Principles of Yacht Design

^MAX

Windage of hull :

R — J-P' v2-

c

B •

r

AH 2 HA O

AH

MAX

Vq : Apparent windspeed [15+3.6 mfs]

Wind resistance coefficient of hull ( ~ 0.5)

MAX L J

F^: Freeboard forward [1.39 m] p.: Density of air ( is 1.29 kg/mJ)

Windage of mast :

* = 4 P.

■ V2.

C ' t ' L

AM 2 A

a

: Wind resistance coefficient of mast ( ~ 1.0)

: Average mast thickness [ 0.139 m]

Windage of rig :

R =

.V2.

C '

/ . L

AR

2l

a

AR

: Wind resistance coefficient of rig ( ^ 1.2)

: Thickness of stays and shrouds [0.008 and 0.01 m]

L : Length of stays and shrouds H [76.7 and 23.9 m]

(Add RaR:s for different lengths and thicknesses)

A AH AM AR

Fig 9.2 Estimation of For the mast the frontal area is taken as the mean thickness times the windage height, and the drag coefficient is set to l.O, somewhat lower than the undisturbed value of 1.2 used for the stays. This is reasonable, considering disturbances from spinnaker halyards etc, which act as turbulence stimulators. The drag of stays and shrouds may have to be added over components with different diameters. Geometrical values for the YD-40 are given within square brackets, as usual, but no drag values are given, since the windspeed will vary in the example below.

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