The more I learn, the more I realize how little I know.

Wednesday, December 24, 2008

Figuring out the length of paracord for a Solomon Bar

Knowing how much paracord you'll need for a knotting project (like square knotting a solomon bar for a lanyard) can be a big help. Sometimes you'll get a clue like in The Ashley Book of Knots, for square knotting he says "The length of the cords required is generally about seven or eight times the length of the finished product."

But it turns out that's not too helpful because it's too general.

So the goal is to figure out how much paracord it takes to tie a solomon bar but also to work out some method and formula so we'll know how much cord we'll need for any project in the future.

This is a Solomon Bar which is just a series of square knots.



The formula is

Finished-length-of-solomon-bar = Starting-length-of-paracord multiplied by X or

f = s (x), where f = Finished-length-of-solomon-bar, s = Starting-length of-paracord, x = the change made by tying knots

and to find out what x is, I'll tie some knots and measure the paracord before and after.

I start with two lengths of navy blue paracord (leader lines) and two lengths of orange paracord (working lines). The starting length for each of the orange cords is 37".

I start tying my square knots.



I finished tying at 7" but it doesn't really matter. I just needed a decent sized finished-length to measure.


Since all I want is the length of the paracord used to tie the knots, I subtract the remaining orange paracord which is about 3" on each side (37" - 3" = 34").

So two strands of 34" each makes 7" of solomon bar.

With a starting length (34") and a finished length (7"), and using the formula f = s (x), we get x = f / s = 34" / 7" = 0.206 but 0.2 is good enough. We're figuring paracord not building rocket ships.
And that's it.

So let's use the formula on a real example -

Say you want a solomon bar length of 5" for a lanyard you're making...

starting-length = finished-length divided by 0.2
s = f / (0.2)
s = 5" / 0.2 = 25"

The fomula says you'll need each length of paracord to be at least 25" long.

(If you went by Ashley, you'd have set aside 35" - 40" of paracord for a 5" solomon bar instead of the 25" it actually requires.)

Try it on another real situation -

You want to know how long of a solomon bar you can tie with your 2 lengths of paracord 62" each.

finished-length = starting-length times 0.2
f = s (0.2) =
f = 62" ( 0.2) = 12.4"

The formula says you can tie about 12 1/2 inches.

But remember, we're just trying to come up with a close approximation. The x = 0.2 is a guide so always add a few inches on the end of each working line. And the 0.2 is only good for the solomon bar - each chain of knots will be different. Also, the number that comes out of the formula is for one strand so double it for total length of paracord. One more thing - your x for a solomon bar may be slightly different than mine but now you can determine your "x" for this and other knot chains. Experiment.

And since this formula is only concerned with ratios, and with all things being equal (like using the same diameter cord for all 4 strands - 2 leaders and 2 working), it should also work on any diameter cord.

Well, in theory, maybe... But will it?

Here's a solomon bar made with string -


The starting length for each working strand was 14.5" - 1" remaining on each so
f = s (0.2) = 13.5" (0.2) = 2.7" of finished solomon bar.

What does the tape measure show?

Please comment on this. Easy to understand? Too complicated? I can do more of these, if you're interested. Thanks.


2 comments:

Anonymous said...

What a good idea ~ my wife knits and is always doing a test swatch to make sure the needle gauge is correct for the pattern and project she is working on.

I can see this being very helpful and will start to build a table as the length factor will obviously change depending on the cord being used and the tension.

There are few things more frustrating that not having enough cord to finish the planned project after investing many hours into it (and creating too many Longer than necessary waste pieces, gets expensive)

Thanks for the tip...

Frayed Knots said...

Nicely done! I still use the old 3.5 x length, but that's because I
(a) do wider fabrics than just one bar,
(b) usually incorporate other knot features (diamonds, "X"'s and chevrons) into the finished item,
(c) need extra line at the ends to do finishing work and have enough to pull with and
(d) Use the cut off ends to form other items of small knotting (earrings) or for use in puddings for bellropes or beckets), so the detritus is actually used.

For a straight line Solomon bar, this is a very nice formula but if making a terminal knot, you might want to amend it to add some line to allow same.

since 12/17/08