Aluminium rib and oil cooler in left wing of Myrsky

Perjantai 2.2.2018 - Member of Tuesday Club

Suomeksi

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Photo: Photo archive of the Finnish Air Force Museum

The oil cooler of the Pratt&Whitney R-1830 Twin Wasp engine in VL Myrsky is located in the lower part of the engine mounting, in front of the foremost wing spar. The cooling air is led in through a three-port air intake opening in the leading edge at the root of the left wing. The supply air flows from the air intake to the cooler in an air duct. From the other end of the cooler the warm exhaust air flows through an air duct to the exhaust opening which is located on the lower surface of the leading edge on the right wing.

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At the root of the left wing the end of the air duct is attached to the leading edge rib which is made of aluminium plate. The other ribs of the leading edge are made of plywood. The aluminium rib has a hole with a flange matching the size of the air duct.

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One of the tasks in the Myrsky restoration project was to build this aluminium rib. The drawings of the rib were available, so fortunately precise instructions for the task existed. First a mould had to be made in order to be able to bend the rib into its final shape.

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The profile of the rib was cut out from a paper copy of the drawing and glued on thick plywood. Tracing the edges of the drawing two similar rib-shaped plywood pieces were sawed. The mould was needed to bend the edges of the aluminium plate rib so that they form a rim 22 mm wide.

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The plywood mould was used to draw the shape of the rib onto 1 mm aluminium plate and 22 mm was added around the shape for the rim. The preliminary shape of the rib was cut and attached tightly between the two plywood moulds.

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The following step was to bend the overlapping edge of the aluminium plate over the edge of the mould to make the rim. The plate was forced carefully to bend using a rubber hammer so that the aluminium wouldn’t break at the pleat / knuckle.

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When the edge had been roughly bent, the rim was forced to its final shape using a sheet metal shrinker. The outer edges of the rib were now ready and the work could proceed to the next phase.

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A hole for the air duct was made to the middle of the rib, following the dimensions in the drawing and taking into account the width of the flange for attaching the duct. The shape of the hole was drawn on the rib. The hole was made by first drilling a line of small holes following the drawn shape and then cutting along the holes using plate shears. The plywood mould of the rib was needed again: a similar hole was made in the middle of the mould. The aluminium rib was fixed tightly between the moulds. Then the edges of the hole in the aluminium plate were preliminarily bent against the edge of the plywood mould to form the flange and the final forcing was done using the sheet metal shrinker.

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Now the rib for the leading edge at the root of the left wing was ready. Two similar ribs were made – one will be installed on the test wing and the other on the actual Myrsky wing.

Photos: unless separately mentioned: Lassi Karivalo

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Restoration is none straightforward work - funny stories from workshop

Keskiviikko 31.1.2018 - Reino Myllymäki

Aviation Museum Society visited in the Finnish Air Force Museum on Saturday 27th January 2018. There was possibility to visit in the workshop where the VL Myrsky fighter MY-14 is restored. The progress during the first half of the year 2017 was remarkable. During the last half the team has had other duties, too. Therefore the progress has slowed down a little. Almost all original parts are fastened to the aircraft.

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The original cockpit ventilation pipe has been found but it was dented. The straightening work was big. Especially a dent behind curves was laborious to be straightened. When the straightened pipe was fastened, it was easy to note that foot controls will hit to it. The original production drawing has disappeared but according to the installation drawing, the pipe has no dents. It is possible, that the needed dent has been hit in the production.

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Another pipe laborious to be straightened, is located in left hand side of the cockpit. An aluminium pipe changes shape from round to oval.

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During the storage cleaning a rod with a special shape was found. It was easy to identify. It is a connection rod between the throttle lever and an electricity switch needed to warn the pilot when the engine idles and the landing gear is up. The orginal part is now installed and substitutes already installed reproduction part.

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Another original part, which was found after production of the new part, is the locking wire of the tail wheel. The reproduction part has been allowed to stay in the MY-14. The original part ensured that the reproduction part has been produced right way.

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A very interesting part was found in the storages. After another unidentified part was found, both of them could be identified. They were brackets of the manual starter. One is bracket of the hand crank and another is part of a reserve clutch. The will be installed in the MY-14.

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The pilot seat of the VL Myrsky has sandums. Since the rubber features are different in warm and cold, the aircraft has different sandums for summer and winter use. However, it is possible that same sandums were used all year.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Myrsky rear fuselage covering

Perjantai 26.1.2018 - Member of Tuesday Club

Suomeksi

The VL Myrsky is a fighter plane having mixed construction. The wings are made of wood and the fuselage consists of a tubular steel frame covered with a covering structure that gives the aircraft its shape. The rear fuselage covering consists of wooden upper, lower and side skin panels which are attached to the steel tube frame construction. The covering consists of wooden arc-shaped formers and wooden stringers and the skin is made of 1.2 mm plywood.

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Photo: Finnish Aviation Museum photo archive

In the first Myrsky serial production individuals the lower, side and upper coverings of the rear fuselage were built directly onto the tubular steel frame. Later the lower and upper coverings were pre-built on an assembly jig and attached onto the frame in one piece. The sides, however, were still built directly onto the frame of the plane.

