A customer recently mentioned having an odd question to ask.  His firm does stability testing on boats and ships, and has rented 1000lb NIST Class F Cast Iron Test weights in the past.  He was looking to do a similar test in the U.S. Virgin Islands and having problems finding a local vendor for test weights.

Curious, we asked what exactly do you use the weights to test?  Normally around here, the weights are put on a truck scale for a yearly calibration or to test a floor scale out.  The customer said, he does stability testing on ships and other small craft such as yachts. With larger ships, large blocks of concrete (which are weighed before the test) are often used; however with smaller vessels where deck space is tight, your 500, 1000 and sometimes 2500 lb test weights are ideal and are easy to handle.

They have the added benefit of being certified weights, thus there is little question about accuracy. On some smaller vessels they used the 50lb weights and moved the weights by hand during the test. Basically the test weights are placed on board and then moved transversely from side to side to apply a known moment as the heel angle is measured. Using the principles of naval architecture, the vertical center of gravity is then calculated.