Regulator Bungee

[large_diver]

Mer,

Here is a report I wrote up a while back on setting up the long hose and bungeed back-up. I believe I use 1/8" bungee for the necklace. 1/4" is just not flexible enough for something you are pulling over your head all the time.

As for how long -- start with more than you need and tie it loosely (say 2-2.5 feet)-- you can always tighten it up and cut off the excess later.

http://www.scubadiving.com/members/divetips.php?s=253

Hope this helps.

 

[sig]

Hi Mer,

The bungee cord is 1/8" and 34" in length. The surgical tubing is 1/8" x 1/4" and it is 24" in length. I got the bungee at Lowes and the surgical tubing at home depot.

 

[peter_steinhoff]

Guys,
this is all nice and dandy, but the neckless needs to be secure.

It really shouldn't be able to come off becuse when you need your backup, you need it bad and it must be there.

Some divers are afraid that an out-of-air diver is going to grab their backup instead of the longer hose. That is not the case for two reasons. One is that you as a buddy should be aware of your buddys situation and donetae your longhose before he even reaches you. The other thing is that if you dive in a correct position, horizontal, it's almost inpossible to grab the backup because your primary reg is in front.

Now, there are two acceptable ways to rig the backup reg.

One is to use surgical tubing and fasten it under the tiewrap that holds the mouth piece.
The other way is to use bungees and tie knots in the end and secure that under the tie that holds the mouthpiece.

I think you can find pictures under http://wkpp.org (look for equipment pictures)

Halcyon sells a pre-configured neckless but it is more intended to be able to quickly put a neckless on a reg without cutting zip ties. Good when you want somebody to try having the backup in a neckless instead of an octopus stowed somewhere.

As a final point I want to mention that I used to have mine rigged in a "tubing-loop" that could come off if you pulled hard. Well, it came off twice in situations that wasn't to much fun.

Best,
Peter Steinhoff
http://dir-diver.com


Ohh, one more thing.
If you want to have the backup under your chin but you are not using a longhose, which you btw don't have to in an OW environment, breath from the longer hose, the octopus, and rig the shorter hose as backup. If you have a low performance reg as backup you can just unscrew it and change positions.

 

[ScubaToneDog]

peter_steinhoff once bubbled...
Guys,
this is all nice and dandy, but the neckless needs to be secure.

Actually with the double fisherman's knot using bungee its a hell of alot more secure than anything else out there. Beats surgical tubing hands down.

Great thread!

 

[divermasterB]

ScubaToneDog once bubbled...

peter_steinhoff once bubbled...
Guys,
this is all nice and dandy, but the neckless needs to be secure.

Actually with the double fisherman's knot using bungee its a hell of alot more secure than anything else out there. Beats surgical tubing hands down.

Great thread!

I used the fishermans not bungee this weekend and it came off twice. I finally switched to put the bungee under the zip tie, with a not on the other side.

 

[ScubaToneDog]

When working with knots in bungee's you need to work the knot down while the bungee is stretched. Fishermans knots are of the constrictor family. Normally they dont need to be tightend very hard as they constrict and hold very well under strain when tied in a line. In the case of an elastic line they must be tightened under stretch to work equally well.

 

[Grajan]

is that it isn't one.

It only becomes a double fishermens when the two halves of the knot are pulled together, making it much stronger.

What we have here is two single fisherman knots. Worse still the loops are side loaded, providing an opening force not present in the correct (normal) application.

Add to this the dubious knotting properties of bungee cord and you have a recipe for failure, something that has already happened to me twice.

I don't have a good answer yet so ideas welcome.

 

[Grajan]

Treating each side of the reg as a separate problem (which it clearly is), what you want to do is tie the bitter end of one line to the middle of another line in a way that allows the bitter end to slip along the line but that has the lines tensioned at right angles.

The correct knot for this application is a round turn with two half hitches (knew I did all that scout stuff for something...).

I have just tested this and it is solid as a rock. A single turn with the two hitches works fine. It does not need to loop round the line twice.

Now - how am I going to explain this to Jarrod?

 

[ScubaToneDog]

Im tellin :mean:

You can make the double fisherman work if you stretch the standing end as you tie the knot. It works, and I know it works because I am playing with the necklace right now. It takes a little patience.

I do like the round turn 2 half hitch idea, but how do you keep the round turn in place and isnt the 2 half hitches just like a regular fishermans knot tied twice?

 

[Grajan]

It is a different knot. I have been looking for an illustration. Lets see if I can describe it effectively:

Bitter end - the free end of the cord.
Line - the area you want to tie to.

1. Pass the bitter end once over the line (going round again as you would with a bar does not work)

2. With the bitter end, put two half hitches round itself, creating a sort of noose round the line.

3. Tighten the hitches to grip firmly onto the line.

This slides on the line OK but correctly loads the knot preventing any tendency to undo, but a granny knot placed in the remaining bitter end and pushed up to the half hitches would add even more security (if a little more bulk).

This is very different to the "double" fishermans if you look at it as it is designed to operate with perpedicular lines (as we have) instead of parallel lines.