Dismantling of rotten parts of left wing of Kurki

Tiistai 6.3.2018 - Member of Tuesday Club


The I.V.L.K.1 Kurki plane was transported from the Päijät-Häme Aviation Museum in Vesivehmaa to the Tuesday Club workshop and the restoration work of its left wing has been started. The wing (5.75 m long and 2.32 m wide) is covered with 1.2 mm thick plywood. Rotten areas in the plywood covering of the wing have had to be dismantled.


The plywood covering of the wing has several stricken holes which are easy to repair. The worst problem is the extensive rotten area around the national insignia on both sides of the wing. During the storage of the wing water has been dripping on this part of the wing and the plywood covering has been badly damaged. Also the aileron covering is badly rotten.


The wing surfacing is intact and in reasonably good condition outside the rotten area and the stricken holes. The intact parts of the wing were washed clean using a miraclean sponge soaked in water and wiped dry with a cloth. Chemicals were not used when cleaning the plywood covering of the wing.


When the plywood covering is badly rotten, there is no other option than to remove it entirely and use new plywood to cover the area. This is how parts of the Kurki wing had to be restored. First a sketch was made of the rotten area to document the location of the national insignia, the maintenance panels and the aileron control wire holes. This documentation was necessary in order to place all the items correctly in their original locations when the new covering has been installed.


The rotten plywood covering was dismantled using a carpet knife. The dismantling covered the area between two or three ribs on both sides of the wing. Usually the dismantled area is extended as far as the ribs, which makes it easier to install the new covering. 


When the rotten plywood covering was removed, further damage was revealed: there was mould on the inner surfaces of the plywood covering and the upper edges of the rib plywood sides were rotten and the sheets of plywood had come apart. The frayed upped edges of the rib sides can fortunately be repaired using glue, they don’t have to be dismantled and renewed.


When the rotten wing covering had been dismantled, the remaining plywood nails and screws had to be removed from the ribs. Some nails could be carefully pulled out using pliers but some nails broke in the procedure. The broken nail stubs were either filed down to the rib surface or struck into the rib using a punch. The brass screws were easy to remove.


The work will be continued by preparing the dismantled areas for covering. First the rib plywood sides will have to be repaired as well as all the damaged areas in the inner structures of the wing. New supporting battens will have to be built in order to assemble the new plywood covering in the dismantled area.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, I.V.L. K.1 Kurki

Vihuri cockpit on final phase

Sunnuntai 4.3.2018 - Member of Tuesday Club


The cockpit of VL Vihuri (VH-25) will soon be placed on display at the Finnish Aviation Museum. The last phase in the cockpit restoration work includes the side coverings. The sides are covered with aluminium plate and plexiglass so that the museum visitor is able to have a view inside the cockpit and see all the equipment there.


While the covering of the sides has been going on, the last of the cockpit equipment have been installed. The Tuesday Club was able to get hold of a machine gun camera control unit which has been in a Vihuri. The only problem was that the unit didn’t have the bracket which is needed to attach it to the instrument panel on the left side of the front cockpit. There was no information available about the original bracket. Therefore the bracket was designed by the Tuesday Club and built using aluminium. The bracket has now been made and the control unit is ready to be installed.


The cockpit and display lighting was completed before Christmas. The finalisation and installation of the lighting control unit was left to be done later. A container was made from aluminium plate to house the lighting control unit. The whole package was installed on the supporting frame under the front cockpit. The lighting control unit was placed behind the cockpit side covers, hidden from view and also protected from possible vandalism.


The covering of the lower parts of the cockpit sides using 1.5 mm aluminium plate has been completed. The aluminium plates cover half of the cockpit sides. The plates were attached at their lower edge to the supporting structure’s hem under the cockpit. The upper edge of the plates was attached to the covering panel which runs along the side of the cockpit. The upper sides of the cockpit will be covered using transparent plexiglass. The plexi installation has already been started.

Photos: Lassi Karivalo

Kommentoi kirjoitusta. Avainsanat: aviation history, Tuesday Club, museum aircraft, Valmet Vihuri, VH-25

Alodine 1200 S and MY-14

Tiistai 20.2.2018 - Reino Myllymäki


There were several different process in order to enhance the corrosion protection of aluminium alloys in the 1940s. For example, the bulkheads may got either VLO 32742 part 40 and 41 processes (anodic treatment and bichromating) or part 42 process (treating in chromium nitric acid).


That kind of processes or agents were not in use anymore. MY-14's bulkheads are reproduced from new material by using design drawings and survived parts of bulkheads. Now they were yellow chromated by Alodine 1200 S process. Same process was used for the bottom access panel and instrument panels.


