Hmmmm, the image for the structure --neat!-- implies
several lashings? --of each pair of up-&-outward spars
to each other at roughly right (but maybe not quite) angles,
and of these lashed/crossed ends atop spars angling to a
common center point; and of the multiple such spars at
that point!?
7/16" rope seems awfully thick for lashing, although you
do have substantial diameters; but, still, maybe 3/8 or even
5/16" would work better. KM-III, as Scott notes, is quite
a pricey lashing material --and darn strong! (And it has
a mantle but not a mantel.
)
As for "frapping turns", I can't see how they make all
so much difference, in many things (seizings) --where
they span so many wraps it's not possible for them
to pressure other than some few outer ones--;
in a case w/fewer wraps, there might be more effect.
Frankly, I'd like to see some full wraps of the bound
spars --i.e.,. 360degrees, for a sure grip--; the
clove
hitch does this, but it could as well be a round turn.
I'm really curious about how such large lashed items
get put into place : is it that you are focused on the
lashing of the up-&-out spars (at the lower, base end,
only ; the top point-joints come together ... ?); and
then how are these pairs set upon the centered spars?
If my surmise is correct --and how else to interpret the
structure image--, then the lashing of the up-&-outs
is to be loaded/oriented somewhat differently than a
vertical+horizontal joint --they'll be at equal, mirrored
angles to the 3rd spar, against which they'll bear.
--dl*
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