Working on the gills at Tikkakoski

Maanantai 17.10.2022 - Reino Myllymäki

Suomeksi

When the transporting of ace Kyösti ” Kössi ” Karhila’s war trunk from Katajanokka to the Air Force Museum at Tikkakoski was added to the trip to Mikkeli, the opportunity offered itself to go and visit the Museum restoration shop to see and discuss the Myrsky restoration with the assistant conservator Antti Lappalainen.

The main switchboard has been under work lately (of which there’s been a blog) and the engine radiator gills. They were, of course, rather an advanced construction because they moved lengthwise with the fuselage, without adding drag when deployed. According to historical documents the idea was taken from the gills of Junkers Ju-88, although in this bomber the gills opened outwards, at least according to photos.

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Of the Myrsky gills mainly parts of the gill actuating motor and some bearing housings have remained, in other words much has been done and must be done as neo production. A big entity are the actual gill plates, which superficially seem simple, but are rather complicated entities.

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The gill mechanism, that leans on the cowling support frames, works so that the gill motor transforms the rotating movement through an axle and chain to screws, which when rotating move the gills lengthwise on their axles. The gills can be left in any position between their fore and after positions.

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To install and accommodate parts of the gill mechanism, the engine exhaust pipes had to come off, that’s how cramped it’s beginning to be around the engine. In the photo above the before mentioned gill axles are visible in the foreground on the floor.

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The gills are rather ”interestingly” shaped by the machine guns. In the photo carpenter/artisan Mika Rautasaari holds in his hand a mould or last of a gill that was milled out of wood in the spring. Based on this mould the part of the gill by the machine gun will be made.

The final stretch in the restoration of MY-14 is looming on the horizon.

Photos: Reino Myllymäki

Translation: Matti Liuskallio.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, MY-14, VL Myrsky

A glance under the cowling at Tikkakoski

Lauantai 10.9.2022 - Reino Myllymäki

Suomeksi

The undersigned had a chance – and need, too – to visit Tikkakoski to see how the restoration of MY-14 proceeded there. The work on the aluminium sheets forming the front part of the fuselage of MY-14 to make the opening hatches was nearly finished.

Of the original sheets of aluminium there remained only a small piece around the root of the antenna mast. It had been part of MY-5 at its time. MY-5 and MY-6 have proved to differ from the other aircraft of the main production batch, even though they belonged to it.
The form of the fuselage front was changed with the consequence among other things, that the “bulges” of the solenoids for the gun breech clogs became smaller. In other words the cross section of the MY-14 front fuselage is a bit more “stately” than MY-5. Those with sharp eyes will notice the small deviation at the root of the antenna mast.

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Photos: Finnish Air Force Museum.

On the front fuselage sheets there are hatches for entry to the filler caps of the oil-and fuel tanks. There are similar hatches elsewhere, too, but for some reason the width of the hatch for the fuel tank is 10 cm, whereas the width of all other hatches is 11 cm. Because of the 1 cm difference, the parts of the hatch differ from all other hatches. The reason isn’t known, one only wonders….

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By turning the sheets, more peculiarities appear. The hatches have “happened to be” in a strange position, so that the sheet stiffeners had to be modified so that the side reinforcements, that form the lips of the hatches, could be fitted.

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The jigsaw puzzle consisting of pieces of sheet metal is impressive, and the sheets could not have been cut according to plans, but the cutting lines had to be improvised. Such is the situation in restoration, but the state of the affairs has probably been the same when the aircraft were constructed at their time. Some of the braces attach straight to a counter piece in the fuselage, which means that a piece has been cut off from the sheet below. In another place the brace is attached straight to the sheet of aluminium beneath.

After a couple of hour’s wondering, the MY-14 stabilizers were packed in my car, where their journey continued to Vantaa.

Photos by Reino Myllymäki, unless otherwise indicated.

Translation by Matti Liuskallio.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, MY-14, VL Myrsky

The fitting of Myrsky's NACA-ring bracket formers and brackets for riveting

Tiistai 19.7.2022 - Tuesday Club member

Suomeksi

In the restoration of VL Myrsky II the construction of the engine cowling or NACA ring front part, which is demanding, has been under work already for a couple of years. The Myrsky engine cowling consists of the engine covering NACA ring’s solid front and rear parts and the openable engine cowlings between them. This blog deals with the installing of the bracket formers to be riveted to the solid front part of the NACA ring. Later in this blog the solid front part of the NACA ring will be called NACA ring for simplicity.

The Myrsky’s NACA ring has proved to be very difficult to make, and we have not managed to avoid extra work. This was caused by amongst other things the uncovering of the lost Myrsky major series NACA ring drawings at the end of last year. They differ especially in the upper part from the initial series Myrsky’s NACA ring drawings, according to which we have been building the MY-14 NACA ring.

The difference between the drawings was, that in the major series NACA ring the diameter of the upper part of the ring is larger than that of the initial series. Because of this, the NACA ring that we had built had to have its upper part diameter increased, so that it would correspond to the shape of the major series shape of MY-14. The enlargement was possible by forging the upper part of the aluminium ring to the measurements of the major series.
To facilitate the change, we had to dismantle the ten NACA ring bracket formers or cantilever consoles that had already been positioned. The NACA ring is fastened from these bracket formers to the eyes in the valve housing of the engine. The dismantled bracket formers were taken to be chromed, so that their surface got a glossy gold hue.

There are 14 bracket formers in the NACA ring altogether. Of those, ten are situated in the part of the NACA ring, which equates the rotation block. Four bracket formers are situated aside from the rotation block in the expanding upper part of the NACA ring. The opening of the air horn and the flame tubes of the four machine guns are situated in this area.
The ten chromated bracket formers were re-installed. The four bracket formers that are near the air horn and the machine guns’ fame tubes are still in the shaping and fitting stage. Before installing the bracket formers, a bracing ring made of 1 mm steel plate was assembled around the NACA ring. This is to ensure that the NACA ring holds its precise form when the bracket formers are installed to the NACA ring.

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At the same time a jig was made out of a steel plate, to assist in focusing the bracket formers to their places. With the aid of a set up jig, which was made out of steel plates and locked in the “central hub” of the assembly table, two bracket formers can be positioned into place. After that the jig is moved forward to position and install the next bracket formers. The positioned bracket formers were fastened to the NACA ring with a couple of small bolts. The final fastening will be done by riveting.

