50+:1 15m sailplanes

Earlier, "Bill Daniels" wrote:

With carbon rods, you could probably build a 60 meter glider...

Now, let's hang on for a second while I use that as an excuse to
hijack this thread.

As strong as those pultruded rods and strips are, they offer only a
20% or so increase in stiffness (per weight or per volume) over wet
layups of dry carbon tape. For gliders, and especially for long-winged
gliders, the structural design is bounded by stiffness, not strength.
As such, pultruded carbon rods buy you only a relatively modest
premium over more conventional arrangements of carbon materials.

It's the stiffness, in both bending and in torsion, that keeps gliders
from fluttering themselves to pieces. It's also the stiffness that
keeps exterior finishes like gelcoat happy.

The reason I so dearly love those pultruded rods and strips is that
they represent an extremely effectively packaged solution for the
low-tech glider builder like me. I don't need any expensive autoclaves
or fiber alignment equipment or resin calibration/saturation stuff. I
just grab a bunch of pultruded strip off the spool and go with it.

As for 60-meter gliders (that's just under 197 feet for us
metrically-challenged folks), I happen to believe that they're
possible, but not very probable. But I see the limitations as being
more operational than meterological. There are few places to launch or
land one of them, let alone a contest full of them.

Personally, I think that 15 meter ships are close enough to the sweet
spot for all practical purposes. They fit easily in trailers, hangars,
fields, and launch grids. The pieces are relatively light. And 18
meters is only a wingtip-change away.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com