7x19 or 6x19 IWRC too flexible?

[Brion Toss]

Hello,
First of all, why do people say "professional rigger"? We'd never say "professional doctor" or "professional engineer", or even "professional barista". I believe this is because of an unconscious assumption that rigging is so easy, so thud-simple, that only a really exceptional person could possibly manage to get paid for it.
Next, I have used 7x19 for standing rigging, and always under protest (including for the Hess cutter in the Rigger's Apprentice. Yes, it is easier to splice, and yes it is stronger than 7x7, but its big problem is that it is far more elastic than either 7x7 or 1x19, and no amount of "prestretching" will cure this. See, there are two forms of stretch we are dealing with here: constructional and working. The constructional stretch is simply the process of the wire yarns settling into place. With 7x19 it is about .33% for stainless, .25% for carbon.This translates to about 2 9/16" for your longest wires in stainless, less for the shorter ones. But once the constructional stretch is out you still have tuning stretch to deal with, and this, at even moderate design load, would be at least another 2" for 7x19, much more than with 7x7 or 1x19, and this never goes away; every time you load it, it stretches and recovers that much. In addition, 7x19 is far, far more corrosion-vulnerable than other constructions, because of the ratio of surface area to volume of the teensy yarns. So while one can use 7x19 for standing rigging, the answer you got was a bit facile, to say the least. Oh, and the ban on 6x19 -- why? Does 6x19 IWRC count?
Next, the diameters you are talking about aren't making sense. Why was it okay at 9/32" in 1940, but now needs to be 5/16"? What construction was specified in 1940? Not many boats were spec'd for 1x19 back then. And most important, how did you arrive at your load numbers? Something is not right here. Please stay with us a bit longer; I suspect that a closer look will give you better answers.
Fair leads,
Brion Toss