How to tie and seize shock cord?

[MiddleAgesMan]

The rudder blade on my Goat Island Skiff is held in place with shock cord that allows it to kick back if it encounters the bottom. The designer shows two wraps of shock cord wrapped around the open-backed rudder box.

I ran the cord and tied the ends with a square knot but that doesn't seem to be likely to survive long term.

I seized the ends to itself on each side of the square knot and all appears to be secure, for now.

My concern is the seizing method...I wrapped and tied and wrapped and tied some small stuff but I'm still concerned about everything letting go under stress, in either normal or extreme use.

Since shock cord's diameter is reduced as it stretches, what is the best method to seize it to itself to keep a knot from slipping?

On a related note, what is the best method to seize the cut ends so they don't unravel?

[Ian McColgin]

Each end of the shock cord can have an eye siezed really tightly and then the siezing racked. That will be secure. Any good seamanship or knot tying primer can give the details. Have each eye hooked to a hook on each side. Easy.

G'luck

[JimConlin]

Stainless hog rings hold well on shock cord.

[htom]

I put on plastic disposable gloves and work some epoxy into the last half-inch or so, and when it's set, cut it off square; tie with a Zeppelin bend and seize the ends.

[Ian McColgin]

Siezing a zeppelin bend??

Hog rings rust and epoxy is nice but rusts. Really, just sieze and rack an eye. Dirt simple and lasts at least as long as the shock cord.

[Tom Robb]

Ian,
Sieze & rack is spot on, and salty to boot, but epoxy "rusts"?

[Ian McColgin]

What was I writing? I meant to write that epoxy is expensive. Failure to proof.

[Bill Perkins]

If a stable loop knot in each end would solve your problem the Anglers loop works in bungee cord . If you need to join the 2 ends one loop could be tied through a hole in a small wood toggle . This in turn would button into the other loop .

http://www.ehow.com/video_4468150_tie-anglers-loop-knot.html

[MiddleAgesMan]

Thanks for the suggestions, guys.

I know what an eye is and I know about seizing...I have no idea what "racking an eye" is about, though. Also, seizing on something that changes diameter as it comes under tension seems problematic...the type of seizing I've done on three-strand would get loose and go wonky when the shock cord is stretched (and the diameter is significantly reduced).

I learned a new knot, though, the Zeppelin (thanks, HTom). I like everything about it except the way it leaves the loose ends standing perpendicular to the standing part. Not seizing it doesn't suit my aesthetic eye but seizing it by bringing the loose ends around to align with the standing parts turns a small, compact knot (visually small) into a very large knot (visually, at least, and no longer compact).

I stumbled on a knot that appears to hold in the stretchy stuff--the Waterman's knot. I didn't think it would work but after it slipped a little as it came under tension it seemed to lock up and stay in place. The loose ends come out parallel and right next to the standing parts so seizing those down will make it pretty secure, streamlined (and aesthetically pleasing to my eye ;) ).

Which brings us back to seizing shock cord...what do you use for seizing that can hold the parts securely when their diameters are changing from 1/4 inch to, say, 3/16th to 1/8th inch? Do you put the whole thing under near-max tension and then seize normally?

[John Meachen]

The answer to the original question lies in the question itself.Given that the diameter of the shock cord reduces as it stretches,the solution is to seize the shock cord while it is under tension.The means of applying the tension can be a two part tackle secured at one end of the bench and the material I have always used for the job is waxed whipping twine.Alternatively fit a CL257 and a rope downhaul.

[P.I. Stazzer-Newt]

Paired Nail Knots make good seizings - and trim the ends off.

[Dale Genther]

While we are on the subject of shock cord. Does anyone know of some that is made to be UV resistant. All the stuff I've used has turned to junk in less than a year in the sun.

[dredbob]

The "vice versa" is reputed to hold in bungee cord, as well as other slippery and hard to tie material. It's a "new", ie. non traditional knot invented by Harry Asher. Just google on it, there are plenty of pages showing it.

Bob

[Ian McColgin]

It appears that we have a bunch both unfamiliar with shock cord and unfamiliar with any standard knot texts. See if we can do this in words, as siezing is just a winding.

Firstly, all siezing needs to be fairly tight and in rigging one would even use a siezing mallet to get the windings really snug. Not needed for this application. Just wind right off the spool (the spool can act like a handle for good tensioning) such that you're compressing the schock cord pieces to about 50% original size. That will be more than the stretch of use so it will hold.

Have the bitter end of your thread some six inches or so out past the throat of the eye pointing down the line. Make a bight down in the very throat where the siezing will end and bring the line back to about the short end of the eye. Hold both parts of the eye and both parts of your siezing line with the thumb and hand pointing down the standing part and start winding with your other hand. After a couple of turns to really hold the start of your siezing, you can really crank down on it. When you get to the end, nip off leaving about six inches, pass the end through that loop, and pull the other end to capture everything. A little feel and you'll know when the join is about half way from each end of the siezing.

Now the racking, which is just some winding perpendicular to the siezing held between the two parts of the bungee. That's to keep the siezing in place, add security against bungee slip, and tighten. Finish by joining both parts with a reef (square) knot buried at one end or the other in between the bungee parts.

This way will leave one fewer rackings on one side than the other but the siezing part is faster than methods that lead to a more symetrical conclusion.

The total siezing need be no more than four or five times as long as the two bungee parts are wide.

G'luck

[MiddleAgesMan]

Paired Nail Knots make good seizings - and trim the ends off.

That's another new one for me--the nail knot. I found this on my favorite knot-tying site:

http://www.marinews.com/Nail-less-Nail-Knot-439.php

It wasn't too difficult putting the standing part of the loop under tension but I had to tie it with the loose ends free. The nail knot seems to have enough umph to embed the wraps into the shock cord just fine. Since the waterman's knot was holding with the free ends loose, now that they are snugged down I think I have something that will last.

Regarding the question about UV resistant shock cord--while researching my particular problem I found a rigging guide for one of the high-performance small designs from Oz. They said to expect to change out your shock cord a couple times per racing season. :(