another annoying rappel question??

[Scott McCrea]

Looks like Gary is correct. Nylon Highway #9 has his article. Anyone can download the issue (and more) here: http://www.caves.org/section/vertical/nhindex0115.html

[gdstorrick]

Post deleted.

[puffadder]

It is me.The author of this question.I have to say something.damn it. what the $$#6 is going on??While the majority of locals were at TAG..I took a friend to curahee,and had him practice changeovers ,over and over and over...ok..so i set up a tr on no name,and hang my bluewater ii for the rope work.I rappelled from the top using the rack..with spacers.SON OF A %%^ IF IT DIDNT WORK!!!...iT FLAT OUT DIDNT.WAS VERY HAD TO OVERCOME...spacer idea is a flop.Ok..lets get down to it..I 'm thinking something is wrong.later on,I am doing changeovers,and the rappel is smooth.I had my friend use my rack.1st time for him .so changeover ,voila..no problems.I sent him up top..ascended..and then had him rap down using rack.Guess what?. He who is heavier than I am..also had great difficulty..conclusion..not convinced that spacers are the ticket.so,what is the problem here? backing up..even with abar dropped..was a real struggle.I am at the conclusion..could the rack be torquing??subtle tension..or is it the rope diameter.or even the rope itself?? bluewater ii..has stretch and is really close to dynamic as far as feel..but it also has a greater diameter..I believe this is 12mm....so..why is it that if the rappel is straight on,or straight down..no problem..but a slope ,or lip..problem....with this said..what is the safest minimum number of bars ?

[Marduke]

I have a feeling you need someone experienced to show you the proper techniques for rappelling with a rack. It may be bad techniques, a bad setup (wrong size spacers), rack attached incorrectly.

Moving at the lip on a slope is always different than a vertical rappel, since the forces involved are different. That's where technique becomes VERY important. If you rig your rack so you can back smoothly over the lip, you'll find yourself in a VERY dangerous situation of having too few bars for the decent, and you'll go into an uncontrolled rappel.

BTW, lines breaks and spaces would make your text much easier to read...

[NZcaver]

Marduke is correct. Advice and opinions are shared everywhere on the forum, but there is no substitute for proper training (in person) and hands-on practice. Especially when folks are trying something new.

I suggest trying to find some vertical cavers experienced with racks and spacers, and ask them about setting up some training/practice. Local grottos are a good place to start. Please be safe!

[puffadder]

Its all aa matter of repetition. I am not worried about it,none of this is a matter of life and death.In comparison to other devices,this one has the most friction.Comparable to drag coefficient..So then,the trick is..to overcome the drag. My friend actually said to add another set of spacers.To me,this is modifying something that ought not to be modified.One thing I noticed about the spacers,cant move that bar now even if I wanted to.thereby decreasing the racks potential.The problem I believe is Today,I was watching the rack torque on its long axis..To be honest,I prefer the drag.feel more secure.Bacl in the 80's I left the line to go to our bde recon.Pathfinder school ..and many many huey rappels later..falcon airstrip on bragg.One night in Feb..We did a btn jump,and recon went in on the previous sun.We rapped in on uh1h..(this was before the crashhawks came to bragg) 1982 or so..anyway..waiting on the left skid,ruck sack pulling..holding on with death grip..freezing,gravity wanted me so badly.Ater about a minute,I leaned forward to grab the deck on a downdraft,and when i did..I heard a faint click.All that back and forth motion actually was working the wrap over the gate.I am glad as hell I heard that.Moral of the story..many yrs later..fast rope in Panama,same thing different day.gravity.This rack problem is just a matter of technique.no worries.I am removing the silly spacers.ps..I always hated helicopter rappels..I hated jumping them too..although jumping from a blackhawk was infinetely better than a huey..anyway..Just gonna remove spacers and keep going.It will become 2nd nature.

[Marduke]

Removing the spacers will give you MORE friction. By adjusting the spacing of the rest of the bars, you can easily adjust the friction to anything you want.

But it sounds as if you have attached the rack incorrectly. I can't imagine any way your rack could torque about the long axis if attached and used correctly.

Also keep in mind, this is NOT something that you should be learning "by trial and error". This is something you should be learning from an experienced instructor.

[NZcaver]

Your rack is torquing on its long axis?? Weird and scary. What make/model is it?

Again, ditto on everything Marduke just said. Lose the spacers.

Learning by "trial and error" can get you killed! This is a little different from your experience in the military.... in terms of equipment, training, and philosophy (I also rappelled out of Hueys, and jumped from perfectly good aircraft).

[chh]

Technique is the problem here, or really worn solid bars, or someone drove over your rack with a truck.

Is it a solid bar rack or a U-bar? If it is a solid bar rack, are the bars extremely worn? Sometimes if you wear deep grooves in solid bars with a certain diameter rope, and then go bigger it can do funny things to the friction you might otherwise expect. Not to mention potentially mess up your rope.

Also, at a certain risk of crossing everyone here I'll go ahead and say that trial and error IS how we learn. And how we learn to anticipate how to approach different scenarios and assess risk. But, DO try to keep the errors small...

