.

I am just a humble rope pusher but I guess when a line takes load it has to expell energy in some direction and heat would be an obvious transfer.

I have seen broken mainsheets from large 180ft super yachts where at the most used point, the prefeeder from the captive winch, the rope looks brown and scorched and the core is glass like.

We also noticed that the part of the rope that went through a prefeeder or fairlead on a sheet was at only 30% of its original break load. Where as the spliced end was still capable of taking full load.

We were testing a variety of ropes at a commercial hydraulic test centre in Southampton uk.

Our results were very consistent and overseen by the manufacturers.

#1605 Estar

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Posted 06 August 2014 - 10:05 PM

^^ interesting. Thanks. I wonder if this is one area where things get worse with scale. . . . More heat at a thin surface boundary and more rope mass insulating that heat from dissipating?

I never saw any smoke, nor any discoloration in my test pieces. Some of this would also depend on how fast you pulled. Because of Brion's comments early in the thread I always pulled moderately slowly, keeping within the official test spec, but in the "real world" loads often come on much faster than this.

I am aware of the heat issues related to smoking a highly loaded line around a drum, and the rope MFG's have developed special covers for those applications. I guess your pre-feeder location heat is also from external friction? Some of which apparently bleeds into the core? The bend radius results suggest you could also be getting internal fiber on fiber friction even in a 20 degree deflection. Would water cooling help?

This is an area which would require significant lab gear to test/measure properly/carefully. My personal judgement is that while it is obviously relevant to super yachts and the powerful end of racing yachts, it is probably not a major factor for most of us. Unless anyone has a clever suggestion it seems beyond my capability to make internal measurements in a highly loaded piece.

#1606 olaf hart

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Posted 06 August 2014 - 10:17 PM

The larger the diameter, the less surface area per unit of volume, so the size argument makes sense.

Except that the material is a poor conductor of heat, so it might not be operating with sudden loading.

#1607 allen

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Posted 06 August 2014 - 11:40 PM

^^ My testing was with 7/64 line but I pulled fast.  I would get a puff of smoke as the knot failed. If I pulled slowly, the knot would hold.  Pull speed is a very significant variable.  That is where I took issue with the Water Bowline testing on youtube. They pulled very slowly and it held.  In my testing it slipped and the extra tuck I took kept it from slipping.

 

There are many variables here and different modes of failure.  The way you test can determine if you excite some of these failure modes or not.

 

I have another sub topic and will post it shortly.

 

Allen



#1608 allen

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Posted 06 August 2014 - 11:47 PM

I installed some dynamic climbing rope on my traveler with great success.  Shortly after installing it, I handed the tiller to a mate and we soon after did an accidental gybe.  The last one I did split the boom (wood) but this one did no damage.  Now I can gybe faster without worry. It is a wonderful change.

 

But in the last race this orange line shed many parts of its cover and I had orange bits all over the deck.  Some of the line is down to the core.  I race once a week so this is likely the 11th race. Each race is just a tad over an hour.  The word on this when the idea was posted was that Stan Honey used this on a race to Hawaii.  Either he didn't adjust the traveler much or there is a lot of variation in the cover of these dynamic lines.

 

I still have a lot of new orange line as I bought way more than I needed due to the shorter line needs of a traveler vs a mountain climber.  When I run out of my orange line, I hope someone can help with what I should be looking for in a replacement.  @thinwater, are you listening?



#1609 Essington

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Posted 07 August 2014 - 01:37 AM

Estar, I'm also curious about the NER testing as they are using NER product, so that likely means Endura (the stuff I've been using), or maybe STS HSR (NER's version of dynex dux, the stuff I'd like to be using ... If I could get some).

Ego, none of my shackles actually move against their metal counterpart in use, so there is no chafe on the shackle, and no wear on the beckets. In the major load areas, the soft shackles have a much higher breaking strength than the metal does, so I'm comfortable with my safety factors even over the square corners. I could probably radius those edges, but I've not felt a need to yet.