Alodine 1200 S process for MY-14's parts was provided by Patricomp Oy.

Photos: The Finnish Air Force Museum.

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

Armoured pilot's seat of VL Myrsky

Sunnuntai 18.2.2018 - Reino Myllymäki

Before WWII, the fighter pilot's seats were normally not armoured. However, Russians were predecessors. The Finnish Air Force started the armouring during the Winter War, mostly that work was concluded before the Contiuation War. For example, the pilot's seat armours for Gloster Gladiator II biplane fighters were ordered on February 26th 1940 and for Morane-Saulnier M.S.406 monoplane fighters on March 5th 1940. Furthermore, Hawker Hurricanes were armoured after Winter War and the armouring of Brewster is totally own story.

The Finnish Air Force ordered 100 armoured pilot's seat from Swedish Avesta steel factory. These seats were intended to 50 Fokker D.XXIs ordered from the State Aircraft Factory but they were suitable for Fokker C.Xs, too. Now we know that the pilot's seat of Fokker D.XXI and VL Myrsky were same kind of. That means that VL Myrskys could have pilot's seats made in Avesta. These armours were 10 mm thick.


The armour of the VL Myrsky's pilot's seat is three-piece. Pilot's head armour is fixed to the upper part of the steel-tube fuselage frame. Other two pieces form the pilot's adjustable seat.


The original pilot's head armour of the MY-14 has preserved as a part of the steeb-tube fuselage frame. Photos: Reino Myllymäki.


The armoured back rest is an original part but it has been in a crashed Fokker D.XXI fighter. It has been straightened and needs some changes.


However, the armoured seat was lacking. It was produced as new production part by a subcontractor. Brewster 239's seat was used as a model since the drawings of the seat lacked. The result looks like original!


The brackets of the seat lacked too, but luckily the drawings were preserved. Mr Matti Patteri converted the drawings to the cutting files by CAD and the brackets' blanks were cutted by laser by Prolaser Oy. Blanks were welded by the restoration team at the Finnish Air Force museum.

The armoured pilot's seat will be covered by felt, flannel and pegamoid. The felt will be glued to the seat.


Photo: Reino Myllymäki

Some parts such as the adjusting screw and sandums were conserved or restored earlier and are now fixed to the MY-14.

Photos: Historic photo: archives of the Finnish Aviation Museum.  Other photos unless separately mentioned: the Finnish Air Force Museum.

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

About metal parts of Myrsky wings

Perjantai 16.2.2018 - Member of Tuesday Club


There are many metal parts in the wooden wing structure of the VL Myrsky. The majority of these metal parts connect to the wing structure and the parts have to be installed at the same time when the ribs of the wing are attached between the wing spars.


Several of the metal parts are involved in the fastening of the landing gear at the root of the wing. These parts include e.g. the fastening of the diagonal rear strut of the landing gear which is attached to the rear spar, the fastenings of the landing gear strut which are attached to the seam of the fourth rib on the rear and front spars and the bearing and locking disc of the retracting actuator of the landing gear which is fastened on the front side of the front spar. The metal brackets, which fasten the wing to the fuselage, are fastened on the upper edge of the front and rear spars. In the mid-wing area there are also the fuel and compressed air tubes for the auxiliary fuel tank and the trimming mechanisms for the ailerons.


Some of the existing metal parts of the wing are original parts which have been installed in a Myrsky. They come from the wings of Myrsky which have been stored in the forest and decayed there for decades. The parts were salvaged from the forest, the moss was removed and the parts were cleaned, sand-blasted and painted grey. Also the original bolts and nuts belonging to these parts were salvaged and cleaned to be used again.


All of the metal parts needed for the wing were not found, so the missing parts have had to be made. The original parts and their drawings have been used when making the new parts. New parts have been needed to fasten the landing gear and also to fasten the wing to the fuselage.


There are four metal brackets on the upper edge of the front and rear spars which are needed to attach the wing to the fuselage. This means that when the Myrsky fuselage will eventually be placed on top of the wing, only four bolts will be needed to lock the wing and fuselage together.


Before the front and rear spars of the wing were fastened on the assembly jig, holes were drilled for the landing gear fasteners and for the bolts connecting the brackets of the wing and fuselage. When the wing spars had been fastened on the assembly jig, the installation of the ribs and the metal parts was started. It didn’t take long before all the metal parts had found their place and had been fastened on the wing spars.


The fuel and compressed air pipes of the auxiliary fuel tank were collected from the Finnish Air Force Museum. The original parts were rusty and had to be honed clean. The fuel tubes were painted yellow using a standard colour (Dicco 6 / RAL 1003 Signalgelb) typical for tubes on an aircraft and the compressed air tubes were painted blue. Then the tubes were pushed in place through the holes in the ribs.

