Craftsmanship > Traditional Archery and Accoutrements
Build a Unistrut Endless String Jig
RobD:
There are essentially two types of bowstrings - Flemish and endless. BOTH are *totally* traditional. Though no primitive bowstring has survived the millennia, it is highly speculated that the strings of our ancestors were created as an endless loop of strands, and held fast to bow limb tip groove or pin nock with a bowyer's knot (timber hitch). This allowed for the *constant* tweaking of those hemp, flax, sinew, whatever bowstrings as the environment and bows played havoc with their elasticity. Using bowstrings with preformed loops (Flemish or endless) that force the string length within a narrow length parameter, are best left to modern strings using polyester (Dacron) and HMPE (High Modulous PolyEthylene - Fast Flight, Dynaflight, 450, etc.) string fibers.
Yes, one can go totally primitive trad and craft bowstrings of hemp and linen ... but let's get real - those kinda string fibers are just inferior to modern spun fibers, which are safer and offer far better performance for hunting.
I prefer endless bowstrings. They can be built with far greater accuracy and offer far better shooting consistency than Flemish bowstrings because they're built on a jig, whereas Flemish twist bowstrings require no jig at all and can be built "in the air". 99.99% of all Olympic archers use endless bowstrings. 'Nuff said.
A decent twin arm bowstring jig can cost upwards of $300. I designed and built the first one arm bowstring jig back in the early 60's and it more than gets the job done. In fact, years ago I used a few of these "one arm bandit" string jigs to make and sell custom bowstrings. They're too easy to make and use, and will build perfect length strings every time. My first jigs were made solely of wood, but there's a far better way these dayze - Unistrut!
There are more than a few viable ways to build a Unistrut one arm endless string jig. This article addresses how I built a pair of them, and to introduce the concept of using unistrut for the jig body and using one jig arm instead of two.
Study over what I've done and you'll see lots of your own on-hand material and parts substitutions that'll work just as well, if not better. As a side note, for those who prefer using a twin arm jig, the unistrut jig body will accommodate that just fine!
Some comments on the jig design and build parameters ...
The Unistrut I used came only in 10' lengths. Normally, I like a 6' long jig, but I didn't wanna wind up with a 4' length of nearly useless unistrut. So I cut it in half, for two 5' lengths. Using a 12" length of 2x4 for the end post adds another 5" to the extension, coupled with the overhang of the pivot arm, that allows for a 71" loop-to-loop string - more than enuf for my needs. If I wanted to make longer strings, I'd just increase the length of the end post tail arm.
While I've used both 1/4" and 3/8" pivot bolts, the more robust 1/2" is just plain better.
I like using fir for the 2x4 wood - heavier than white wood (pine), it's just more durable.
It doesn't matter much what size string end hold down screw and wingnut is used - 5/16" works just as well.
One $2.11 8' length of 2x4 fir is enuf wood for 2 jigs.
WOOD
18", 2x4 - pivot arm
12", 2x4 - tail arm
12", 2X4 - jig feet (optional)
18", 3/4" birch dowel - posts
12", 1/2" ply - pivot and tail blocks
HARDWARE
Unistrut (SuperStrut)- jig beam (home depot, 10', $19)
3", 1/2" bolt - pivot arm
1/2" id washer - pivot arm
1/2" id lock washer - pivot arm
1/2" id wingnut - pivot arm
1-1/2" dry wall screws (3) - tail arm
2" flat head screws (partial thread) (3) - pivot arm
2", 1/4x20 machine/wood screw - string end hold down
1/4x20 wingnut - string end hold down
1/4" id washers (2) - string end hold down
1" dry wall screws (4) - jig feet (optional)
1/4" id washers (4) - jig feet (optional)
TOOLS
wood saw (table, circular, jig, hand) - cutting all wood
metal saw (metal cutting bandsaw, hacksaw) - cutting the unistrut
drill (electric, hand) - drilling all wood
3/4" speedbore bit - pivot/tail post holes
1/2" wood bit - pivot bolt hole
1/8" wood bit - wood screw holes
FASTENERS
slow set epoxy (30-45 minute) - posts, pivot bolt, post binding
binding for string posts (carpet thread, floss, string fiber)
There's more to come as I'll show just how I use the jig to spin up a string, but for now here's some jig pix ...
One Arm Endless Jig on the bottom, most of the jig parts on the top ...
The pivot arm ...
Pivot arm bolt system - a scrap piece of plywood is used to secure the pivot arm ...
