IRC Bulb Weight refers to the Bulb as defined by the ISAF Equipment Rules of Sailing. This document is provided as clarification that all under-fin spacers and infills shall be included in the total Bulb Weight.
The ERS defines Bulb as
E.1.2(e) A hull appendage containing ballast at the bottom of another hull appendage primarily used to affect stability.
Ballast is defined as
C.6.3(e) Weight installed to influence the stability, flotation or total weight of the boat.
E.1.1 defines Hull Appendage as
Hull Appendage Any item of equipment – including the items listed in E.1.2– which is:
• wholly or partly below the sheerline or its extension when fixed or when fully exposed if retractable,
• attached to the hull shell or another hull appendage, and used to affect: stability, leeway, steerage, directional stability, motion damping, trim, displaced volume.
And clarifies that:
Any of the following shall be included in the hull appendage:
• corrector weights,
• integral ballast, and
• associated fittings.
Therefore, all under-fin spacers and infills shall be included in the total Bulb Weight.
Addition in reply to a specific question:
Q. We have read the latest IRC bulb weight clarification were it clearly states that all under-fin spacers and infills shall be included, but we are not clear about the bolts/nuts/washers. Do you mind clarifying if we should consider these items as part of the weight?
A. As any retaining bolts and attachments, as well as infills and adjustable weights, are only there as part of the bulb and would not be there if it was not for the existence of the bulb, these would be included in the bulb weight.
RORC Rating Office