[PUP] PPM design

[Tad Roberts]

  This is where (In my opinion) design by committee falls apart.  Any
design, and more especially a "Perfect" design will seamlessly integrate
every facet and factor involved (and there are literally thousands of
those).  Thus no design decision can be made in isolation from every other
design decision.  The choice of construction material dictates the
stability, hull form, speed, displacement, cost, etc, etc, etc.. If
stability is an overriding factor, it's limits will dictate construction
material, hull form, displacement, range, and interior arrangement.  There
are numerous factors which are impossible to achieve (realistically) with
certain other givens.  Everybody wants a 50' semi-custom aluminum yacht that
costs under $500k.  That is impossible without major compromise in every
department.  

 

Once upon a time designer's addressed this dependency problem with what was
referred to as the "design spiral".  This exercise involved addressing each
major issue (material, powering, form, weights, stability, etc) in turn,
over and over again as one works around the spiral and narrows the choice of
variables.  The first and outermost point of the spiral is the "Design
Statement".  This covers what the boat is for, who it's for, speed, range,
crew, cost, rough dimensions, constraints, etc. If the boat must meet
Lloyd's rules for Special Service Craft that's a major constraint.  The
completed design is somewhere way down in the very center of the spiral. 

 

Modern design practice refers to a Design "Cone".  This reflects design by a
team, each working in their individual area of expertise.  Again they work
from a broad outer area into a central point which is the complete design.
One person works on weights, another on hull form, a third on powering. All
are working simultaneously, hopefully informed by the other groups as to
what is happening.  This cuts elapsed time considerably from the older
spiral method of continuously revising work already accomplished. 

 

All the best, Tad

www.tadroberts.ca <http://www.tadroberts.ca/> 

www.passagemakerlite.com <http://www.passagemakerlite.com/> 

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