#1610 Estar

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Posted 07 August 2014 - 01:58 PM

A, I have been using dynamic line a decade in both my traveler and anchor snubber. My trav line has the equiv of 10's of transpacific on it. The only time I have suffered any cover damage is chafe on the snubber in a hurricane (Lenny). So, I would suggest either the stuff you got has a particularily vulnerable cover or your trav set up is particularily hard on it. Unfortunately I got the line so long ago I don't remember specifically what it is, but it is Beal brand.

Ess, brion and NER were testing the STS line. Part of the objective was to answer some questions raised by an odd colligo dux failure, but (of course) NER preferred to test their own heat treated line rather than dux.

#1611 allen

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Posted 07 August 2014 - 02:42 PM

A, I have been using dynamic line a decade in both my traveler and anchor snubber. My trav line has the equiv of 10's of transpacific on it. The only time I have suffered any cover damage is chafe on the snubber in a hurricane (Lenny). So, I would suggest either the stuff you got has a particularily vulnerable cover or your trav set up is particularily hard on it. Unfortunately I got the line so long ago I don't remember specifically what it is, but it is Beal brand.
 

That is good to hear. I think the damage was likely done by the cam cleat.  It is a Harken 150.

 

The rope is Sterling Rope Evolution Duetto Dry Rope 8.4mm.  The damage was building but was minimally noticeable until this last race.

dynamic_rope.jpg

 

This next picture was taken before the dynamic line was installed.  The traveler is 5:1 with the block on the rail making the first turn.  There is teflon "million dollar" tape over the screws on the bronze half round.

 

traveler.jpg



#1612 Estar

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Posted 07 August 2014 - 04:15 PM

^^I agree probably the cam cleat. I have a line driver in my system, which may be a more gentle hold (but my trav loads have to be much higher), rather than cam cleats. The rest is much like yours.

Did you have no problem with cover wear before the climbing line? I had always understood climbing line had tightly woven very durable covers compared to sailing line . . . . But I could be wrong.

If I were you I would talk to both harken and beal about suggestions.

#1613 allen

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Posted 07 August 2014 - 04:30 PM

^^ I had no problem with the traveler line before switching over to climbing line.  I used some old line I had around that was probably 50 years old and yet no issues.  I have enough of the climbing line to make a couple more control lines but when that is gone I am sure not going to use the same line.  The cover is tightly woven, much tighter than yacht braid.

 

Allen



#1614 Estar

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Posted 07 August 2014 - 04:39 PM

Interesting. Beal will probably be able to give you some insight into cover durability, as that is important for climbing line. I will be curious what you learn. The stuff I have has worn like iron . . . More abrasion resistant in the snubber application than "yachting" line.

I wonder what sterling would say if you showed them your pic of their product. It's not an application they design for, but I still expect they would be surprised it shredded like that so quickly.

#1615 allen

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Posted 07 August 2014 - 09:36 PM

^^ Sterling said they had never seen a line shred like that.  They suggested a different one of their ropes, Marathon, and also suggested using single rope instead of half rope.  I had picked half rope as it would give me almost twice the stretch for a given impact load.  

 

Half rope has 31% stretch for 110kg shock load

Full or single rope has 36% stretch for 220kg shock load

 

Harken had nothing to add.  Thinks the cam cleats are pretty easy on the line.

 

Sterling might be sending me a sample.  He offered 10 meters and I need 12 so we will see.

 

I need to check that the teflon tape didn't come off.  That would be an easy explanation.  Especially given your 10 year use without issue.  I will check Saturday.

 

Allen



#1616 allen

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Posted 10 August 2014 - 02:37 AM

^^ The million dollar tape was gone and there were some edges that might have caused some problems but nothing obvious.  I spent a couple of hours cleaning things up, did some filing and sanding and reapplied the teflon tape.  Hopefully this new line will last as long as it has for @Estar.

 

Sterling is sending me a couple of different samples. I will test them and write up what I find.

 

Allen



#1617 Estar

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Posted 12 August 2014 - 12:08 PM

By the way . . . . several people have asked me about the durability/chafe resistance of the soft shackles in 'chain hook replacement mode'.  Here is a photo of one I used all this year, including in some decent strength wind up in Labrador and Greenland.  It's dirty but pretty much no chafe or wear.  This is one of my earlier 'simple stronger' designs.

 

Attached File  photo.JPG   147K   32 downloads

 

 






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