Piuma Project - A Friendly Family of Ultralight Motorgliders

Piuma Almerico

Some notes

The Piuma Almerico was designed as a result of numerous modifications and refinements undertaken on the Piuma Twin Evolution, which ultimately resulted in a new faster and more efficient motor glider.

In fact, during the construction of the author's Twin, a construction that in the meantime was proceeding slowly due to work commitments, the possibility of new changes had arisen, aimed at seeking a further improvement in efficiency, easier centering and opportunity to incorporate in a single version all the refinements introduced in the various versions of the Twin.

After the decision to also revise the fuselage to make it even smaller in the front section, other substantial changes were evaluated, such as the increase in wing elongation and the choice of more glider profiles that would allow us to exceed efficiency 25, a significant goal for a side-by-side two-seater motorglider of amateur construction.

The result of all the design, refinement and reconstruction work, which lasted about 5 years, is summarized in the Project Book and in the Construction Manual, as well as in the 25 tables of the new drawings, completed in 2012.

The author then suspended the construction of the Twin Evolution and introduced some changes on the two-seater Almerico to make it a single-seater for personal use by modifying and replacing some parts already built of the two-seater (parts available if interested in any builder); the Almerico single seat is almost completed at the end of 2020.

Almerico project information

Both the high braced wing, the propulsive engine and the cross rudders of the Piuma Twin Evolution were kept, while for the landing gear was chosen a leaf spring solution in lamellar ash and fiberglass, resistant and teardrop-shaped, complete of wheel fairings; an alternative narrow landing geary was designed, as for the Twin Evolution, but in this case some levers have been provided to make it retractable.

The Piuma Almerico is a side-by-side two-seater, with the front area low enough to allow a wide front and side view and the new dashboard also favors in this; the seats are in a more lying and forward position, padded and comfortable for touring use.

The fuselage has been completely redesigned and has a smaller section, wider and less high, thanks to the tail boom protruding under the fuselage, a solution that reduces weight and improves aerodynamics; now it is more rounded and streamlined than the Twin Evolution.

The numerous but light frames of the fuselage give shape and strength to the whole and support the landing gear, the wing struts, the engine, the seats and the various levers and drive mechanisms (joystick, flaps motor, etc.).

The engine of choice is the 60 Hp 4-stroke HKS 700 and the engine mount, radiators and oil tank, as well as the space for the small muffler have been designed for this engine, which unfortunately is no longer in production; unless you find some used specimens, similar engines are recommended for weight (not over 60 kg) and power from 50 to 60 HP.

The engine is positioned high above the wing, with the propeller pushing a little higher than the wing; the fairing is provided, while the tail plane is a cross, low enough to be only partially hit by the vortexes of the propeller.

The instruments panel is a glider-type cantilever, in fiberglass or carbon, to combine lightness and rigidity, while for the use of a parachute, the attachment in the anchoring plates of the wing struts has been provided; for its positioning, please refer to the manufacturer of the same.

Balancing with this configuration may require ballast in the case of flight with the pilot alone; this must be checked during the centering phase and in the extreme front area there is a space for shaped lead blocks.

Other characteristic data are the following:

Airfoil, chord and winglet: the airfoils were chosen more by glider: FX 61-168 (16.8% thick at 37% chord) at the root and FX 60-126-1 at the end, twisted by about 3 ° negative; the maximum chord is 1150 mm, increasing the wing aspect ratio compared to the Twin Evolution, an element which together with new smaller and lighter winglets contributes to the improvement of overall efficiency.
The wing covering is in birch plywood with different thicknesses according to the area, with application at 45 ° and internal stiffeners with thin styroform 6 or 10 mm between the ribs.
Air brakes: They are positioned further back on the wing so as to have less influence on the displacement of the center of pressure during their use (less variations in attitude); the drive mechanism has been changed to have less effort and more effectiveness.
Ailerons: Their actuation is with a rigid bar and the hinging is central rather than upper, therefore better aerodynamics and efficiency.
Flaps: They are operated electrically by means of 2 bars (instead of 3 as on the Twin); they are smaller, but the slot system ensures excellent effectiveness.

Technical information

Wing Span Wing Area Length Height Empty Weight Gross Weight Fuel Capacity HP/HP (range) V.N.E. Top speed Cruise Stall clean Stall full flaps L/D max Aspect ratio Min. Sink rate (56 mph) Load factors (breaking) Load factors (security coeff. 2) Take-off Landing Bldg Time (man hours)	43 ft. 122 sq.ft. 21.3 ft. 6 ft. 600 lbs. 1000 lbs. 12 gal 60 (50/60) 112 mph. 110 mph. 90 mph. 44 mph. 38 mph. 26 15.4 200 ft/min. + 8 -2.2 + 4 -1.1 500 ft. 500 ft. 1.200

Construction Plans

The Construction Plans consist of the following:

N. 25 very detailed drawings in dimensions of about 100 x 60 cm (40’ x 24’), with references in Italian and English language, which describe both the normal version with normal landing gear and the special version with retractable landing gear in the fuselage. In the Triptych there are now various color photos of constructed details.
The Construction Book is 56 pages (with 97 photos and drawings); it also contains information on wood, plywood, glues, aluminum alloys, Dacron, painting, general electrical system, for the trim and for the flaps.
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 of all the necessary materials, the calculation of the center of gravity and the instructions for the first flights, as well as the Check-list of pre-flight checks and the weights for the parts to be build.
The Project Book which in over 90 pages of calculations with more than 140 photos, tables, drawings and graphics, explains in detail how the Almerico was born, the sizing of resistant structures with the verification calculation, as well as the calculations for the Drag, Lift, Moment, which show the efficiency at various speeds.
From the calculations on the torsion of the wings we obtain the VNE and the VA, while from the Lift with and without the Flaps we obtain the various stall speeds.
Also included is a DVD with 3800 photos of the construction phases of the various Piuma, including Almerico, many photos of the completed and flying Piuma single-seaters and two-seaters and some videos in flight, as well as a detailed note of all the necessary aluminum alloy construction parts.
Also included are CAD drawings for water or laser cutting of all flat metal parts, which can be made in these ways.
There is also a file with the CAD drawings for water or laser cutting of all the frames in avio birch plywood.

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 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”).

The construction time is estimated at about 1200 hours, having the metal parts made by a workshop.