Dustin_B Posted July 18, 2003 Share Posted July 18, 2003 I got this question from a friend but I know very little about rope elongation. I tried doing a search but couldn't come up with anything (although I know there was a discussion about this awhile back). What are advantages/disadvantages of low rope elongation? What is 'unsafe'? Should this be a major concern while shopping for a rope? I kind of thought that stuff like a high impact force is more important (high meaning better)... gracias What do you know about rope elongation? I'm looking to buy a new rope but they [REI] only have one rope that is close to what I want. A 60 meter, 9.8 bi-weave dry rope for alpine use. Only thing is that it has the lowest elongation of all the ropes that I see. About 4.4%. They run from there up to 7.7% or so max. What do you think about that? I'm trying to decide why one would want a low elongation rope since the more it stretches the better it'll react in a fall. I wonder if a rope with lower stretch is not as 'safe' in terms of stressing pro or anything like that. Any thoughts on that. I'm sure the rope is fine for leading but just wondering what you thought. Quote Link to comment Share on other sites More sharing options...
Dru Posted July 18, 2003 Share Posted July 18, 2003 for the same impact force, the rope with lowest elongation is best cause it will stretch the least. less stretch is good cause it means you fall less distance when you whip and can keep u from decking or hitting a ledge or slab generally speaking though, low elongation = higher impact force and vice versa. what's the impact force of the rope in question compared to other ropes of the same diameter? Quote Link to comment Share on other sites More sharing options...
Dustin_B Posted July 18, 2003 Author Share Posted July 18, 2003 Impact force is 10.5 KN, elongation 4.4 % this rope Quote Link to comment Share on other sites More sharing options...
erik Posted July 18, 2003 Share Posted July 18, 2003 sounds like your friend is over thinking the whole process. fatter ropes tend to have lower elongation. the elongation is what is used to dissapate the impact force of the fall. who cares, buy the sale rope and retire it when it is done. too much thinking about gear leaves little brain power for the lead!!!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
Kevin_Ristau Posted July 20, 2003 Share Posted July 20, 2003 A Ropes's impact force is probably more important than elongation. A rope with a low impact force will transmit less force to the protection system, which is desirable when the protection or the rock is suspect. As Dru said however, a lower impact force usually means more elongation. Quote Link to comment Share on other sites More sharing options...
chris Posted July 20, 2003 Share Posted July 20, 2003 You should check out Beal's website. Their theory is that the lowest possible impact force is best. A low impact force=lower forces on climber, belayer, anchor, and gear. A longer stretch is the trade off. Mark Twight advocates this as well, in the his instructional book. Quote Link to comment Share on other sites More sharing options...
chriss Posted July 20, 2003 Share Posted July 20, 2003 Please note that the 4.4% elongation for that rope is "working load". That is for a static load. Dynamic (in a fall) elongation is way different. I've read that some climbing ropes can go into the 30-40% stretch range before parting. Impact load is important too, as said. But lower numbers are not always better there either. chriss Quote Link to comment Share on other sites More sharing options...
chris Posted July 22, 2003 Share Posted July 22, 2003 I was looking up some stats today to compare two 10mm, 60m ropes from different companies. I'm afraid Chriss has his information backwards. Dynamic load, in this case, was 7.1% versus 8%. Static load, however, was 30%. To me, this makes sense. To determine static load elongation, they simple keep pulling at the rope until it fails, versus a shock load. Quote Link to comment Share on other sites More sharing options...
chriss Posted July 23, 2003 Share Posted July 23, 2003 I'm afraid not. The "working load" elongation is done with a 80Kg mass, in a static load situtation. Meaning the mass is hung from the rope, NOT dropped on the rope. Sorry if I confused you about the breaking elongation. This can be done in either static OR dynamic loading. As both conditions can be made severe enough to break a rope. Dynamic stretch as measured in the fall testing is NOT "working load" elongation NOR maximum elongation at failure. chriss Quote Link to comment Share on other sites More sharing options...
chris Posted July 31, 2003 Share Posted July 31, 2003 OK, I'm a screwup (Mom was right) ChrisS had his info right on, and I had my head up my cork. Sorry 'bought that. I'm going to go have another Cheers Quote Link to comment Share on other sites More sharing options...
matt_m Posted July 31, 2003 Share Posted July 31, 2003 yeah - its an add for beal ropes indirectly but i think it's extremely good info http://www.impact-force.info/anglais/impact.html even more important for trad and big (+80kg) climbers Quote Link to comment Share on other sites More sharing options...
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