Piuma Evolution

Among all the models of the Piuma this is by far the most built.

In consideration of the fact that now almost all the manufacturers adopt more powerful and heavier engines than the KFM 107 of the original project (the most used is the Rotax 447) in the autumn of 2020 I decided to update the structural calculations for a weight in flight order of 275 Kg (605 lb), also indicating on the drawings the changes to be made for those who do not wish to keep the normal 250 Kg (550 lb) version, which provides a light engine under 30 kg (66 lb).

Basic peculiarities

The Piuma Evolution differs from the original Feather for the following modifications:
  • Fuselage shape: the cockpit is 1 inch wider. The rear portion is completely tapered and the lower side is rounded for a more attractive appearance and improved aerodynamics, obtained also by tapering the rear area under the engine to zero.
  • Geometry of the wing: the chord at root is 43.3 inches (the original is 47,2 inches) and the aspect ratio is 13/1 (original 11.2/1). Dihedral is 2° instead of 3° and the wing airfoil changes from 16% to 15% of maximum thickness. Especially thanks to this new wing, the efficiency has exceeded the value of 20.
  • Geometry of the tail and rudders: the tail and fin area now are smaller and slimmer; the tail is now cantilevered, with 2 little airfoil struts. The 8 steel cables of the Original Piuma have been eliminated, which were a source of considerable resistance.
  • Wing struts: they are smaller than the previous ones and consist of a drop-shaped aluminum alloy profile; this also improved efficiency.
  • Engine: the engine heads are partially hidden by the wings in the Original Piuma; in the Piuma Evolution they are in full airstream and this allows better possibilities of exploiting the KFM 107 engine. The current availability of small and powerful single-cylinder units with anti-vibration counter-rotating masses always makes the construction of the light version interesting, even if with the continuous improvement of the energy / weight ratio of lithium batteries, the use of the electric motor will become increasingly popular.
  • Nose wheel: it is electrically retractable; it is also possible to build it fixed, faired and steerable with the indications contained in the project; now almost everyone prefers it in this second version, very comfortable when moving on the ground.
  • Main Landing gear: the stratified wood landing gear covered with epoxy glass (or epoxy carbon fiber) is much more aerodynamic and shaped like a drop: some builders have really made works of art, as can be seen from the numerous photos.
  • Seat: it has been shaped for a more relaxed position, like a glider, also comfortable for long journeys: there are detailed drawings and many photos of the construction and can be used, with the correct sizing, even by persons 6 feet tall (or little more).
  • Instrument panel: it is designed by "glider", it can house the GPS and many instruments and is undoubtedly more beautiful as regards aesthetics; the dashboard is also illustrated by numerous photos.
  • Tail trim: it was made electric, with a control instrument on the dashboard; in the plans everything is drawn and explained in detail.
  • Air brakes: the controls and the brackets have been improved and designed on a 1 to 1 scale; there are also designs for a slightly more sophisticated “special” version.

The best L/D is now 20 and the normal cruise is about 75 MPH at 65% power with the Rotax 447, the more used in the construction.

Technical informations – 550 lb version

Wing span
Total wing area
Aspect ratio
Total tailplane area
Lever arm of tail plane
Length overall
Max height
Empty weight
Max take-off weight
Max wing loading
Recommended load factors (security coeff. 2)
Ultimate load factors
Max level speed
Normal cruising speed
Stalling speed
Never exceed speed
Best glide ratio (at 43 MPH)
Max climb rate at sea level
Min sink rate (at 39 MPH)
38.7 ft
114 sq.ft

15 sq.ft
10.8 ft
19.7 ft
5.3 ft
350 lb
550 lb
4.8 lb/sq.ft
+3.5 -1.4
+7 -2.8
72 MPH
62 MPH
35 MPH
84 MPH
330 ft
330 ft
460 ft/min
165 ft/min
25/30 HP

Technical informations – 605 lb version

Compared to the above data, this modified version provides the use of a 40-50 HP engine, an empty weight of 400 lb, an economic cruising speed of about 75 mph and a greater climb rate (from 800 to 1000/min) which obviously depends on the type of propeller used. With further small changes and modifications, extensively detailed, it is possible to reach a maximum weight of 300 kg (660 lb).

Construction plans

After the latest update of autumn 2020, they consist of the following:
  • N. 14 very detailed drawings, with references in Italian and English, in the dimensions of about 100 x 60 cm (39’ x 24’); in drawing no. 1 - Triptych - there are now 11 color photos, 7 of which of Flying Piuma and 4 of the most used engines.
  • Construction Book and Use Manual updated in autumn 2020 is now 70 pages with 120 photos and 30 explanatory drawings and tables. The first 10 pages are dedicated to materials and equipment, about 30 pages to the various parts to be built and to assembly; follows the detailed note in 6 pages of all the necessary materials, the calculation of the center of gravity and the instructions for the first flights. There are also drawings for the construction of more sophisticated air brakes, drawings for the tank, for the assembly ladder, for the seat and the engine mount for Rotax and Hirt engines, as well as the Check-list of pre-flight checks and a hypothesis of weights for the parts to be built. All the information necessary to build the 550 lb or 605 lb version for particularly tall and heavy pilots have been added.
  • Project Book: this too has been expanded and updated in autumn 2020. Now there are 70 pages (with over 100 photos, graphs and tables) containing the structural calculations for a weight in flight order of 605 lb, the calculations of Lift, Drag, Moment and L/D and in general for the prediction of flight characteristics and various speeds (VNE, VA, Vso, etc).
  • Also included is a DVD with 3800 photos of the construction phases of the various Piuma, many photos of the completed and flying Piuma and some videos in flight.
  • In the DVD there are also the CAD drawings for laser or water cutting of all the flat metal parts to be made, as well as a note in Excel of all the metal parts to be cut, turned or milled with reference to the drawing where the part is located.

Other useful information for the builders

The cost of materials, excluding engine and instruments, is around 4000 $ (at 2020 prices); the cost of the engine and of the instruments is quite variable, depending on the choice of the type of new or used engine and on the more or less essential instrumentation; from the photos you can have a broad overview of the possibilities offered.

The construction time is estimated at about 900 hours, having the metal parts made by a workshop.

The dimensions required for the construction of the 6005-T16 aluminum alloy tail boom are: diameter 127mm (5”)-thickness 1.5 mm (1/16”)- length 5.2m (205”).