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

Left wing of Kurki to Tuesday Club

Keskiviikko 14.2.2018 - Member of Tuesday Club


Since spring 2016 the Tuesday Club has been working on the restoration of the I.V.L.K.1. Kurki fuselage and right wing and the building of the wing struts. This work has been almost completed. Now it was time to bring the left wing of the Kurki to the Tuesday Club. Up to now the plywood-covered wing has been stored at the Päijät-Häme Aviation Museum in Vesivehmaa.


The wing arrived from Vesivehmaa on Tuesday, January 30th, transported by the Finnish Defence Forces. The transportation had been arranged by the Finnish Air Force Museum. The truck left Tikkakoski in the morning, bringing to the Päijät-Häme Aviation Museum the ejection seat simulator of MiG-21 that had been used by the Air Force and is now withdrawn from use. When the simulator had been transferred into the museum, the Kurki wing was loaded on the truck and the journey towards the Finnish Aviation Museum in Vantaa began. When the truck arrived at the Aviation Museum, the wing was moved directly into the restoration space of the museum.


The right wing of the Kurki – which has now been almost completely restored at the Tuesday Club – as well as the left wing have suffered major damage during the 90 years of storage. There are punched holes in the plywood covering of the wing and during the storing period water and moisture have damaged the covering and inner structures of the wing. The plywood covering has partly moulded beyond repair and will have to be renewed.


The first task will be to clean the wing surfaces and remove dust and dirt. Then the repairing work of the damaged parts can be started. The hard work ahead is expected to be completed in autumn.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, I.V.L. K.1 Kurki

Aluminium rib and oil cooler in left wing of Myrsky

Perjantai 2.2.2018 - Member of Tuesday Club



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.


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.


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.


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.


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.


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.


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.


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.


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.


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.


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


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.


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.


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.


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


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.


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.


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.


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.


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.


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.


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.


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.


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

Kurki has a wing!

Lauantai 30.12.2017 - Member of Tuesday Club


A lot of work was needed before the right wing of the I.V.L. K.1 Kurki was ready for testing how to attach it to the fuselage. The Tuesday Club of the Aviation Museum Society had repaired the plywood covering of the wing and the damages in the inner structures and built the missing four wing struts. Also the restoration of the Kurki fuselage was almost completed, so it was time to test how the wing would be attached.


The Kurki wing had been restored in the work space of the Finnish Aviation Museum and now it was carried to the mid-hall where the restored Kurki fuselage was waiting. A lot of excitement was in the air when the assembly work was started by picking the wing up by a stacker and moving it slowly to the proper installation position.


Boards had been placed on the fork of the stacker so that the whole length of the wing could be supported. Two cargo lashes were attached to the ceiling beam of the hall and wrapped around the wing to ensure the lifting. The cargo lashes were tightened as the stacker lifted the wing higher.


When the correct installation height had been reached, the stacker was moved away and the cargo lashes now carried the whole weight of the wing. The wing was tilted so that the locating lugs were in line with the wing assembly holes in the fuselage.


Then the wing was pushed against the Kurki fuselage and the locating lugs at the root of the wing slid into the holes in the fuselage. The installation was surprisingly easy and the lugs were locked in place using bolts.


More stress was coming: would the two original wing struts and the two new ones (which had been made based on the original ones) fit the Kurki wing now that it was in place? The new wing struts had been made assuming that the two old wing struts found in the Vesivehmaa museum hall (and used as models) had belonged to Kurki. There was no evidence to support this assumption.


The original and repaired straight wing strut on the leading edge of the wing was installed first. The quill-shaped fastener at the lower end of the wing strut was attached to the brackets on the fuselage. This went well and the connection was secured with a bolt. Then the upper end of the front wing strut was lifted up in an angle to meet the brackets on the wing. After some adjustments the fastener was attached to the brackets. Now the front wing strut had been installed.


It was time to install the straight wing strut to the rear part of the wing. The rear wing strut had been made based on the original and repaired strut main tube and covered with plywood. The wing strut had been attached by its lower end to the brackets on the fuselage. Then a problem arose. When the strut was lifted up in an angle towards the brackets on the wing, the strut was positioned about 15 cm in front of the brackets. This meant that the brackets on the fuselage and on the wing were not in a perpendicular line. The brackets on the wing are located about 10 cm further back than the ones on the fuselage.