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When the chromated 10 bracket formers had been installed, the actual brackets were installed at their tips, with which the NACA ring is locked with connection pieces to the eyes of the valve housing of the engine. The bracket on the former is a prong-like piece, bent from 1 mm steel plate, which has a welded socket for the fastening bolt at the end.
To position the bracket to the end of each former, a two-branch steel tube jig was used, which was locked to “the central hub” of the assembly table. With the aid of the jig, the exact position of the bracket and its angle at the end of each former can be determined. The brackets were fastened tentatively with small bolts. The final fastening will be done by riveting.

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The brackets are installed at the end of the formers at an angle of 7.5 degrees. So they will meet the valve housing eyes to fasten the NACA ring to the engine. The brackets of the formers and the eyes of the valve housing are locked to each other with connecting pieces. The connecting pieces are fastened with bolts to sockets at the end of the former and with two bolts to the holes of the eyes in the valve housing.

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When all ten chromated bracket formers with their brackets had been installed in place, the shaping work of the four bracket formers and their brackets to be installed on the upper part of the NACA ring was started. The bracket formers by the outer flame tubes are distinctly shaped more open-angled, compared with the other V-shaped bracket formers, to enable the flame tubes inside them. The bracket formers that are fixed on either side of the air horn differ from the other bracket formers in shape. In a way they are only half-sized compared with the other V-shaped formers.

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First the open-angled bracket formers at the flame tubes were shaped to be installed. They were fastened tentatively in place with the aid of a jig, made especially for these two brackets. After this the shaping of the prongs, attached at the end of the bracket formers with sockets, so that they could be shaped into the form of more open bracket formers. The position of these brackets differs from the other bracket formers so that the bracket is right at the top of the bracket former. The installing of the bracket formers of the NACA ring upper part are still under work.

Photos: Lassi Karivalo

Translation: Matti Liuskallio.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, Tuesday Club, MY-14, VL Myrsky

The Myrsky elevators? priming

Keskiviikko 6.7.2022 - Tuesday Club member

Suomeksi

The VL Myrsky II (MY-14) elevators’ coating, which had started in April was finished at the beginning of May. As coating fabric, a 165 g/m2 linen fabric was used.

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After the elevators were finished, the fabric was tightened to resemble a drum top with NC-SPEED nitro cellulose varnish. The varnish was dyed red with iron oxide. The tightening of the fabric was done phase by phase. It began with 50% thinned varnish. Thinner 8 was used for the purpose. From that we continued through 75% varnish to a full 100% varnish. Unthinned varnish was applied twice to the fabric cover of the elevators.After the elevators were finished, the fabric was tightened to resemble a drum top with NC-SPEED nitro cellulose varnish. The varnish was dyed red with iron oxide. The tightening of the fabric was done phase by phase. It began with 50% thinned varnish. Thinner 8 was used for the purpose. From that we continued through 75% varnish to a full 100% varnish. Unthinned varnish was applied twice to the fabric cover of the elevators.

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Between the times of doping, the fabric surfaces were sanded smooth. After every application of varnish, the fabric tightened more. After four layers of varnish the fabric of the elevators had tightened to the wanted drum top level.

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After tightening of the covering fabric, it was time to prime the elevators. TEKNOS  Futura3 primer was chosen, and Teknosolv 1621 white spirit as thinner.

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The priming was done by spraying, using the Futura 3 which was thinned to 75%. Before spraying, the openings in the elevators were covered to prevent the paint to get inside the elevators.

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After spraying, the surfaces were sanded manually. At the same time, it was noticed that there was a slight depression on the trailing edge side of the elevator, along the whole length of it. Filler was applied to this area. After the filler had dried, the area was sanded to the form of the curvature of the elevator profile.

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The second layer of the primer was also done with 75%  Futura 3 primer. After spraying the surfaces of the fabric were sanded smooth. Special care was taken to the serrated edges of the protective strips on the sewn seams, so that the serrated edges could be sanded, so that they no longer feel like uneven spots on the surface of the fabric.

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The elevators of the Myrsky have now been primed twice. We are debating that a possible third layer of primer could be sprayed on the surface of the elevators.

Photos: Lassi Karivalo

Translation: Matti Liusvaara.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, Tuesday Club, MY-14, VL Myrsky

Tuesday Club started its spring season with full capacity

Tiistai 1.3.2022 - Tuesday Club member

Suomeksi

The Tuesday Club was not able to start its spring season in January because the amount of people allowed to work in the restoration workshop of the Finnish Aviation Museum was still limited due to the Covid-19 pandemic. Only the restoration work on the Myrsky MY-14 could be continued in January. Only half a dozen Tuesday Club members could work at a time, wearing masks. In the beginning of this year the Myrsky project has concentrated on the NACA-ring and the port wing landing gear doors, as well as finishing the Myrsky demo-wing before the Myrsky restoration exhibition will be opened.

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Along with the Myrsky restoration work, a couple of Tuesday Club members have been working to finish the painting of the Mil Mi-8P (HS-6) helicopter tail boom stabilizers and to take the large parts of the Super Caravelle towbar to be sandblasted. The tyres of two 1920s aircraft wheels have also been dismantled so that the wheels can be repaired. These wheels have been received from the Finnish Air Force Museum to be assembled on the Caudron C.50 (CA-50) aircraft.

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As the national Covid-19 restrictions have been lifted due to the decreased health risks caused by the pandemic, it was agreed with the Finnish Aviation Museum that the number of people working in the restoration workshop can be increased. This enables us to launch other Tuesday Club activities in addition to the Myrsky work.

On February 23rd we continued from where we stopped before Christmas, particularly with the Caudron C.59 conservation and the Super Caravelle towbar restoration. We still work in two groups of 10 Club members, one group on Tuesdays and the other on Wednesdays. The Myrsky team, with less than 10 members, is working on Tuesdays, Wednesdays and Thursdays.

