NEW PROSPECTS FOR SMALL GLIDERS | MODEL CONSTRUCTION

Judging by the pace, which is professional equipment in a recently available class gliders A1 soon and these “school” paritel can be divided into two distantly spaced from each other level. One, the elite, will be designed for construction and use at competitions of the international scale (accordingly to deal with such a technique will be able to a few units). The second mass, having no hopes for achieving elite results, and therefore, remaining on frankly mediocre level.

That prospect, of course, are not happy. But the published drawings of models, escaping forward, to the “adult” technique for circuit decisions, technologies used supermaterials and complexity of manufacture. Not always the chosen way to improve justified and engineering literate. However, the trend has been. And in the end it will bring the results of every kind, not to mention the increase in flight properties.

However… here is the amendment. All would be well if there were not one, sharply distinct “branch of” design “school” of gliders proposed by the magazine “modelist-Konstruktor” a few years ago. First publication in 1989, judging by the small number of responses, was among modelers as ordinary, though in the proposed design was already provided a very promising solution. But the following article… After its publication in the “M-K” № 1 for 1990 came a lot of letters as “the outrage of professional development and the impossibility of creating such technology in General”, and congratulations to the author and publisher. Wide response is clear: new types of models had invaded a pure sports classes and therefore attracted attention not only as “uchebok”. It is important that the design principles and the use of simple materials in many respects differed from the traditional methods of creating gliders.

What’s next? During the two-year “quiet” sorpresa new technology has made another step in its development. Moreover, it’s a proven and competitions. Suffice it to say that models of this type won the championship of the Moscow region; the same equipment the guys became winners of the Moscow championship. I must admit that they are in class A1 boys are not the worst models, and therefore prizes say a lot. But this — read more in the article itself. How and what changes have been very promising development…

Before I talk about the new model class A1, it is necessary to warn to the end to assess the design, understand all the details and features of the schema will fail if you additionally will meet No. 5’90 “M-K”. Some of the information in some degree duplicating the previous article, not included in the proposed today because of the limited amount of journal publications. So here you will not find any detailed comparative strength analysis of the wing, nor regarding the formation of the popularity of the classes of small gliders in the international arena.

So the new technique. The basic material for its creation was the lime of different density. For most parts found pure white variety with high density and strength, respectively. Of course, this is not the only suitable material. Probably higher prochnostnye features would spruce (which comes to musical instruments and what can be purchased in Moscow near the metro “Botanical garden” in the store when the company “Lira”) or a grained pine high quality.

The main (and almost only) binder for Assembly of the frame was epoxy resin grade K-153. Replace it with nitrogly generally meaningless, as the power circuit was originally designed for the lack of extended seams in favor of several separate, but very high quality fused nodes. At the same time To-153 — one of the few resins which not only has a good combination of strength and elasticity (for wood type basswood gives the equi-strength joints), but also with long-lasting thickening and low viscosity allows bonding method of loading.

The principal dimensions of the model glider.

Almost all components on the model were first assembled on the pins and the clips dry. Then use the “brush” (a thin needle is clogged the end of the rails) on the joints was applied the resin. Prolonged gelling time of the binder ensures reliable absorption of the resin over the entire area of the joint. The excess is removed with a wire ring (head sewing pins) after some time, when the resin acquires the density of honey. Now, if during growth the viscosity of the resin from time to time to turn the frame on all joints, a uniform adhesive fillet of constant radius.

In total, this technology stitching is very time-consuming and takes a lot of time (especially considering the continuous control up to the full gelation). However, if you acquire experience, at once manages to shed almost all of the joints, for example, the center section of the wing! After all, in comparison with conventional designs for the new technology these joints much less.

But most importantly, the reception of the cast resin allows to achieve simply amazing strength qualities. The technology is versatile and suitable for all model elements. Even the stabilizer, where savings of fractions of a gram, is assembled by the proposed method. In spite of the fillets at all joints with radius of about 1.5 mm, it was found that in the amount of ten the butt of the frame units of the stabilizer added only 0.3—0.4 g. In this case the strength is such that the tail gets really everlasting in any treatment model.

Pre-pasting joint surfaces required only for large areas. The glider is only needed at the point of joining of the tail boom and forward fuselage. By the way, in these compounds, the resin should be applied abundantly, to pour a “cushion” of glue on the connected seam. This will eliminate neproblem and loss of strength associated with the absorption of the epoxy into the pores of the wood. The excess resin after curing is removed in the finishing operation details.

The fuselage. The design of this element of the model is so simple that it requires no explanation. Therefore, it is possible to stop only on technological features. After assembling the beams, the bow and cradle the wing serverlists holes for screws. Drilling depth should exceed the depth of the planting screws 2-3 mm, and the diameter of the drill to be equal to 0.5 of the cross section of the neck of the fastener. The screws should be carefully selected, as most have rough ragged cuts. Socket pre-formed by screwing the screws. Then they filled svezhenakleennyh resin and after exposure for 15-20 min, when the bulk of the resin will go into the pores of the wood, the screws are screwed themselves. For protection from gluing them to protect the simple pasting of a stearin candle is enough to make the metal parts easily twisted.

