Russian Aider How-To

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Moof

Big Wall climber
A cube at my soul sucking job in Oregon
Topic Author's Original Post - Jan 30, 2009 - 11:39pm PT
Originally on Bigwalls.com (http://www.bigwalls.com/forum2/index.php?topic=496.msg3652#msg3652);:

Warning: In multiple places there are high load webbing joints where you must sew through 3 layers of thick webbing with lots of stitches. You'll break you're wife's machine if you try it on a home machine, and probably won't even get it under the foot. A low end single stitch industrial machine will do fine with #69 or #92 thread, and can be gotten at Harbor Freight for ~400 bucks ($279 for the head, and $129 for the table last I checked), or watch craigslist till one in good shape shows up. A speed reducing pulley, or servo motor with a low speed setting is HIGHLY recommended as most of the sewing is small runs, and high speed is NOT needed. Better yet, rework this design for a bartacker if you have one.

Marking nylon for sewing isn't as easy as you'd think. A dot of sharpie works, but is ugly and might weaken things. I use a craft store chalker. It uses powdered chalk and as a little metal nubby wheel that does a good job of easily making marks that last long enough to get your sewing done, yet the marks quickly disappear in simple handling.

Hard Supplies:
1. Hook from strapworks.com, 1" bent wire hook made by Suncor Stainless, about $4/ea. It might be worth filing the hook end to a rounded point before you sew them in place, but I really haven't found it necessary, and I'm lazy.
2. Aluminum Double Pass 1" from innermountainoutfitters.com, about $3/ea. They also carry CMI burly ones if you want overkill, and somewhat more annoying snugging up and double backing. Onrope1 has some $5 ones I have not tried.
3. Heavy Duty nylon ladder locks from seattlefabrics.com, strapworks.com, or owfinc.com, about $1/ea.

Soft Supplies:
1. 1/4 closed cell foam, 6lb polyethylene recommended (google it). Anyone ever use something better? Neoprene maybe?
2. 100 weight Polartech 100 fleece, or smooth nylon in ~200 weight (Cordura is a bit harsh on skin after awhile, avoid it) or equivalent.
3. Nylon or Polyester 2" seatbelt webbing. I prefer a slightly softer feel of the Nylon stuff I've gotten over the stiff Polyester stuff REI carries.
4. Nylon Webbing, 1", about 74" total per leg (7' per color for ordering purposes). I find tubular nicer to sew with than thick flat. Climb spec is also a bit thick and I break a lot of thread and needles when I try to use it, so I recommend starting with Mil Spec. The ridgier texture might also creeps less in the buckles?
5. 48" thin flat 1" webbing , 24" per stirrup.
6. 28" thick flat 1.5" or 1.75" webbing for foot rash guards.

Cut List (per aider):
For a 15" calf circumference (right below knee) cut the following (all 2x, 1 each for each leg):
1. 15"x3" 1/4" foam, chamfer the corners 3/16" (adjust up or down for size, inch for inch)
2. 18"x7" fleece covering (adjust up or down for size)
3. 14.5" 2" seatbelt webbing (adjust up or down for size)
4. 28" 1" tubular webbing, one end cut at 45, increase inch for inch over 17" circumference (length is to the middle of 45 cut, used for cinch strap around calf)
5. 42" 1" tubular webbing one end at 45 degree for jug loop and most of stirrup, adjust up if you are huge
6. 14" 1" tubular for stirrup buckle (adjust up if you are huge and want to keep the buckle low and out of the way)
7. 2x 14" 1.5" or 1.75" thick flat for rash guard
8. 24" thin webbing (stirrup cinch strap)


Padding:

In Process

Rash Guard:

a. Sew in the 1" ladder lock with a box X, and sew fold the loose end twice and sew. This tab makes a nice grabby, and keeps it from unthreading from the plastic buckle.
b. Sew the ladder lock assembly onto the first rash guard strip, 6" of total sew length centered on the rash guard. Leave ~1" between the end of the box X to the sewing on the rash guard.
c. Sew the two rash guards together to make a tube. Double sew so it doesn't fall apart too easily from abrasion. For 1.5" webbing you really have to keep the sewing within 1/8-3/16" from the edge, or the 1" stirrup webbing won't fit inside without bunching up.


Stirrup Assembly:
a. Start by sewing one 1" metal buckle to the end of the 14" piece of webbing with a 1.5" joint. Set aside.
b. Fold 4" of the 42" piece over and make a 1" joint.
c. Thread the 14" through the bottom of the hook and line it up below the Jug loop. Mock up this spot with the cuff pieces to mjake sure you understand where the 28" calf piece will lay over the hook. Sew a 1.5" joint.


