International 14 Mailing List
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From: Jim Champ (jimc@hjones.compulink.co.uk)
Date: Thu 29 Jul 1999 - 19:11:03 BST
> On rotating rigs - I'd like to simplify the rules by getting rid
> of the technical restrictions on rigs, including rotation, double
[snip]
> penalty, and continue to get faster. Frank Bethwaite makes an
> excellent case for the aerodynamic benefits of rotating masts. As
> for Julian's comments about high rig loads preventing the use of
> rotating masts, perhaps he just needs to find a more clever
> engineer?
Think maybe I could usefully unlurk on this topic... We've always
permitted rotating masts in Cherubs, and indeed I have one of Nicola
Bethwaite's old wood masts hanging up in the garage, very similar to
the one that she and Julian used when they won the 76 Cherub Worlds.
I've always liked the idea lot, and played round with things
intermittently. The rig loading problem is a big issue, but not
insuperable (I've played about with a mast that steps, pivots &
rotates above gooseneck height for instance) but also a major issue
is how you support the topmast with a masthead kite and still retain
decent gust response in the mast. The big multis don't really see to
panic about gust response, and seem to support the thing by runners
and/or shrouds without spreaders to the top mast. Spreaders are a
problem, since making them stay static while the mast rotates is
problematic, to say the least, whilst diamonds are fine for
supporting the mast below the hounds, but they must stop about 6
inches short of the hounds to avoid getting caught up in the shrouds.
Any kind of diamond that goes past the hounds will again get tied up
in the shrouds as the mast rotates. Also the bend characteristics and
direction that give a decent responsive topmast with an over rotating
rig means that the spinnaker is pulling the topmast in quite the
wrong direction and into a very odd shape!
In the Cherubs, then, over rotating wing masts haven't really been
seen since the 70s to any great effect, and certainly no-one's
attempted anything with a masthead or near masthead kite. I think I'm
right in saying that the only development class where they are widely
used nowadays is the NS14, where you're talking about no kite and a
small rig that needs every available ounce of power - certainly not
the case with the 14. So permit them by all means, but be careful
about rushing out to build one!
In this discussion you guys might also be interested at looking at
the UK Cherub rules, since we've devoted a lot of effort in the last
few years to simplifying them. Its handy not being an ISAF
administered class! http://www.sailingsource.com/cherub/hullrule.htm
cheers, Jim C (UK Cherub webmaster)
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