The upper skin plywood panel in the rear fuselage of Myrsky doesn’t meet the upper edge of the side skin panel in a butt joint but slightly overlaps the side panel. In a similar way the side skin plywood panel’s lower edge overlaps the upper edge of the lower panel’s upper edge. This is how the rear fuselage covering has a lap joint structure.

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The Tuesday Club built tubular steel frame assembly jigs for assembling the upper and lower coverings of the Myrsky. The jig dimensions match accurately the dimensions of the Myrsky steel frame construction. This ensures that the upper and lower coverings which are completed on the jig will fit precisely the Myrsky tubular frame.

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The assembly of the rear fuselage upper covering was started in the Tuesday club by attaching the formers on the jig. The wooden formers have been made in the youth workshop operated by the city of Vantaa. The jig frame has brackets for attaching the roots of the formers in the correct position. Corresponding brackets exist on the Myrsky steel frame.

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When all the formers for the upper covering were in place, the wooden stringers connecting and supporting the formers were attached and modelled to their final shape.

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When the formers and stringers had been glued together, the upper covering skin plywood could be preliminarily installed. The skin on the upper and lower covering will be finished later.

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The upper and lower coverings without the plywood skin have already been preliminarily assembled on the Myrsky MY-14 fuselage at the Finnish Air Force Museum.

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Photo: Finnish Air Force Museum

The Tuesday Club has made two rear fuselage coverings for the Myrsky. Why two? One covering belongs to the Myrsky MY-14 which is under restoration. But what about the other one? It will be assembled on the less famous Myrsky MY-5 steel frame. The MY-5 frame is one of the four existing but damaged Myrsky tubular steel frames.

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The MY-5 steel frame has been reserved for the model wing which has been built in the Myrsky restoration project. The model wing is the 2,5 m long root part of the right wing. When the model wing is completed, it will be attached to the MY-5 frame. The MY-5 frame will also have another model wing: the root part of the left wing, about 1 m long which will be built in the restoration project. The other rear fuselage upper covering which was made now will be assembled on this frame. Maybe the Tuesday Club will have the energy to build also the lower and side coverings for the MY-5...

The Myrsky MY-5 frame with its short model wings and upper coverings will eventually be placed on display at the Finnish Aviation Museum. At the moment the MY-5 tubular steel frame lies unrestored at the Finnish Air Force Museum in Tikkakoski.

Photos: Unless separately mentioned: Lassi Karivalo.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Myrsky wing begins to take shape

Tiistai 7.11.2017 - Member of Tuesday Club

Suomeksi

The Tuesday Club of the Finnish Aviation Museum Society has finally reached the phase when the renovated Myrsky MY-14 wing is assembled. To reach that point a lot of work has been necessary - to build the wing spars and ribs. The building of the wing spars has taken 2,5 years and they were finished in late spring 2017. Building the ribs took 650 hours of work.

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Before the wing spars could be attached to the wing assembly frame (the jig), some holes had to be made for the feed-through and fitting of equipment which will be later installed into the wing. Holes are needed for machinery and equipment which operate e.g. landing gear, guns, bombs and auxiliary fuel tank, ailerons, etc. The frame of the wing will first be built between the wing spars, including the equipment inside the wing, before the leading and trailing edges are assembled.

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During the autumn the main work item has been to make the holes into the wing spars. At the same time supporting braces for the ribs have been installed between the front and rear spars. The connecting steel plate joint of the wing halves has been under construction as well. The original Myrsky wing was 11 meters long and weighed 440 kilos whereas the renovated Myrsky wing will consist of two parts, this solution was chosen mainly for practical reasons.

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The matching imbedding and holes for the bolts attaching the connecting steel plates were made to the attachment point of the wing halves, i.e. the root of the wing spars. It is important to attach the steel plates to the spars at the correct angle so that the two wing halves will form a uniform wing which corresponds to the original Myrsky drawings.

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On Tuesday October 17th 2017 all preparations had been made to attach the Myrsky right wing spars to the assembly jig. The assembly jig made of steel beams and pipes cut to measure had been prepared well in advance. First the rear spar was attached to the jig and then the front spar. The spars were locked in place using steel rods installed across the jig frame.

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When the wing spars were firmly attached to the jig, the preliminary installation of the wing ribs between the spars took place. The ribs had been made last spring. They were not yet glued in their places at this phase.

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As a proof of Tuesday Club work quality, the ribs settled firmly and tightly in their places between the spars. The upper edges of the ribs were also in line – this was noted by placing a steel ruler on top of the ribs.

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The wing spars attached to the assembly jig and the ribs between them are an amazing sight. This is an important milestone for all the Tuesday Club members who have been involved in the building of the Myrsky wing. This moment almost corresponds a “topping out” in a house construction.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Covering work of Myrsky ailerons

Sunnuntai 29.10.2017 - Member of Tuesday Club

Suomeksi

The aileron frames of VL Myrsky II (MY-14) had been finished in the Tuesday Club by the beginning of September. The ailerons were built according to the original Myrsky drawings. A pair of photographs proves this: an original photo of a Myrsky aileron from the State Aircraft Factory and a photo taken of the aileron made by the Tuesday Club. However, the Tuesday Club used modern Casco Outdoor wood glue.

