rotating mast stay attachment

[rwatson]

If you get a chance John any more detail, or links to diagrams or pictures, on those methods would be very much appreciated.

[brian eiland]

Originally Posted by brian eiland

Mast Tang for Rotating Mast

Many smaller cats with rotating spars simply shackled all three (forestay & two shrouds) all together onto one tang.

I preferred to provide two separate attachment holes on the mast tang. The forestay was attached to a point that was closer to the face of the mast while the shrouds attached further out. This promoted a greater leverage by the windward shroud to firmly rotate the mast, since the forestay already had a greater angle and leverage, and would resist the rotation. This two hole arrangement necessitated the forestay hole as the lower of the two holes. (got an old drawing for my Firefly tri if I can find it)

I always found it was easier to put a rotation limiter at the base of the mast, rather than a rotation inducer.
Headstay attachment on rotating mast?

I had occasion to rumage around an old cedar chest and found a few sketches from my old Firefly Trimaran project. So here I post the tang sketch and a couple for the mast base casting.

Note that the mast rotates on a graphiite reinfoced nylon ball. Its rotation center was placed more reward of the mast centerline so that upon rotation the trailing edge of the mast did not act to close off the slot between the main and jib sails. This casting also was designed to provide a pivot point(hinge) for rasing the mast from horizontal layout forward of the ball (mast laid out in front of boat and pivoted up from there.

This boat was also boomless so there existed no pressure by the boon to induce rotation of the mast...all the more reason to insure rotation and then limit it by a limiter. The traveler for this boomless mainsail was circular to prevent flattening of the mainsail as the traveler was let out to its extremes.

[rwatson]

Thats looking a bit more like someone meant it to work!

The idea of the mast stays pulling the mast in the right direction seems to be a common theme in serious schemes.

I am a bit wary of systems that require the 'right' tensioning of the side stays - it complicates setup for a trailerable boat, and really shouldnt be required for a well engineered solution.

The forestay is still a problem, even though it is closer to the mast.

Thanks for that insight, it is very interesting