If you’re gonna teach ’em, for goodness sake teach ’em right! The answers to your little quiz in 27 May contained a glaring error.

According to QSNews, the length of a hip rafter is arrived at by dividing half the span of the roof by the cosine of the angle of pitch. Wrong! This would give you the length of the ordinary jack rafters. The correct answer is obtained by dividing the hypotenuse of a isosceles triangle where the adjacent sides are both half the span of the roof, by the cosine of the angle of pitch. Thus the answer should be (square root ((6/2×6/2) +(6/2×6/2))) / cos 30° = 4.90 m, not 3.46 m.

That is a prime example of one of problems with the QS profession today, where those who can’t, teach. If anybody wants a job where they will be trained properly, please contact the writer.

Graham Stow, DRA Bristol

Source

QS News