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The ailerons of an airplane often have fabric covering even if the plane itself has duraluminium or plywood covering. On the plywood-covered Myrsky the ailerons were also plywood-covered. According to the original drawings the ailerons had 2,5 mm plywood covering in the area between the aileron spar and the aileron’s leading edge but 1,5 mm plywood in other areas. At the aileron’s leading edge the front edge of the plywood covering reached about 3 cm over the wooden leading edge strip. The seam of the 2,5 mm and 1,5 mm plywood plates was located on top of the aileron spar.

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When the aileron covering was discussed at the Tuesday Club, the decision was to use a structure different from the one on the original drawings. The 2,5 mm plywood would be difficult to bend into the curving shape of the aileron’s leading edge so instead of the original material thickness, 1,0 mm plywood - which is easier to bend - would be used first to cover the area between the aileron spar and the wooden leading edge. Then the whole aileron would be covered with 1,5 mm plywood.

Using this method there would be no need to bend the thick plywood at the aileron’s leading edge and also the plywood seam on top of the aileron spar would be avoided. The original material thicknesses (2,5 mm and 1,5 mm) in the different areas of the aileron would be reached as the result of combining the two plywood layers. The Tuesday Club wondered why the Myrsky designer had originally chosen a more complicated and structurally weaker method to cover the aileron.

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The right wing aileron was covered first. A piece of 1,0 mm plywood was cut to measure, matching the area between the aileron spar and the aileron’s leading edge covering the whole length of the aileron. Some milling work was required before the piece could be fitted to its place. Then the plywood covering was glued into place. Two-component epoxy glue was used with some cellulose fiber added. The glue was spread on the surfaces of the aileron spar, the ribs of the leading edge and the leading edge batten and the plywood covering was pressed on them.

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 A compressed air stapler was used to make sure that the plywood covering fixed tightly onto the aileron structure. To avoid the staples to drive too deep into the covering plywood, small additional pieces of plywood were placed between the staples and covering. When the glue had dried the staples and the protecting pieces of plywood were removed. Then the front edge of the plywood on top of the aileron’s leading edge and the rear edge on top of the aileron bar were ground thin and slightly slanting.

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Now the covering the whole upper surface of the aileron with 1,5 mm plywood could be started. The decision was to use two pieces of plywood and to place the seam in the middle of the aileron. In front of the aileron spar the plywood is attached to the 1,0 mm plywood which was already in place. In other areas of the aileron the thicker plywood would be glued onto the aileron spar, ribs and the trailing edge batten.

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First a cardboard pattern was made, matching the area of the aileron. Two pieces from the 1,5 mm plywood were cut based on the pattern. The plywood pieces were milled and fitted into place for gluing. The covering plywood piece closer to the wing root was glued into place first and after that the piece toward the wing tip.

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When gluing, the plywood pieces were first attached to the aileron spar using a couple of nails to keep the pieces in the correct position. Then epoxy glue was spread on the plywood which had already been installed and on the spar and the 1,5 mm plywood was pressed tightly against them. Staples along the edges of the plywood and the spar ensured that the plywood was tightly attached.

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The work continued to fix the rear part of the plywood onto the aileron structures. Epoxy glue was spread on the ribs and on the trailing edge batten and the plywood was pressed against them. A heavy steel plate was placed on the plywood as weight and clamps were used to press the read edge of the plywood against the trailing edge batten.

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When the glue had dried the clamps and staples were removed. Finally the front edge of the plywood on top of the aileron’s leading edge was ground slightly slanting to match the curved shape of the leading edge.

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Now the upper side of the right wing aileron had been covered and the following phase will be to cover the lower surface of the aileron. Before that the inside of the upper surface and the inner structures of the aileron have to be protected with varnish. The lower side of the aileron will be covered using a similar method as was used on the upper surface. When the right wing aileron has been covered, the work on the left wing aileron will be started.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Screws and plastics

Tiistai 8.8.2017 - Reino Myllymäki

You can check the success of the restoration work of old aicraft by looking the screws. If you will find some Torx or Phillips screws, something has went wrong.

The Phillips (PH) screw was invented by John P. Thompson who sold his invention to the Phillips Screw Company in 1935. Although 85 % of U.S. screw manufacturers have sold the licence in 1940, the State Aircraft Factory did not use Phillips screws in VL Myrsky.

The Pozidriv (Pz) is derived from the Phillips screw and it is therefore an younger invention. Phillips and Pozidriv screws are almost past now, since the 1967 invented Torx (Tx) is a common solution now.

So, VL Myrsky has no PH, Pz or Tx screws. Only slot head screws and hexagonal head bolts.

