Soft stays to mast
 

Salutations,
Long time Rigger's Apprentice owner, and lurker on this site.

My question is about a small sportboat with a carbon fiber mast. I'd like to get away from metal tangs or t-ball fittings if possible. I thought it might be possible to install a small carbon or G-10 compression tube through the mast, with some carbon cheeks around the holes, eased edges, and then pass the upper end of the stays through in opposing directions, each with a simple stopper knot (such as the double-eight from Colligo's site), with the knots living on the outside/opposite side of the mast from the stay that they stop.

Any idea what kind of percentages are achievable with such stopper knots?

Additionally, I thought it would be slick to double the line back on itself by turning the last several inches inside out, passing the self-jacketed line through the hole, and then tying the stopper knot in the end. Think there's any chance the line would un-invert itself through the knot? I guess the tail could be stitched if so?

I think I've seen similar on the Swift Solo site, but not sure if it would scale up just a little to a three person 18' boat.

Thanks,
CAM

edit: see white line here:

Probably not okay
 

Hello,
Clever ideas, and definitely the sort of thing that helps evolve the use of HM rope for standing rigging, but I can tell you that those knots will evert or break under standing rigging loads; they are used for soft hanks, with low relative loads.
Beyond that, your letter proposes way, way too many untried variables for me to comment on here. It's not even clear what we are seeing on that carbon mast, let alone any quantifiable results on the advisability of it. So please, by all means carry on with the Bright Ideas, but remember that you are in still-largely-untested waters here.
Fair leads,
Brion Toss

Thanks for the reply.

I thought getting stopper knot strength reduction percentages would be a useful comparative way to judge this kind of use- after that, it's just installation details (eased edges, fair leads) and maintenance (chafe, slip, inspection). This won't be a install-and-forget kind of rig.

Colligo's site has some stopper knot info, but it is more sales-pitchy, less technically complete than I would like.

And if you're curious, from a careful reading of the Swift site, the pic shows:
--the forestay in yellow with a t-ball fitting (although my second choice would be to cow-hitch the line, rather than add the thimble...),
--to the right are the lowers connected to a metal tang with a through-bolt,
--and the big ball of rope just above the mast, to the right of the spreader is the stopper knot for the starboard trapeze string,
--and the port trapeze string is leaving the same hole and heading toward the deck or right in the pic.

CAM