translation of seine twine sizes?

[rdykiel]

I'm sorry for the rookie question but this has been annoying me for a while: what is the correspondence between the sizes for twine seine and the actual width of the twine (e.g. 1/8 inch)? Also, do you have any guidelines regarding proper size selection for lashing applications on a small sailboat (24 ft). E.g. I have been using a "thin" twine for lashing a radar reflector to a 3/16 shroud wire, and a "thicker" one for other things; if I wanted to lash a pinrail to my shrouds which size should I use? Ideally I'd like to carry the minimal set of sizes on my boat where stowage is at a premium, so 2 sizes would be great (thin and thick).

Thanks, and happy New Year!

[Ian McColgin]

I don't know about sizes but materials matter as well. When I set up any sort of lashing, I consider the strength of the twine, which is usually not all that reliably reported in any standard manner - safe working load, breaking strength, or whatever. So I figure useful working load about half whatever is on the lable and I take off another 40% for putting the line through a 180 degree bend. So each run of the lashing is worth about a third of the rated strength of the line. Then I add more as feels right.

It will be interesting to me if responsible and properly trained riggers agree with this rule of thumb. It's not failed me but that does not mean the engineering assumptions are correct.

G'luck

[Brion Toss]

Hi,
I rarely use "thin" twine, as it is too hard to handle. The stuff is still usually plenty strong -- heck, it will always be plenty strong if you make enough turns -- but size isn't the only thing that matters. Aside from ease of handling, appearance is a factor; too often lashings that could be handsome are bulky visual intrusions, or tweezy bits of fuss. Ropework should be handsome.
A good rule of thumb for seizings: use twine (or seizing wire) that is about 1/8 the diameter of the material you are seizing. This will satisfy structural as well as aesthetic considerations. For palm-and-needle whippings, where thinner twine is appropriate, use twine half the size of seizing twine.
Fair leads, and Happy New Year,
Brion

PS,
We are still sipping that whiskey.

[rickc]

For those of us stuck in the prairies of Canada far from the sea the question remains wh\t do the sizes of twine represent. Brion Toss catalog lists 20, 40 etc as size but what does that translate to in everyday units
Thanks

[Brion Toss]

Hi again,
Oh that. #36, the most generally handy one, is about 1/16". #72, suitable for beefy jobs, is about 1/8". For your boat, I suspect that #30 and #60 might be right, if you only had two sizes. At the very least, using those two would help you calibrate for your ideal.
Fair leads,
Brion

[rdykiel]

Cool, will be ordering shortly :-)