On Mon, 12 Jan 2009 03:57:11 -0800 (PST), wrote:

Thanks for the info. I incorrectly assumed the dual wires was for
safety. I know the Pitts S-1 and Christen Eagles have dual wires, but
only at the main spar and I though I read somewhere that they had to
be dual for safety. Obviously these planes can alter their incidence
by adjustments at the outboard wing struts. They must have a
different pressure distribution to keep them from twisting?

When you have a biplane, you've got a lot more choices....those box
structures are pretty strong, just on their own. I fiddle around with
very lightweight RC aircraft, built from 3 mm Depron foam. A single
sheet of the foam isn't strong enough for a wing (unless the plane
weighs only 30 grams or so). But a biplane setup (with 1/32" plywood
cabane and interplane struts) is good for five times the weight, even
without adding bracing.

Stealth Pilot wrote:
dual wires will *never* be for funk safety.
if one of the wires were to break the transference of load to the
other wire (immediately doubling its stress) would likely cause a
catastrophic failure. far better to have one adequately sized wire.

The Fly Baby has dual bracing wires (e.g., two to the forward spar, two
to the aft) for lower-cost construction. It's important to keep about
the same tension on both wires in the pair. There was a fatal accident
a few years back where the it's suspected someone failed to do that.

Ron Wanttaja