Jubilee tapered mast


Figure 1 Jubilee general layout drawing

The Jubilee is a stable, all-weather 18 foot day boat, locally designed and made for Port Phillip Bay. The class rules allow the mast to be tapered fairly over the top 8 feet to a minimum dimension fore and aft of 1 3/4 in” and athwartships of 2 1/8 in.”

Recently a customer requested a new Jubilee mast but he wanted more flexible tapper to allow the sail to unload under heavier gusts.

We prepared a sample of the modified Jubilee section for customer approval before proceeding to manufacture the new tapper. As can be seen the new section has a much reduced second moment of area in the athwartships axis, this will allow permit the mast to twist under less load as requested. As the customer is not sailing under class rules the modified section was accepted and we proceeded to manufacture the new mast.


Figure 2 Traditional Jubilee section


Figure 3 Revised sample section for customer


Figure 4 The mast is marked out and the initial cut is made


Figure 5 The outer section of the mast is removed



Figure 6 Cleaning up before making inner cut


Figure 7 The inner section is cut, the sides are then compressed and the section is stich welded.


Figure 8 The cut section is then placed in a 30 ton press and pressure is applied to close the section evenly


Figure 9 The tapper is now clamped and seam welded


Figure 10 The seam is then cleaned and polished


Figure 11 The completed tapper and mast ready for fitting of crane