When the wing strut was rotated 180 degrees around its axis (the leading edge of the strut now pointing towards the trailing edge of the wing), the wing strut settled nicely between the brackets on the fuselage and the brackets on the wing. The Tuesday Club team noticed that the fastening quill on the lower end of the wing strut tube had been originally welded at an angle of 5 degrees to compensate the difference in the positioning of the brackets on the wing and the fuselage. This was something the team hadn’t noticed earlier and this couldn’t have been observed by naked eye.


The team had to face the fact that the wing strut tube had been covered the wrong way round: its leading edge was pointing backwards to the trailing edge of the wing and vice versa. The chance of getting it right had been 50/50 but it didn’t happen. Now the decision had to be made whether to dismantle the strut tube covering and do it right or to solve the assembly problem by modifying the fastening part on the lower end of the strut or the brackets on the wing in order to change the angle of the strut.

A new approach was taken: the unfortunate rear wing strut was first replaced by an original strut and then by a new wing strut which had been made using a new main tube. The fasteners at the ends of the new wing strut had been welded at a 90 degree angle to the center line of the strut. The original wing strut met both fastening brackets nicely and accurately. Fortunately also the new rear wing strut could be installed – with some assistance - to meet the brackets.

Before the test assembly of the wing will be completed, decisions will have to be made on how to install and fasten the diagonal wing strut which is positioned between the front and rear wing struts. There are no separate brackets for the diagonal strut on the wing or on the fuselage – and there is no drawing, photo or instruction about this either. The diagonal strut was preliminarily installed between the straight wing struts in order to find a solution how to attach it. Some ideas already came up but the decisions will be made after the Tuesday Club Christmas break.


When the wing and wing struts had been attached to the Kurki fuselage, the team knew that it had two original Kurki wing struts, three eligible wing struts that had been made according to the original ones plus one wing strut that could be modified to fit.


For the first time since 1927, after 90 years, the Kurki fuselage has wings. To be more precise, at the moment it has one wing. The left wing is waiting in Vesivehmaa for its restoration work.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, I.V.L. K.1 Kurki

Kurki wing struts ready for painting

Tiistai 26.12.2017 - Member of Tuesday Club


The Tuesday Club of the Finnish Aviation Museum Association has completed the missing wing struts in the I.V.L. K.1 Kurki restoration project. The wing struts have been built at the workshop of the Finnish Aviation Museum according to the original wing struts. They were built already in summer, covered with plywood, but without the connecting fasteners. The club members spent all autumn making the metal fasteners and installing them on the wing struts.


The wing struts of the Kurki are fastened on the lower edge of the fuselage and connected to brackets of the front and rear wing struts using quill-type fasteners. These fasteners are locked between the brackets on the fuselage and on the wing struts using bolts. Between the straight struts there is a diagonal N-shaped strut which has slot-type fasteners. The fasteners at the upper end of the wing struts can be adjusted.


The work on the new fasteners was started by measuring accurately the two existing original wing strut fasteners and examining their structure and the way they had been made. The basic structures of the quill-type and slot-type fastener are the same.


Each fastener consists of an installation tube about 10 cm long and of the actual fastener, which is pushed inside the installation tube and attached to it by welding. The installation tube has a dimension which matches the steel frame tube inside the wing strut. The installation tube and the attached fastener are pushed inside the end of the wing strut tube and locked in place using two steel bayonets which go through the end of the wing strut.


The work on the wing strut fasteners was started by lathing the six installation tubes that are needed. Then the quill-type and slot-type fasteners, which will be pushed into the installation tubes, were made by lathing, welding and milling. Two holes were drilled into each installation tube. The fastener was pushed into the installation tube and spot-welded in place through the holes. The welded spots were ground even and smooth. This is how all four quill-type and two slot-type fasteners were made.


Then the fasteners and their installation tubes were attached to the ends of the wing struts. Some of the installation tubes slid easily into place in the strut tubes, but some didn’t. Therefore some of the wing strut tubes had to be filed on the inside to make the installation tube fit. The next phase was to lock the fasteners to the wing strut pipe by using two steel bayonets.


The work on the first wing strut was started by making sure that the fastener was attached to the wing strut in the correct position. Then the fastener was locked in place with clamps. Two holes were drilled through the end of the wing strut using a 5mm drill piece and then screws were temporarily placed into the holes to prevent the fastener from moving. Then the holes were enlarged by using a 10 mm drill piece in order to match the diameter of the locking bayonet.


A total of 12 locking bayonets are needed and they were made by cutting 55 mm long pieces from a steel bar 10 mm in diameter. The length of the bayonet was based on the fact that the wing strut metal tube is 50,5 mm in diameter and a reserve of 2 mm is needed at each end for riveting. A small cavity was drilled on both ends of the bar so that the end would enlarge when riveted onto the wing strut bar.


