Q1: Is it permissible to use a prop other than the standard 15 inch Martec non-geared folding prop?
A1: Yes, certain other 15 inch props are permissible.

Class Rule 1.2 states that ” Except where variations are specifically permitted by these rules, J/105s shall be alike in hull,. keel, rudder . Similarly, Class Rule 1.3 states that “All yachts competing in one design or class sponsored events, shall comply with standard specifications published by J/Boats, Inc. and these class rules. No alterations or modifications are permitted unless explicitly permitted by these rules”. On the other hand, it has been a long-standing view of the TC that the intent of the rules is not to legislate hardware brands. If the piece of equipment functions as intended, then it is permitted provided it does not provide an undue advantage over standard equipment. See RI 00-03, RI 02-15.

The J105 has always been delivered with a 15 inch Martec folding prop. The TC has analyzed whether the following replacement props are permissible (all 15 inch):

Flex-O-Fold Standard and Racing versions (geared)
Gori Standard and Racing versions (geared)
Martec (geared)
Max Prop (feathering)

Most of these props are “geared” props, which means that the blades are connected and open up in unison. Arguably, this feature provides an advantage over the non-geared Martec since with the Martec, particularly in light air and choppy conditions, a single blade could potentially open up. On the other hand, owners of standard Martec non-geared props are of course free to rubber band their props

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