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The slot head screws of the State Aircraft Factory in connection with a Parkesine abrasion shelter and the alarm buzzer. Photos: Finnish Airforce Museum.

Do not ignore plastics! You can find selluloide "windows" in the aircraft of the 1920s. VL Myrsky has maybe none selluloide parts but Parkesine has been used in VL Myrsky as buttons and abrasion shelters. The Parkesine was invented in 1856 and the selluloide in 1870. Selluloide has been used as film material until asetate substituted it in 1950s.

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The propeller controllers button has made from Parkesine and the instruction panel from Paxolin. Photo: Finnish Airforce Museum.

You can find a lot of Bakelite or phenol formaldehyde resin from the VL Myrsky. Some buttons are made from casted Bakelite. Paxolin is a composite material of Bakelite and paper. Paxolin has used for example in the instruction panel of the propeller controller.

The most important use of Bakelite is plywood. Theodor Goldschmidt invented Tego-film in late 1920s. Tego-film is Bakelite extracted in a silk paper. German manufacturers did not succeed in plywood manufacturing by Tego-film. But the Finns succeed accidentially in 1929. Before WWII Finland was the second greatest plywood manufacturer in the World. The number one was Soviet Union.

It was possible to produce weatherproof birch plywood and laminated veneer lumber by Tego-film. Veneer lumber was used in propeller blades, antenna mast, spars and tail strucure. Birch plywood was used in spars, ribs, tail structures and in the cover of the wing and the fuselage. The diagonal plywood was used, too. The grain direction has turned 45 degrees in the diagonal plywood.

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The cabin aft glazing and canopy have been made from Plexiglas. Photo: Finnis Aviation Museum.

The third - or is it fourth? - plastics used in VL Myrsky is acrylic (PMMA). It was invented in 1928 and commercialised as Plexiglas in 1933. The canopy and the cabin aft glazing have been made from acryl. It is possible to made curved shapes from acryl. However, it is not very durable material. Nowadays the polycarbonate (PC) is more durable but also more expensive material. The polycarbonate was invented in 1898 but commercialised after WWII.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Cockpit bulkhead for MY-14

Torstai 27.7.2017 - Reino Myllymäki

VL Myrsky has two aluminium bulkheads. The front bulkhead is vertical and it is located just after the engine stand. The rear bulkhead - the cockpit bulkead - is inclined and is located in front of the cockpit. The engine with accessories is located in front of the front bulkhead. There is between bulkheads a space for the fuel tank, the oil tank, cartridge boxes and the box for spent cartridge cases - and the veapons.

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After WWII the aluminum plate was expensive and therefore the middle parts of the cockpit bulkheads of the MY-5, MY-9 and MY-14 have exploited and only the borders are left. These parts have lot of through holes with Parkesine abrasion shelters.

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The restoration of the cockpit bulkhead started from drawings. The shape of the bulkhead transferred to a cardboard. The existing parts of the bulkheads set against the drawing. The shape of the bulkhead was correct but some of the through holes were in different places. Some holes were coated by riveted aluminium discs and now holes were made in new places. All of them was modelled to the new bulkhead.

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The new bulkhead was made from 0,4 mm duraluminum plate by using the cardboard as a model. The needed thorough holes were made and the abrasion shelters were made from the original Parkesine. Some of the thorough holes had rubber barrels and they were renewed by using partially original spare parts. The original aluminium coating discs were exploited except one which destroyed during the dismounting.

The restoration work of the cockpit bulkhead is incomplete.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Switch box of landing gear motor for MY-14

Torstai 20.7.2017 - Reino Myllymäki

Not long ago I found a design principle of VL Myrsky: They tried to use mechanic and electric systems and avoid pneumatic and hydraulic systems. Only landing gear wheel brakes are hydraulic and the fuel transfer from drop tanks to the main fuel tank is based on compressed air.

All other systems are either mechanic or electric. There are three electric motors: starter, gill adjustment motor and the motor of landing gear and flaps.

According to the guidelines of the steering committee of the VL Myrsky II restoration project the mechanism of the landing gear system will not be complete. The landing gear will be moved in and out but not electrically. The reason for that is that almost all parts of the system are missing and the aircraft will stay over landin gear in the show. The complete system would be very expensive.

When the aircraft has a electric motor, it has switches and switch box, too. The switch box of landing gear's electric motor is situated near the motor and the battery in the rear part of the cockpit.

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The switch box of the MY-14 is still alive ... at least almost. The box is twisted and in poor condition. Instead of it, a useless original switchbox has been taken to be the basis of the restoration work. One Siemens LMS 1-2 solenoid switch has been found in the Finnish Air Force Museum and another in the Hallinportti Aviation Museum. The covers and the main switch were found in the storages of the Finnish Air Force Museum. The switch panel has taken from the switch box of the MY-14.

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The switch panel was disassembled, cleaned by phosphoric acid and LPS oil and the locked up screws were opened. The Bakelite marking strip was cleaned and the new markings were painted on white. The parts of the main switch were blasted by glass balls and the rebound cable was renewed.

