A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Bruce J. Pennino
Date: 2018 Mar 22, 08:21 -0700
On the topic of ship speed, I worked for a while at a research/engineering place where we calibrated Pitot tubes and similar devices. For those unfamiliar with a Pitot tube, it is an "L" shaped open tube where the short leg is impacted by air or water as the tube extends into the flow. The higher the speed of the flow (or the ship) the greater the water rise in the tube. If the probe is used in the air, there are various means of converting the air pressure rise (above ambient) or water rise to speed. Of course there have been several terrible air accidents where the Pitot tube has frozen or failed in some manner. Anyway , a long time ago I was working on a historical exhibit of early methods to measure velocity of flow using various types of propellar meters. I discovered in a closet a 6 ft long very heavy ellipsical cylinder( 2-3 inches in short dimension) with a Pitot tube sticking out of the bottom of the enclosing cylinder. I aked my boss, an old USN fellow, he told me it was a modern ship log. The device protruded through the hull of the warship. Is this correct?