Piuma Twin Evolution

A few notes

The design of the old Piuma Twin was completed in 1999 and various flying constructions were built with satisfaction, however highlighting the need for excessive ballast for single-pilot flight; over the years, improvements and modifications have been introduced and this has prompted the remaking of almost all the designs to incorporate the variations, which materialized in 2009 in the new Piuma Twin Evolution project.

Twin Evolution project information

The Piuma Twin Evolution therefore incorporates all the improvements suggested by 9 years of Twin construction, with the front elongation of the fuselage of 20 cm for a better centering without ballast for 2 people and a rear configuration similar to the Evolution single-seater of which it follows the rudders cross that allow to lighten and stiffen the tail boom and the part relating to the tail; the engine mount in aluminum alloy and steel with double cushioning was also designed to avoid unsafe assembly by the builders.

Some simplifications have also been introduced in the control levers and lightening in the wooden part of the fuselage, while the dashboard is now cantilevered, more like a glider; the various versions of the Twin have been unified here in the one best suited to the philosophy of the project, that is the one with a wingspan of 13 meters and 12.20 square meters of surface.

The good aerodynamics allows a fairly fast flight even with a modest power engine, therefore economical in purchase and consumption; a 45/50 HP motor weighing less than 50 kg is in fact sufficient; a used Rotax 503 mono or bi-carburettor in good condition is an excellent choice, while on the new one you can find excellent Simonini or Hirth 2-stroke carburettor or injection engines.

More powerful (and heavier) motors are not recommended, as they would cause centering problems with a considerable need for ballast; the exception is the 60 HP 4-stroke HKS 700, which, compared to about 5 kg (11 lb) more, allows for smaller tanks and less fuel, having a consumption of about 35% lower than 2-stroke engines of equal power, practically equalizing the total weight.

Flight comfort was held in high regard, given the touristic vocation of the motorglider; the cabin is 108 cm (42’) wide with ergonomic and well padded seats. The pedals are double and the joystick is central, while the throttle levers, brakes and spoilers are positioned on the left side (that of the pilot), even if it is not difficult to split everything. The driving position is similar to that of a comfortable car, with the joystick in place of the gear shift and the pedal unit in place of the brake and accelerator.

Technical information

Wing Span
Wing Area
Empty Weight
Gross Weight
Fuel Capacity
HP/HP Range
Top speed
Stall clean
Stall full flaps
Min. Sink Rate
Load factors max.
Bldg Material
Bldg Time (man hours)
Take-off distance
Landing distance
42.7 ft.
132 sq.ft.
21.3 ft.
5.6 ft.
600 lbs.
980 lbs.
11 Imp gal
106 mph.
103 mph.
92 mph.
44 mph.
35 mph.
220 ft/min.
+ 4.6 -2.3
400 ft.
400 ft.

Construction plans

The Construction Plans consist of 16 drawings in dimensions of 100 x 60 cm(40’ x 24’) or larger. All the ribs are drawn in scale 1 - 1 and many metal details (levers, brackets, etc. are also in scale 1 -1. The drawings are very detailed and nothing is left to the imagination, making it easy to build each necessary piece.

The Construction Book with the Use Manual and the Project Book updated in autumn 2020 are also provided with the plans.

The Construction Book and Use Manual is 50 pages with 70 photos, explanatory drawings and tables; the first 11 pages are dedicated to materials and equipment, over 30 pages to the various parts to be built and assembly; follows the detailed note of all the necessary materials; also included are detailed instructions for centering and for the first test flights, as well as a note of the weights of the various parts of the construction.

The Project Book (90 pages with 32 photos plus 80 graphs, drawings and tables) illustrates the sizing methods, the verification calculations of the resistant structures, as well as the flight characteristics based on Lift, Resistance and Moment (from which VNE, VA, Vso, Efficiency, Vy, etc).

Also included is a DVD with 3800 photos of the construction phases of the Piuma by many manufacturers, numerous photos of the completed and flying Piuma and some videos in flight.

The DVD contains 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. There are also various files with CAD drawings for laser or water cutting of the flat metal parts to be made.

Other useful information for the builders

The cost of materials, excluding engine and instruments, is around 5000 $ (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 1000 hours, having the metal parts made by a workshop.

The pipe dimensions required for the construction of the 6005-T16 aluminum alloy Tail boom are: diameter 127mm (5”) - thickness 1.5 mm (1/16”) - length 5.2 m (205”) + 2,6 m (102”).

There is an old video on YouTube (from 2008) by the builder Luca Baldi who reports, together with negative comments on the Piuma built, the test flight of his old version Piuma Twin, which ended with a landing on a field plowed with deep furrows, probably due to the rupture of the propeller due to over-revving the engine, with consequent overturning of the vehicle (driver unharmed).

I make available here the Report of what happened compiled in those days, so that anyone can form their own opinion on the matter, both of the builder and of the Piuma Twin built.