Measurers Guide Update - Sail Measurement and Black Bands

The Technical Committee has received many enquiries as to how the new “decksweeper “ type sails are to be measured and how Black Bands are to be applied.  In the past with the present “standard” sail shape the measurement guide adequately covered and we could simplify our procedure by taking maximum offsets and in some cases eliminating some of the roach area measurements.  The new sails have presented new challenges and the new guidelines hopefully cover these areas. The role rests with the measurer to obtain the most accurate measurement within the “Measurement and Calculation of Sail Area Guidelines”.  A new Sail Measurement form is now on the IACA website to cover these changes. A tick box allows the “foot round” calculation to be done at 2/3 (B x E) for standard sails or ½ (B x E) for decksweepers.

Our class rules still state that sail area is to be measured in accordance with the “IYRU Measurement & Calculation of Sail Area Instruction” (last issued May 1985). The IYRU was changed to ISAF and now to World Sailing but no change has ever been made to the guidelines.  A copy of the original 1985 version is now on the website.

The A Class operates under Open Class Rules, which state, ”Class rules where anything not specifically prohibited by the class rules is permitted”. On this premise and following discussions with World Sailing the majority of the Technical Committee could find no justification why “Black Bands” are required and this calculation is now removed from the Sail Measurement and Mast Measurement forms. Updated copies show this reference now removed.

We have not changed any rules on this and realize this may cause concern with some people but at this stage nothing in our rules states we must use Measurement Bands.   

Lastly, we have included a section on endplates and sail flaps for guidance.

Please ensure these guidelines are read in conjunction with the International A Class Catamaran Class Rules.

Graeme Harbour

Chairman IACA

Technical Committee  8/2/16 

Measurers Guidelines 01-02-2016.pdf

IYRU Measurement and Calculation of Sail Area Instruction.pdf