Rope shrinkage from splicing

[benz]

I was making up some bowsprit shrouds from polyester-covered Vectran, and twice had my very careful measurements come up short. At last I realized that increasing the diameter of the rope by shoving rope inside of it made it shorter. I'd like to know if there's a chart or a formula available to calculate how much length is lost to a splice for a given diameter of rope. It will take out the guessing when I move on to other diameters.
Thanks
Ben

[Brion Toss]

Hello,
We've been working on developing such a chart, but it varies according to brand, as well as diameter and, near as I can tell, the phase of the moon. So for now the best practice is to mark your tail, mark the circumference of the eye, and then beginning at the eye circumference mark that is farther from the end, measure some arbitrary distance -- say, 4ft, and mark the standing part.
Splice in your eye, and then remeasure the distance to that last mark; it will be less than it was, by the amount of shrinkage that the splice causes.
Fair leads,
Brion Toss

[benz]

All right. Well, the moon was waning gibbous when I did my splices, and it seemed to take eight to eight and 1/2 inches out of 7/16 Poly covered Vectran. If I can make that stay constant, I'll be OK for most of my project.
I hope to see some updates on the shrinkage chart one of these days.
Best,
Ben

[Brian Duff]

i typically layout the first splice and mark the line 10' down or something, do the first eye and measure how much i lost, use that for the other end of the line.

do this each time.

[Brion Toss]

Originally Posted by benz

All right. Well, the moon was waning gibbous when I did my splices, and it seemed to take eight to eight and 1/2 inches out of 7/16 Poly covered Vectran. If I can make that stay constant, I'll be OK for most of my project.
I hope to see some updates on the shrinkage chart one of these days.
Best,
Ben

Better check your numbers. I don't have our notes with me, but I'd be surprised if the shrinkage exceeded 3" per end.
Fair leads,
Brion Toss

[benz]

Great idea, Mr Duff, thanks.
And Brion, 8" seemed a shocking amount to me as well, but so far two splices have come out exact using that measurement. Of course I'll be constantly refiguring as I do more splices.
Ben

[Brion Toss]

Hi again,
On reflection, it's not merely shocking, it just isn't possible to shrink 8". Are we talking about per splice? And where are you measuring from? How much bury, and how much taper?
Fair leads,
Brion Toss