RG-65 Rules, Appendix 1 question

Hello! I believe I understand the text :

“In each section of hull, there will be no point of underwater body below 0.3 cm another point of the same section located closer to the centreline axis of the hull”

But the diagram in appendix 1 has got me confused. There are 2 places where it measures 0.3cm… the first is for the hollow underside… that one I understand. The other appears to be from the waterline to a flat-spot on the bottom of the hull. That one I do not understand. What is that one about? (It’s on the left side of the picture, FWIW, and here’s a link to the appendix : http://rg65.rcsailing.net/wp-content/uploads/2009/06/appendix1.gif )

Rick Lindsey

Eliminates catamaran and/or tunnel hulls, and step-side hulls.

By this rule, they are trying to maintain either a flat (slab) side (balsa sheet panels) or a continuous curve to hull, with no hollows or insets.

Just my take on it … Earl, Tato, German, Haegar, Maximo ???

Yes, it can be confusing. A clarification is at:


If there’s still a question, post it and we’ll get it settled with the International authority.



Hi, Dick,
you are right. As far as I know, a similar rule exists for IOMs

Thanks, Earl. The picture at your link makes way more sense. I suspect that the picture in the appendix isn’t drawn quite correctly, since the “0.3cm” marking on the left does not appear to be a hollow, but rather a flat spot, and the rule doesn’t seem to outlaw flat spots, just hollows?


Right. Hence the clarification in the Q&A, provided by Maximo.