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The coming weeks will be spent in cleaning the parts which were dismantled from the Caudron’s fuselage, and after that the parts will be painted. Two landing gear wheels were received from the Finnish Air Force Museum for the Caudron. The wheels and spokes are cleaned from dirt, grease and rust. Mechanical and chemical methods are applied.

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The Caravelle towbar has been dismantled and all dismantled parts have been cleaned of rust, either with phosphoric acid or by sandblasting, and the painting work can be started. Before painting, the sandblasted parts were washed to remove the sand dust, which remained on the surface. Then the parts were carefully dried, using compressed air. Some parts have already been painted with clear Isotrol varnish which will prevent rust.

Photos: Lassi Karivalo

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky, MY-14, Caudron C.59, CA-50, Mil Mi-8P, HS-6, Super Caravelle

Situation update from Tikkakoski

Torstai 24.2.2022 - Reino Myllymäki

Suomeksi

A visit to Tikkakoski on February 11th made it possible to write one situation update, that was published on February 20th, 2022. But on February16th the restoration group at Tikkakoski sent more updates, mainly pictures.

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The covering sheets around the wind screen are nearing to being completed. Mind you, of the original sheets only one survived, around the root of the antenna. All the others are made of the blanks, constructed by Antero Flander. Riveting was a huge job, 2500 flush rivets! Now the first covering sheets have been primed and surface painted, although the olive green will yet be revived and the final lines between the colours will be repainted with the camouflage painting.

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The tail fairings have also received priming and surface coats of paint. Fitting them in place can start now, as the stabilizers are at Tikkakoski for test fitting.

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The fire plate has been painted matt black and refitted. The disassembled exhaust pipes, too, have been refitted on February 11th.

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The front firewall switch case has been fitted with a cover, on which a” bulge “ was made by forging against a wood last. Other wood lasts have been made for forging, partly with CNC-milling, partly by hand crafting.

The “bulges” by the machine gun breech block solenoids that look small in photos, are in fact quite large. They, too, have been made by forging against wood lasts.

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The “bulge sheets” by the outer machine guns have been constructed in such a manner that the breech cover can be opened and closed without taking the whole sheet off. On top of that, it was observed that the cartridge chutes of the outer and inner machine guns differ from each other in the extent of material thickness. They were probably designed by different draughtsmen.

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The MY-5 fuselage is getting finished with speed.

Photos: The Air Force Museum, unless otherwise mentioned.

Translation by Matti Liuskallio.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, MY-14, VL Myrsky

Myrsky's demo wing was moved to mid hall of Finnish Aviation Museum

Tiistai 22.2.2022 - Tuesday Club member

Suomeksi

When the underside of the demo-wing, built in the VL Myrsky II (MY-14) restoration project, had been painted with Futura 3 adhesive primer, it was ready to be moved from the restoration workshop of the Finnish Aviation Museum into the museum’s mid hall. An exhibition about the VL Myrsky II restoration project will be built in the mid hall.

The demo wing will be used in the exhibition to show the museum visitors what the wood-structured wing and the equipment were like in the Finnish WWII VL Myrsky fighter. All the equipment of the Myrsky’s wing have been assembled into the demo wing, including landing gear, operating mechanisms of the ailerons and the hanger for the auxiliary fuel tank / bomb. To allow a better view of the wing structure, the upper side of the wing has not been covered with plywood.

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The demo wing includes a 2,5-metre section of the starboard wing and a one-metre root part of the port wing. The demo wing was used for testing how to build the Myrsky wing’s root part before starting to build the actual wings for the Myrsky MY-14. Now the demo wing will be used as a showpiece.

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For moving the demo wing into the exhibition, pallets with wheels were fastened at both ends of the wing, which weighs nearly two hundred kilos. The demo wing was supported on racks made of steel and plywood, fastened on the pallets. The wing was locked into a vertical position with the leading edge downwards.

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Having the wing in this position was the only way to manoeuvre the wing through the flight simulator room in the Aviation Museum’s mid hall and into the space reserved for the exhibition in the mid hall. Even this way the wing had to be wriggled through the hall inch by inch.

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The wing was moved from the museum’s restoration workshop to the mid hall’s outer door on a lorry with a hoist. The transfer took place on a very rainy day, so the wing was protected from the rain by wrapping it in plastic.

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The wing package was pushed out of the restoration workshop on the pallets with wheels, then the hoist straps were fastened. The wing was lifted, using the hoist, and moved onto the bed of the lorry. The lorry transported the demo wing to the mid hall’s outer door. There the wing was lowered in front of the door with the hoist, then it was pushed on the pallets through the door and into the simulator room in the mid hall. The one-metre section of the port wing was also brought to the mid hall on the same lorry.

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In the simulator room the four-metre demo wing on its pallets was manoeuvred between the simulators until it was at a right angle facing the doorway to the mid hall exhibition area. The demo wing was gently pushed into the space which is reserved for the Myrsky exhibition. It was a close call, because there was only an inch between the pallets and the door frame. When the demo wing had reached its destination, the rain protecting plastic could be removed.

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Now the demo wing will be prepared for exhibition. First the pallets will be removed, then the starboard and port side wing halves will be joined, and the landing gear will be assembled into the starboard wing. There will be also a Myrsky’s rear fuselage in the exhibition, with the wooden vertical and horizontal stabilizers, which were built in the Myrsky MY-14 restoration project, and the original metal elevators will be assembled, too. In the Myrsky restoration project the Aviation Museum Society’s Tuesday Club has concentrated, among other things, on the wings, tail, landing gear, oil cooler and engine cowlings. The Finnish Air Force Museum has been working on the fuselage restoration. Hopefully the MY-14 restoration will be completed next year. Then the genuine Finnish WWII Myrsky fighter would be on display for the public. 

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The VL Myrsky II restoration project exhibition is open between 5.3. – 31.5.2022 at the Finnish Aviation Museum during its normal opening hours. The exhibition is in the mid hall, used for changing exhibitions, and a museum ticket is needed. The ticket prices are: adults 12 €, reduced groups 6 €, children below 7 years € eur and Museum Card 0 €.

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I warmly recommend a visit at the Myrsky exhibition which will open in March. There you will learn about the restoration work of Myrsky MY-14 and about the history of the Myrsky fighter, which was the only WWII fighter of the State Aircraft Factory to reach series production phase.

