It's important to note that the remarks made about structural calculations
are accurate, but also note that boats are subject to unknown forces. Many
structural methods used for boats have varying qualities, depending on who
did the work and how much of a hurry they are in. Structural design for
boats uses structural engineering yes, but large margins are built into the
process by using common design rules. Design rules are such things as
expected 'hull pressure factors' based on hull type, weight and speed. The
hull pressure factor is then used to determine spacing of hull support
members, then hull skin or plating is selected (flexural modulus) according
to typical design rules for allow percentages of flex. Finally, the
structure inside the hull, on the required spacing, is determined ...again,
from the hull pressure. It is here, and in skin type and thickness, that
structural engineering and experience come into play. There are many ways
to frame up or provide internal support to a hull, and it requires
engineering knowledge and experience. There is no reason that any
interested person cannot work their way through the learning material and
then do the design, especially for smaller and lower-powered boats (skiffs).
Larger boats should be designed if you are confident that you have the
appropriate training and experience. Note that most states (US again
....sorry) use the term 'architect' for a yacht designer and as such usually
do not have licensing associated with this type of work. Two states,
Washington and some other I can't remember, classify the design work and
have varying requirements. Pressure from governments tends to support
higher regulation and licensing requirements while pressures from industry
support less (to prevent loss of business, higher prices, smaller businesses
not surviving etc). If I were you, I'd go ahead and buy the books that
apply, read them, then decide how far you want to take it...the training and
education or the design work itself. Armchair sports or playing the game.

Brian

--
My boat project: http://www.advantagecomposites.com/tongass

"VG" wrote in message
...
If you call ABS they will be able to answer that question.

Not everybody live in US. Not so easy to call ABS when you can barely
write,
but no speak english. I can understand a slowly oxford english, but a fast
texan (or australian to change country) is far beyond my abilities.

I think the
bigger questions is do you have an engineering background?

Yes.

ABS requires you to know how to calculate section modulus, know
the mechanical properties of your materials, and generally
have an engineering knowledge of structures.


Not a problem. My real problem is to determine the forces that will be
exerced on the hull. In mathematical conditions, I can do some things. But
real life sometimes differs from mathematics.


"VG" wrote in message
...
With at least some lines dealing with displacement (ie non planning)
powerboats in plywood (classical, not stich and glue) , length 30'.

subsidary question :
Does "Guide for building and classing Motor Pleasure Yachts" from ABS
deals
with above powerboats ? Or other regulations 'Lloyds ???)

Thanks for using your time to answer.