Pin-axle for mounting the keel to the beam end it is better to not seal the drilled hole and punctured. The fact is that when you puncture with a sharp awl layers of wood just parted, and a beam remains the same-strong, with no impairments. The surrounding areas you can additionally wrap a thin nylon thread with the resin.

Fuselage:

1 — bow-boot (lead; fastened with M3 screw, M3 nut pressed in the right part of the download), 2 — nose portion (lime, medium density 8 mm thick), 3 — strip (a thin fiberglass or a wear-resistant film of the “Solarfilm”), 4 — the location of the clock mechanism (option), 5 — front-screw 3X35 mm, 6 — tool tray (plywood 2.5 mm), 7 — pad (made of anodized aluminum 1 mm), 8 — rear screw (2,5X25 mm) 9 — tail boom (thick lip section 8H11 mm; from the back edge of the wing to the front edge of the stabilizer of cross-section to reduce the wedge to 4X5 mm), 10 — tow hook (OVS wire Ø 2.0 mm), 11 — screw fixing hook 2,5X25 mm (2 PCs), 12 — pad (steel 0,5 mm), 13 — outline of the keel (aluminum knitting needle Ø 2 mm, after molding, the ends should be degreased and wrap a thin cotton thread), a 14 — axis attachment of the keel (OVS wire Ø 1 mm; to seal the plot to dash off and degrease; to put in a pierced hole in a beam), 15 — tube (medical needle), a 16 — base (lime 2.5 mm; workpiece thickness of 4 mm is processed after Assembly), 17 — winding (fine thread), 18 — tool insert of the stabilizer (plywood 1.2 mm), 19 — tape attachment (the ring is from the fingertip), 20 — keel (Linden 1 mm), 21 — lined (lime), 22 — fastening hook (nylon tape), 23 — hook wick (OVS wire Ø 0,8 mm), 24 — wick.

The front part of the fuselage Assembly.

The details of the mounting of the wing and the tow hook.

The details of wing mounting and the tow hook.

The best option is finishing the fuselage — thin color film production in the former GDR (not to be confused with the “Oracle” is a completely different thing!). Weight loss on the finish will be minimal, and the quality is beyond any criticism. In the presence of a film of type “Solarfilm” it is useful to clip a narrow strip and weld it from below, where the film will serve as landing skids. In this model for two years of operation on low fuselage — no scratches. In the absence of such materials is acceptable and wire, and plywood skis.

Wing. By design, it special changes has not undergone. Are different only section of details in connection with the transition to dense durable wood, and a greater percentage of scale now make up the “ears” of the wing. As an experiment, the trailing edge is made wedge-shaped. The purpose of innovation was to obtain a smooth lower profile of the shank (plating superimposed on the belt a width of only 1 mm) and more optimal transition to the joint edges with ribs in the sense of strength. However, a more reasonable need to accept the variant proposed in the early publications: a simple rectangular rail cross-section 2X6 mm. and It is easier to mount, and the stability of its form during the long time operation above.

Tubes-canisters for the connecting pins are stuck through the glue holes in the edges. Tubes must be degreased, the surface is rough kick with needle files, and always wrapped in thin cotton thread. The main point of coil: protection of wood from cracking under the load of layers.

The tight wing — textured Mylar film. It comes in the paper shops as “film filled with” in rolls of a width of 300 mm and a length of 10 m in a roll. By the way, even in the same party in different rolls can be film very different thickness (from 12 to 36 microns). Glider used Dacron with a thickness of about 25 microns. Below the wing where there is a danger of separation of the plating under her tension during warm-up, the film is laid on the glue BF-2. After the lower plating will be carefully welded to the entire frame, including to the rear end of the trailing edge, the excess is trimmed and the wing covered from the top (Welt turned film under the front and rear edges). Here already it is better to apply the glue BF-6, as it gives a cleaner glue line. Useful before beginning the lacing of the wing to drill all the ribs near the front of the scarf drill bit Ø 1-1,5 mm. These channels allow air to move through the ribs of transition from the cavity of the wing and the “ears” that is a must when heating iron sheathed wing (and preferably when changes in air temperature or pressure). At the ends of the supporting planes of the film is also folded, forming a “castle”. If the air channels get closed, they must rassverlivajut.

Working with Mylar film, despite the prevalence of this excellent material, are not familiar with. Many do not even know that well, you can cover the plane only in the presence of iron with fine temperature control. The fact that different varieties of films and adhesives require experimental selection armoreska welding, which can avoid the formation of bubbles under the film and achieve high-quality fixing on the wood. Please note — this temperature is much lower than the stretch!