Photos: Lassi Karivalo.

Translation: Erja Reinikainen

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky, MY-14, MY-5

The stabilizers to Tkkakoski, wheel to Vantaa

Sunnuntai 20.2.2022 - Reino Myllymäki

Suomeksi

The undersigned had a chance to visit the Air Force Museum at Tikkakoski on Friday Feb.11th 2022. As earlier, the trip had many purposes. The day before yesterday I went to photograph the Sasky aircraft at the Mänttä agency and on Friday the main purpose was to scan the photo albums of Paavo Kahla and Kurt Södergård for the coming Paavo Kahla book.

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But since I was at Tikkakoski, I went to see the Myrsky - II project situation. Now I had reason more than usual, because in the boot of the car came the MY-14 stabilizers from Vantaa to Tikkakoski for the fitting of the fairings.

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The stabilizers had a coat of paint on the surface, only the black camouflage colour on top of the olive green was missing. The paintwork on the plywood surfaces of the stabilizers seemed very good compared to the original parts, as can be seen in the photos.
The surface paint work on the metal surfaces made at Tikkakoski wasn’t altogether satisfactory. The blue on the lower surfaces was spot on, but the olive green was a bit too brown. This is why the undersigned went to Teknos with an original fuselage hatch and rudder trim for colour definition.

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Also the fire plate had been painted at Tikkakoski. The matt black doesn’t really show in any photos, and we don’t know for sure, whether the Myrsky aircraft were painted like this, although this is strongly supported by the painting of the VL Humu’s respective parts.
In the return load to Vantaa there was besides the fuselage hatch and rudder trim, a wheel of the main landing gear, for the demo wing.

Photos: Reino Myllymäki

Translation: Matti Liuskallio

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, MY-14, VL Myrsky

MY-14 fuselage covering with plywood is progressing again

Sunnuntai 12.12.2021 - Reino Myllymäki

Suomeksi

According to the photo update from the Air Force Museum from today, it’s plain to see that the covering of the fuselage of MY-14 with plywood is progressing, as well as the making of the aluminium hatches in the covering.

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The front fuselage cover hatches have been made of Antero Flander’s blanks, which have been cut to measurements and riveted together. Easier said than done, because there are myriads of 2,6 mm rivets, double the amount compared to the Brewster, so they say. And they aren’t even load carrying parts.

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The covering sheets themselves are of 1mm thick aluminium thin sheet. The pins of the Dzus-locks on one of the cover sheets are original VL produce, apart from them the parts are neo products.

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The port side plywood covering is about to be finished.

Photos: Reino Myllymäki

Translation: Matti Liuskallio.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, MY-14, VL Myrsky

Filler ring and supporting ring of Myrsky?s NACA-ring

Maanantai 25.10.2021 - Tuesday Club member

Suomeksi

The NACA-ring of the VL Myrsky II is complicated to build. Fortunately the most difficult phases of work have already been completed at the Tuesday Club when building the ring for the Myrsky MY-14 engine, which is under restoration. When the NACA-ring and its parts have been chromated and the fastener consoles, among others, have been fastened on the inner surface of the ring, the NACA-ring can be test assembled on the Pratt & Whitney R-1830 engine, which is available at the Finnish Aviation Museum.

It is rather fortunate that this engine is on display at the Aviation Museum and there is no need to travel for the test assembly all the way to Tikkakoski, where the Pratt & Whitney engine has already been assembled on the MY-14 fuselage, under restoration at the Finnish Air Force Museum. The engine, which is available at the Finnish Aviation Museum, has been on a DC-3 but it suits well for the test assembling of the Myrsky’s NACA-ring.

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The Tuesday Club team has been working lately on the filler batten ring (täyterengas), which will be fastened on the edge of the NACA-ring (NACA-rengas), as well as the supporting ring (moottorin suojuksen kannatinkehä) for the engine fairing. The supporting ring is fastened on the filler ring and its edge extends 30 mm outside the NACA-ring’s edge. The supporting ring forms a base outside the NACA-ring’s hem for the edge of the engine fairing. The supporting ring is covered with leather (nahkapehmuste) to absorb the resonance between two aluminium surfaces, which is caused by the engine.

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First the filler ring, a 40 mm wide ring cut from 2,5 mm thick aluminium sheet, was fastened on the edge of the NACA-ring. The filler ring was shaped to match the curvature of the NACA-ring’s edge and preliminarily fastened on it with clamps. Then the filler ring was fastened with small bolts. When the ring was firmly in place, the bolts were replaced with flathead machine screws so that the surface of the filler ring is smooth when the supporting ring is assembled on it. Eventually both the filler ring and the supporting ring will be riveted on the NACA-ring.

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85 mm wide strips were cut from 1,5 mm thick aluminium plate for constructing the supporting ring. One edge of each strip was bent to form a small gutter. Then the strips were shaped against the filler ring to match the curved shape of the NACA-ring. In the shaping process the supporting ring is also pressed tightly against the filler ring surface. When this had been achieved, holes were drilled through the supporting ring and the filler ring, and the supporting ring was fastened on the filler ring using small bolts.

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The filler ring and supporting ring had to be made also where the machine gun barrels penetrate the NACA-ring. This was not easy because the machine gun barrels form “bumps” on the edge of the NACA-ring. This means that the filler ring and the supporting ring had to be shaped to match the gun barrel “bumps”. Several rounds of modifications had to be made before the filler ring and the supporting ring fitted nicely into place at the barrel “bumps”. During the modification process it had to be checked that the edge of the supporting ring extended exactly 30 mm outside the hem of the NACA-ring.

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When the supporting ring had been preliminarily fastened, a line of holes was drilled through the ring and the filler ring under it for the future riveting work. Crosshead bolts were placed temporarily into the rivet holes. Now it could also be checked how the air intake duct of the air horn fits against the supporting ring between the machine gun barrels.

Photos: Lassi Karivalo

Translation: Erja Reinikainen

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky, MY-14

Work on Myrsky's landing gear wheel hub cover is continued

Torstai 26.8.2021 - Tuesday Club member

Suomeksi

The Tuesday club team has continued preparing the cover which is fastened on the wheel hub of the starboard wing landing gear on the VL Myrsky II (MY-14). At the moment the metal support is being made for the inner edge of the cover. The support circles the edge of the cover, and it is made of 15 mm thick square steel tube. It is fastened at a 10 mm distance from the edge of the cover.