A 5 mm hole was drilled through the bar. This hole is needed for the cover which is installed on the locking bayonet hole in the plywood cover of the wing strut. The cover prevents moisture from getting inside the wing strut. The original Kurki wing struts had round covers, 20 mm in diameter, which were connected to the locking bayonets using aluminum wire. In the restoring work this structure won’t be used. The locking bayonet holes will be protected by using wide-headed pop-rivets which are pressed into the holes in the bayonets.


When the holes for the locking bayonets had been drilled at both ends of the wing strut, the bayonets were pushed into place one by one. The ends of the bayonets were riveted onto the wing strut frame. The fasteners were now in place on the wing struts and the work was nearly ready: only the covers were missing. The remaining wing strut fasteners were assembled in a similar way and all the wing struts were now ready for painting.


The wing struts will be painted using silver-bronze varnish. The plywood-covered wing struts won’t be painted before the right side wing of Kurki has been preliminarily installed onto the Kurki frame. The wing has been under restoration work in the Tuesday Club as well. This preliminary installation will ensure that the two original wing struts have actually belonged to the Kurki. These two original parts were used as models for making the missing wing struts.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, I.V.L. K.1 Kurki

Lights installed in Vihuri (VH-25) cockpit

Keskiviikko 20.12.2017 - Member of Tuesday Club


The last phases in the restoration work of the Valmet Vihuri II (VH-25) cockpit included the installation of the cockpit lights, the instrument board background lights, the light of the sight and the display lights when the cockpit is in the museum. Finally the sides of the cockpit will be covered with aluminum plate and plexiglass.

Originally the Vihuri had a 24V direct current electrical system. The positive pole of the system was insulated from the fuselage of the plane and the negative pole was connected to the fuselage. However, in the restoration of the Vihuri cockpit a 12 V alternating current system was chosen. In this system both poles of the system are insulated from the fuselage. The mains voltage (240 V AC) is transformed into a low voltage (12 V) and rectified to direct current. This power supply (12 V DC) is connected to the Vihuri lighting control panel, which supplies power to each lighting fixture.

The front and rear cockpits of the Vihuri has small red lights on both sides of the cockpit. The light is tinted red in order to disturb the pilots’ night vision as little as possible when flying in dusk or in darkness. The amount and direction of light can be adjusted simply by turning the shade around the glass of the lighting fixture.


Three original cockpit lights were available and could be installed into the VH-25 cockpits, but the fourth lighting fixture was missing and had to be made. Fortunately the base of the fourth light was found. The body, the glass and the turning shade of the lighting fixture had to be made to resemble the original ones. The body was made of aluminum, the “glass” was cut from red plastic and the cover was made from aluminum plate.


When the fourth cockpit lighting fixture was ready, all four lights were installed in the cockpit by attaching them to the original fasteners in the upper parts of both cockpits. The original incandescent lamps were replaced by led lamps. Leds were chosen because the cockpit lights are always on when the VH-25 cockpit is on display in the museum and the heat emitting incandescent lamps wouldn’t be a good solution. Installing the led lamps into the original lighting fixtures wasn’t a problem because the leds have the same type of socket (BA 15d) as the original incandescent lamps.


The original power cables of the four cockpit lights in the Vihuri are protected by transparent plastic tubes. A similar installation was chosen in the restoration work, but using similar thin silicon tube. In the original installation there were two cables (positive and negative) from each lighting fixture installed into the plastic tube and the negative cable was connected to the fuselage. The cabling was changed so that both cables are inside the tube and they connect the lighting fixtures to the lighting control panel. The red lights were turned on when the power was connected.


Three background lights were installed behind each instrument board. Unfortunately there were no original background lights available and all of them had to be made. Fortunately the instrument boards still had the clips for the lighting fixtures so that the size and shape of the lighting fixture could be estimated.


The tube-shaped bodies of the lighting fixtures were lathed from plastic. A cable was pulled through the body and the wires were attached to the base of the fixture. Led lamps with G4 caps were attached to the base. When power was supplied to the cables, the background lights illuminated the instrument boards.


The cabling was made by using one cable from the lighting control panel to each instrument panel. According to the drawings of the original installation, the wiring was branched at the instrument panel to supply each of the three lighting fixtures. The light of the sight was installed in a similar way.


In the Vihuri the background lights of the instrument boards and the sight light had originally armored cables. The armor, i.e. the braided metal covering of the cables, was meant to protect the power supply from disturbing external signals. However, the armored cable used in the restoration work of the instrument panel lights had three cables whereas the original one had only two. Therefore the three-wire cable was pulled out of the armor and replaced by the two wires leading to the instrument board lights. At the same time the armor was stretched in order to make it thinner, resembling the original one used in the Vihuri.