The Dacron filler has one feature. Unlike conventional films, he would like two stages of shrinking. The first is achieved at a relatively high temperature. The tension is formed “late”, after a second or two after removing the iron. Stress tension — between. A characteristic feature of this stage — the improvement in shrinkage with intensive cooling of the film due to the blowout. The second stage is reached when even higher temperatures. It features: instant education tightened a quick smoothing wrinkles on the corners of the frame, strong tension Dacron. If a similar mode was used after correcting the wing on both surfaces (upper and lower), this ensures complete stability of the arrangement of planes for three to five years.

Another important point: during the shrinking of the film, which is carried out at elevated temperatures, do not touch the adhesive areas. Otherwise, the Dacron then “open” (or rather, he glued seam). To get rid of bubbles is possible, only cool iron to welding and propadu them again seam.

Before the shrink tubing be sure to wash off glue residues located on the outer surface of the hull. To make it easier with acetone or solvent No. 646 or 647. Moreover, immediately after the passage of the moistened cotton light washed away the spot with a dry cotton wool. Small stains can be removed with a slightly damp (more dry) soft cloth. After washing, you can protect the sheet from scuffing, passing through the outer edges of the panels with a narrow brush with Amalita.

Generally trim in brushed Dacron filler is admittedly perfect. Sufficient strength, the reliability of the gluing of the wood, the absolute insensitivity to atmospheric influences her dignity. By the way, it should be noted that we have not observed reduced strength of this film compared to the glossy. The perception among modelers opinion of her “fragility” is most likely connected either with the use of Dacron for heavy motor vehicles, or using only the first stage of the shrinking. But to the question of the strength we get back when talking about the tests of the airframe, and now it is necessary to mention only one fact: in the three years of operation of the model on carrier planes did not have any leashes! It is at a sufficiently thin profile and high elongation! And the winnings by weight in comparison with conventional coatings of long-fibre paper, I think anyone do not need to tell… How about the fact that the rough surface of the wing provides a more stable year results.

After finishing work on the wing it is first corrected to a flat state (during the covering can be considerable twist, but one shouldn’t be afraid). Is then given by balancing the twist: both “ears” at their ends — 3 mm “minus” and the right side of the center section of the rib of the transition is about 2 mm on the plus. In this form, the covering must be treated with iron on both sides (otherwise, you can get the console different torsional stiffness). The finish heat treatment is the key to creating a perfect load-bearing planes. The holes in the Central rib under the wing mounting screws in Dacron are burned using heated wire and the channel holes are impregnated with epoxy resin. When assembling the center section and “ears” with the tweezers on microcrack stretch rings with a width of approximately 1.5—2 mm cut from a rubber nipple. Threads is absolutely unacceptable! During an emergency landing rings burst, and ultralight “ears” without the efforts (and failures) to pop off the pins. By the way, these wire parts are easily lost, and therefore it is better to prepare several of their sets. Tightly as to seal them in the center section or “ears” is not: during descent the pins rotated in both nests.

Stabilizer. The only difference from the early publications, is a smaller section on some parts. Trim stabilizer — glossy metallized Mylar film with a thickness of 0.015 mm (15 microns). Due to the fact that at hand was only a sort of “dark metal” with a pronounced titanium color, and glued it into liquefied BF-2 is bad, the covering is imposed on “the Moment”. To density of milk he bred as BF-2, using solvent No. 647 (acetone and No. 646 gives the worst results), and adhesive residues from the skin wash off with plain gasoline, which minimizes “Time” in non-sticky film. Pin for rubber rings and wick hook mounted on the resin-covered stabilizer.

Stabilizer:

1 — ending (Linden 3 mm), 2 — front flange (lime 2X8 mm; by the end of the section to reduce to 2X3 mm), 3 — rib (light lime 2 mm), 4 — the Central rib (light lime 5 mm; the back edge to reduce the thickness to 2.5 mm), 5 — pin (bamboo section 1X2 mm), 6 — trailing edge (Linden 2X3 mm) 7 — solitaire (Linden 0.5 mm), 8 — hook wick (OVS wire 0,8 mm Ø, to glue after covering with the use of threads).

Balancing these models

The area of the “ears” of the wing, DM²:3,56

The area of the center section, DM²: of 8.42

Carrying wing area, DM²: 15,54

The surface of the stabilizer, DM²:2,33

Total bearing area, DM²: 17,87

Average aerodin. chord (SAKH) mm: 110

The coefficient effect. stabilizer: 0,97

The installation angle of the stabilizer, deg.: 0

Wing setting angle, deg.: +2,8

Alignment (relative to SI), %: 53

Twist, deg.:

both “ears” at the ends……-1,7

the right end of the center section……+1,3

Takeoff weight of the model, g: 223

Weight model (g)

Wing:

“ears”……13.5

the center section……50

pins……at 0,9

Total: 78,8

Fuselage:

beam-to-nose . . 59

wing screws, strap . . 3.7 V

screws, hook, strap . . 4,8

Kiel……..2,2

Total: 69,7

Stabilizer: 4,8

Lead load and fasteners: 70

Flight weight of the model: 223,3

N. PAVLOV, engineer, group leader

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