Guys,
Reichard makes a good notation regarding the deck that may have been missed in my long statement on the other page. The trim angle is measured on the deck and with a tool just as it was in the Manuals, see this photo.
http://www.ec12.info/Final%20Weigh-In.htm If built correctly, the crown of the deck is a straight line between the center top of the transom to the tip of the bow. This is the reference point for the trim angle. Without more sophisticated tools, this is the best and most convenient place to do calibrate from.
What the angle is to the waterline (measured length) is only a relation to the weight of the boat for the conditions you are sailing in. It has been found that the lighter the air, the lighter the boat and a lesser positive angle to the bow is best and visa versa.
The waterline of the boat is a measured length reported in a tank by the amount of ballast that is installed. When ballast is installed, or removed, (behind the primary ballast) the boat will float as it will from the building and the deck line will be what it will be.
A trim weight is introduced to create the angles you want (deck to the level water of the tank, like in planet) for the various weights you will select from. This is usually four.
To be technical, if you change the angle of the trim, it will change the waterline length to an nth degree because of the curves to the bow section and at the stern. Hence, you seek the trim you want and then check the waterlines at light ballast and heavy ballast to see if you are within the required 42-43" restriction.
When we are talking waterline in the EC12 it is that of a rule. When we are talking trim angles it is that which the EC12 has been found to best move through the water at various conditions. To me that is what is meant by sailing on her lines. To me there is no technical or designed line on this hull that represents "Her Lines."
When Bill and I approached the problem for the first time having not a clue what we were doing, this was the concept we perceived from the Optimizing Manual and applied it with common sense. This was documented in <b>The Weight</b> section of the <b>Electronic Checklist</b> and the two pages under that heading. To this date nothing has presented a reason to move from that concept. We have ignore the technical because we could not quantify it and so it became a living thing.
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