For Riggers: Cypres Loop knot

[TimHurford 0]

The first pic is straight from the Cypres manual, which shows the surgeon's knot and locking knot flush against the cypres disk. The second pic is from a rig's manual, which shows the trailing end of the cypres loop going under the loop at the back of the disk and tied of with a single surgeon's knot.

So ... is there anyone who is using the second method? Does it offer any advantages over the manufacturers (ie. Cypres) recommended method.

Any other thoughts?

I recently opened a rig and thought it was knotted incorrectly until I found this pic in a rig's manual (the rig opened is in fact not the same as the rig that the manual is written for - but the knot was the same!)

[councilman24 37]

Well, it took me a few minutes to find the second one, in the Icon manual. That's why I've never seen it before, I've never seen an Icon. I guess we'll have to ask Airtec if they approved it or Aerodyne is off on their own. The U.S.A. FAR's now require AAD's to be maintained according to manufacturer's instructions, even though they're not TSO'd, but not necessarily used according to them.

Might ask Dave Smith at the APF what their position is. Acutally, I just sent him an email and copied Cliff at SSK.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[TimHurford 0]

Thanks Terry!

Researching the surgeon's knot - it is most often used on it's own as a non-slip knot (other than in skydiving applications of course!). Curiously, surgeon's infact (well, the one that I asked anyway!) use two surgeons knots followed by a locking knot to tie off sutures - overhand; underhand; overhand - but then again they are using much finer thread!

The knot not (no pun) sitting against the disk was my primary concern - although when tensioned, the knot is held securely. I can't see any reason to thread it that way, it isn't as if there is any threat of friction or burrs from the cypres disk (not to mention adding 1/9" to the length!)

Yep - Icon Manual - although it wasn't from an Icon - that's where I found it. The Icon manual though is up there with the Vector manual in terms of clarity and quality, and easy reading!

[linestretch 0]

Quote

I can't see any reason to thread it that way, it isn't as if there is any threat of friction or burrs from the cypres disk (not to mention adding 1/9" to the length!)

I guarantee that you will see more knots routed in this fashion, or similiar. It's an easy way to take a little slack out of the closing loop, rather than untie the seated knot, and then move it just a little. I do it a lot, and was shown by several riggers how to do it....and have open a lot of rigs that were done like this. I'm not talking about the knot itself, just that the not is going under the looped end in your second picture...you follow?

my pics & stuff!

[TimHurford 0]

Sure. I can see that it is an easy way to tighten the loop a pooftenth without untying the knots ... from what I can see and having played with it under tension, it is certainly locked solid. Of course, you'd do this to take up slack, rather than routing it this way routinely, right?

... I guess it's just not 'in accordance with the manufacturers directions'.

[RACEDOG 0]

I've got a MICRON that was repacked at the Relativeworkshop by factory riggers and when I opened it for repacking the Cypres loop had been routed as in the second photo...but the knot was as suggested by Cypres manufacturer so routing this way to shorten a little is probably a common thing.

Rich

[MrHixxx 0]

Quote

Of course, you'd do this to take up slack, rather than routing it this way routinely, right?

I do it routinely this way. It allows adjustment of the length more easily, because the knot isn't tensioned as tight as it is against the disk. It also allows removal of the loop quickly by pulling up on it, which is a bonus for me as I change the loop every repack regardless of its condition.

-Hixxx

[councilman24 37]

Reply from Kai at Airtec, forwarded to me by SSK:

"We see no problems with this knot configuration, and no advantages
either.

I see the described knot as an alternate method, not as a
replacement of the standard way.

Greetings from Wünnenberg, home of the "smilie" :-)

Kai "

I've learned my new thing for today. Must be nap time.

I'm old for my age.
Terry Urban
D-8631
FAA DPRE

[masterrig 1]

I haven't done the 'alternate' method for the Cypres loop on a routine basis, but, I have done it to shorten the loop just enough to get the right tension on the pilot-chute. Works rather well.

Chuck