Thanks for the kind words.
That's a St. Mary's Coxcomb
http://www.frayedknotarts.com/tutorials/coxcombing/smary.html, a three line overlapping continuous series of half-hitches.
I start them off by stropping the working lines side-by-side to the core, then determining which way I want the coxcomb to go.
Taking the line OPPOSITE the direction to be traveled, make a half-hitch in the direction desired and snug it up, then take the middle line and bring it OVER the first and half-hitch and snug up, then the last line, do the same and then for each successive hitch, ALWAYS take the TOP line OVER the other two, make your half hitch and snug it up. Continue in this vein for a few more passes and the pattern will show immediately. Continue doing one half-hitch after another and try to keep the amount of strain you put on the half-hitches consistant (or as near as possible) so you don't get a lot of hills and valleys in the spiral detail, and constantly keep pushing the finished half-hitches up along the core as you go.... shoving them home as you go with your nails or a tongue depressor to get an even covering.
That's the whole secret... consistent pressure and "fairing" up the work as you go.
When you arrive at the finish point, simply strop the lines down close to the last hitch and either put a bit of varnish on the last three half-hitches, or use super glue or whatever, just to "tack" the end in place. (Go back and do this to the beginning as well.) Trim the excess and cover as below.
As for finishing them (not shown in the website) I use 7x6 turk's heads, passed either three or four times as required for a tight covering. You'll find that wrapping some heavy white cardstock around the coxcomb and then doing the turk's on top of it, getting it fairly tightened, then moving the turk's along to final position, winkling out the cardstock and doing the final tightening will immensely simplify this job.
Do a "dummy run" first using a measured amount of line and seeing how far you can cover with, say 2 yards of line. It is a simple matter to then divide the distance covered by the line used and come up with how much per line you'll need to do a specific length. ALWAYS add about 5% to the calculation! Far better to have extra line than to run out just shy of your target!
AS far as either parcel string OR 2.mm polypro, I'd not bother with either.
Talk to Des Pawson and see what he has in a nice cotton or flax right-hand laid line.
On the pipe rails, (and pardon my English to Metric conversions... they may be a bit off) to cover 25mm of 38mm dia. rail took about .49 meters of line for each of three lines, including the 5% insurance. It takes QUITE a lot of line to do.
Hank up your line so as not to be pulling gobs of it thru the hitches... if you dont, you'll have progressively softer line as it works out against its lay. If using a radially-woven cord, be careful not to "kink" it as you do the hitching...easily done and ever-rued.
