Yes there is a rule on radius of the beams. Rule 6.2.
I would suggest it is a good idea for everyone to read through the rules at some stage. If you read the rules and check your own boat it saves the embarrasment when it doesnt measure at a regatta.

http://www.theracingcat.com/uploads/Mosquito_BRR.pdf


"Sixth Element"
1782 MK2 w/spinnaker.
Lake Bonney Y.C.
National Sec. / S.A President / S.A Measurer / Commodore LBYC