American Scientist

To the Editors:

Henry Petroski’s “Bottle and Can Openers as Levers” (Engineering, March–April) was, as are all his articles, interesting and informative. Throughout much of West Africa the people use a bottle opener that is both crude and more effective than the ones cited in the article. This opener is similar to the Dreher opener, a Class 1 lever. It consists of two round-head screws partially sunk side-by-side in a wooden stick. The user catches the flat, bottom side of the screws on the rim opposite the user and pulls off the cap. Unlike all the openers cited by Dr. Petroski, this lever does not permanently bend the cap, so that it can be reused on a partially filled bottle.

The sticks (handles) of these openers are sometimes carved, so that the opener can be sold as a tourist souvenir.

Edwin J. Kay, Professor Emeritus
Lehigh University
Bethlehem, PA

To the Editors:

I enjoyed Henry Petroski’s column on can openers and bottle openers in the March–April issue. The P-38 military can openers were of particular interest. I buy P-38 and P-51 can openers at local military-supply stores and give them to homeless people as part of a ministry of some local churches. Homeless people cannot be encumbered with bulky items, and many canned goods they acquire are not pop-top. Therefore military can openers are very welcome items.

Dr. Petroski speculated that the name P-38 might have been based on the fact that they are about 38 millimeters long. My P-38s do measure about 38 millimeters and the P-51s measure close 52 millimeters, suggesting that the sizes are approximate, perhaps because precision in their manufacture is not necessary. It turns out that 38 millimeters is very close to 1.5 inches, and 51 millimeters is very close to 2 inches. So maybe the International System of Units was not used in the original specifications.

The smaller P-38s are preferred by those who keep them in their wallets, but the larger P-51s are easier to use.  As one left-handed homeless person once pointed out to me, military can openers are apparently all made for right-handed people.

T. J. Blasing
Knoxville, TN