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The square tube is a supporting frame for the cover, cut from aluminium plate, and it also forms a fastening surface for the stiffeners which are fastened on the inner side of the cover. The stiffener plates, cut from aluminium plate, are riveted on the cover so that the square tube is between the cover and the stiffener plate. The stiffener plates are waiting to be assembled. The stiffeners on the test wing’s wheel hub have already been riveted. The wheel hub cover of the test wing has been used as a model when the actual covers for the landing gear are made.

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The upper edge of the wheel hub cover is curved, and the square tube had to be modified in a mangling machine to make it match the cover shape. The shape was modified step by step. When the square tube began to curve, its shape was compared to the curved edge of the cover and mangled again. When the desired curved shape had been reached, the square tube was cut into pieces which will be fastened on the cover’s upper edge.

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The lower edge of the wheel hub cover is not curved but angular. A piece of the square tube was cut for the cover’s lower edge. To modify the square tube into an angular piece, a cleft was sawed at the point where the cover edge has its steepest angle. Several clefts were made where the slighter angle is. The tube was bent, using the clefts, to meet the shape of the cover’s lower edge.

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The following phase was to mark with tape the line of the corner joint, where the curved square tube on the upper edge of the cover meets the angular square tube of the lower edge. The tube ends were cut slanted according to the marked line. The slanted tube ends were placed against each other and fastened on the cover plate with clamps. At first the tube ends will be lightly welded together so that the whole tube frame can be moved from the aluminium cover plate for the actual welding work. When this has been done, the square tube forms a complete supporting frame along the edge of the wheel hub cover.

Photos: Lassi Karivalo

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky, MY-14

Stiffeners were riveted on cover of landing gear oleo strut on Myrsky's starboard wing

Maanantai 23.8.2021 - Tuesday Club member

Suomeksi

The Tuesday Club team has continued its work on the covers for the Myrsky fighter’s landing gear on the starboard wing. U-profile stiffening battens were riveted on the cover of the oleo strut, which was otherwise ready. The stiffeners were cut from aluminium plate and pressed into shape. They are riveted on the inside edge of the cover. The cover and stiffeners have already been chromated.

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The riveting was started by fastening the first of the four stiffening battens on the edge of the cover with cleco fasteners. Clecos, which are fastened in the rivet holes with nose pliers, are used for the temporary fastening of work pieces which will be riveted or welded together. In spite of the cleco-fastening, the rivet holes had to be slightly shaped with a round file to make the rivets slide nicely into their holes.

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The rivets used were 3x6 mm flathead rivets. The stiffeners were riveted on the cover plate rivet by rivet. A compressed air riveting gun was used. All four stiffeners have now been riveted. The cover plate has been preliminarily assembled on the oleo strut of the starboard wing. It fits nicely into its place.

Photos: Lassi Karivalo

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky, MY-14

Works on Myrsky carburettor air intake and NACA-ring

Tiistai 22.6.2021 - Tuesday Club member

Suomeksi

The half-finished air horn and air intake ducts have been preliminarily assembled on the VL Myrsky II which is under restoration. The Myrsky had a Pratt &Whitney R-1830 radial engine and a similar engine is available at the Finnish Aviation Museum. Fortunately it has been possible to test the assembly at the museum and there is no need to travel to the Air Force Museum at Tikkakoski, where a similar engine has already been installed on the Myrsky’s (MY-14) fuselage.

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Holes for the fastening bolts were drilled on the cast aluminium air horn and the air horn was fastened with a couple of bolts onto the carburettor of the engine, located in the museum hall. It fitted nicely into its place. Then the two air duct sections could be assembled into place between the air horn and the NACA-ring.

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The Tuesday Club team noticed that the section of the air duct, made of steel plate because of its location above the hot engine, did not fit properly. The reducers made on its lower part were too shallow and the air intake duct couldn’t be pressed sufficiently deep between the cylinder head covers. The air intake duct was heated using a welding flame and shaped to fit better. Then the two air intake duct sections were assembled above the engine and fastened on the air horn. Even when half-finished it is a great sight!

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The consoles of the NACA-ring, which are needed to fasten the ring on the brackets on the cylinder heads, had to be modified before riveting on the edge of the NACA-ring. Especially the console hems have needed shaping. The console is riveted on the NACA-ring by its hem. The hem has to meet the curved shape of the NACA-ring and to take into account the filler batten, which is a 2,5 mm aluminium batten riveted on the edge of the NACA-ring, and the 1,0 mm aluminium supporting frame of the engine fairings. The supporting frame is 75 mm wide, and it is riveted on top of the filler batten so that it extends 32 mm outside the edge of the NACA-ring. It forms a shoulder on which the edge of the detachable engine fairing rests and meets the edge of the NACA-ring in a butt joint. There is a very general overview picture of this structure attached.

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Translation: NACA-renkaan reuna = Edge of NACA-ring, 3,5 mm porrastus = 3.5 mm offset, Kiinnityskonsoli = Console, Moottorin vaippalevyjen tukikehä = Supporting frame of detachable engine fairing rests, Täytelista = Filler batten, Moottorin vaippalevy = Detachable engine fairing rests.

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The hems of the NACA-ring consoles were shaped using pliers and a plastic-headed hammer and a piece of wood. A 3,5 mm offset was made on the upper end of the console for the filler batten and the supporting frame. All console hems have now been shaped and are ready to be riveted into place. Before that can be done, the filler batten and the supporting frame on top of it will have to be riveted onto the edge of the NACA-ring. The supporting frame is made of four sections and the sections are ready to be installed.

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Up to now the filler batten has been fastened on the upper edge of the NACA-ring with clamps. Now it is debated how the riveting of the filler batten and the supporting frame on the NACA-ring edge will be done so that the filler batten settles exactly to the same level as the NACA-ring’s edge.

Photos: Lassi Karivalo.

