Evolution or revolution?

As performance sailboats have grown in size, a continual major constraint on development has always been sail- batten technology. But development in this field has recently been greatly accelerated by pressure - and dollars - from the America's Cup and Volvo Race fleets; Alex Vallings and Fraser Brown of market-leaders C-Tech explain

Sail battens are a key component in the never-ending search for faster, more reliable yachting. Largely unseen but vital - one or two failures and the performance consequences are obvious. As other components get substantially lighter (carbon masts, Cuben and carbon 3DL sails and PBO rigging) sail battens have become an increasing proportion of the weight aloft. At the same time, the trend to increased mainsail roaches, stiffer sails and bigger, more heavily loaded boats with greater stability has made shortcomings in batten durability and therefore construction more evident. The strength problems associated with making battens lighter have limited progress in this area until recently, when the advent of our own CT Sailbattens - primarily carbon but very different from their predecessors - marked a big step in both performance and durability.

The 2003 America's Cup provided C-Tech with a tremendous development opportunity, out of which grew CT Sailbattens. The basic requirements for effective sail battens are durability, weight saving and reproducible bend characteristics. With weight saving as one of the key factors in the design brief, the battens C-Tech supplied for Team NZ and Alinghi in 2003 were manufactured entirely in prepreg carbon. Total weight for a full set of ACC battens varied from just 10kg (super-light) to 16 kg (heavy air).

Load and restraint specification [1] [2]
Having applied the laminate specifications to the meshed model geometry, the next stage of the analysis is to apply the necessary loads and restraints. There are several methods that can be used for applying the boundary conditions, but this article will consider only two. The first method for loading and restraining a finite element model has been proposed by Luke McEwen of SP Technologies.

1. Equilibrium load case [1]
1.1 Load cases for FEA
One approach to the analysis is to run a 'realistic' load case, which includes all the W1 loads acting on the structure under some steady-state sailing situation. For most analyses...

To read the remainder of this article please go to the August 2004 edition of Seahorse, available at selected newsstands or by calling: + 44 (0) 1590 671899 or by email at: info@seahorse.co.uk

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