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INAV 1
 
Definitively nothing so far from a "Nurflügel", the INAV 1 arose from the necessity of the INAV of a versatile and simple wooden built glider, with good performances that could be built by clubs. Was Dr. Horten who lectured on the new design in the "Tercer Congreso Argentino de Vuelo Sin Motor" ("Third Argentinean Congress of Flight Without Engine") in 1953. The salient aspects of it were published in the magazine "Vuelo Silencioso" of June of 1953 and the comments of the construction of the first prototype and results of the first test flight in the magazine "Vuelo Silencioso" of May of 1954: 
 
It is foreseen to develop new types of gliders in the Design and Building Division of the INAV. Although the facilities in La Cruz still are not in operation, yet this is not an impediment to begin with test gliders, as it has been established by the Statutes of the INAV. The Directive Commission in November of 1952 told me to begin the work with a single seater glider, whose specifications have been given by the General Director of Flight Without Engine, Mister Ernesto Vignera. 
 
According to him, the employment of the INAV 1 is: 
   
The Directive Commission, in their meeting of May 1953, has also given its authorization to accomplish this mission, and I have proposed to develop a new design based on the training sailing ship, but with a wing of bigger  span. This design is constituted by the fuselage, the tail group, wing takings and half of the ribs of the training sailing ship .
 
The existence of three different necessities demonstrate that the urgency of developing own gliders is big for the Argentinean sailing. We should not increase the great number of existent gliders in the world with one more, we instead should have to take into account for the project the necessities that arise from the circumstances in the Argentina Republic. with regards to the flight performances, later meteorological measurements will give the basis for a design with optimal values. For the "INAV 1" (training sailing ship) the minimum performances have been established by the General Director of Flight without Engine, and those of the high performances sailing ship are that of the maximum allowed increase of the span. 
 
About the design it has been required that the sailing ship can be built for the clubs in "kit" form, it is, is not wanted a light construction, and that the wing of two parts be built in wood and be connected to the fuselage in such a way that with taking out a bolt the two wing tips reach the ground. This is very convenient for rig - out the machines after landing in distance flights. There have also been prescribed spoilers and a rigid command of ailerons, with push tubes . The fuselage was required with: the front of steel tube, good dampening in the landing skate and single - wheel, with adjustable treadle, open and closed booth, all the commands with ball bearings and a compensation tab in the stabilizer. All these desires were accomplished and also other more, as the hook trigger of the of gravity center,  to facilitate the tow by automobile or winch and the tow with an airplane with single hook. In the first prototype I desisted of the static balance for compensation of pilots' different weights, since the sailing ship possesses a profile of the series NACA 23 that practically doesn't have variation of the center of pressure and due to this, the glider has a great excess of stability. If the test flights agree with what I think, we can desist of this compensation and the tab in the stabilizer will be sufficient for all the weights of the pilots to fly with stability in all the speeds without pressure in the neutral position of the stick. 
 
As you can see from the drawings, I chose the shoulder wing. 
 
This gives good visibility upwards and backwards, which is necessary in the turns in thermal. Forward, below and sidewards, the glider have enough visibility, while ahead and below it doesn't exist. With the cover interchangeable open booth demanded by the General Director of Flight without engine, the visibility to the winch or automobile  can be good during the tow. 
 
The height of the wing tips on the ground was reached with a dihedral of 5,7°, this gives, in combination with the dampening of the slip due to  the lateral surface of the fuselage, simple flight qualities in what refers to the movements around the longitudinal axis. For pilots with little training and blind flights this quality is a great advantage. Also the small surface of the stabilizer gives little sensibility around the traverse axis, facilitating this way the blind flight. 
 
With regards to the vertical axis I made everything to obtain a maximum of 
maneuverability, being this pleasant to the pilot. For this reason the  ailerons have been developed with the border of attack of Frise type and the rudder has been dimensioned to the maximum possible size. In spite of all these, it is necessary to wait to know what flight qualities will result in tests and if these will have be modified according to those planned. 
I want to remark that no apparatus is finished when carrying out its first flight and that the test and the improvement of flying qualities constitute an important part in the development of new machines. 
 
The single - spar wing, of two parts, is connected to the fuselage like a cantilever shoulder wing with three bolts. 
In the leading edge, made with compensated veneer, are located  push tubes with ball bearings, and near the end of the wing, a rope attached to the main spar is used to rig - out the glider to the ground. The aileron, aerodynamically compensated , pivot on the main spar, likewise the spoilers in mid - span of the wing. These last ones are insured against automatic opening and are operated by ropes, the auxiliary spar that is connected to the fuselage with a fastener, resists in the event of an accident accelerations up to 15 g. in forward direction, and with bigger accelerations breaks as a fuse while the tubes of  steel of the booth support bigger accelerations. The front part of the fuselage was designed in such a way that it supports 20 times the glider and pilot's weight. 
 
The direction of attack of the stress is calculated with an angle of 30° up and with 5 g. sidewards, in such a way that, if the security belts don't break, the pilot will be completely protected. If a more serious accident happens, the tubes in the vicinities of the pilot's seat will support 30 g., while the tubes of the front part will open to the outside. With all this, I believe, we have made everything in the tubes' structure to increase the pilot's security, although it results in a weight increase from about 10 to 12 kg. in comparison with a normal construction . 
 
The covering of the fuselage can be made with a fine aluminum foil or with cloth, or if we can produce it, shatter - proof plastic material. On the instruments and the termination of the pilot's booth I don't say anything, because this is left to the clubs. 
 
The later part of the rounded fuselage, built in wood with three longitudinal cords and veneered with compensated wooden, with the keel down,  takes a tail group of conventional construction, also in wood, and the rudders are worked by wires. Behind the center of gravity is located a wheel with dampeners; at the tail, a skate dampened by a tennis ball and in the front part of the fuselage a  wooden skate, also dampened. 
To finish I want to express my hope that in a short time it will be possible to begin the shop works and that in the next year, in the Fourth Congress, we wil be able to show the prototypes in flight.
 
                                      ("Vuelo Silencioso", June of 1953)
 
 
INAV 1A 1B 1C
Wingspan 13.5 m. 13.5 m. 17.2 m.
Wing area 11.90 m2 14.20 m2 13.70 m2
Finesse 15.3 12.9 21.5
Empty weight 165 kg. 175 kg. 190 kg.
Wing loading with a load of 100 kg. 22.2 kg/m2 19.3 kg/m2 21.2 kg/m2
Maximum glide speed 230 km/h 150 km/h 180 km/h
Minimum speed 62 km/h 47 km/h 60 km/h
Minimum sinking speed 0.80 m/seg at 68 km/h  1.04 m/seg at 63 km/h 0.62 m/seg at 65 km/h
Best glide ratio 22.0:1  15.4:1 27.0:1
 

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