If you examine the three sketches above, you will see three distinct wing configurations.

NANADOVIC:
The first is the pure Nanadovic config, in which two wings are placed such that the horisontal wing gap is zero, and the rear wing is 1/3 chord below the front wing.  Nanadovic (a Yugoslav aerospace engineer and longtime faculty member at the University of Belgrade whose graduate work was to find the most efficient combination of gap and stagger for a biplane wing) did his research way back in the 1930’s, and he concluded that for a plane equal in all other respects, his particular wing positioning resulted in “improvements over a monoplane of the same profile of 25% less drag, 15% more lift, and 51% better speed range”

This was his original creation.  The first TCF config above conforms to his formula.

MIGNET:
Still in the 1930’s Henry Mignet hit on the idea of pivoting the front wing of a plane very similar to that of Nanadovic in wing placement.  He did away with ailerons, and opted for a 2-axis control system in which both the pivoting front wing and the rudder were controlled by the control stick/wheel.  This resulted in a very easy to fly plane which (like the Nanadovic concept) was not able to spin.  A parachutal descent where the plane gently rocked back and forth while still under full control, is all that resulted in a stall.

Mignet was a excellent marketer, and aided by his little publication about the Pou du Ciel, soon hundreds of “Flying Fleas” were being built and flown in Europe and also in the UK.  But Mignet’s design had a fatal flaw in the control system.  A combination of poor airfoil choice, and a very flawed control system saw the plane unable to pull out of steep dives, and a number of fatalities resulted.  The control system was quickly rectified, but the reputational damage had been done, and the Flea never regained widespread popularity.

Both the Nanadovic and the Mignet configurations owed a great deal to the interaction between the two wings.  Essentially, air flowing off the trailing edge of the front wing would be pulled down and over the top of the rear wing, resulting in what can only be described as a cross between a fowler flap and an extended wing.  In fact, Flea designers take it as read that the “wing” is from the leading edge of the front wing and the trailing edge of the rear wing.

La FARGE:
Jean de la Farge was an Argentinian, who worked with Mignet in Argentina, where the two of them set up a partnership to continue evolving the Flea.  The partnership didn’t last, and they parted ways.  But la Farge pursued his ideas – he added a pivoting rear wing to the mix.  He called his design a “Pulga”.  Both wings now pivoted in concert, and to counter the significant nose-over torque when the wings were deflected, he added a third flying surface to the top of the tail.  This third wing controlled pitch, especially in landing, where both wings were fully deflected to 12 degrees.

The interesting thing in all this is that ALL THREE designs flew very well – so the differences in their configurations wasn’t huge by any means.

The TINY CEDAR FLEA is going to be capable of emulating all three designs, simply by (1) locking both wings in position) – Nanadovic (2) Pivoting the front wing only (Flying Flea) and allowing both wings to pivot (Pulga).  The mechanics of this are simple.  Add a locking mechanism at both wings, and choose to either fix them or allow them to rotate.

On the one hand, this will allow me to experiment (initially on the 25% scale model) and then later on the full-size plane with all three configs, and try to draw some conclusions about their performance (pitch control, fast flight, slow flight, landing, turning and so on.

On the other hand, it will give prospective builders (and flyers) the option of choosing between the three configurations to suit their personal preferences.  And thewn to change their minds if they wish.

 

Three planes in one.  It doesn’t get better than that!