The Vihuri cockpit will be on display in the Finnish Aviation Museum. The red lights in the cockpits, the instrument board lights and the sight light were adequate for the pilots but they won’t be able to illuminate the cockpit enough for the museum visitors. Therefore four 30 cm long led tubes were installed as display lighting. The leds were attached to the upper edges of both cockpits, trying to install them as unnoticed as possible. Depending on the position of the cockpit in the museum, the lights will be controlled so that the leds are on only on the side where the viewer is standing. In this way the lights on the opposite side will not produce disturbing glare.


Now the cockpit lights in the Vihuri as well as the instrument board background lights, sight light and the display lighting were working. The last phase was to organize the various cables from the lighting fixtures to the lighting control panel into a tight group. This was done by attaching the cables to the cockpit frame tubes by using original clips and new clips made to match the original ones.

Kommentoi kirjoitusta. Avainsanat: aviation history, Tuesday Club, museum aircraft, Valmet Vihuri, VH-25

Sandums and safety wires on Kurki skis

Sunnuntai 26.11.2017 - Member of Tuesday Club


The skis of an aircraft are kept in a proper position by flexible rubber ropes (sandums) and restricting safety cables which are connected to the tips of the skis and to the landing gear frame. When the plane is taxing, the sandums flex according to the movement of the skis and when the plane is in the air they keep the skis in an angled position with the ski tips pointing slightly upwards. The safety cables make sure that the skis remain in the correct flying position even if the rubber rope breaks. Without the restricting cables the skis would move uncontrollably, making it impossible to land safely. There is a cable from the tip and from the heel of each ski, connecting to the landing gear or the fuselage of the plane. Steel wire has also been used instead of cables.

The I.V.L.K.1 Kurki, which is being renovated by the Tuesday Club of the Finnish Aviation Museum, had skis with some traces of old sandums and safety wires still left. The sandums were rubber rope, about 2 cm thick and the safety wires were steel wire, 5 mm thick. However, judging by the old photographs taken of Kurki, it is quite certain that the present skis have not originally belonged to Kurki. The skis have been made according to the State Aircraft Factory standards and might well have been under the Kurki, but the existing sandums and safety wires don’t match with the old photographs taken of Kurki.

The Tuesday Club decided to install sandums and safety wires which match the ones on the old Kurki photographs. The remains of the existing sandums and safety wires were removed. There was still one more difficulty to overcome: there are differences in the old photographs showing how the sandums and safety wires are connected. The Club members decided to follow the installation principle shown on the photographs taken of Kurki in early spring in 1927.


The installation of the sandums was started by lifting up the Kurki tail, allowing the skis to hang in the flying position. The correct length of the sandums keeps the skis in the appropriate angled position when the rubber rope is tight. The rubber rope is flexible when the plane is on the ground or in a taxing position on its tail wheel.


Before the sandums and safety wires could be installed, the fastening brackets had to be made on the landing gear. There were no brackets left on the landing gear to hold the upper ends of the rubber ropes and safety wires. This may be because on its last flights Kurki had float gear which don’t need sandums or safety wires.

According to the old photograph, the sandums and safety wires on Kurki are installed so that the sandum and safety wire from the tip of the ski are attached to the same fastening bracket on the landing gear frame. The safety wire from the heel of the ski is attached to its own bracket on the landing gear. The missing brackets were made of aluminium plate, painted black and attached to the landing gear frame.


A piece of appropriate rubber rope was found at the Finnish Aviation Museum to make the sandums. The rope was cut to measure and the end of the sandum rope was passed through the block wheel on the tip of the right side ski and bent into a loop. The loop was locked at its base, using first thin steel wire and then flax yarn to make the actual locking weave. The yarn was spun around the base of the loop into a tight braid.


A similar loop was made at the upper end of the sandum and the loop was connected to the bracket on the landing gear using a bolt. Now the right ski had its sandum in place. Using the same method the sandum on the left ski was installed.


Suitable 3.7 mm thick wire to make the safety wires was found at the Finnish Aviation Museum. The length of the wire was measured from the fastening points on the skis to the brackets on the landing gear frame. The length of the wire has to allow the ski to move when the plane is taxing and to restrict the movement of the ski in case the sandum breaks. About 10 cm was added to the measured wire length to allow a fastening loop to be made at each end of the wire.


Modern schackles couldn’t be used when making the wire loops. The original Kurki wire loops were made by splicing the wire. This means that the ends of the wire threads are braided into the wire itself.


The fastening loops were made with the help of a metal chute loop which supported the wire. The loop was attached on a splicing jig and the jig keeps the loop firmly on place when the wire is being spliced.

