Are composite homebuilts dying out?

"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.

"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

I can second that statement about the outrageous amount of time spent
puttering around! I've also had that feeling about my composite plane
complying with the 51% rule. It more than quailifies. Just barely
above the level of a plans only design. I saw the plugs for making the
molds when I visited the Glasair factory. They told me they keep them
around in case someone were to forget to put the mold release in the
mold and they needed to make a new mold. The persons that think making
parts from a mold are not so easy, should trying building the
completed plane from those parts from start to finish with no help
working alone and then look back and see if they still support that
statement.
Rich

On Sat, 15 Aug 2009 09:53:25 -0400, "Peter Dohm"
wrote:




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

"Peter Dohm" wrote in message
...
"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.


Why do you feel it's more difficult to build a plug, than a fuse section?