GT said:
I really question why people use dynamic rope to their hand jammer, any dynamic loading on a toothed jammer is likely to severely damage the rope.
since you really question it i will form a response to this and your other points. i use dynamic rope on my hand jammer to reduce the dynamic loading on my toothed jammer compared to static rope, and thereby reduce the liklihood of rope damage or parting in an unplanned fall onto that jammer/rope combo. i understand there is a hazard of damaging the rope and i choose an accepted method to reduce that loading. i do not believe that 'any' dynamic loading is likely to severely damage the rope as you say. if that were the case there would be a lot more stories of broken ropes but this seems to be exceptionally rare.
In my mind putting a section of dynamic rope into the system gives people a false sense of security in that the dynamic properties of the rope will reduce a load on the jammer in the event of a fall and may protect the rope.
studies shared above show that dynamic rope *does* reduce the load in the event of a fall. it makes sense to me that this would help protect the rope. by the way i am not advocating using jammers in a planned way to catch big falls and like most people i really don't want to fall onto a jammer. but, slips on to jammers do happen in the real world and there is a very easy way of mitigating some of that risk with the method described. i don't think its a false sense of security but a considered approach to mitigating foreseeable hazards.
In my (simple!) mind it's easier to park that idea and use 5-6mm accessory cord and not even consider using a toothed jammer in a situation that could result in dynamic loading.
it seems you choose to dismiss the manufacturers instructions and put greater reliance on your own vigilance with an accepted increase in risk of human error that your non-standard use requires. thats a trade off you choose to make and i'm not forcing you to adopt any given system.
but there are foreseeable circumstances of dynamic loading onto a toothed jammer with the conventional setup that are somewhat outside of the users control. e.g. imagine prussiking up towards a bolt rebelay and when nearly there, the bolt fails, dropping you until the backup bolt takes the weight. could that occur with your setup and do you use toothed jammers? i believe it's worth considering.
further, imagine ascending a sloping traverse line that might be quite long. in that situation i would consider using a jammer on the sloping line with the aim of arresting any fall if i slip. would you consider that? likely the alternative would be clip the sloping traverse line with a cowstail and accept a zipline fall down to the next traverse anchor, and whatever uncomfortable landing might wait there. which is safer?
all the above assumes 'dynamic' load to mean any sudden loading of a rope that was previously slack, usually in an unplanned way. if you have a different understanding of dynamic fall to me then please share.