7x19 or 6x19 IWRC too flexible?

[redbopeep]

I am replacing 3/8" 1x19 SS standing rigging. Since I plan on building and maintaining the rig myself and I have little hope of competently splicing 1x19 wire rope (I can handle 7x19...just learned--thanks to the Riggers Apprentice and 35' of 7x19 and a bunch of thimbles...),

I am looking at using 7/16" 6x19 IWRC in 316 SS (larger size to meet the strength needed) or using 3/8" 7x19 galvanized which meets the strength required (with all the required serving...)

3/8" 7x7 while stiffer doesn't meet the strength requirements (and can't find it anyway...) OK, now, big question--are either of my wire rope options (which meet my strength and "splicability" requirements) going to be ok in standing rigging application? The concern is whether it would have too much stretch or the flexibility will be a problem--if so, how?

Thanks!

[Brian Duff]

what kind of boat ? size, etc

[redbopeep]

Originally Posted by Brian Duff

what kind of boat ? size, etc

Can you assist with knowledge of the 7x19 or 6x19 IWRC?

Thanks!

[Brian Duff]

Yes, I can assist. (we can)

what type of boat, size of boat. I mean whose design?

Or just beam, displacement, draft and ballast type/placement/weight and rig type if thats all you care to share....

[redbopeep]

I just had a professional rigger who has done lots of traditional rigging answer my question regarding 7x19--but not through this board. For anyone searching for the same info, the answer I got was to pre-stretch the 7x19 (method was described that I'm sure all you professional riggers here already know about) expect about 2" of stretch. After the pre-stretch, don't worry about using 7x19 or 6x19 IWRC but don't ever use fiber core for this app. If concerned, go to the 7/16" on the galvi for the longest shrouds and backstay but stick with the 3/8" galvi for the rest.

Best to all

[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

[redbopeep]

Hi, Brion,

Thanks for taking the time to reply. The issues you bring up about 7x19 (or 6x19 IWRC) are the same issues that brought me to post the question on this board about stretch and suitability for standing rigging. I think we're both on the same sheet of music about the matter and I appreciate your precise and detailed response to my original question.

Ouch! regarding the matter of professional riggers--I routinely and respectfully use the term "professional" in regard to a trade to indicate that the person has much experience or undertakes the trade discussed frequently and should have knowledge above and beyond that of the layperson. I, and many others, use the term professional in discussion of trades such as professional driver, professional engineer, medical professional, or other trades.

If you'll re-read my response (which may not have been well-written), you'll note the 6x19 IWRC was ok, the rigger I spoke with was simply making the point that fiber core wire rope is not what one wants. The 1940 rig design and spec (way back then, yes) did specify 1x19 of various diameters for various parts of the rig. No mention of SS, so assumed galvi. The present 5/16? vs 9/32 is not documented, its just there on the boat, perhaps that whole upsize thing that so many folks do... or perhaps for the convenience of the rigger who didn't have 9/32 1x19, who knows...

Thanks again for your answer to my question.