Yes, but why store them on the cap shrouds when not needed and have
the chafe and useless weight? Why not have them functioning as
redundant lower shrouds with enough back angle to help keep the mast
in column against the inner stay?

Unless the inner stay is also removable, there are things other than a
sail that can put loads on it. Missing stays and going aback with the
headsail laying against the innerstay could put a big load on the mast
and put it out of column in an extreme situation. Having the
backstays stowed in a position where they provide some support could
be a rig saver.

The back stays won't do the full job in the forward position but it's
up to you to figure out when the rig needs the extra support. I would
size them to function in the aft position. With normal factors of
safety, they will still be able to do a lot in the forward position.
On thing to be wary of is how much load they can put on the mast in
that position if they, rather than the mainsheet, is taking the load
of the mainsail. This is an issue with all backstays and aft lower
shrouds, however.

BTW, I did the indeterminent structural analysis on the standing
rigging and spars for the Rose, (later the Surprise) in "Master and
Commander" for her U.S. Coast Guard certification. Very cool to watch
the computer bend everything farther and farther and see the shape of
one of these rigs at the point of probable failure.

Also designed the rig and spars (as well as everything else) for this
ship:

http://home.maine.rr.com/rlma/Boats.htm#Barque

Although yacht rigs are pretty far off my radar screen except for my
own boat, I've thought about them a bit over the years.

--

Roger Long



"Rich Hampel" wrote in message
...
Go with running backstays ....
They are a royal pain in the ass as they need to be readjusted on
each
tack BUT the wide base angle (distance from the bottom of the mast
to
the attachment point on deck) is large so that the mechanical
efficiency is much more efficient (in comparison to fixed
intermediate
stays), can use less strong tackle & wire/line, etc.
The 'nice' thing about runners is that they can be slacked and
stored
on either the cap shroud or the lower aft stays when not needed.

With fixed intermediate stays the base angle is too small (the
intercept angle of the stay with the mast) to be of any significant
structural support strength, etc. needing *humongous* strength in
the
deck/base and significantly stronger 'wire' than a runner. A fixed
intermediate stay add unecessary 'weight aloft', doesnt do a good
structural job (because of the low interc ept angle with the mast
attachement).
Its all about the 'trigonometry' of the attachment points. and the
huge
forces generated by the small intercept angles.
Choose Runners if possible inspite of their being a PITA
;-)


In article , Len
wrote:

I want to install a cutter-stay and two back stays on my 50ft alu
sloop, 1) to add a cutter-jib to my sailing options and 2) to stop
the
annoying pumping-motion of my mast.

So my options a

1) Running backstays, which are relatively hard to install reason
why
I would prefer:

2) Fixed backstays, to be installed on the existing puttings of the
lower stays and the other end on the exsisting mount of the
intermediates. When fixed like that, there will "room voor the
boom"
on downwind courses.

Problem is the very small angle the fixed backstays will make
compared
to the mast. They will be fixed to puttings one meter before the
mast.
The other end will be mounted 14 meter high in the mast.

What do you think about the forces such an installation will cause
when using a cutter stay in heavy weather?

Regards, Len.