Oh Boy, "the grail." This what we are supposed to do on hot early evenings on the veranda with our favorite beverage. Okay, here we go...
Remember the key word was "Dummy." It began in late 1998 with the reading of both manuals to understand this EC12 and the building of it. Upon reading Optmizing, Bill Cullen and I knew we were in for a long run. I will not get into it all but what we embarked on was a post graduate course and likely a thesis in the end. It was never scored, so what did we know. However, to condense this, Bill built an incredible transparent test tank to presision instrument standards and we produced the numbers on the Final Weigh In page on the building site.
Page 27 of Optimizing carries a statement that we could understand with relation to the lines of the keel and the waterline. The problem was, what waterline! The chapter, Trim Angle, was not the whole story but only a segment of balance, ballast plots, righting moments, inertia and the perceived force of the sail plan on all of this. This is when it became a course.
The waterline of the EC12 is that which you set it to be at any given time for conditions of sailing you determine to be. Legally, it must be between 42 and 43 inched by rule. By common since, it must be on its lines while under power and in the seas that it is.
It was our perception in the see through tank that the keel and the deck were parallel. We did not measure it nor thought there was a need. Maybe there is and maybe Paul is right but at the time the concepts of drag on a presented surface and the resulting laminar flow at and across the rudder were clear. (a high bow angle would present a larger surface to the oncoming water and a low angle would create turbulence across the rear of the keel and the rudder.)
Water, for general purposes, is level with the planet. Therefore, our quest was to make the keel and deck parallel to the surface of the water when the boat was underway and under power. You can't do that in a tank without it being in a wind tunnel as well. So, it was decided to use the tank for what it was designed, measuring.
Based on the theory that the boat should sail on its lines and using the multiple ballasting options a fully prepared boat for sailing was placed in the tank at the least weight that would produce a 42" waterline measurement. This would be where you would want to sail the boat in drifting conditions, zero to one. Then trim the boat to a positive angle but near zero. Likewise, the boat was ballasted close to the 43" waterline measurement and trimmed for 1 degree positive for heavier sailing conditions. Over the course of this, a weight and a location was chosen to be one. We were thinking of moving the trim weight for the conditions after testing but found it was not needed. it sits in one place today.
Optimizing is the total sum knowledge and presentation of the testing Lon and Larry Robinson did. Like any technical document it has to be viewed as a whole. It was the whole of it, through several charts and text the trim angle spread and the ballasting properties were determined from their recordings. The results of our efforts in the tank is presented on the building site and is still being used today in my building. How precise is it? I do not know. I only have my eye to judge the profile of the boat in the water in various conditions to support those efforts. When the boat is under power, in the planned wind, she is level with the planet for the weight and trim designed.
What I have found on the East Coast that the competitive sailors have used a shorter and higher single pour for a 42.5" measured waterline with one degree positive angle on the deck. When we all gather I take my proper place further down due to my lack of mental prowness in tactical matters not because my boat is slow.
Paul, the search for the "grail" can be fun. One rainy night in equatorial South America I sat under the wing of my plane with a local discussing the aspirations of higher goals (Latins do that a lot)and he said, "You must climb only part of a mountain to know it is a mountain." Maybe it is the heat.
Woody, you do have it right and I hope this supports it.
Larry, you are @%# disturber! [:)]
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