Subject: [harryproa] Re: Bruce No.
From: "robertbiegler" <>
Date: 4/22/2006, 6:53 AM

--- In, "oceanplodder2003"
<dana-tenacity@u...> wrote:
> Just been reading an article on these, seems 1.9 and above is a fast
> boat, do we know what the no. is for Harry?

The Bruce number is simply the square root of sail area divided by the
cube root of displacement.  The numbers caclulated from metric or
imterial units differ by about a factor 4.  For Harry, calculated from
sail area and displacement in metric units and racing trim (empty
weight plus two crew) it's 7.02, calculated from imperial units it's
1.76.  At designed cruising displacement, the numbers are 6.12 from
metric units and 1.53 from imperial units.

As for a Bruce number of 1.9 or above, that's for pretty extreme
racers requiring a lot of attention and skill.  Ellen Macarthur's B&Q
comes in at 7.95 in mteric or 1.99 in imperial.  Fujifilm, one of the
ORMA 60 trimarans is at 9.52 or 2.39.  That's the kind of boat which
is fully powered up in 8 knots of wind.  Most monohull cruisers come
in at 4 to 5 or 1 to 1.25, reasonably fast multihull cruisers at about
6 or 1.5.  Personally, I wouldn't recommend much more than that unless
you either sail a boat small enough that a capsize is a mere nuisance,
or you are an adrenalin addict with exceptional skill and attention
span and you can afford the cost of the occasional salvage.  Though if
you do crave that sort of excitement, I am sure Rob can provide it.


Robert Biegler

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