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky II, MY-14

Myrsky's starboard wing half was turned for installing landing gear

Sunnuntai 13.6.2021 - Tuesday Club member

Suomeksi

The assembly of the landing gear has been started on the wing halves of the VL Myrsky II (MY-14), which is under restoration at the Tuesday Club. Thorough test assembly has already been done on the test wing which was prepared in the Myrsky-project. The test wing is a 2,5 metres long root piece of the wing, meant mainly for testing the landing gear installation. The landing gear will first be assembled on the starboard wing half.

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The wing halves were painted with undercoat paint and after this work they remained on the worktable the upper side up. First the starboard wing had to be turned so that the landing gear well is facing upward, and the landing gear can be installed. The wing halves have already been turned around several times during the different work phases. For this purpose steel supports have been made for the wing tip and the wing root and they are used to support the wing when it is lifted and turned.

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Two lower photos: move the cursor over photo and you will see more photos!

The turning supports were fastened on the wing tip and the wing root. Then a lifting device was moved to both ends of the wing and the lifting devices were connected to the steel supports with cargo straps. Then the lifting devices were pumped, and the wing was lifted in the air, supporting it manually all the time. When the wing had been lifted high enough, the wing was tilted in order to turn it around. The wing was carefully manoeuvred onto one side by supporting it from the other side. When the wing had been turned, it was lowered back on the worktable and it was placed horizontally by supporting it at the ribs.

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Photos: Jorma Laakkonen.

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Photo: Jorma Laakkonen.

Now the landing gear well was facing upwards, and the landing gear assembly could be started, following the procedure developed when testing the gear on the test wing. The first preliminary test was to place the landing gear oleo strut in the well with its wheel hub and axle. At the same tame the wheel well doors were fitted into place. These include the diagonal support door, the oleo strut door, the wheel hub door and the opening door, which is fastened on the fuselage side edge of the wheel well. All parts seemed to settle nicely into their places.

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Photo: Jorma Laakkonen.

Now there is ahead the demanding work of fitting all the hinges and fastenings of the starboard landing gear into place so that the landing gear extends and retracts smoothly. The aluminium covers will also have to be assembled into place on the diagonal support, on the oleo strut and on the wheel hub. Another challenge is to fit into place the aluminium cover on the fuselage side of the wheel well and to make its opening and closing mechanism work as planned. This door is opened automatically by a spring lever when the landing gear is taken out. When the landing gear is retracted the wheel presses against a pin in the mechanism and closes the door.

Photos: Lassi Karivalo except if otherwise mentioned.

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky II, MY-14

MY-14's vertical stabilizer gets its fabric covering webbing ribbons

Sunnuntai 6.6.2021 - Tuesday Club member

Suomeksi

When the webbing ribbons for the fabric covering had been sewn on the horizontal stabilizer ribs of the VL Myrsky II (MY-14), the sewing work continued on the vertical stabilizer. The vertical stabilizer has a wooden structure, according to the original drawings.

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Photo: Heikki Kaakinen.

The Tuesday Club team used the original drawing of the vertical stabilizer, prepared by the State Aircraft Factory and dated 30.9.1942, as instructions for the work. The drawing shows very well how the ribbons must be sewn. The bill of materials on the drawing shows a detailed list of the accessories needed in the work. The list includes the covering fabric, the webbing ribbons, cover ribbons and sewing threads. A 20 mm wide diagonally woven linen ribbon was used as the webbing ribbon.

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Photo: Heikki Kaakinen.

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Photo: Heikki Kaakinen.

In order to keep the webbing ribbons in place on the rib of the vertical stabilizer when doing the sewing, the ribbon was stretched on the rib and its one end was glued on the plywood of the leading edge and the other end on the plywood of the trailing edge. Contact glue was used in this work.

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Left photo: Heikki Kaakinen.

One more work phase had to be completed before the actual sewing could be started. The edges of the plywood sheet covering the leading edge had to be bent inwards so that the edges won’t chafe the fabric covering and gradually damage it.

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Photo: Heikki Kaakinen.

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Photo: Heikki Kaakinen.

To bend the plywood edges, 3 mm holes were drilled where the drawing indicated. Then the edges were bent against each other and tied temporarily into this position using painter’s tape. Linen thread was pulled through the drilled holes and then the threads were tied together into a tightening loop, connecting the edges of the plywood. Then the supporting painter’s tapes could be removed, and the sewing of the webbing ribbons could be started.

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Photo: Heikki Kaakinen.

The webbing ribbons for the fabric covering of the vertical stabilizer were sewn in a similar manner as on the horizontal stabilizers. At the tapered part of the rib the edges of the ribbon were stitched together. At the broader part of the rib, where the round lightening holes are, the thread was slipped through the lightening hole and fastened on the ribbon’s edge on the other side and repeating back again. A radial pattern of the threads was formed in the lightening hole. Now the vertical stabilizer had its webbing ribbons in place.

Photos: Lassi Karivalo except if otherwise mentioned.

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky II, MY-14

Webbing ribbons for fastening fabric covering of Myrsky's horizontal stabilizer are sewn

Tiistai 1.6.2021 - Tuesday Club member

Suomeksi

The VL Myrsky II fighters had originally wooden horizontal stabilizers. The aeroelastic flutter caused the damaging and even breaking of the stabilizers. Therefore the Myrsky’s horizontal stabilizers were replaced with metal stabilizers, which endured the flutter.

The documents concerning the MY-14 which is under restoration don’t mention whether the aircraft got metal horizontal stabilizers before it was written off. However, the board of the Myrsky restoration project decided that the restored MY-14 would have metal horizontal stabilizers. One of the reasons for this was that there were original metal stabilizers available, but somewhat damaged and without covering.

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Photo: Heikki Kaakinen.

The original horizontal stabilizers with aluminium structure have already been repaired and painted by the Tuesday Club and they have been waiting for the fabric covering for a while. The metal stabilizers are covered with fabric in the same way as the corresponding wooden stabilizers. First fabric webbing ribbons are sewn on the ribs of the stabilizer. The fabric covering is fastened on these ribbons by sewing. The fabric is tightened using several layers of nitrocellulose varnish and finally painted according to the aircraft’s paint scheme.

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Photos: Heikki Kaakinen.

