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ePaper created 2014-06-11, 13:05:34 | version 1.30.01
44 Swing testing was first introduced to sailing in 1972 in the Finn class boats, which are 264 pound sailing dinghies used in the Olympics. It has since become the standard method of weight distribution testing for other classes of sailing dinghies. FastforwardtoAucklandin1987,wherethechallengewastoswingtestboatsweighingapproximately10,000pounds,nearly38times morethanaFinn. Designengineerswereemployedtodeveloptheapparatus,andundertheNewZealandGovernment’sDepartment of Scientific and Industrial Research (DSIR) supervision, carried out the swing testing of 18 boats with the volunteer assistance of some of the Stewart owners. This very precise and tedious work was carefully completed over the period of two days. To insure that theory was both practical and accurate, an experimental swing of Pionnier was conducted before the official swing tests were conducted. Pionnier was swung as presented, and the oscillation time recorded. Lead ballast weighing 162 pounds was then placed at each end of the boat at deck level and the boat was once again swung and the time recorded. This oscillation time was of course longer-exactly as predicted by the design team. The 324 pounds of weight was then shifted to the middle of the boat at deck level at the position of the fulcrum where the boat was being suspended. She was swung a third time and,as predicted,the time was nearly identical to the first oscillation time. On the strength of this successful test, the engineers proclaimed that they were satisfied that their equipment and methodology would do the job. The first group of boats were weighed on 18 July of 1987,and the remainder on 10 October. As each boat was suspended off the ground in the swing gear,her owner,standing on a ladder,would give the rudder a mighty pull backwards. When released,the boat would swing like a pendulum. Six volunteers,three on each side of the keel with accurate stop watches in hand, would time five oscillations of the boat and average the times of the five swings. To insure accuracy, this process was repeated three times for each boat. Testing was also undertaken to ascertain where and how far the centre of gravity of the boat was situated below the gunwale.This was accomplished by suspending a 200 pound weight from the bow,and as the bow dropped down,measuring the actual distance that the keel moved aft. The designers entered this data into their computer and based on the design formula, could determine how far below the gunwale the centre of gravity was situated.The designers were reasonably happy with the figures as long as there was no breeze affecting the boat or the plumb bob during the test. Otherwise, they were comfortable that the moment of inertia method,i.e.the pendulum effect was extremely accurate. A very interesting video of much of the initial swing test was made by Stewart owner Wayne Boberg. A short clip from this video is included in the attached DVD. To date the author was not able to find evidence of any such testing taking place on keel boats anywhere else in the world. Subsequent to the testing, weight was added where necessary and the boats were considered to be equalised. The next running of the Citizen Match Racing Series went off smoothly. As more Stewarts were built,all of the newly launched boats were weighed,and appropriately equalised.Between 18th April 1980 and 10th October 1987 there were 13 more weighing procedures. All boats that participated in class racing had to eventually be weighed and swung before being issued with a new racing certificate. Additionally, most of the other boats that raced, even if only occasionally, also took the opportunity to find out their weight. During those 7-1/2 years, 35 different Stewart 34’s were officially weighed. The most actively raced boats were often weighed annually to insure compliance. As mentioned before in this book, the engineers, Messrs. Brickell, Moss, Raines and Stevens Ltd. stated that in their opinion the long standing weighing and adjusting procedures of the Stewarts as originally recommended by naval architect Ross Tilshead was vindicated by these swing test results.The Association perhaps unnecessarily spent $12,000 to prove him correct. 9 - Success of the Stewart Class Bob Stewart’s 34-footer received universal praise from skippers and yacht designers for its “breakthrough design” that was “well ahead of its time.” The fact that the Patikis launched and raced during the 1960’s trounced their competition was understandable. To remain very competitive nearly 50 years later is unbelievable. That said, it takes much more than just a fast boat to make for a successful racing class. We’ll look at some of the reasons we believe have contributed to the Stewart