Ensign boat weights

David Roseman
dlr@eolas.com
July 5, 2006

The Ensign Class has imposed a 2800 pound minimum weight this year. Here is Rule 5.J, as transcribed from the 2006 Yearbook. Note that it is significantly different from the 2005 rule, which, as of today, is still shown on the ECA website.

"Ensigns shall weigh at least 2800 pounds, including the hull, all screw-captured or bonded in place (attached) parts, standing rigging, and all installed running rigging. Standing rigging is defined to include the mast and boom and their fittings, but not the spinnaker pole. Boats weighing less than 2800 pounds shall add screw-captured or structure bonded weights as necessary to obtain a minimum weight of 2800 pounds. A maximum of 150 lbs of corrector weight shall be added as follows - 50% of the weight at the base of the mast, and 50% located 45 inches aft of the main bulkhead, fastened to the top of the floorboards or to the bottom of the seats, split 50:50 port and starboard."

We have developed a weighing system which uses four load cells, and some commercial grade amplifiers. This is a work in progress. We will probably re-do the electronics, and last week noticed a problem that introduces a systematic over-estimate of the weight. Here are some details about that problem.

When the boat is hoisted, the longitudinal bars that connect the lifting cables to the lifting straps are pulled toward the boat at an angle of about 10 degrees.

Therefore, the load cell is measuring a vector that is mostly the weight of the boat, but which partially reflects the deflection toward the boat.

We intend to eliminate this problem by adding transverse stringers, as shown below:


I think that the weighing system is accurate to about 1%. The load cells have been calibrated before each weighing session, and the calibration system is said to be accurate to 0.5 lbs in 2000 lbs. I have tried to calibrate each load cell within a couple of pounds of the standard, and this will be more exact if we build new electronics. The corrected boat weights as of today are here.

The question was raised as to whether earlier Ensigns are lighter than later versions. There doesn't seem to be a correlation between boat weight and hull number, a proxy for date of manufacture.


Please send any comments to me.