Wait why'd I write hex ? Guess I can't stop thinking about those new hex-core processors. ^^;
Well you know what I meant. Guides for connecting a line between two fixed points yet there aren't any for a line that has to go in moving arms in a weird pentagonal shape.

Also, am I just blind at noticing the edit button ? Didn't mean to post a second post quite so quickly.

Are these the umbrellas with concentric lines (meaning the inner spans are shorter than the outer spans), or are they the umbrellas with all the lines parallel and evenly long?

Actually as I think of it, my answer would be the same, in both cases. In my umbrellas (and my straight lines, too) I use a system of alternate lines running in opposite directions to counterpose the strains. Meaning in my umbrellas (which are all the concentrictly-rigged variety) I start off two strands of flex running in opposite directions, alternating on every other row. The flex isn't tied off for each individual span, or ring, instead it travels along the skeleton to the next, but one, series, if that makes sense. And about half-way out I strain and tie off the line to isolate the effects of weight or temperature driven line stretch. It's two person job to pull and match the tension of these opposing runs, but it works well and I don't have any major distortion, even under load in heavy storms.

I use the same tactics in long lines: opposing, alternate lengths, tensioned against each other during set-up and from time to time when readjusting. Often I do get sort of trapezoidal shifting on the longlines which span multiple T-bars, but it isn't really a problem.

At the beginning, middle and end of each line, I find that a simple knot and a short tail works best to allow me make occasional tweaks. In my area we have wide annual temperature swings, on the order of about 120F over the course of a year. This makes a big difference in line stretch over time.

A tightly rigged set-up is pleasing to the eye, but I don't get fanatical about it, though.

My umbrellas are not hexagional, but rectangular and not square, either. My advice about stringing would be same no matter what shape.

BTW, I prefer to have the center poles of umbrellas loose, rather than set in concrete. They are set in (or actually, in my case over) pipe supports that are set in concrete, but it is useful to have the actual stems loose enough to pivot.

HTH,

L

Yes, and different types of line have different stretch properties. The plastic coated, all plastic, cotten, synthetic clotheslines will all stretch out differently and all have a weight load just like a fishing line would. I use the knots just like Liriodendron does and find they need adjusted after the first few uses to compensate for the stretch. I have mine set in concrete, but loosely so that the pole can be rotated in the hole.