The Tuesday Club team has now started the sewing of the webbing ribbons on the MY-14’s horizontal stabilizers. To make the work easier, one of the stabilizers was fastened into an upright position against two trestles. The first step was to stretch a 20 mm wide linen upholstery webbing ribbon on the stabilizer’s ribs. This was done by gluing the ends of the ribbon on the rib at the leading edge. This way the ribbon will stay in place when sewing it onto the ribs.

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After the gluing the sewing could be started. The instruction drawing for sewing the ribbons on the wooden horizontal stabilizers was applied, because the instructions for the metal stabilizer have not been preserved. According to the instructions multithreaded 0,5 mm linen thread was used in the sewing work.

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The sewing work was started at the trailing edge end of the rib. The edges of the ribbon stretched on the upper and lower edge of the rib were stitched together. This was the method used at the tapered end of the rib where there are no lightening holes.

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When the work reached the broader part of the rib where the round lightening holes are, the sewing method was changed. Now the thread fastened to the edge of the ribbon was slipped through the lightening hole and to the other side to the ribbon’s edge, and back again. The webbing ribbon was sewn onto the rib following the original instructions, weaving the thread through the lightening hole.

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Photo: Heikki Kaakinen.

When the ribbons had been sewn on all the ribs of one stabilizer, the procedure was repeated on the other stabilizer. Now the horizontal stabilizers are ready for fastening the fabric covering. In the original drawing’s instructions the fabric quality has been defined as linen fabric 5.F.I.

Photos: Lassi Karivalo except if otherwise mentioned.

Tranlation: Erja Reinikainen

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky II, MY-14

Myrsky engine's air horn and air intake are made

Perjantai 28.5.2021 - Tuesday Club member

Suomeksi

The air flow entering an aircraft’s carburettor is controlled in the air horn, which is attached to the carburettor. When necessary, there is an air intake duct connected to the air horn. This is the case in the VL Myrsky II fighter, among others. In the Myrsky the two-sectioned air intake duct is connected to the air intake, located at the top of the NACA-ring, and is led between the upper cylinders to the air horn of the two-throat carburettor behind the radial engine. The suction air flow is controlled with the damper located in the air horn as well as the warm air flow, which comes through the engine space and protects the carburettor from freezing.

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The Myrsky’s air horn is made of cast aluminium. The front piece of the two-section air intake duct, which is fastened on the NACA-ring, is made of aluminium plate. The tail section of the air intake duct is made of steel plate because it is located at a hot place between the cylinders. The tail section of the duct also connects the front section of the air intake duct to the air horn and is fastened to them with fastening clamps.

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No original Myrsky engine’s air horn or parts of the air intake duct have been preserved and they had to be made in the restoration project of the MY-14. The sections of the air intake duct have already been made. The front section of the duct was made according to the drawing from 1,0 mm thick aluminium plate, using a mould. The tail section was made from 1,0 mm thick steel plate. The sections of the air intake duct have been fitted into place and the front section of the duct is being fastened to the opening in the NACA-ring.

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The SASKY Municipal Education and Training Consortium at Sastamala helped to manufacture the air horn from cast aluminium. They were interested in the ongoing Myrsky restoration project and asked if there was some restoration work which could be made as 3d-printing by the SASKY students. The Tuesday Club team suggested that they could make the rather difficult air horn - and they accepted the challenge.

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Photo: SASKY

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The project was started at SASKY by 3d-printing a plastic 1:1 scale model of the Myrsky’s air horn according to the drawings. Then the actual cast mould for the aluminium cast was made based on the 3d-print. The 3d-printed model was dipped several times in a ceramic solution and a ceramic layer was formed, layer by layer, on the plastic model. Flow channels and air extract were also made on the cast mould. Then the plastic 3d-model was melted from inside the ceramic shell, and the cast mould for the air horn was ready. The liquid AlSi 12 aluminium was poured into the mould. When the aluminium had cooled the mould was broken and the flow channels were removed, and the surface was ground smooth.

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The cast aluminium air horn is now at the Tuesday Club and is ready for further work. Some extra material has been ground off. Holes for fastening bolts will be drilled. The Tuesday Club wishes to thank the SASKY Municipal Education and Training Consortium for preparing the aluminium cast of the air for the restoration the restoration project of the VL Myrsky II (MY-14).

Photos: Lassi Karivalo except if otherwise mentioned.

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky II, MY-14

Wing root fairing of Myrsky?s port wing at Tuesday Club

Sunnuntai 11.4.2021 - Tuesday Club member

Suomeksi

The joint of Myrsky-fighter’s (VL Myrsky II) fuselage and wing is covered with a wing root fairing, made of 1 mm thick aluminium sheet. The wing root fairing consists of a short front section, which covers the leading edge of the wing and reaches under the fuselage. The longer rear section of the wing root fairing covers the seam of the fuselage and the wing, all the way to the trailing edge and around it.

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The rear section of the port wing root fairing was sent to the Tuesday Club for further modifications. It came from Flanco Oy where Antero Flander had forced it into shape against a mould. The Finnish Air Force Museum, working on Myrsky’s restoration at Tikkakoski, had made the sturdy plywood mould. The wing root fairing was made from three aluminium sheets, forced into shape against the mould and then welded together.

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The parts of the port and starboard wing root fairings, which cover the front section of the fuselage and wing joint, had already been sent from Flanco Oy to the Tuesday Club in Vantaa where the parts were welded together. The moulds for the front sections had been made by the Tuesday Club. Flanco Oy has helped in making several other metal parts that are needed in the restoration of the Myrsky MY-14.

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The Tuesday Club team had now both sections of the port wing root fairing and they could be preliminarily fitted into place at the root of the port wing.

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The front and rear sections of the wing root fairings will be finalized at the Tuesday Club, joined together and test assembled. The front and rear sections will be joined together with a joint where the aluminium plate riveted on the lower side of the rear section’s front edge is pushed under the front section’s edge. The holes have not yet been made for the flange nuts, which are used for fastening the wing root fairing sections to the side of the fuselage and to the wing surface.

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The wing root fairings will be test assembled when the wing halves, made and undercoat painted at the Tuesday Club, will be assembled on the fuselage frame of VL Myrsky MY-5 at the Finnish Aviation Museum. However, it will take some time before the wing root fairings are ready for the test assembly.

