|Floating a Design|
Experts explain why tank testing is crucial to a successful custom project.
By Chris Martin — February 2003
Whether it's a custom yacht or a new version of a production design, designers and builders are looking for something that is truly different and does exactly what they want. But how do they know if the design will work? They could build it, sea-trial it, and modify it as needed, but such trial-and-error building gets very expensive very quickly. The more practical option is to test an exact model of the design--model testing.
What is model testing, when is it done, and what kinds of tests are performed? To get the answers, we consulted several well-known designers.
Model testing involves moving a small, accurately scaled replica of a boat through a water-filled towing tank and observing and measuring how it behaves. From these observations,
engineers can make fairly accurate predictions of how the full-size version will behave and how much power will be needed for the desired speed. According to Ed Monk of the design firm Edwin Monk & Sons, "Model tests can provide valuable information about how a boat will perform, allowing accurate performance prediction and helping to discover any running or seakeeping problems while they are easy to correct."
Jack Sarin of Jack Sarin Naval Architects says that a truly custom design, which "likely has a unique hull shape," and a design "where optimum performance is particularly critical" make ideal testing candidates. He also says that testing should be performed early in the design process, "but only after a couple of circles around the [design] spiral have fleshed out the issues of weight and trim and a reasonable arrangement has been settled upon by the client." It's also important that the designer be present for tests. Ed Hageman, a well-respected hydrodynamicist used by both Sarin and Monk during tests, says, "[The designer] is the one who knows in detail what ought to happen and easily might be the only one to notice when something is amiss."
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.