"Tim" wrote in message
m...

"cavelamb" wrote in message
...


That was Burt Rutan's particular gift to the state of the art.

A soft foam piece that was easy to develop into complex shapes,
and stayed in the part as a stiffening core.

Or remove the foam completely after layup, if it's not needed.

"Mold-less" construction.

True, but in lies the rub. It's just as much work to build one aircraft,
as the plug for a mold that will build many. Large panels and even two
piece fuse sections save a lot of work, and can produce even lighter
panels.


I don't believe that it is even 20 percent of the work needed to build a
reusable plug--and it is certainly less than 10 percent of the work needed
to build a plug plus a reusable mold.

The real problem, from my point of view, is that the kit manufacturer
receives all of the benefit of series production, while the customer is left
with extraordinarily critical fitting and bonding steps and an unacceptably
high cost of scrapped parts. Those are processes which should be
accomplished by experienced labor using stable and accurate jigs--however,
that is exactly the service that is effectively prohibited under the 51
percent rule. The result is that the customer (builder) spends an
outrageous amount of time just puttering around and studying the next step
in the process, with the project occupying a lot of space in an expesive
final assembly area, in the fear of creating some very expensive scrap--or
even more time consuming repairs. In effect, when building a composite kit
and simply counting labor hours, the 51 percent rule has become a 91percent
rule.

Peter