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The main switch was cleaned by soda blasting and equipped by the base plate of the original switch. The solenoid switches got base plates of the original switch box, too. The base plates had to be straightened and cleaned by soda blasting.

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The mounting brackets were straightened, blasted by glass balss and painted first by strippin lacquer and then by the paint finish. The box was cleaned by washing agent and Miraclean. The result was protected by Renaissance vax. The fixing screws were straightened.

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Finally, the switch box was fixed to the fuselage.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

VL Myrsky has wooden aerial mast

Tiistai 18.7.2017 - Reino Myllymäki

The aerial mast is on the right side of the front fuselage. The aerial cable is drawn between the mast and the vertical tail. The aerial lead-in is in the rear part of the canopy aft glazing.

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It is hard to imagine that the material of the aerial mast is wood. Exactly, the material is the laminated veneer lumber made from birch veneer and Bakelite.

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The aerial mast of the MY-14 has survived. OK, without painting and now almost splitted. The mount for cable was corroded as well as the root bracket.

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The restoration of the aerial mast was started by straightening the joint surface between halves by planing. The wooden filling block of the top of the mast was renewed according to the drawing and the original part.

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The cross section of the mast is like a drop. The mast has been lightened by making two cavities to both halves. There is none wirings and therefore the only one reason for cavities is lighten the weight. The cavities were cleaned and lacquered by Isotrol.

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The mast halves were glued together by an epoxy resin. The outside of the mast was cleaned and lacquered. The cable mount was renewed according to drawings and the original part. The original root bracket was blasted by glass balls and lacquered. After that, the mast was fixed to the bracket by a slot-headed screw look like the original.

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According to the remaininig paintings, the aerial mast has been painted first completely gray and after that the wooden part has been painted to black. The restoration work followed that observation. The result looks like the aerial mast in old photos.

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In addition to propeller blades and the frame of the boardin step, the aerial mast is the fifth original wooden part of the MY-14.

Historical photo: via Kalevi Keskinen, others: The Finnish Air Force Museum.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Potplate and engine for MY-14

Lauantai 15.7.2017 - Reino Myllymäki

VL Myrsky II has a 0,75 mm thick domed steel plate between the engine and the engine stand. It directs air stream and protects fuel tank, cartridges and cockpit against fire. There is no remaining pot plates of VL Myrsky II. Therefore it has to be made.

Antero Flander from Flanco Oy in Rautalampi started the work. He made the potplate according to the drawing E61328. Some finishings were lacking but all parts and markings concerning needed cuttings included to the delivery.

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There is one blog about pot plate: 13.3.2016.

The pot plate was finished at the Finnish Air Force Museum workshop to correspond to the report for amendment number C302 and drawing E61328-I. According to the repair description dated October 30th 1944 the top of the pot plate of the MY-14 has converted to detachable.

The pot plate has been cut in two places and a hole was cut for the carburettor air intake. Needed holes for screws were drilled and the seams were strenghtened by strips. The flanged nuts were riveted. The edges of the hole for the carburettor air intake were strenghtened by strips and equipped with a leather border.

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The engine stand was otherwise usable but the vibration observers were too poor and the bolts were disappeared. The barrels of the observers could be restored.

The vibration observer rubber of the VL Myrsky II is equal to one used in the Fokker D.XXI with Twin Wasp Junior engine. However, the hole for bolt is bigger. By using an original part as a model, a drawing has benn made and Korja-Kumi Oy in Tampere manufactured new rubbers according to the drawing.

The barrels were restored but needed bolts, nuts and washers were bought from a hardware store. A STW C3 engine has been installed to the stand. The STW C3 is a Swedish-built copy of the original Pratt & Whitney R-1830 SC3-G engine. The weight of the engine was 653 kg and a truck was needed in the installation work.

Firstly, the project tried to acquire a pure SC3-G engine for the MY-14. Although at least 127 engines were bought to Finland, none was survived! An alternative S1C3-G engine has been in Douglas DC-3 passenger plane and stored years at the Finnish Aviation Museum. During the fall 2016, a second alternative has been found: STW C3 of the Saab B 17A target tug aircraft.

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STW C3 engine in the workshop of the Finnish Air Force Museum.

"I thought during last winter, that STW C3 is the most authentic engine for MY-14 in Finland", said conservator Harri Huopainen from the Finnish Air Force Museum. But the engine was not complete and needed a lot of work.

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The engine of MY-14: a S1C3-G engine from the show of the Finnish Air Force Museum.

Due to that, the former DC-3 engine type S1C3-G from the show of the Finnish Air Force Museum has been chosen for the MY-14. The only difference between SC3-G and S1C3-G is the rated altitude of maximum boost. According to FAA´s flyer A-699, the SC3-G can be converted to S1C3-G by changing the fuel and by adjusting the ignition timing.

So, the fixed engine needs to be removed...

First photo: Antero Flander, others: Reino Myllymäki.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Why there is thermos bottle in structure of Myrsky?

Torstai 13.7.2017 - Reino Myllymäki

If you look at the old photos of the VL Myrsky II, you can find a thermos bottle in the middle of the studs, wires and pipes. What is the function of that Airam thermos bottle?

