Cap Shroud Layout

[daryl_wilkinson]

I like (A) because the caps are easy to make adjustable ( I used a track on LFC this could be set up for on the water adjustment ) but the caps can interact with the bottom spreaders and break them. So I am leaning toward (B) or (C). (B) for a stiffer rig (C) for a softer rig set up. But I still like (A) I suppose because I have had it before? Undecided of Watlington.

[kevin_ellway]

Having a quick read on euler buckling.

http://en.wikipedia.org/wiki/Buckling

The interesting thing is not just the effect of the length on buckling but also the effect of the end support. i.e. fixed or able to rotate.

if the longest un-supported section of the mast is from the gooseneck to the lower spreaders/D2's. The top of this section is effectively fixed (held in column by the rest of the mast above spreaders)  and with a deck stepped mast the bottom is also fixed( held in column by the lowers and the mast below the lowers, however with a mast sitting on a stump to the gooseneck the base of the mast is effectively pinned and able to rotate so the unsupported length is multiplied by a factor of 0.707 rather than 0.5 before being squared.

Thanks for the reference Phil, so buckling load is proportional to length^2, not ^3 as I recalled from uni 30 years ago!
Anyway, it is practically impossible to have encastre end conditions on a mast. You would have to set the bottom in concrete. There will always be rotation at the mast base and at any wire fixing point, so the column will act as though it is pin jointed at all support points. It is, however, clear that supporting the mast midway between the gooseneck and hounds will substantially increase its buckling load limit.

[JimC]

Halo, which was the first C-tech rig, started with a floor stepped mast with caps over the ends of both spreaders and back to the gooseneck with lowers, and ended up with an unstayed stump with the gooseneck on and the caps to the base of the remaining spar. I'd repeat that layout if I sailed a spinnaker Canoe. You end up with loads of tension on the checks but the mast feels very safe. As a boat owning forward hand I was never been able to think of an argument for a push kicker on a pre 2005 rig Cherub when I considered the 'orrible things it does to mast bend and low down sail shape, all to lose a bit of wire that wasn't a problem to me anyway...