Hi, and welcome back.  While I wait for parts to arrive for the CNC, I’ve been hard at work checking and double-checking the Tiny Cedar Flea design.  Here is where the design currently stands:

As you can see – the fuselage has been lengthened a little, and deepened at the nose to accommodate the 990cc v-twin Industrial Engine (Generac).  Also, since this design is heavily influenced by the work of David Isley (Pou Renew #48) in 2012 which was in response to the pioneering work of  Axel Darling (Pou Renew #41) 2011, I have adopted Axel’s precise measurements, and so his calculations for both the Neutral Point and the Centre of Gravity apply fully.  As it turns out, my estimated CG location is actually quite close to Axel’s numbers.

Axel’s analysis of the optimum front/rear wing areas and positioning concludes that

  1.  A smaller front wing (he recommended 4.4m span) and a larger rear wing (he recommended 5.8m span) was optimal – running counter to the accepted Mignet formula.
  2. The horisontal and vertical separation of the wings had to be equal.  If these two conditions are met, then there will be laminar flow over both wings, allowing for wing incidence of up to 20 deg, and a lift coefficient of  2

The Tiny Cedar Flea has vertical and horisontal spacing of 700mm

If we look at the plan view, we can see this “Canard”Pou and the horisontal separation quite clearly

There is no need to fiddle with placement of the engine, battery, pilot seat, gas tank (etc) in order to get the CG to align with the optimal for this configuration.  This is the beauty of designing the plane from scratch.  I can position the wings exactly where they need to be.  All I have to do is to move the wings forward/backward so that the CG position align with what will be physically measured.

Knowing where the CG needs to be situated now allows me to position the main gear.  The angle from the tyreprint to the CG (both vertical and horisontal) needs to be 15 degrees.  Super simple.  Now I can add the necessary bulkheads precisely where they are needed in order to anchor the gear.

You will also notice the third flying surface – the “Pulga stabiliser”.  This third surface is also a pivoting wing, and is linked to the front wing, providing extremely positive elevator control.  I have borrowed this directly from Jean de la Farge in Argentina, who collaborated with Mignet himself.  His additional surface according to him was a lifesaver.

The cabin area has been widened to accommodate larger pilots.  It is now 498mm wide.

Construction will still be along the lines of strip-built kayaks – glass/wood/glass sandwich, bent and glued over formers to provide the shape.  But I’ve decided to build the TCF out of Paulownia, rather than Cedar.  Not as pretty, but much lighter, and a lot cheaper.  I toyed with using Balsa for a while, but it is way too expensive. I considered abandoning wood entirely in favour of DOW blue foam – but I like working in wood, and I love what wood looks like.  In fact, it is important to understand that the sandwich material doesn’t matter – all the strength comes from the glassfibre skin on either side.

Finally, below is a sketch of the venerable HM293.  The differences in aesthetics, as well as the aerodynamics is very obvious – but equally as obvious, is the fact that the TCF is fully a Flying Flea.