Ron Webb wrote:
"Shin Gou" wrote in message
om...

A friend of mine is planning to build a trike (powered hang glider).
Could anyone recommend some books about hang glider wing aerodynamics
and design?

Thank you in advance.

Shin Gou


Shin

The Rogallo wing http://en.wikipedia.org/wiki/Rogallo_wing
has a trick associated with it. I do not remember the specifics, but it has
something to do with rigging the outside trailing edge so that it deforms
differently than it otherwise would. This is what makes it stable.

We had a Russian fellow killed up here a few years back, because his new
design did not include this.

I can't find a referance to this specifically, but this:
http://www.davisstraub.com/Glide/airworthiness.htm
might help.

Tell your friend to be careful. The differance between a good trike and a
death trap is very small.


Tell your friend it's cheaper to buy a used hang
glider than to build, much less design, a wing
for a trike. I have one which was originally
designed for a trike, A Flight Designs Demon,
you could have for US$500 if you're interested.
There's lots of them lying around, though.

What the above poster was likely referring to is
called "Washout" and is often built into a flex
type hang glider wing through the incorporation
of "Luff" lines which are attached to the
kingpost and attached to the trailing edge of
the sail at symmetrical stations out to the tip.
Generally, there are four to a side but that is
not a hard, fast, rule. When a hang glider
dives, not having the stabilizer group aft, it
is at risk of "tuck" and immediately that will
be followed by a "tumble" if you're not too
close to the ground. If you are close to the
ground, say within 50 feet, a tuck will be
immediately followed by "thunk" and likely
"cra-ack" which is generally the last sound that
particular pilot will hear in his lifetime.
A tumble is equally likely to culminate with
such noises as "thunk" and "cra-ack" and is
usually terminal to the pilot and glider. A
tumble enjoys the dubious distinction of other
noises such as on-lookers screaming and the more
knowledgeable among them shouting "Deploy!,
Dude! Deploy!" under the assumption that you
have a parachute. But, I digress.
Without luff lines, a hang glider tends to dive
steeply enough that it cannot recover. Luff
lines hold the trailing edge in place relative
to the kingpost, and the rest of the
non-flexible structure of the glider. In a dive,
the air pressure increases on the upper surface
of the wing, and since the wing is flexible, it
gets depressed into the structure of the glider
airframe. The luff lines hold the trailing edge
"up" in that situation, causing the nose of the
glider to be raised, restoring the appropriate
angle of attack and re-pressurizing the under
surface, which is the desired result. The pilot
feels this as increased pressure outward or
forward on the control bar and must exert more
physical pull on the control bar to counter it.
I must note here that the luff lines actually do
their work in situations of increased speed as
well as in decreased angle of attack. Anyway, if
the pilot overcomes this pressure the glider
will eventually stall. Theoretically, even if
the nose were pointed in the same exact
direction as gravitational force, an aircraft
can be in a stall condition. A friend described
this to me from his aerobatics lessons in a
Pitts S2.
The bottom line is, tell your friend there is
not much reason to design a wing unless he's
inclined to compete with the big hang glider
manufacturers. Some of their test pilots have
died, so more than one is required to get a new
design into the marketplace.

AL