In the late 1990s, the Brilliant Technical Committee (BTC) of Mystic Seaport undertook an effort to collect the aerodynamic and hydrodynamic data necessary to improve the accuracy of sailing performance analysis of historical sailing yachts. At the time, the data available for sailing performance was for sloop rigs and modern hull shapes, and did not support accurate performance analysis of schooners with historic hull shapes, such as the schooner Brilliant. To address this shortcoming, the BTC designed a program to collect upright resistance and sail shape data for the Atlantic class through a series of full scale and model scale tests.
The Atlantic Test Program, as it was formally called, was designed and executed between 1998-1999 by a team of respected yacht designers, engineers, and sailors. Walt Stubner and Norm Peck coordinated a group of contributors including Olin Stephens, Dave Luce, Ron Uhlin, Jay Spalding, Chuck Henry, Jim Marshall, and Howard Grant. In line with the program’s objective of contributing to the publicly available data on sailing performance, Norm Peck has shared the program’s documentation and data with SYRF.
The Atlantic Test Program had two primary objectives. First, the program aimed to develop a sailing performance prediction for the Atlantic class sloop using state-of-the-art instrumentation. The instrumentation, designed specifically for the program, would allow for the calculation of sail coefficients to provide a baseline for evaluating computational methods for predicting sail performance. Second, the program sought to develop full scale and model scale data suitable for validation of analytical and numerical methods for sailing performance predictions of classical sailing yachts. The program would compare the hull drag (upright resistance) measurements to those developed through predictive programs developed at MIT and used by the IMS.
Prior to the Atlantic Test Program, Olin Stephens and Ken Davidson conducted a similar series of tests to define the upwind sail forces of a sloop rig as part of their Gimcrack program in the 1930s. The committee consulted Olin Stephens and drew upon the success of the Gimcrack tests to design test procedures for the Atlantic tests.
Detailed test procedures were developed for the three vessels and personnel to be used in on-the-water testing, with the sailboat (Miss April, Atlantic #130), chase boat, and water current team each following a unique list of procedures. The procedures outlined the specific instrumentation and data points to be collected by each party, as well as the necessary duration of each test run. Measurements were to be made during both tow and sail tests across a range of wind speeds and headings. These measurements were to be collected by new instrumentation systems, designed in collaboration with Ockam, to enable observations of the aero and hydrodynamic velocity triangles, sailing parameters, and upright resistance.
On-the-water tests were performed on July 30 and August 2 of 1998. Although the full test matrix was not completed during these two days, the following test runs were completed: Tow Test 1.9-6 knots, inclination tests, upwind sail tests (14 knots of wind), overhead sail photos, weights and balance, laser beam drawing of hull. The results of these tests did not yield new insight into how to best sail the Atlantic, but provided numerical confirmation of known concepts. Indeed, plotting of the average drag against average wind speed yields results which are surprisingly close to the existing predictions. For instance, the full scale tests show that at 5.8 knots upright, an Atlantic has a hull drag of 70 pounds, compared to a hull drag of 95 pounds upwind at 24 degrees of heel, yielding a 25 pound difference of additional induced drag. Translated to sailing performance, adding additional crew weight to the rail, and thereby reducing heel, will simultaneously reduce hull drag and increase boat speed.
Additional tests were planned to be completed, but due to personal reasons, many of the committee members were unable to fulfill their remaining responsibilities. Even so, the Atlantic Test Program made significant progress towards understanding the performance of historical sailing vessels. The procedures and instrumentation it developed provide a solid foundation for similar tests in the future.
The Atlantic Test Program documents are available through the SYRF Technical Resources Library links below.
If you use any of the data provided on this page, please use the following information for your citation.
Author: Gil Alwang, Norm Peck, et al.
Title: Atlantic Test Program
Publisher: Sailing Yacht Research Foundation [distributor]
Electronic Retrieval Location: http://sailyachtresearch.org/resources/atlantic-test-program