August 2006 Vol. 23, No. 8 – R/C - RCSoaring.com

Lest you think the milling
machine assembly, and
production of the first usable
parts, occurred in a matter of
minutes. let me say that I
invested about 800 very
intense hours initially before
the first rudimentary usable
parts were produced! Many
problems were yet to manifest
themselves, and in fact the
whole exercise has been one of
problem solving.
At first I thought prototyping
in foam would be a good idea,
and then milling the vacuum
beds out of hard material
would follow. As it worked
out, Foamular 400 insulation
foam has enough compressive
strength and is stable enough
to be used many times over for
vacuum beds. If a bed is
destroyed it is a simple and
inexpensive matter to retool a
replacement.
Aligning the cores in the soft
foam vacuum beds was a
problem solved by simply
gluing a hard spot such as
1/64" plywood with a
reference hole that mated with
brass tubes set in the vacuum
table.
Vacuum is supplied by a Fein
shop-vac with bypass cooling
allowing continuous
operation.
Soon after the first tail-surface
parts were produced I was
successfully milling wing
cores.
All flight surfaces for the
Encore are now CNC milled,
and then vacuum bagged.
This method has allowed a
variety of airfoils and plan
forms to be prototyped. The
resulting wing has a consistent
airfoil and the robustness of a
solid foam core wing.
The CNC process is perfect for
modular design, allowing most
of the parts of the Encore to be
interchangeable with earlier
versions.
Next month, CNC milling and
vacuum bagging of Encore
wings will be featured.
Computer Numerically Controlled, CNC, 3 axis mill used for 3-D milling of Encore flying surfaces and
miscellaneous parts. 2.5 Hp Makita variable speed router is used for milling. This mill is a Shopbot,
bench-top model, with a working area of 33"x24"x6". This particular model utilizes a DOS format for
programming. The computer uses a 450 MHz Pentium II processor and runs Windows 98. The Jet “Dust
Dog” dust collector with the pleated filter is visible in the background.
14 R/C Soaring Digest