Wind Load (lb/ft) | |||
---|---|---|---|

MPH | Plate | Sphere/Tube | Airfoil |

10 | .30 | .10 | .01 |

25 | 1.9 | .60 | .07 |

50 | 7.6 | 2.4 | .27 |

75 | 17 | 5.4 | .60 |

100 | 31 | 10 | 1.1 |

125 | 48 | 15 | 1.7 |

150 | 69 | 22 | 2.4 |

175 | 93 | 29 | 3.3 |

200 | 122 | 38 | 4.3 |

225 | 154 | 48 | 5.4 |

250 | 190 | 60 | 6.7 |

## Wind Load

F = a * cd * [d * v ^{2}]

Wind speed (mph)

Area (ft^{2})

Air density (slugs)

Shape (Cd)

Total force (lbs)

## Introduction

This formula determines the force on an object in a wind. I.E. A length of tubing or flat surface that is part of a structure. The force per unit area would be found by setting the area to 1. The results are based on standard temp and atmospheric pressure. A safety factor should be included in any design using this formula.

## The Generic Formula

Force: f = a * cd * [d * v^{2}] brackets denote air pressure (standard atmosphere) Where: f = force (lbs) a = frontal area (ft^{2}) cd = coefficient of drag d = air density (slugs) v = wind speed(mph) Cd: Drag coefficient of shape 1.5 for flat plates 1.2 flat faced triangle .3 bullet .4 sphere or tube .1 airfoil Example: What is the pressure on the rudder of an airplane spinning 2 rotation per second with a vertical tail volume of 10sq/ft and a rotation arm from the cg of 12ft? preparation: The tail speed can be determined using... v(ft/sec) = 2pi * r / t = 6.28 * r / t r = radius, t = time(sec) for one rotation so: 151(ft/sec) = 6.28 * 12(ft) / .5(sec) ...1/2 sec per rotation 102(mph) = 151(ft/sec) * .68 ...since 1ft/sec = .68(mph) using: f = a * cd * [d * v^{2}] given: f = (lbs) a = 10(ft^{2}) cd = 1.3(flat) d = .00237(slugs@sea level) v = 102(mph) v^{2}= 10404(mph^{2}) solution: f = a * cd * [d * v^{2}] = 10 * 1.3 [.00237 * 10404] =321(lbs) total wind pressure