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The Airam thermos bottle is a balance bottle of the variometer. The variometer get the static pressure from the pitot tube as the speed and altitude meters.

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When the aircratft is climbing, the air pressure lowers and there is a growing pressure difference in the variometer. The variometer does not meter the pressure difference directly since the comparison pressure comes from the balance bottle. The pressure of the bottle is changing slowly and therefore the difference is different than theoretically it should be.

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The balancing bottle is a standard Airam thermos bottle. The capacity is 0,44 litres including the 0,5-1,0 meter long capillary pipe.

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The variometer has has 8 to 10 second delay. If the climbing changes rapidly to the lowering, the variometer can indicate still climb during the start of the sinking. Otherwise the variometer indicates the climbing and the lowering and their speed.

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The original Airam balancing bottle has been donated to the project by the Airam. The bottle's place is above the map box in the left side of the cockpit. So, it easy to understand if somebody presume it pilot´s hot chocolate bottle!

Historical photo: The Finnish Aviation Museum. Other photos: The Finnish Air Force Museum.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Control column for MY-14

Torstai 6.7.2017 - Reino Myllymäki

The original control column of the MY-14 is not preserved. Only the rocker, balusters, the root and the wiring were left in the steel framework of the MY-14. All parts in the frame were corroded. Luckily, the surfaces of the sliding bearings were in good condition.

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A control column of the VL Myrsky in the show in the Jämijärvi airshow in July 2015. Photo: Reino Myllymäki.

The Finnish Air Force Museum had two incomplete control columns of the VL Myrsky. Another of them was restored wrongly. By using parts of both control columns, the MY-14 could get it.

The Bakelite cover has been taken from the wrongly restored column. The firing button was found in the storages. The root block of the column was in better condition than the one in the MY-14´s frame and it was accepted to restoration. Otherwise MY-14´s original parts were accepted.

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The MY-14 cockpit on June 20th 2017. The crank starter and the switch of the alarm buzzer on the left top. The propeller control lever and the throttle levers below them. The tail wheel lever, the trim control box and the map box at the bottom. The meaning of the brackets above the map box will be found from the next blog. Photo: The Finnish Air Force Museum.

The parts of the mechanism were blasted by glass balls and painted separately. The stick of the control column was left unpainted and lacquered by Isotrol Klarlack only. The red help texts were repainted. The wiring renewing would demand the dissassembly of the riveting and therefore only the visible part was renewed.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

MY-14 got propeller control and throttle levers

Torstai 29.6.2017 - Reino Myllymäki

VL Myrsky II fighter has a VLS 8002 constant-speed propeller. According to name, the propeller keep the rotational speed by changin the blade pitch.

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The object on the gear box is the constant-speed unit. Notice the quality of the leading edge of the NACA ring. Photo: The Finnish Aviation Museum.

VLS 8002 in a propeller construction of the State Aircraft Factory. It has three wooden blades with Hamilton Standard 3 E 50 hub. The hub is not made by Hamilton: it is finished in Finland by using Swedish preform.

The constant-speed unit is designed by Hamilton and it can change the blade pitch between 27 and 47 degrees.

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The blade pitch can be adjusted by a control lever in the cockpit. In front the blade pitch is decreasing and the rotational speed is increasing. In back vice versa. The lower pitch is used in the climbing and the higher pitch in the cruising.

The propeller control lever of MY-14 was very corroded. The friction plates and knob were disappeared and the parts of the control levers of the MY-5 and the MY-5 had to be utilised.

The steel parts were glass ball blasted and painted by Isotrol primer and paint. The duralumium parts were cleaned by oxalic acid.

The new friction plates were lathed by using original Parkesin as a material. The Parkesin is trade mark of nitrocellulose called to "lusto" in Finland. In addition, the knob was lathed from black Parkesin and fixed by aluminum rivets.

The original instruction plate of the control lever has preseved but in three parts. The material of the plate was Paxolin plate. Paxolin is fenol laminated paper. The paint was removed machanically and repainted by Miranol paint. The parts were glued together by epoxy resin and the result was fixed by aluminium rivets.

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The casing pipe of the Teleflex wire of the propeller control system was cleaned by steel wool and some spacers' nuts were substituted by original parts. The steel casing pipes were so corroded that they had to be renewed.

Since the engine is not yet installed, the Teleflex wire was not installed. In addition to that, the front part of the casing pipe system is still lacking.

The throttle lever system consists of two levers. One controls the mixture and another is the essential throttle lever. There is a push-to-talk switch in the knob of the lever. In all, the throttle lever system is not a simple system since there are adjustable restrictors and a bar to enable the whole control range at the high altitude.

All three throttle lever systems of the MY-5, the MY-9 and the MY-14 were in so poor condition that using an original spare part was a good idea. Unfortunately it was not complete.

The throttle lever system was disassembled. The plywood friction plates were grinded until the system ran correctly. The steel parts were painted and a new knob were made. The push-to-talk switch was substituted by an original spare part. The wiring was renewed but the fastenind bands were original spares.

