Reliability Rule 1 it must not break. Weight and performance The lighter the rig (that does not break) the better your chance of arriving ‘first’. The efficiency of the mast’s response in working with the sails; the ‘engine of the boat’.
At HDS we already had one advantage – we knew this platform very well since it was engineered by HDS for Banque Populaire back in 2008. Several different initial spar concepts were modelled in terms of geometry, stay locations, the relationships between cable rigidity and tube stiffness, different sail configurations and so on. More than 140 base models were tested in total. For every candidate concept we ranked all of the relevant outputs… global performance, reliability, weight, the operating profile (and also build cost).
In the end the choice was easy! The spar we ended up with was the simplest design and in turn the lightest in weight with an accept- able VCG. The simplicity was derived from a configuration requiring the least number of separate elements, therefore also minimising risk and maximising reliability.
We then entered the design phase, where we benefited from
having a powerful array of the latest conceptual and calculation tools, able to take us all the way from general arrangement models to final scantlings.
The great majority of these tools have been developed over the 46 SEAHORSE
years in-house by HDS. It is the core of our business; since 1994 we have been refining specific advanced calculation tools for: Composite mechanics (Alamo) Stiffness/geometry (Ophelia) Scantling optimisation and associated mechanics (Optima/Sandra) Parts (Sandra/Nastran/Hypermesh)
Mast design starts with defining stiffness, also taking into account the practicalities of the mould required for manufacture. Our in-house tools can now comfortably define mast stiffness, the loading and rig specifications, stress levels and laminating details for some 40 different sailing conditions.
Once the general concept is established (stiffness and geometry), we then optimise the mould and scantlings. The aim is to optimise the mechanical characteristics of the composites while sticking to the chosen stability and stiffness criteria.
From this optimisation phase we get a final weight, details of each lay-up ply and target centre of gravity. For a given stiffness we then finalise the mould and laminate schedule to deliver the lowest weight/inertia ratio.
Next is the definition of the parts. This is another 100% in-house step. The work starts with hand calculations and sketches. Once a concept looks promising enough, sketches are digitised and then carefully modelled using Solidworks and Nastran.
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