RE: "hull speed" equation formerly "Potter Pride"

Eric Johnson (ej@tx3.com)
Thu, 17 Dec 1998 23:03:14 -0800


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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> In a message ej@tx3.com write:
>
> "That rule is believed because it is accurate and true and based on real
> physics and vast empirical data :) Call me old fashioned, but
> I'll stick with
> what all naval architects say about displacement hulls."
>
> >>
> Flash AP News:
>
> Earth proven to be flat...
>
> Waterline length rules!!! All other factors declared irrelevant.

You're putting words in my mouth. I never said that. It IS important
however, and particularly important in potterdom. we're not regularly going
to beat 25 footers in adequate weather.

Mac put it better than I did, but 1.34 x swrt (lwl) is STILL the speed of a
wave in water with the crest LWL apart. It requires a huge amount of extra
drive to exceed it for any extended length of time.

> Catamarans and Ultralight sailboat owners fined for exceeding "Hull Speed"
> limit... Judge orders craft sunk!

This is a POTTER list. There is no sail-powered potter that regularly
exceeds that limit in still water.
Gravity is still 9.8m/s/s by the way :)

> BTW:
> That 18th century law (engraved in concrete, unquestioned to date, and
> followed by rote should slow down all those Ultra lights and
> Catamarans down
> to a crawl... For sure...

Sure they exceed it all the time. The potter is not a regularly planing
craft like these of a FJ or Flying Dutchman or anything else. The rule is
still a valid one - not inviolable, but if a P19 owner, for instance, is
regularly getting 5.5knots, they should count their blessings and not strive
for much more top end.
>
> << Yeah no kidding. Everyone knows that waves in water move so much faster
> than they used to :P
>
> El nino did it!
>
> Made them waves go so much faster...

must have been. Maybe la nina will slow them back down again...

> Even more surprised at how many people subscribe to that ole tanker
> formulae...

guess I'm an old fasioned guy.