Using a splicing tool the threads of the wire were opened before the loop and the open ends of the wire threads were braided between the wire threads. Thread by thread the end of the wire was braided firmly into the wire. The spliced section was covered using flax yarn. Varnish was applied onto the spliced section covered with yarn to make the surface water resistant. All four connecting loops of the safety wire were prepared in the same way. When the loops were ready, all wires were painted using black Isotrol-varnish to protect the wires from corrosion.


The tips and heels of the skis had the original bayonets still in place for attaching the safety wires. However, the fastening brackets for the safety wire loops were missing. The brackets were made from aluminium plate, painted black and attached with bolts on either side of the bayonets. The lower ends of the spliced wire loops were placed between the brackets and locked with bolts. A thin copper tube was used as a sleeve on the bolts to prevent the wire loop from moving loosely on the bolt.


The upper ends of the front wires were attached to fastening bracket on the landing gear frame where the sandums already were in place. Bolts with copper sleeves were used. The upper ends of the rear wires were attached to their own brackets on the landing gear frame.


The safety wires were attached using modern 6 mm hexagonal bolts. The Kurki skis still have the original block wheels for the sandums with slot head bolts.


In fact all original bolts on Kurki are of the same type. This is why all the new bolts on the sandums and safety wires will be replaced later with slot head bolts. This kind of bolts are not available in hardware stores any more but hopefully some will be found in a special store. If not, the Tuesday Club members will modify them from standard modern bolts.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, I.V.L. K.1 Kurki

Myrsky wing begins to take shape

Tiistai 7.11.2017 - Member of Tuesday Club


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.


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.


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.


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.


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.


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.


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.


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


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.


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.


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.


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.


 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.


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.


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.


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.


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.


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.


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

Side panels of Kurki engine mounting

Lauantai 21.10.2017 - Member of Tuesday Club


When the frame of I.V.L.K.1 Kurki was brought in spring from Vesivehmaa to the Tuesday Club work space for renovation, it was in poor condition. After a year of hard work it is now nearly ready. One of the latest renovation phases was to build the openable side panels that were missing from the wooden engine mounting. The side panels are opened when maintenance work on the motor is done. The panel covering the upper part of the engine mounting was made already in spring.


Old photographs of Kurki showed how the side panels of the plane had looked like. Cardboard models for the side panels were made based on old photographs and dimension measurements taken on the engine mounting. The rough shape of the side panel was then cut from 1,4 mm aluminium plate (quality class 6061). The rough cut was improved when placing the plate on the engine mounting. The side panels are locked on the mounting by their rear edge using Fokker-pins. When the panel shape was correct and matched the engine mounting dimensions, holes were drilled into the rear edge of the panel for the Fokker-pin locking bayonets.


Five original locking bayonets were still left on both sides of the engine mounting frame, but the actual pins were missing. A few pins were available at the Finnish Airforce Museum but the rest of the pins had to be bent from steel wire. A couple of the brass locking bayonets had been damaged and had to be replaced by new ones made of brass screws of appropriate size. Some work was needed before the Fokker-needle bayonets found their way into the holes on the rear edge of the side panel.


Based on old photographs the side panels had stiffening bends along the edges of the panel. Based on the photos, the knuckles were made at a distance of 5 cm from the edge of the panel. Some practice on the rotary machine was needed before appropriate knuckles were completed. However, making the stiffening knuckle caused the plate to stretch and bend a little and the plate had to be flattened and straightened. The straightening work was done using different methods and tools, such as a wooden hammer and tongs. Finally the panel fitted evenly onto the sides of the mounting.


The engine mounting side panel surface has a circular grinding pattern, typical of the 1920’s. A similar grinding pattern had already been made on the upper panel in spring. The meaning of this pattern was originally mainly cosmetic. In the 1920’s the aluminium plate manufacturing process didn’t produce uniform quality and therefore the plating looked somewhat mottled. Applying circular grinding on the panel, the surface could be made look even and uniform in colour.


The circular grinding pattern was made using a nog plate installed on a pillar type drilling machine. The panel was moved forward under the nog plate half a pattern at a time. In the first phase the pattern was made on both panels on the area between the knuckle and the edge.


In the area inside the knuckle the pattern couldn’t be made before the panel fitted tightly on the engine mounting and the hinges were installed. The openable side panels are fixed on the engine mounting by their front edge using a piano hinge.


Some effort and shaping work was required before both of the side panels with their hinges were preliminarily fitted in their place. Now the circular grinding of the remaining areas could be done and the work to install the piano hinges could be started.