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Finally, the levers were fixed. The result is excellent, isn't it?

Histotical photo: The Finnish Aviation Museum. Other photos: The Finnish Air Force Museum.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

My-14 got something that she shouldn't have

Torstai 22.6.2017 - Reino Myllymäki

Suomeksi

According to the modification announcement dated late July 1944 at the State Aircraft Factory, the alarm buzzer of the landing gear should be substituted by the pilot light in VL Myrsky II. The maintenance instructions do not tell anything about the alarm buzzer.

That is a warning system in order to warn when the engine runs idle and the landing gear is up. It was intented to avoid belly landings. The buzzer could be turned off by a switch.

The alarm buzzer has disappeared but the bracket remained. According to that, the MY-14 had an alarm buzzer. It had not been changed to the pilot light during the repairs.

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There were several alarm buzzers including brackets in the storages of the Finnish Air Force Museum. The best one has been restored for the MY-14. The orginial bracket was accepted but the mounting plate was renewed. The Siemens switch is an original spare part but the lacking press button was manufactured in the workshop.

The alarm buzzer is located in the rear part of the cabin, front of the radio.

Photos: The Finnish Air Force Museum.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

About the parts of the Myrsky landing-gear struts

Tiistai 6.6.2017 - Member of Tuesday Club

Suomeksi

Though the test-wing under construction for the VL Myrsky (MY-14) by the Aviation Museum Society’s Tuesday Club is not yet ready for the installation of the main landing-gear parts of the landing-gear assembly have already been made and are ready to be installed.

Unfortunately, only some original parts, such as wheels including brake mechanisms and parts for fastening the landing-gear assembly to the wing-spars, have been found. Thus, we need to have a number of the parts for the complicated landing-gear assembly manufactured.

Luckily, we have most of the drawings needed for the manufacturing of the landing-gear parts available. Also, the landing-gear of the 1:4 scale Myrsky model made by our Myrsky-project manager Matti Patteri is proving most helpful.

Patria Oy has taken the responsibility for manufacturing the oleo-struts. The Tuesday-Club’s Myrsky-project team has taken the responsibility for all other parts of the landing-gear. Thus, in addition to having the main responsibility for the wooden parts, the project team will also work on some metal-parts for the Myrsky.

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The topmost object is the landing gear of 1:4 model of Myrsky manufactured by Mr. Matti Patteri.

This far, we have already finished the lower and upper forks of the scissor-joint that is a part of landing-gear retraction mechanism at the lower end of the oleo-strut as well as the axle beam components  attached to the wheel-hub. Also the lug-tube that will go on to the middle of the oleo-strut and to which the forks of the landing-gear retraction mechanism as well as the rear landing-gear support strut will be attached. The upper fastening fork that goes onto the top end of the oleo strut has already been made.

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Matti Patteri has been responsible for the design and guidance for the manufacturing of the metal parts including the laser-cutting as well as for the making of the jigs needed for the welding-work. Welding-work has also been performed at the Vantaa Vocational College Varia. The machining of some of the small metal parts has been done by Elmer Oy.  

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

One original wooden part to MY-14

Torstai 1.6.2017 - Reino Myllymäki

Suomeksi

The VL Myrsky II restoration project has three steel-tube fuselage framework (MY-5, MY-9 & MY-14). They have lain on the ground below an open sky at least 20 years. Therefore wooden parts have decayed and steel parts have corroded. The project has got ready for substitute all wooden parts by reproduction ones.

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There is boarding step located below the rear side of the canopy in the left side of the fuselage. The boarding step has a small hatch in order to keep the fuselage streamlined when the step is not in use.

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The boarding steps of MY-5, MY-9 and MY-14 were all very corroded and the hinges of hatches were stuck. Luckily, one unused original spare part has been found in the storages of the Finnish Air Force Museum. One supporting tube was broken and there is a hole in an aluminium box.

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The steel structure, the hatch with hinges and the plywood frame have been taken from the unused spare. The lacking tube was taken from the step of MY-14. It was welded to the steel structure.

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The aluminum box was taken from the step of the MY-5. The metallic parts were blasted by glass balls and painted. The dented aluminium parts of the box and the hatch were corrected. The original screws of the plywood frame and box were substituted by equivalent new screws.

It seems that MY-14 will have at least one original wooden part: the plywood frame of the boarding step.

Historical photo: The Finnish Aviation Museum. MY-9 photo: Reino Myllymäki. Other photos: The Finnish Air Force Museum.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

MY-14 got more equipment

Keskiviikko 24.5.2017 - Reino Myllymäki

Suomeksi

There is a metallic map box on the left hand side of the cockipit of the VL Myrsky II.  Luckily we have an original part. The proper box is in a good condition but a little crooked and the leather strap was in poor condition.

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The map box was blasted by glass balls, straightened, primed by Isotrol lacquer and painted to colour tone Ral 7045 (gray). The leather strap was renewed but the popper is original. The strap was riveted to the box. The box was fixed by renews bolts and screws to the cockpit.