Photos: Lassi Karivalo

Translation: Erjan Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky, MY-14

Wheel well and aileron inspection hatches on Myrsky?s test wing

Sunnuntai 21.3.2021 - Tuesday Club member

Suomeksi

When the undercoat painting of VL Myrsky II’s (MY-14) wings and tail part surfaces had been completed, the activity of the six Tuesday Club members working on the Myrsky project could be targeted to other things. The new work item is the test wing and the construction of its wheel well and the installation of the ailerons’ inspection hatch covers.

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The wheel well of the test wing is in the square space bordered by the front and rear spars and the wing ribs. The wall of the wheel well is made of 2 mm thick plywood. The wall billet had been cut earlier, now it was fitted into place by bending the plywood into a circle, in the space bordered by the spars and ribs. At the fitting stage the plywood wall was too tall for its space. When the wall had settled into place as desired, the excessive height was cut away and the plywood wall was fastened. The next phase was to make from plywood the corner pieces to cover the empty spaces in the corners of the wheel well.

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A supporting curb will be built on the upper edge of the plywood wall of the wheel well. The pressure lathed aluminium cover will be fastened on the curb to shield the wheel well. The covers have already been lathed for both wheel wells of the test wing. The supporting curb and the cover on the starboard wing half are already in place. The wheel wells and their covers will be hidden under the aluminium wing root fairings, which cover the seam of the Myrsky’s fuselage and wing.

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The supporting curb for the wheel well’s upper edge on the port side wing half was made from plywood strips which were glued together and forced into a mould. When the glue had dried, the supporting curb was unfastened from the mould and modified into measure and is now waiting to be installed.

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Simultaneously with the building of the wheel well, the fitting of the half-finished aileron inspection hatch covers was started. This task has been waiting while the ailerons were being painted with undercoat paint.

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The aileron is fastened on the wing with three hinges. The hinge knuckles inside the aileron’s leading edge are fastened on the journaled hinge arms on the wing with bolts. On the lower side of the aileron’s leading edge there is an inspection hatch for each hinge.

The opening of the inspection hatch has a cover made of 1 mm thick aluminium plate. The Tuesday Club team has one original hinge hatch cover as a model. The cover is for the hinge hatch in the middle of the aileron. However, the team made new covers for all aileron inspection hatches. On the front side of each inspection hatch opening there is a slot on the aileron’s surface for fastening the cover.

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These slots for fastening the inspection hatch covers had been covered during the undercoat painting of the aileron, when a strip of linen fabric was fastened to reinforce the leading edge. The covered slots were cut open with a sharp knife, then the inspection hatch covers were fitted into place, one by one. When the hatch is closed, the front edge of the cover is slipped into the slot in the aileron, then the cover is pressed against the aileron surface to cover the opening. The cover is locked into place with one or two screws, located on the rear edge of the cover. The screws are pressed and locked into the locking holes with springs. The new aluminium hatches don’t have the locking screws yet.

Photos: Lassi Karivalo

Translation: Erja Reinikainen

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky, MY-14

Undercoat painting of Myrsky?s wings was finished

Lauantai 27.2.2021 - Tuesday Club member

Suomeksi

The undercoat painting of the upper sides of Myrsky’s (VL Myrsky II, MY-14) wing halves took about two months. Now the work is ready. The undercoat painting procedure of the upper sides followed the undercoat painting of the lower sides of the wings. First the plywood surfaces are painted with pale grey TEMALAC AB 70 alkyd paint which contains aluminium flakes, and it is covered with a couple of layers of dark grey Teknos Oy adhesion primer Futura 3.

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Photo: Jouni Ripatti.

The painting of the upper surfaces of the wing halves with aluminium flake undercoat paint was described in the previous blog. Before the dark grey adhesion primer could be applied on the aluminium flake undercoat paint, the painted surface was ground smooth and some uneven spots on the plywood surface had to be spackled.

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Photo: Jukka Köresaar.

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The Teknos Oy's Futura 3 RAL 7005 adhesion primer was spread with a mohair roller. When the paint had dried, it was noticed that the painted surface wasn’t as smooth as it should have been. Some uneven “orange peel surface” was detected. The painted surface was therefore ground smooth manually and with a disk grinder, using 180 sandpaper grit.

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Photos: Jouni Ripatti.

The paint dust was removed and a new layer of Futura 3 paint was applied. This time the paint was thinned with white spirit to a solution of 80%. The soft mohair roller was changed into a harder foam rubber roller. This time the result was satisfactory, but in some places some uneven paint surface could still be seen. However, after grinding the Futura 3 undercoat paint surface was very smooth.

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Photo: Jouni Ripatti.

When the small uneven areas were ground, the paler grey aluminium flake paint was revealed from under the darker adhesion primer and the surface looked patchy. It is important, that the two undercoat paints have different shades. Because of this it can be seen when the lighter grey layer of alkyd paint becomes visible when the top layer of the adhesion primer surface is ground.

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When using the disk grinder to grind the Futura 3 surface, the bare plywood surface appeared in some places. This was not the purpose. These places were patched with a layer of adhesion primer. When the patched spots had dried they were ground manually, using first a rougher (150) INDASA Fine sanding pad and then a finer (240) INDASA Super Fine sanding pads.

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Now the upper and lower sides of the MY-14 wing halves have been painted with undercoat paint and they are waiting for the paint finishing. The upper surface will be dark green with black camouflage and the lower side will be DN-blue. The paint finishing will not be done at the Tuesday Club, it will be bought from outside. The main reason for this is that the restoration space of the Finnish Aviation Museum is not sufficiently dustless or suitable for the large-scale spray painting of the wing surfaces.

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The Tuesday Club team can now continue with the other remaining work in the construction of the Myrsky’s wing. The installation of the step plates on the upper surface of the wing root has been started. The step plates have been cut from 2 mm thick plywood and they haven’t been painted yet. The aluminium wing root fairings, which protect the seam of the fuselage and the wing, are fastened on the inner edge of the step plates.

Photos: Lassi Karivalo except if otherwise separately mentioned.

Translation: Erja Reinikainen

Kommentoi kirjoitusta. Avainsanat: aviation history, restoration, VL Myrsky, MY-14

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