Pre-Preg

Three further points with pre preg;-
1-Uni directional (UD) pre-preg, which is extensively used in wings, is
difficult
to form into compound curves;- it wrinkles
2-stray fibres, with pre-preg stray fibres can puncture the vac bag. The
wing
skins don't come out of the moulds until after the wings have been fully
glued
together. It's a bad day to discover a single stray fibre has killed the
vacuum
during the cure of a skin and you've just glued it to a good
spar/skin/installed
controls etc
3 - wet lay up wings post cure at 60C, normally out of mould. Pre-Preg
cures
at least 80C maybe hotter but this must be done in the mould. This means
the part and mould thermal expansion must be closely matched and the
longer the part , the more compound curves, the more difficult this
becomes.

Dry fibre resin infusion probably offers the best way forward as it can
provide
similar fibre fractions to pre preg but without the above and earlier
mention
drawbacks.

Fraser

At 21:58 05 December 2016, Casey wrote:
On Monday, December 5, 2016 at 2:23:59 PM UTC-5, Jonathan St. Cloud
wrote:
For the guys with an engine weight does make a difference. Imagine if
th=
e 100 pounds of engine and fuel were offset by construction methods that
lo=
wered the empty weight of the glider by even 50-70 pounds. YOu would
funct=
ionally have the same wing loading range as a pure glider.
=20
Just saying.
On Thursday, December 1, 2016 at 4:09:14 PM UTC-8,

=
wrote:
4 Pretty much nobody cares much about weight, except the little
gliders=
.. For all the rest we just want to know how much water can we get in it.

Different building methods in same factory brings several issues I could
th=
ink of.
Cost of buying and storing different materials, cost of process, possible
m=
istakes in manufacturing, return on investment, different flying
characteri=
stics. Just throwing this out there.