I-16 Material Surfaces in Detail

A great deal of confusion exists in the minds of many as to the exact nature of 1930s and 40s Soviet aircraft construction and finish. What was the actually skinning in use? What materials were employed? In this article we will attempt to answer some of these questions by focusing on the I-16 Type 10. The Polikarpov I-16 was built using a variety of construction methods which neatly define the technology of the 1930s in the USSR. Many of these same methods would be employed throughout the 1935-47 period on aircraft of every description, and so this aircraft serves as a fine example of these practices for our examination.

Here is a depiction of the I-16’s surfaces showing the materials used in its construction, without any further coating or finish. Duralumin sheet was used to cover the engine (with detachable panels), the cowling face, the wing inner and leading edge sections, the stabiliser leading edge and fillet, tail cone and vertical fin fillet. Fabric was used to cover the main wing surfaces, the stabiliser and all control surfaces. Pinked fabric strips were applied in these areas over the major ribs and formers in the usual manner. The cowl band was stainless steel.

The fuselage and wing root areas were made up of laminated spruce strips, these wrapped around the shape of the unit over wooden formers. The wood strips were both secured and impregnated with phenol-formaldehyde resin, this giving the normally light wood an orange-brown appearance.  A strip of hard wood (usually ash) was used to blend in the adjoining wing and fuselage sections.

The wing section and cowl featured semi-recessed riveting, with the moving panels secured by fasteners (dzuz type, mainly). The fillets were secured to the fuselage using ordinary wood screws.

The fuselage and wing forward sections were then covered in fabric (common linen). This fabric was impregnated with another type of phenol-formaldehyde resin, being similar in chemistry to that used on the wood strip, but clear in colour [this is may well be the lacquer designated “17-A Clear” as identified by the NKAP’s documents]. The lacquer served to bond the fabric to the various surfaces and form a protective coating, both, and gave a flexible, sandable finish (rather like Fibre-glass). Resined fabric was not applied to areas where moveable panels were located, and was applied underneath the stabiliser and fin fillets, which were added afterwards.

With the airframe thusly covered, various amounts of filler putty were then applied. Special attention was directed at any area where a large joint may occur, or other un-serviceable gaps, and the putty could be applied freely over any surface (e.g. shown here to fill dents in the cowling face) which was not movable. The airframe was then sanded smooth, attempting to obtain the best aerodynamic surface possible.

In some cases, often relating to specific factories, the amount of filler putty used could be quite substantial. This was often the case in early manufacture examples, as the non-skilled work force found their feet and gained experience in mass production techniques. However simplistic, the use of filler putty in this way was hugely effective. Indeed, this method was something of an ideal Soviet solution, costing virtually nothing (in terms of expense) and yet yielding superior results via the application of labour.

At this point the aircraft was ready for painting. Two distinct methods were employed in the Soviet aviation industry, and perhaps as expected, sometimes with further permutations to these, as well. In the first case, the desired military or camouflage finish was applied directly over the fabric/puttied airframe. Generally speaking, A, AE, AEh and AII lacquers all adhered well over such surfaces, and tended to chip away significantly only over dural sheet areas which had neither putty nor primer applied to them. AMT lacquer was indifferent to the types of surfaces to which it was applied.

The second option was to first finish the entire airframe with a coat of ALG aviation primer. Far and away, ALG-1 was the most common of these primers used in this way. ALG-1 could also be sanded, when required, and its colouration was such that it blended together with the filler putty almost seamlessly. After priming, the aircraft would then be finished as above.

It was not unknown at some factories, and in certain cases, that part of the airframe would be comprehensively primed, and other areas not. It was usually the case that primer was not applied to the canopy framing, as these were often anodised strip. Paint flaking from these items is absolutely legion in the photographic record, especially when looking at non-AMT finishes.

This derelict Type 5 shows typical finishing for the period. Souvenir hunters have removed much of the fabric on the fin. This was usually done to obtain the red star insignia, which was obviously regarded as a highly collectable item. A similar would-be collector attempted to cut away the fabric over the fuselage, but no doubt found the resined material to be too difficult to remove. Note that the canopy framing is mostly unpainted. This appearance was quite typical, the paint having fallen away almost completely. Indeed, it was sometimes the case that no attempt was made to paint this framing in the first place.

Another derelict I-16, in this case perhaps a Type 24, shot on AGFA colour slide film. Despite the various colour oddities of this film type, it is manifestly clear that this aircraft was comprehensively primed with ALG-1 at the factory before finishing.

(Leftt) One of the modern I-16 Type 24 replica Warbirds built by Aviarestoration in Novosibirsk ca. 1992. The I-16’s unique construction method is demonstrated here before the aircraft was painted.

(Left) Yak-1b production at Factory 292, Saratov, ca. 1943. The uniform over-all appearance of the aircraft in view, except for the rudder fabric surfaces, strongly suggests that these examples have been thoroughly primed with ALG-1. Note that the appearance of the aileron fabric matches that of the rest of the airframe and not the rudder, indicating that they have been primed as well.

(Right) The I-301 prototype at Moscow, ca. 1940. The entire fuselage and wing surfaces have been covered with resined fabric, even to include the dural sheet covered intakes at the forward root area. No such covering was applied to the engine panels, as these had to be removable for servicing. The cowling panels seem to be wearing etching primer of some kind, and the condition of the starboard wing is uncertain.