Gavin Griffith-Jones <<gavin_gj>>
writes:

As an aging ex-hang glider pilot, I am less inclined to carry
heavy gliders around, and have less time to drive to hang gliding launch sites
(and often, from one to the next). I am also quite happy to forgo foot launch
and landing, in favor of wheels. This aircraft concept is intended to meet the
following needs:

1. Convenience - as a self-launching motorglider, it offers much greater scope
for finding a suitable site (compared to hang gliders) - any large field, beach,
airstrip etc. will suffice for operation.

2. Performance - designed to have glide performance equaling or bettering that
of a hang glider, it will be capable of lengthy cross country flights as a
glider.

3. Portability - it can be carried on a typical station wagon. The wing element
will travel on a roof rack; the other components can travel on or in the
vehicle. (It can be stored in a normal garage as well as a car - the wing
component hanging from the roof).

4. Economic - based on traditional flex wing hang glider technology - alloy
spars and sailcloth. This is a relatively cheap way of constructing a wing
(compared to composite technologies). Not just economic to build, the flex wing
also has advantages of being robust, easy to check for damage, and easy to
maintain. Design details

Controls

The aircraft will offer conventional 3-axis controls (stick and rudder pedals).
I believe this will appeal to a larger potential market (GA pilots, glider
pilots, pilot training building hours), than 2-axis weight shift control. Roll
control - will use ailerons (or possibly spoilerons). This opens the way to have
a longer, tighter wing (think a hang glider with the VG on full); giving better
glide performance. Pitch control - will use weight shift; the entire wing
(including keel and tail surfaces) will pivot fore and aft with respect to the
pilot. Yaw control - achieved through a cable-operated rudder surface, which
provides the 3rd axis of control (allowing for better coordinated turns).

Structure

Stabiliser - a fixed horizontal stabiliser - providing pitch stability via down
force (for longitudinal dihedral). This is NOT used for pitch control (that is
done via weight shift). The stabilizer is removable and can be stored in the
same bag as the wing.

Main wing - based on a flex wing hang glider, with the following modifications:

1. Cable - operated ailerons. These surfaces can be folded away as part of the
wing, after battens have been removed.

2. Increased wing span, and a tighter sail, are possible (increasing flight
performance) as billow shift is not needed (due to the use of ailerons for roll
control).

3. Higher performance airfoil shape (negative moment coefficient airfoils) can
be used, due to the use of a horizontal stabilizer for pitch stability.

4. The keel and crossbars will need to be reinforced due to the absence of wire
bracing. In a conventional topless wing, these are rated to around -3G; they
will need to be around twice as strong to handle +6G. The crossbars can (if it
makes economic sense) be constructed of alloy rather than carbon (a few extra KG
here is of less importance, as the wing will never be foot launched / landed).

5. Sidewires - are optional - a tradeoff between a wire braced structure that
can be lighter, at the cost of increased drag.

Engine - a small petrol engine (most likely sourced from paramotor technology)
provides enough power for self-launch. Positioned near the CG (as shown) means
it can (if desired) be removed, and the aircraft flown as a pure glider. The
propeller can be forward-folding to reduce drag in gliding flight.

Pod - A streamlined pod encloses the pilot for reduced drag. A main wheel allows
for takeoff and landing.

Prototyping

1. While a composite pod would be ideal for light weight, strength (including
consideration of crash protection) and streamlining, a prototype could use an
alloy frame and fiberglass / fabric fairing (as is done on many trike-style
microlights).

2. While directions for development of a customized wing have already been
discussed, a convention topless wing could be used for prototyping - with
strengthened keel and crossbars, and the addition of ailerons.