Another day at the office

[wheels 543]

Just a wee job the lads have been doing

[rigger 47]

Is that to be part of a system on the west coast North Island?

[wheels 543]

Something to do with an oil rig. KM will tell more I am sure.

[Guest]

Yes I believe so Rigger.

 

Part of a tow rope that will be being hooked up as I write to the largest floating movable structure in NZ waters they say. That's a section that gets put into the system to give some elasticity.

 

We did a small 72mm pure Dyneema for the rig a few weeks back. That was used to pull a well stuck anchor out.

 

The scale of this stuff is pretty good, for NZ at least. Rigger, Smithy and a few will have played with larger but knot in NZ waters I'd expect.

 

A photo of the yellow dyneema (what many mistakenly call Dynex). Suss the pallet to get an idea of the size to the thimble hence rope. Over 400t break load on that bad boy.

One of the other rope with the most commonly found size (16mm) of anchor warp in NZ sitting on top.

And a blue 96mm Dyneema tow rope for well known superboat (stupid skipper must have thought he had more bollard pull than any tug in NZ... knot!) we did a few months back. Next to that is a dyneema rope commonly found on fizzy trailer winches and it's a 6mm.

 

Yes for those with very keen eyes, there are differing splices for the differing levels of analness. Some industry rules and regs are still very old school so you have to get the latest and greatest them degrade it's performance to comply. MNZ are very good at doing that in some areas. Get 2010 technology then make it work to the same level of stuff made in the 1800's, in fact MNZ still specifics stuff used extensively and made in the 1800's for use on boats being built today. It's beyond bizarre

[smithy09 50]

Youi know what this means? With this rode,

 

 

and this anchor,

 

 

No more anchor watches in Izzy bay

 

[Guest]

No more anchor watches in Izzy bay

Only watching boats hit your anchor.

[Guest]

Just a wee job the lads have been doing

 

 

Would a bowline not have been quicker, and provided the same function?

[Guest]

To much load loss in a knot JJ. As the gear on the big structures is so large handling is a factor taken into account where for us with little structures/boats don't have to worry about carrying a 50mts rope around. When it's that size you're starting to get into kilos per meter and that's dry, get it wet and it can hold another kg or 3 of water. Before you know it 50mts of that big rope could weigh 200-300kg. Once you're there it means handling becomes a lot harder hence they they to keep the size down which means less reserve strength which leads to less room to use knots.

 

If they put a bowline in that they could lose 40% odd of it's load meaning the rope would have to be 65% odd bigger to have the same load capabilities. Splice a eye/thimble in and that doesn't happen.

 

Put a bowline in the yellow or blue Dyneema ropes above and they would have to be near on twice the size to get the break load back up to what it would be if you spliced the eyes in. The fancy newer materials hate knots with a passion.

 

Start playing in the big gear and the whole dynamics of certain aspects change, some dramatically.

 

As a FYI - that dyneema is now being extensively used for mooring oil rigs and other huge platforms. While it costs more than the old school wire they used to use, the operators save moonbeams in having lot smaller gear to shift it around. The wires they used to use had to be a lot bigger than the load required to hold the rig. That's because the weight of the wire over what could be a very large span can get so large they have to up the size of the wire just to carry it's own weight. With the Dyneema ropes that doesn't happen so they can use smaller rope meaning smaller gear to play with them meaning less costs all round offsetting the high material costs.

 

It's all quite interesting for those with sick twisted fascination with ropes and other weird related sh*t like that.

[rigger 47]

Put a bowline in the yellow or blue Dyneema ropes above and they would have to be near on twice the size to get the break load back up to what it would be if you spliced the eyes in. The fancy newer materials hate knots with a passion.

 

towline broke - put Bowline in amsteel blue ~40-50tonned load and the bowline pulled out. Line did not break.

[idlerboat 116]

towline broke - put Bowline in amsteel blue ~40-50tonned load and the bowline pulled out. Line did not break.

 

Hi Rigger, would a bowline with a half hitch on the base of the knot make the differance ? I know that the scale that I deal with is miniscul compared to the stuff you do, but given that the half hitch is down stream of the bowlines "parts" and only serves to restrain it until the knot itself pulls up ?

I also understand that in itself the half hitch could lessen the Knot strength to a degree.

As a further question, traditional "rope culture", describes the bowline as a knot that has one of the least reductions in rope strength with the ability to still undo later.......is the newer high strength ropes (please chime in here KM) far more likely to slip with old school knots than older style ropes.

Further..given the differant properties of the modern ropes, is a differant type of knot with less slip, (but more shearing force) possible to be used ?

(or to put it differantly, is modern ropes, proportinaly more able to withstand knot shearing force ?

 

cheers

[rigger 47]

ID that might help.

The rope maker told us to out an overhand knot on the bight to make an emergency eye.

Once you put a knot under serious load with our gear it is nearly impossible to undo. Have just cut the knotted end off in the past.

 

Their opinion seems to be any knot to make an eye is for emergency use only. Mind you the stuff I work with is pretty easy to splice once you get used to it

[Guest]

Dyneema is a super slippery fibre so pulling knots isn't hard, another reason knot to use them...... go the pun

 

If you do have to use them you need to make sure they are tightly packed prior to a big load being applied and then load it is with some caution. I'd also say a Overhand is probably one of the better options.

 

Bowlines are good but knot one of the best for keeping load. It's all about keeping the little Dyneema Fibre soldiers all lined up in nice rank and file. The more they get out of those nice straight lines the more the whole group loss's focus and strength. Hence knots with more sharp corners will lead to those soldier losing the plot (strength).

 

As Rigger says generally these dyneemas are very easy splicers so that is the preferred option by a long way, a very long way.