Subject: Re: [harryproa] Re: 8.5m multi "box rule"
From: "Rob Denney" <>
Date: 1/23/2006, 9:32 AM

Fixed length is not a proa strong point.  I am not sure whether the weight and windage savings possible with a proa would offset that or not.  It would certainly cost a lot less.  I would love to have a go at designing something for it..   There are a few areas that proas can exploit that are not open to cats.  
Maybe wait and see how the Elementarry being built in Belgium goes against the Tornados (this summer, I hope)  and then look at what should be scaled up and what can be reduced.  Incidentally, I will not be competing in  the Bol d'Or (hope to be racing Blind Date in Denmark), but the boat is available for charter if you or anyone is interested.  I would advise that you do it unofficially with two crew, rather than officially with three. 
Could you let us know the beam, mast height and sail area of the M2 class, please.  On the web page it looked like 70 sqm upwind, plus a similar size screecher, but this does not tally with the Melges sails.  On this subject, I think the melges sails would be too light, and not of optimum plan form for a light air boat which would have a near rectangular main. 

Sorry for misquoting, David mentioned this box rule naturally.

Yes these crazy boats are incredible, I have seen them flying a hull
on flat water, 8kn of speed with 5kn of wind. They work by creating
their apparent wind. But their top speed is estimated at 30kn.

The last horrible wind-less Bol d'Or was done with "winds averaging 3
knots", the winner took 18 hours for the 100 miles. That is beyond my
nerves anyway.

There are two classes. the M1 (only Decision 35 today) are machines
costing half a million swiss francs (about the same in AUD), with a
racing budget of maybe half that on top of it every year. The pre-preg
hull skin is less tha a millimeter thick...
And they are low cost machines versus the f40 they had before! A very
well known owner of D35 is bertarelli, yes the poor guy who owns
alinghi and the america cup... Well I do not have any prospect of
competing (financially) for some time to come, even if I am a rather
optimistic type.... But this might be a job for a Turbo-Harrigami.

But there is the M2 class, and the M2 are much more "accessible" (for
a catamaran, around 100kCHF). The M2 are very close in performance to
the M1, and I would be very happy to be in the 10 first of the Bol
d'Or to start...

A HarryM2 would probably cost much less than that (Rob, am I right?),
because of the structural advantage, and would be competitive with
much less high tech gear than the cats and tris in this class. It
would be nice to be competitive with wood-epoxy hulls and minimal use
of carbon (only rig and beams), against all-carbon-kevlar racing
machines. Kind of David against Goliath. But David still needs a good
slingshot! And HarryM2 would still need a lot a sail.

To decrease cost while keeping good performance, I am wondering if the
whole rig for an 8.5m can be built around "standard" sails. For
example, a melges 24 sail plan (24m2 main, 10m2 jib), of which you
find (not very much) used sails for reasonable prices, while only
needing to recut the jib a bit.

--- In, Mike Crawford <jmichael@g...> wrote:
>   I think it was David Howie who wrote about the box rule, and it just
> shows up in my posts because I keep on replying in the same thread.
>   Any ideas David?
>   BTW, If I wanted to race on Lake Geneva, I'd be much more likely to
> want something like those Décision 35's for which you provided a
> That was you, Dominique, wasn't it?  In any case, I'm astounded by the
> sail area carried by those boats, and am truly amazed with the video
> that shows them flying hulls and sailing at speed without a single
> whitecap to be seen.  I'd simply love to sail one for a few days.
>   Those boats are way too finicky and fragile for something I'd get,
> provided I could afford one in the first place, but there's no denying
> that they are masterful speed machines, especially for light air.
> I love the schooner rig with flexible unstayed masts, I'm viewing this
> from the perspective of racing single-handed in gusty conditions.  In a
> real race, in low wind, with crews that know what they are doing, I'd
> have a hard time imagining anything beating  a Décision 35.
>   I don't truly want one of those fast cats for a variety of reasons,
> but they sure do make me drool.  I'm going to go look at some Décision
> 35 photos now, and maybe watch that video again.
>        - Mike
> dominiquebovey wrote:
> > Hi,
> > Mike just wrote about an 8.5m "box rule". On Lake Geneva, switzerland,
> > there are two multihull classes, M1 (10.8m hull length,
> > Alinghi/Bertarelli is doing this) and M2 (8.5m), see this link:
> >
> > My conceptions of rig stiffness are somehow influenced by the sail
> > areas you see on the diagram... And lake geneva is terrible for wind,
> > with most summer races in ghosting conditions (including the "bold
> > d'or"), but in spring and fall there can be quite a lot of wind.
> > What is the "box rule" you are talking about,Mike?
> >
> >

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