Measurers Corner

Measurer’s Interpretations and Recommendations

Topic:Boom
Question:Is the current boom with diagonal cut legal at 13' 11" length?
ID Number:000038
Date:2011-10-21
Short Answer:Yes 
Answer:Class Rules indicate: Length of the Boom

The length of the boom from the after face of the mast shall not exceed 13 feet 8 inches.

It looks like the specifications were never changed when the new boom was put into effect. 
Section:§IV 6.2 
Status:Affirmed
Action Date:2012-02-07
Sat Oct 19 11:23:57 2019
DateNameComment
2011-11-07Richard RobbinsProvided by Cape Cod Shipbuilding: Shields Boom Evolution

Shields built from 1962-1970 had booms with enormous outhaul sheaves & external outhauls. In 1971 members requested internal outhauls & more outhaul purchase. At this time the boom changed to have an aluminum outhaul casting with a smaller sheave & internal outhaul. The initial boom measurements in the class rules never took into account this casting, only the length of the tube extrusion. These booms were actually 13' 10" in overall length.

In 1995 sailmakers began supplying mainsails with larger clew grommets. The standard outhaul shackle supplied for many years no longer fit new sails. The boom had to be modified to allow for a larger shackle. The new boom design did away with the outhaul casting & in its place a Harken #288 was installed. As this piece of hardware required bolts forward & aft of the sheave, the extrusion had to be lengthened to accommodate. The new boom also included an angle cut so the boom could be placed on deck while still connected to the gooseneck. The overall length of the new boom design is 1" longer than the overall length of the old boom design. The new boom design has been consistent since 1995.

Obviously the foot measurement of the sail has remained the same, but because sail makers supplied larger clew grommets, the outhaul shackle had to change & therefore the boom length had to change. Because we still have older booms with outhaul castings & newer booms that are 1" longer, we recommend adjusting the class rule to read:

6.2 Length of the Boom: The length of the boom from the after face of the mast shall not exceed 13 feet 11 inches.

2012-02-09Richard RobbinsAt Governing Board meeting of 2/7/2012 the boom length was changed to 13' 11"