Cuff:

a. Mark the 2" seatbelt webbing at 1.5 and 2.75".
b. Sew on the 28" tubular with a 1.25" joint.
c. Thread on an aluminum buckle and line the end up with the end of the 2" seatbelt webbing. Sew the loose end down with a 1" joint, putting extra vertical tacking in where hook tube will be (5 tack minimum, 6-10 preferred).
d. Line up the top of the 1" joint of the Jug Loop with the bottom of the 28" calf strap. TRIPLE CHECK IF THIS IS A RIGHT OR LEFT FOOT! Sew a 1" joint to attach the jug loop/stirrup assembly to the seatbelt webbing.
e. Pinch aside a small amount of webbing for the hook tube (or life will suck when you try to wrestle the hook into place). Sew down the remainder using extra vertical tacks at each end, especially at the hook tube area.
f. Contort and insert the hook to verify it fits before sewing on the padding. A blunt screwdriver is very helpful, as is a beer. If it looks good, undue the hook and proceed. If life sucks, figure out what you f*#ked up and try again. Webbing is cheap, as are seam rippers.


Thread on the Rash Guard:

Joint Discussion:

I have not pull tested any of my sewing. However, none of my stuff has ripped or broken on me, and my sewing has vastly improved over the first stuff I made myself years back. I base my joints largely on the discussion in the book On Rope (good resource for vertical dorking). Particularly my style joint is considered the strongest joint style, stronger than a similar number of stitches in a bar tack. Bar tacks create a stress riser, and as a result can only get at most ~66% of the webbing strength no matter how many tacks are used. I'd rather used bar tacks, but I don't have a 1" tacker, but my point is simply that there is nothing magical about bar tacks, they are just the best way to do things commercially and repeatably (see: [url=http://www.xmission.com/~tmoyer/testing/pull_tests_11_98.html]http://www.xmission.com/~tmoyer/testing/pull_tests_11_98.html[/url] for some limited but interesting test results, such as home random sewing beating out commerical tacked stuff).

Stirrup Buckle Joint:

I counted ~180 stitches in the 1.5" joint. I use #69 thread with a 10 lb nominal strength. The buckle strap gets 1/2 the climber's weight (assumes equal distribution between two legs of stirrup), and the joint has another 2:1 through the buckle (ignoring friction that is in the joints favor. On Rope lists a fudge factor of 1.8 as how much strength you get per stitch relative to your threads single strand strength. So:

Force needed to rip 1.5" stirrup buckle joint = 2x2x10lb*1.8*180=12960lbs*
*webbing or buckle will break first

Hook ripout:

I counted ~180 stitches in the 1.5" joint. To rip the hook out of its spot it has to pull the short end of the 14" piece of webbing out from in between 2 other piecees of webbing (it's in the middle of a sandwich). Optimistically this adds a another 2x in strength, but I'm goine to ignore it as I have no reference to tell me how much of the 2x I get. It has a 2:1 disadvantage due to the pulley effect. So:

Force needed to rip 1.5" hook joint = 2x10lb*1.8*180=6480lbs*
*hook will unroll first, it has a WLL of 400 lb, so probably a 2000lb break/unroll strength (5:1 safety factor is typical for non-man rated gear)

Jug Loop Joint:

I counted ~200 stitches in the total 2" joint. Their is a single 2:1 advantage for the joint due to the pulley effect of the biner you'd clip in with. So:

Force needed to rip 2" jug loop joint = 2x10lb*1.8*200=7200lbs*
*webbing will break first, as a single strand is rate for only ~4,000 lbs
*the 1.5" hook joint would be under shear at the same time, and the previous 6,480 lb calculation would apply here, still stronger than the single strand of 1" tubular by a large margin.

I feel pretty comfortable that I'm using plenty of stitches and a good pattern on these. It is my belief that you'll break before my aiders do. When I get spare cash I'll make a couple sacrificial aiders and see if I can get them pulled to destruction by someone for further assurance. At the very least know that I am FAT, and mine have not failed, even the ones I made years back on my crappy ebay special sewing machine. I encourage you to vigorously bounce test and reef on yours on the ground before going up real stuff, otherwise your widow might hunt me down for putting the fool idea in our mind that you could make your own climbing gear.

Thorgon

Big Wall climber
Sedro Woolley, WA
Jan 31, 2009 - 01:05am PT
Wow, totally amazing! Now I wish I was a
parachute rigger! That was the last time I
had "Homemade Aiders"!

Looks like a good aider!
Thor

P.S. Your sewing looks good!
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