F250 and up, max 60 square feet frontal area

TucsonJim wrote:
A simple trigonometry equation would be if you had exactly 60 square feet and it was sloped at 15 degrees. 90 degrees (perpendicular to the air flow)- 15 degrees slope = 75 degrees. Sin of 75 degrees is .966. Multiply 60 square feet by the inverse of .966 to get the equivalent square foot load. In other words, the recommended limit is 60 square feet at 90 degree impact angle, but 62 square feet at a 15 degree slope.

That depends on how they define "frontal area".

Usually, "frontal area" means the projected cross sectional area which, for your example, would be 60 sq ft for both the vertical front and the sloping front.

Ron