Letter Re: Protractors for Field Engineering

Now I know some folks aren’t going to think of a protractor — digital, analog, or constructed — as a survival tool.

But in the USAF survival school certain “angles” were reinforced as survival angles. Support a load with an equilateral triangle. Making a 30-60-90 frame to support a trench. An isosceles to ensure that snow and rain shed away from a survival shelter. And, squares for identifying your location to rescuers. (Sinces traight lines are out of place in nature. )

Of course as an engineer, anytime you build, angles come into play with load. A good analog carpenter grade protractor, a slide rule, and some knowledge can mean a big difference in the grid down situations. – F.J.

JWR Replies: One other important angle to measure in field engineering is the angle of repose–the maximum slope at which uncompacted soil or sand can be made into a mound before it sloughs. This may prove crucial when designing defensive earthworks or even your next root cellar.