1x19 wire twisting under load?!

[Robbie.g]

Perhaps an easy one, and i am showing my lack of 'basic' rigging knowledge, but does standard 1x19 twist much under load?
I understand that Dyform does twist significantly as load is introduced as the lay on the inner and outer strands are the same direction, which is why navtec recommend not using dyform in conjunction with a hydraulic adjuster. But with standard 1x19 the outer and inner strands are layed in opposition. Does this mean that they counteract each other exactly?
Any thoughts?
Thanks

[Brian Duff]

1by 19 does resist twisting. I have not noticed any twisting under load, for example, in backstays made with 1by19 upper and tackle lower - as load is applied the lower fitting stays constant....

[Robbie.g]

Thanks Brian.
What set this off was that a client quizzed me on why the rigging screws on his boat had no locknuts or splitpins on them, and other boats around with open bodied turnbuckles did.
He had the old style Graham rigging screws, a kinda searig style of turnbuckle the early ones of which had no locknut or locking screw. Here in NZ there are many boats rigged back 'in the day' using these, and theres still a few about. Any way i have not yet heard of/seen evidence of on undoing it'self, despite the lack of locking devices, hence the twisting question.. They look like pic 10 in the link below.
http://www.trademe.co.nz/Trade-Me-Mo...-213264608.htm
Cheers

[Brion Toss]

Hello,
These types of turnbuckles usually do have a locking mechanism, in the form of a set screw that engages a radiused slot in the barrel. The kind you show might be ones that have only one threaded end, the one on the wire, so the effect of torque is minimized. That is, the barrel can rotate, but it is a bearing, not a screw, so if the wire torques, it can only loosen the wire stud, and that not far.
I don't like these turnbuckles, having had trouble with metal cracking adjacent to the set screw, and internal corrosion. They also seem much harder to take up than conventional turnbuckles.
Fair leads,
Brion Toss

[Robbie.g]

your dead right that they can be hard the take up on, as unlike the searigs the old style graham turnbuckle have a stud that is only threaded for the first 30mm then it is clear shank with calibration marks, so when the turnbuckle is buried there is a deep recess for the dirt/detritus to collect in this usually leads to the 'crud' getting pushed down, making the treads tight.
You are quite right the later model tb's had a locking grub/set screw to lock the lower[outer] barrel to the middle section of the tb via the groove, but still no lock on the upper [inner/stud] part. For us you see an 'old style graham', we read take the heat and the big spanners with you!! cos they get real tight with age and crud... Guess the crud was the locking device....Ha Ha
Thanks for the replys

i've been reliably informed that these were the fore-runner of the searig turnbuckles, which look really quite neat, in my opinion.... and they have the locknut on top n a grubscrew in the side.
Never heard of any cracking as you say on 1x19, but only once on a dyform backstay, but this could have been helped by the owner 'loosening' the riggingscrew without taking out the grubscrew!!