Re: Potter Pride (now hull speed redux)

Mac Davis (cgula@innet.com)
Thu, 17 Dec 1998 12:13:08 -0500


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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Greetings all:
As I remember it, the "hull speed" rule (1.34 x LWL) defines not a =
barrier, but a point at which the drag buildup due to overcoming bow =
wave resistance becomes so great that the increase in power required to =
go faster is no longer linear. If sufficient power is available, as it =
in many naval combatants, speeds in excess of "hull speed" can be =
achieved and maintained without planing or surfing. In the case of a =
displacement sailboat, speeds slightly in excess of hull speed are =
achievable with sufficient wind in smooth water, but in the majority of =
instances either planing or surfing is involved. An additional factor =
that complicates matters is that a heeled sailboat usually has a longer =
water line than when level.
Season's greetings,
Mac Davis, Kelpie, WWP19#804, Aripeka, Fl

>- - - - - - - - - - - - - - - - - - - - - - - - - - -=20
> West Wight Potter Website at URL=20
> http://www.lesbois.com/wwpotter/
>- - - - - - - - - - - - - - - - - - - - - - - - - - - =20
>> > The incident got me reminicing about the Soling and I had a
>> funny thought:
>> In
>> > class, they taught us the "hull speed" equation. You know the one =

--
>>  > Displacment Hull speed =3D 1.3 something times square root of =
waterline
>> length.
>>
>> Surprising how many people believe that outdated tanker rule...
>
>Yeah no kidding. Everyone knows that waves in water move so much faster =
than
>they used to :P
>
>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.

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Greetings all: 
As I remember it, the "hull speed" rule (1.34 x LWL) = defines not=20 a barrier, but a point at which the drag buildup due to overcoming bow = wave=20 resistance becomes so great that the increase in power required to go = faster is=20 no longer linear.  If sufficient power is available, as it in many = naval=20 combatants,  speeds in excess of "hull speed" can be = achieved and=20 maintained without planing or surfing.  In the case of a = displacement=20 sailboat, speeds slightly in excess of hull speed are achievable with = sufficient=20 wind in smooth water, but in the majority of instances either planing or = surfing=20 is involved.  An additional factor that complicates matters is that = a=20 heeled sailboat usually has a longer water line than when level.
Season's=20 greetings,
Mac Davis, Kelpie,=20 WWP19#804, Aripeka, Fl
 
>- - - - - - - - = - - - -=20 - - - - - - - - - - - - - - -
>      = West Wight=20 Potter Website at URL
>        = http://www.lesbois.com/wwpotter= /
>-=20 - - - - - - - - - - - - - - - - - - - - - - - - - -  =
>> =20 > The incident got me reminicing about the Soling and I had = a
>>=20 funny thought:
>> In
>>  > class, they taught = us the=20 "hull speed" equation. You know the one --
>>  = >=20 Displacment Hull speed =3D 1.3 something times square root of=20 waterline
>> length.
>>
>> Surprising how = many people=20 believe that outdated tanker rule...
>
>Yeah no kidding. = Everyone=20 knows that waves in water move so much faster than
>they used to=20 :P
>
>That rule is believed because it is accurate and true = and=20 based on real
>physics and vast empirical data :) Call me old = fashioned,=20 but I'll stick
>with what all naval architects say about = displacement=20 hulls. ------=_NextPart_000_000B_01BE29B6.9BBE9DE0--