Re: [bolger] Windage
Yes. Even1/2 hp ( say that 15 kt breeze ) will drive a boat like CCS at up to 3 kt. Get
your fenders out!
Mark
Jeff Blunck wrote:
your fenders out!
Mark
Jeff Blunck wrote:
>
> Your probably right in that the windage is of small concern in normal
> weather but just the same, docking can be a big problem with a lot of
> windage on a small boat. Even on the larger Wyoming I'm building, Bolger
> recommends caution in crossing winds when docking and to NOT leave off the
> centerboard.
>
> Jeff
Your probably right in that the windage is of small concern in normal
weather but just the same, docking can be a big problem with a lot of
windage on a small boat. Even on the larger Wyoming I'm building, Bolger
recommends caution in crossing winds when docking and to NOT leave off the
centerboard.
Jeff
weather but just the same, docking can be a big problem with a lot of
windage on a small boat. Even on the larger Wyoming I'm building, Bolger
recommends caution in crossing winds when docking and to NOT leave off the
centerboard.
Jeff
----- Original Message -----
From: "Mark A." <marka@...>
To: <bolger@yahoogroups.com>
Sent: Wednesday, March 19, 2003 2:30 PM
Subject: [bolger] Windage
>
> Interested in the effect of windage on the large house, Bolger power boats
like Cabin Clam
> Skiff, SBJ Cartoon #9 and Idaho, I had a look at one of Jim Michalak's
essays.
>http://marina.fortunecity.com/breakwater/274/1998/0501/index.htm#Sizing
Sails
>
> He gives the formula for wind force on any panel as .0034 x S x C x V x V
in normal air at
> sea level.
>
> S = area
> C= the mysterious, "Force Coefficient", maximum of 2.
> V= wind speed
>
> But because the theme is really the effect of hiking out, I get confused
about whether
> pounds and foot pounds are equivalent here.
>
> So ( with some uncertainty ), I calculate the force of a combined 10 kt
wind on the Clam Skiff
> house's 25 sq. ft front end as 17 pounds. Since about 60 pounds of thrust
or bollard pull
> equals 1 hp, then it takes barely 1/4 hp extra to power against that wind.
A 15 kt breeze
> is still only 38.25 pounds, or a bit more than 1/2 hp.
>
> Figuring this way, it's hardly more dramatic if the boat is trying to go
20 kt dead
> against a 10 kt air: .0034 x 25 x 2 x 30 x 30 = 153 pounds, only 2 1/4
hp.
>
> There's another similar little formula for figuring aerodynamic drag force
I get from Bob
> Brant's 'Build Your Own Electric Vehicle', which is all about cars: Fd =
(CdAVsquared)/391.
>
> Fd = drag in pounds
> Cd = coefficient of drag for the vehicle, a flat plate = 1.95
> A = frontal area in square ft
> V = vehicle speed in mph.
>
> Applying this to the CCS for the total wind effect of 30 kt, or rather
34.5 mph, gets
> pretty much the same answer, 148 pounds.
>
> This either demonstrates the reason why Philip Bolger stopped caring much
about the
> windage on his boats; or that my own lead line's a little short.
>
> Can anyone help me out?
> Mark
>
>
> Bolger rules!!!
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01930, Fax: (978) 282-1349
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>
>
>
Interested in the effect of windage on the large house, Bolger power boats like Cabin Clam
Skiff, SBJ Cartoon #9 and Idaho, I had a look at one of Jim Michalak's essays.
http://marina.fortunecity.com/breakwater/274/1998/0501/index.htm#SizingSails
He gives the formula for wind force on any panel as .0034 x S x C x V x V in normal air at
sea level.
S = area
C= the mysterious, "Force Coefficient", maximum of 2.
V= wind speed
But because the theme is really the effect of hiking out, I get confused about whether
pounds and foot pounds are equivalent here.
So ( with some uncertainty ), I calculate the force of a combined 10 kt wind on the Clam Skiff
house's 25 sq. ft front end as 17 pounds. Since about 60 pounds of thrust or bollard pull
equals 1 hp, then it takes barely 1/4 hp extra to power against that wind. A 15 kt breeze
is still only 38.25 pounds, or a bit more than 1/2 hp.
Figuring this way, it's hardly more dramatic if the boat is trying to go 20 kt dead
against a 10 kt air: .0034 x 25 x 2 x 30 x 30 = 153 pounds, only 2 1/4 hp.
There's another similar little formula for figuring aerodynamic drag force I get from Bob
Brant's 'Build Your Own Electric Vehicle', which is all about cars: Fd = (CdAVsquared)/391.
Fd = drag in pounds
Cd = coefficient of drag for the vehicle, a flat plate = 1.95
A = frontal area in square ft
V = vehicle speed in mph.
Applying this to the CCS for the total wind effect of 30 kt, or rather 34.5 mph, gets
pretty much the same answer, 148 pounds.
This either demonstrates the reason why Philip Bolger stopped caring much about the
windage on his boats; or that my own lead line's a little short.
Can anyone help me out?
Mark
Skiff, SBJ Cartoon #9 and Idaho, I had a look at one of Jim Michalak's essays.
http://marina.fortunecity.com/breakwater/274/1998/0501/index.htm#SizingSails
He gives the formula for wind force on any panel as .0034 x S x C x V x V in normal air at
sea level.
S = area
C= the mysterious, "Force Coefficient", maximum of 2.
V= wind speed
But because the theme is really the effect of hiking out, I get confused about whether
pounds and foot pounds are equivalent here.
So ( with some uncertainty ), I calculate the force of a combined 10 kt wind on the Clam Skiff
house's 25 sq. ft front end as 17 pounds. Since about 60 pounds of thrust or bollard pull
equals 1 hp, then it takes barely 1/4 hp extra to power against that wind. A 15 kt breeze
is still only 38.25 pounds, or a bit more than 1/2 hp.
Figuring this way, it's hardly more dramatic if the boat is trying to go 20 kt dead
against a 10 kt air: .0034 x 25 x 2 x 30 x 30 = 153 pounds, only 2 1/4 hp.
There's another similar little formula for figuring aerodynamic drag force I get from Bob
Brant's 'Build Your Own Electric Vehicle', which is all about cars: Fd = (CdAVsquared)/391.
Fd = drag in pounds
Cd = coefficient of drag for the vehicle, a flat plate = 1.95
A = frontal area in square ft
V = vehicle speed in mph.
Applying this to the CCS for the total wind effect of 30 kt, or rather 34.5 mph, gets
pretty much the same answer, 148 pounds.
This either demonstrates the reason why Philip Bolger stopped caring much about the
windage on his boats; or that my own lead line's a little short.
Can anyone help me out?
Mark