(Mark James Boyd) wrote in message news:3fa6166d@darkstar...
Hmmm....

I was wondering if metal gliders have an L/D disadvantage
due to the metal, or because of the lousy rivets and
poor wing airfoil and draggy struts (of the SGS gliders,
for example).

Mark,

Depends what you mean by an L/D disadvantage. If all you care about
is max L/D, then sure you can make a metal (or wood) glider with a low
min sink and good L/D max. But if you want high performance at higher
speeds, then metal and wood start to show their disadvantages. If you
are willing to spend a LOT of time maintaining the wing surface
(filler, etc) then metal used to be competitive (see all the HPs,
etc). But Schweizer tried to compete with glass with the 1-35 (and
partially so with the 1-34) and failed - there is just no way to
economically get and maintain the laminar flow necessary.

During the 60s there were lots of attempts to make competitive metal
high performance (home-built, mainly) gliders, with mixed success.
Read Moffat's "Winning on the Wind"; he does some great comparisons -
an even thought that a combination glass/metal construction would be
optimum. But time seems to have proven him wrong, at least at
present, and at least at the upper end of the performance spectrum.

Now, for a fun to fly, sports class level glider, metal has it's
advantages, obvioulsly - as all those Blaniks prove!

And there is no way any metal plane is going to feel as nice to the
touch as a glass one, IMHO!

Kirk
LS6 driver and 2-32 fan