how to tie 20mm bands?

[jtkwest]

i recently ordered some 20mm rob allen tubing. and the dive shop guy says he couldnt tie them. i am using spectra wishbones, but when he started to have trouble he tried to put metal wishbone in to see if that would hold but he would cinch down and still be able to pull the ball out relatively easy. he was tying it in the accepted method he uses for smaller bands, (the way i have seen it diagramed in the past on line)) he thinks we need metal bands or something. ???????he says it is so thick and rigid he cant cinch it tight enough.HELP< PASTOR, SETTING STEEL or one of you other master craftstmen .........

[KWM]

Difficult to understand fully what has been done. But you should have no problems at all.
Make sure that the spectra has a 'ball' or something else to stop it pulling through then tie it in place using whipping twine from a chandlers. Use a constrictor knot to do this. It is difficult to get the knot very tight by hand so put a loop in each end so that added force can be used. I fix one end to a fence post, put the handle of a set of pliers through the other and pull with both hands using your weight to make it even easier.

Kev

[James T]

I agree with Kev above - I use 16, 18 and 20 mm bands on a selection of different guns and the wishbones are always secured fine with single or double constrictor knots. I usually just use two pairs of pliers and pull as tight as I can before cutting & melting the end to stop them fraying further.

There are some other great threads on tying your own wishbones on this site.

[Hugh.]

Here you are. sumora, official distributors of Rabitech and Rob Allen

[Mr. X]

Originally Posted by James T

I agree with Kev above - I use 16, 18 and 20 mm bands on a selection of different guns and the wishbones are always secured fine with single or double constrictor knots. I usually just use two pairs of pliers and pull as tight as I can before cutting & melting the end to stop them fraying further.

There are some other great threads on tying your own wishbones on this site.

Ditto. I tie one end of the constrictor-cord to a bench vice & the other around a dowl & the pull real hard. They need to be tied very tight*, more than you would think when compared to tying 16mm bands. I then smear the end & the knot lightly with a soldering iron -- be careful the knot is under a lot of tension. Also, I usually use the RA braid intended for this but ran out (they don't give you much) so I used whipping cord last time.

*By very tight, I mean the diameter when cinched is about half the normal diameter (i.e. 1cm at the cinch vs. 2cm above & below) -- I just checked.

[Meshari]

you can put oil or hair conditioner to decrease friction when doing what mentioned above.
my quistion:
the constictor knot usualy not working with strong bands because the knot i make in the dyneema wishbone is small. can you please show me how to make the knot more bulky

[James T]

check out this italian page on doing your wishbones Realizzazione di elastici circolari if you wanted to do it yourself.

you put a nail in the end of the rubber to start with and then use a grinding wheel to chamfer the edge of the tubing - before removing the nail and inserting your articulated wishbone or dyneema wishbone.

[Mr. X]

Originally Posted by James T

...you put a nail in the end of the rubber to start with and then use a grinding wheel to chamfer the edge of the tubing - before removing the nail and inserting your articulated wishbone or dyneema wishbone.

Interesting. I tried using a small, old grinding wheel I found but it wasn't up to the task, so I just trimmed the edges with "super scissors".

Re. the suggestion for lube when inserting the toggle end of the wishbone, I use saliva or soap suds as both dry tacky rather than staying slippery once everything is assembled. I use the RA T-bar tool, it makes inserting the toggle easy, although snipe-nose pliers work too.

[jtkwest]

thanks dudes once again.. it would seem the dive shop guy is just pussified and didnt pull hard enough. if you want something done right do it yourself. i made two cool spearguns but i cant get any of my pics to post. it keeps saying file is too big...Weak!

[armandozx]

DUDE I have a VIDEO ! that show's step by step in action how it's done if ANY nEEDS it JUST LET ME KNOW ! I WILL SEND !

[settingsteel]

got here late but the rest of the crew got it down pat...if all fails (which it shouldn't) grind them a hair, and it should do...Dude thanks for the kind words, but I'm wayyyyy far from that status

[ILDiver]

I was tieing a constrictor knot on a band this morning and the dang loop (tieing like Kevin from Hammerhead spearguns shows) kept pulling out of the band. What I was noticing was, as I pulled the cord tight, it was loosening as I let go of the pressure. The cord I'm using was not sliding across itself to constrict. So the knotting was tight, the constrictor loop was not pulling down. So before I pulled the next attempt down, I wet the rubber and the cord at the knot. This allowed the cord to slide across the rubber to pull the constrictor loop down tight to the knot.

[Mr. X]

Originally Posted by ILDiver

I was tieing a constrictor knot on a band this morning and the dang loop (tieing like Kevin from Hammerhead spearguns shows) kept pulling out of the band. What I was noticing was, as I pulled the cord tight, it was loosening as I let go of the pressure. The cord I'm using was not sliding across itself to constrict. So the knotting was tight, the constrictor loop was not pulling down. So before I pulled the next attempt down, I wet the rubber and the cord at the knot. This allowed the cord to slide across the rubber to pull the constrictor loop down tight to the knot.

I've always found the regular constrictor knot reliable, sounds like the cord was sticking to rubber surface more than to each other. BTW Several webpages show drawings of a regular clove hitch, which looks similar but will not retain its tightness like a constrictor. Dear Alison used to use a different knot, along the same lines as the various surgeon knots, tying a simple thumb knot & then looping around again (& again & again if necessary). I've started using that in all sorts of ways, for example for anchoring the start of a whipping, but do not yet trust it to act as a cinch knot.

In the images for the link James posted, it looks like the guy tied an extra half hitch after completing & tightening the cinch knot. BTW Here is an English translation of it.

What is the knot used as a stopper in the ends of the wishbone, in the bead/toggle? I looked at the RA wishbones & it looked like it might be just two thumb knots cinched up tight against each other, hard to be sure though.

[ILDiver]

Yeah, the cord for some reason was not binding correct and was not allowing me to get the proper strength in the knot. That is why I mentioned it. I thought maybe jtkwest was running into the same issue. I bought both the constrictor cord and the R.A. band from Florida Freedivers. I tried the cord on the black band too, with the same result. So I took the time to see what was going on. The knot was pulling tight, but the constrictor loop was not locking down. I used water to "lube" the coard and it held.

[settingsteel]

Wax works too IMO better than H2O