[puffadder]

u bar.nut to the right.what i say about torquinq is easy,its attached to a seperate screwlink on the harness..in motion the link and rack are pivoting to the left.remove the link and there is no pivot.with hand on the bars there is no pivot.It is all about the friction from this thing its unreal.Its new..steel.its with the 12mm that most of the difficulties lie..trial and error.? nope.not here.however.its like paddling.you have no idea if you can truly roll up in a v until you do.trial and error..is not the same as pilot error.Hey,no one be alarmed.There s so much experience here its not funny..nor am I wanting to be antagonistsic..I am not experienced with the rack .but it is my newest toy.The torque starts at the eye and adds twist.6 bars is just too much.and 5 is too when using the 12mm.so..my friend says''add another set of spacers.I say no.Negates the very reason for variable friction,so,going back to original configuration.the question I have is..whats the minimum safe number?.Let me tell you..One of my insane friends said''dude go with 2 bars.Its funny but I know what hes saying.Use the carabiner wrap for example.Take it even further.Beginners are taught the wrap on doubled rope...Get alittle nervy,you get curious..what happens if I reduce the number of wraps? Or even..what If 1 wrap on 1 rope?.Thats the same thing with the rack...experiment more..how many bars..4 ,3?? bet thats a matter of personal preference.but there really is a matter of safety..Anyway..screw all this..The bars themselves are thick.so when the 12mm is threaded there isnt much room for movement..5 is ok,but it is still the top bars..this u bar is striaght line.It works well with with my smaller diameters...how many of you reload? trial and error is the very key to finding the perfect round..the maximum safe load? find it.watch for signs of pressure along the way.ok??

[puffadder]

This is the situation in a nut shell.It is not being vertical thats the problem.There is no problem with that.adding,reducing as need be.No.It is the low angle stuff that leads up to the edge.or even the lip.trying to get in the ''l''is just plain tough as hell on 5 bars.Caution here.really.too much force ,could lose control...But I had a thought.It really may not be the rack at all.but the rope..so,heres a question..have you ever used the rack on a 11mm dynamic rope or larger? if so,was it problematic? If not..shit...I am at a loss.and will have to get someone familiar with this and watch.they may see something I am doing without knowing it.I swear though.The other day,close to the edge ,i had to really fight,why?? not even gravity prevailed.got to the edge...,got in position..and voila...let the fun begin.so ..rope daiameter,number of bars,.angle of terrain...its the angles below 60...like I am not heavy enough for the rope to feed through 5 . mabey not.145.This problem does not exist with any other device.I was originally going to buy a stop.I like them.but someone in the know talked me out of it..saying it really may not be reliable in mud,etc..''go with the rack''.I did.I like it.Can see its potential.

[Marduke]

Dynamic rope? The rack was designed for static rope, 8-11mm. Dynamic rope is far too stretchy with the wrong mantle.

From what you describe, your rack is attached incorrectly. A rack should be attached so you are looking at the END of the bars, and the opening should be down and away from your body, not to the right or left.

From the comments of your friends, I again stress the utmost importance of finding someone who is experienced and can instruct you in safe, correct techniques.

Also, complete sentences and paragraphs breaks would greatly add in understanding what you're describing.

[NZcaver]

From what you describe, your rack is attached incorrectly. A rack should be attached so you are looking at the END of the bars, and the opening should be down and away from your body, not to the right or left.

Not to pick a fight, but this is an OPINION shared by some cavers and not by others. Not a hard and fast rule for all, because doing it the other way IS safe and DOES work. Also it doesn't apply quite the same to U-racks as it does to J-racks. But yes, with an open-frame rack this is quite an efficient way to maintain control and add/drop bars.

I understand what muskrat means by "torque" now. Just a little rotation is normal and nothing to worry about. I have my rack (a micro) attached via an oval Maillon Rapide screw link to my Petzl Omni harness link. It is free to rotate maybe 45 degrees each way or so, and in practice I don't even give it a second thought.

Also, at a certain risk of crossing everyone here I'll go ahead and say that trial and error IS how we learn. And how we learn to anticipate how to approach different scenarios and assess risk. But, DO try to keep the errors small...

Good point, Caleb. I guess I was thinking in terms of a new vertical caver using unfamiliar equipment, as opposed to those of us who have been around the vertical caving world for a while and like to tinker with our setups. In the former situation, many others before us have done the trial and error method when learning from scratch. Now we have the luxury of learning the basics from others, generations beyond those who had to do all the original trial and error process themselves. Of course we can still tinker, provided we know enough already to be able to do it safely.

[gdstorrick]

Post deleted.

[puffadder]

This is all actually pretty cool.There is some involvement here. a few comments ago I saw reference to the military experience.That was done with in 1990.Since then,it's been civilian all the way.The last time I ever used a wrap was in 1990.I still know it though.Just like the munter hitch,and a billion others.There was something else too.I got an answer to the dynamic rope question.Thats right..the rack is designed for static..I told you this is a bluewater ii..Static line with a soft feel to it and dynamic properties.I suspect it is the central problem..just a theory..I have 8 dynamics of differing diameters,and 3 statics of differing diameters.This 12mm being the longest @250' gets used now a little more than the other 2 statics because of its length,also ,now is when this problem of fighting drag is most prominent...And yes that torque response is correct..had a feeling that if not minded the twisrotation along axis is also giving resistance..