Sails

Sail Plan

Sail plan

 
 

Beaufort Scale, Wind Speed and Pressure


 
Force Wind
  Speed  
mph
Wind
  Pressure  
g/cm.sq
   Description   Specification
   0   0 - 1    Calm Sea like a mirror.
Calm; Smoke rises vertically.
   1   1 - 3 0.01  (2)  Light Air Scale like ripples, no foam crests.
Wind direction shown by smoke drift.
   2   4 - 7 0.06  (5)  Light Breeze Small wavelets, no breaking crests.
Wind felt on face, leaves rustle, wind vanes moved by the wind.
   3   8 - 12 0.24  (10) Gentle Breeze Large wavelets, foamy crests begin to break, some white horses.
Leaves in motion, light flag extends.
   4 13 - 18 0.54  (15) Moderate
 Breeze
Small waves, frequent white horses.
Raises dust and loose paper, small branches move.
   5 19 - 24 0.98  (20) Fresh Breeze Long moderate waves with many white horses, small trees sway.
Crested wavelets on inland water.
  at 30 m  (at mph)  

 

Sail and Winch Loads in a Force 4

Sail plan specification

 
Sail
1:20
Area
cm.sq
Sail Load
(1)
C of E
A
Clew
B
M.A. Sheet Load
kg
Main - Full   2640       1.32     26   50 (2)   1.9       0.69
Main - 1 Reef   2070       1.04     25   50 (2)   2.0       0.52
Main - 2 Reefs   1510       0.76     23   50 (2)   2.2       0.32
Topsail    670       0.34     11   25   2.4       0.14
Jib    770       0.39      7   21   3.0       0.13
Staysail    613       0.31      6   25   4.2       0.07
Yankee    620       0.31      9   20   2.2       0.14

+ = Position of Centre of Effort.
A = Distance of C of E from luff or mast centre.
B = Distance of Clew E from luff or mast centre.
M.A. = Mechanical Advantage = B/A
Sheet Load = Sail Load / M.A. Double for force 5 and halve for force 3.
Travel = length of sheet to pull the sail from full out to full in.
 
(1) - Sail Load in Kg calculated for a Force 4 wind using 0.5g/cm.sq.
(2) - Distance of main sheet E from mast centre.