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There is a fresh air lever on the right side of the cockpit. The original was in a very poor condition. Luckily a quite complete original part was found from the storages of the Finnish Air Force Museum. Only the another fastening band was lacking.

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The fresh air lever was blasted and painted. The help texts were renewed, too. The lacking fastening band was substituted by a repaired original part. The wire of the lever will be installed later.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

VL Myrsky has crank starter

Torstai 18.5.2017 - Reino Myllymäki

Suomeksi

The Twin Wasp engine of the VL Myrsky II is started by an inertial starter. Normally, the starter is powered by an electric motor. When the starter has enough revs, the pilot pull the starter on and the engine will - hopefully - start.

But the revs can be made by a crank starter, too. The extension rod of the crank starter is located to right side of the aircraft near the leading edge of the wing.

The location of the joint of the extension rod and the crank starter handle is not easy to find in the photos. Most of the photos present the left side of the aircraft. And the camouflage painting is dark just there.

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Left photo: Finnish Air Force Museum, right: Finnish Aviation Museum.

When the aircraft has not coverings, the location is easier to find. The joint is supported by three tubes from three direction. The crank starter handle is located in the cockpit. It has place on the left side at the back of the tail wheel switch.

The crank starter handle of the MY-14 has disappeared as well as MY-5´s and MY-9´s. The brackets have been spared. Luckily, an original crank starter handle of the VL Myrsky has been found from the storages of the Finnish Air Force Museum. Only cleaning was needed.

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MY-14 got brackets from the MY-5 since they were in better condition. They were disassembled, blasted, painted and fixed. After that, the crank starter handle found an appropriate place.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Emergency equipments to MY-14

Maanantai 15.5.2017 - Reino Myllymäki

Suomeksi

VL Myrsky has the emergency equipment consist of a pairs of skiis, an axe, a K-ration pack and a toolkit. They are located after the cockpit and the oxygen bottles below the the canopy aft glazing. They were attached to the plywood plate by leather straps. The access to the emergency equipment bay was arranged by the glazing hatch.

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The brackets of the plywood plate were existing in the all frames (MY-5, -9 and -14). Although the axe did not belong to the emergency equipment anymore, it had still the leather straps. Now the straps were disappeared except small parts between the plywood plate and mounting plates. All emergency equipments were disappeared.

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The new plywood plate has been made according to the drawings. The brackets were blasted and painted. The screws were renewed.

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The mounting plates of the leather straps were renewed. The leather straps were made according to the drawings and the preserved parts of the Fokker D.XXI (FR-137).

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The leather straps were fixed to the plywood plate according to the drawings.

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The pairs of skiis were restored and tared earlier. They were fixed to the plate. The axe was fixed tentatively since the axe and the toolkit did not belong to the emergency equipments during the wartime. The K-ration pack belonged but it has disappeared. The drawings of the K-ration pack were disappeared, too.

The K-ration pack can be redone if the needed drawing will be found.

The historical photo: The photo archive of the Finnish Aviation Museum. Other photos: The Finnish Air Force Museum.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

Wheel-bay cover fastening ring for VL Myrsky II

Lauantai 18.3.2017 - Member of Tuesday Club

Suomeksi

The landing-gear of the Myrsky retracts towards the fuselage with the struts and wheels retracting into bays between the main spars in the roots of the single, continuous wing.

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On the top-side of the wing the wheel-bays are covered with slightly domed covers made of aluminium-plate. The covers are fastened with screws to a plywood ring forming the wheel-bay. Most of the wheel-bays, including their aluminium cover-plates remain hidden under the mid-fuselage covering the centre-part of the single wing, but a part of them are covered by streamlining-plates at the wing/fuselage joints.

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The aluminium-plate wheel-bay covers have already been made and now the making of the three needed cover-fastening rings are underway. One is needed for the test-assembly wing and two for the final wing that will be made for the MY-14.

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The making of the fastening-rings begun by making a mould. As on the drawings, a circle with a diameter of 750 mm was drawn onto a strong wooden board. Then sturdy nail were nailed along the drawn line with a spacing of ca. 2 inches. The fastening-rings will now be made by laminating eight layers of 3 mm thick 30 mm high, long plywood strips against the nailed circle, thus forming a 25 mm thick fastening-ring.

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The first plywood-layer was tightened against the nails and onto it three more layers were glued using Erikeeper plus adhesive intended for outdoors use. The four layers were pressed tightly together using clamps. When the adhesive had dried properly, the clamps were released and the next four layer were added using the same procedure.

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When the adhesive had dried the fastening-ring was removed from the mould and finished. It was then planed into a triangular cross-section with a top width of 25 mm. The other two rings will be made in the same way.

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As the test-wing had been fitted into the assembly-jig and the part between the wing-spars had been assembled the test-fitting of the fastening-ring could be made. And it was a good fit. Also the aluminium cover-plate went into place nicely. The next step will be making and fitting the plywood landing-gear well walls in the wing.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, VL Myrsky II, MY-14

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