The scrap plywood's width just allows it to slip into the unistrut, but it's held in place by the unistrut's lip ...
The end post attachemnt - just like the pivot arm, it's fastened by a slat of plywood with 3 predrilled holes (see inset pic) that's held in place by the unistrut's lip, using dry wall screws into the endpost block of wood ...
Post dowel, string screw, hole ...
String post w/screw and dowel thread binding ...
Easily make from a 24" to a 72" string ...
Fletcher:
That is a good idea. I have made many string jigs using 2 boards with a 'slider'
slot cut into the top board. That takes accurate measuring and cutting on a table saw.
The unistrut is heavier - but may be the easier way to go.
Some suggestions:
1. Mount the unistrut on some cross boards to keep it from tipping.
2. I may do one and try the actual unistrut back nut instead of the wood bolt slider
(I think it will slide easier)
3. Mount rotating loop arms at both ends. I find it faster to serve each end on its own
loop arm rather than removing the half done string and transferring to the other end.
4. Use double head 16 penny nails glued into loop arm rods rather than screws. You will find
that the string tracks better, will not slide on the nail and the end of the nails is rounded so is
not sharp like the end of the screw (avoid nicking or fraying the string)
As to primitive strings:
I have studied articles and photos as old as possible on archery all over the world.
The majority seem to conclude that ancient bowstrings had a loop for the upper limb but were
tied onto the lower limb. Various knots were used to form the loop and to tie the lower limb.
A common lower knot is known as the Bowyer's knot - which is really just a Tiber Hitch.
A number of string had a braided loop for the upper end.
I make my primitive strings out of artificial sinew. It is made of Dacron - very similar to the
B50 Dacron used in modern bowstrings. It does not stretch or shrink like natural fibers.
I have a hard time convincing some of the HC/PC event leaders that this is a better way to go
for safety sake than making competitors use natural fibers. They make the competitors use
eye and ear protection while shooting guns - that is not HC/PC !!!
The loop that I make I call the 'Flemish Braid"
It is similar to the twist - but every 2 turns are alternated so the fibers are not just down one
bundle - that keeps slippage form happening. The artificial sinew is flat and is not as waxed as
B50 - it is more prone to slipping without the braid.
If I could figger out to post a picture - I would show you both my strings and jigs.
OBTW - quite a few Rondys and other primitive archery events do not allow serving on the
string (including loops), and if they allow B50 it must be of natural colors like brown or grey.
That pretty much leaves you to the Flemish twist style unless you have another approved
plan like the artificial sinew. For modern traditional bows I like the endless loop best with served
loops. They hold up longer than the Flemish by my experience.
sake that requiring folks to use all natural fibers.
Riley/MN:
--- Quote from: "Fletcher" ---If I could figger out to post a picture - I would show you both my strings and jigs.
--- End quote ---
'tain't that hard, but you can always send em my way and I can post 'em when I get a chance.
RobD:
--- Quote from: "Fletcher" ---That is a good idea. I have made many string jigs using 2 boards with a 'slider'
slot cut into the top board. That takes accurate measuring and cutting on a table saw.
The unistrut is heavier - but may be the easier way to go.
my very first one armed string jig was a wood board with a slider. easy to build with a table saw and jig saw. the problem is stiffness, or lack thereof with wood. the unistrut is THE answer to that. as to weight, i honestly don't see a difference 'tween the wood and metal jigs. and in the short run, who cares? this isn't something to take afield! it stays at home in yer workshop! :lol
1. Mount the unistrut on some cross boards to keep it from tipping.
i find it better to clamp the jig to a table top - this makes for simpler construction and an easier to store jig. but some folks have added feet as need be. it's all good, it all works.
2. I may do one and try the actual unistrut back nut instead of the wood bolt slider
(I think it will slide easier)
yes, i've done that as well - again, just a variation on fine working theme.
3. Mount rotating loop arms at both ends. I find it faster to serve each end on its own
loop arm rather than removing the half done string and transferring to the other end.
i've done that as well, but find no advantage. mind ya, i've used these kinda jigs to produce in excess of five thousand strings over the decades. 8)
For modern traditional bows I like the endless loop best with served
loops. They hold up longer than the Flemish by my experience.
sake that requiring folks to use all natural fibers.
again, it's all good as long as what's used works best for you, not me or anyone else.
--- End quote ---
Spotted Bull:
You guys are gonna make a string maker out of me!! I needed this kind of information!! Keep it coming!!
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