[PUP] PPM design

[John Marshall]

You make some good points, Tad.

To be honest, I'd like to see the price floor raised closer to two  
million dollars to make this project fun. At that price, we can do  
some cool stuff.

At $500K, existing boats like Diesel Ducks and Nordhavn 46's are  
probably about as good as you are going to get.

Besides, custom-built boats always cost a lot more than they seem to  
when you start.

John Marshall
Serendipity - Nordhavn 55
Sequim Bay, WA


On Nov 1, 2008, at 3:28 PM, Tad Roberts wrote:

>  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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