The piano hinges were cut to match the dimension of the engine mounting front edge and fitted onto the vertical wooden front edge. Also the places of the screws for the hinges were marked. Now the hinges could be riveted onto the front edges of the panels. The places of the rivets were marked on the front edge and holes were made for the rivets. 3 mm aluminium rivets were applied using a compressed air rivet gun. After the riveting the side panels were ready to be installed and brass screws were used when fixing the piano hinges onto the vertical wooden front edge of the engine mounting.


The side panels were now fixed to the mounting by their front edge and when they were closed against the mounting, all of the Fokker-pin bayonets didn’t fit into the holes on the rear edge of the panel.


It could also be seen that the lower edges of the panels were slightly bulging. The panels had obviously been slightly bent when riveting the piano hinge. Therefore two additional locking bayonets had to be installed on the supporting wood on the lower edge and the corresponding additional bayonet holes had to be made on the panels. After this addition the side panels fitted tightly in their place against the engine mounting.


The work on the missing side panels was now completed.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, I.V.L. K.1 Kurki

Museum plane surfaces were cleaned in Finnish Aviation Museum

Lauantai 14.10.2017 - Member of Tuesday Club


A common problem in aviation museums is that the planes on display are covered with dust. The Finnish Aviation Museum makes no exception. The planes hanging from the ceiling as well as the ones on floor level were in need of cleaning. One of the reasons for this is that the museum doesn’t have the staff to keep the plane surfaces clean.


The Tuesday Club members of the Aviation Museum Society decided to lend a helping hand and arranged two events in the halls I and II in the Finnish Aviation Museum to clean the planes standing on floor level. The work had to be limited to what could be done without a man lift and without building any scaffolding.


The surfaces of the planes were vacuumed, wiped using a damp cloth and dried. The wiping cloths were rinsed in plain water. Cleaning chemicals were not used to avoid possible harmful effects. A half-tall A-ladder was needed to reach the surfaces that were higher up, such as the upper surfaces of fuselages and wings. Tall A-ladders could not be used for safety reasons.


The plane surfaces where partly covered with a thick layer of dust and the cleaning rags had to be frequently rinsed in water. The water in the bucket soon turned nearly black and had to be changed. Also the cleaning rags became quickly too dirty to use and had to be thrown away and replaced by clean ones. Judging by the amount of water and rags used, the majority of the dust and dirt was definitely wiped off and rinsed into the Vantaa city sewer system.


After the work of several hours nearly thirty planes had been cleaned and are now tidy and clean for the museum visitors to see. Unfortunately this doesn’t apply to all of the planes in the museum, including the Convair Metropolitan, the DC-3 or the Lockheed Lodestar – not to mention all the planes hanging from the ceiling of the museum halls. A man lift or large-scale scaffolding would be needed to clean the surfaces so high up in the display area. Using a man lift would be the most appropriate arrangement but the museum doesn’t have one.

Although man lifts are not cheap to purchase or to rent, we hope that the Aviation Museum could invest in one so that all the large planes and the hanging ones could be kept clean and tidy – as the old planes deserve. Or maybe a supporter of the Aviation Museum could donate a new or a second-hand man lift to the museum?

Kommentoi kirjoitusta. Avainsanat: aviation history, Tuesday Club, museum aircraft

Work on Kurki wing is well on way

Sunnuntai 1.10.2017 - Member of Tuesday Club


So far the main emphasis in the refurbishment of I.V.L.K.1 Kurki has been in repairing the fuselage and in building the missing wing struts. As this work is now nearly finished, the repair and conservation of the right side wing has been started. In early autumn the wing, which has up to now been waiting in the mid hall of the Finnish Aviation museum, was brought into the conservation room in the museum basement where the Tuesday club members started working on it. Some preliminary work had already been done in spring when some of the rotten wing covering was dismantled.


The main phase in the restoration of the wing is to renew the plywood board covering and the rotten parts in the inner structure of the wing and to patch the holes in the covering. The rotten covering plywood had to be dismantled between the backmost spar and the trailing edge, covering almost the whole length of the wing. Also in the mid-wing section dismantling was necessary from the trailing edge up to the foremost spar.


Rotted and damaged ribs and their plywood sides were revealed when the covering was peeled away. All the plywood sides of the ribs between the backmost spar and the trailing edge were badly damaged and needed to be replaced. The shape of the rib was drawn on a piece of new plywood and this piece was glued onto the side of the rib. The rib sides between the backmost and foremost spar, made lighter with holes, needed to be only partly renewed. In addition the frayed upper edges of the ribs were repaired with glue.


At the same time also the holes in the upper surface covering of the wing were patched either by using pieces of new plywood or by using intact pieces dismantled from the old covering.


When the plywood on the upper surface of the wing had been taken away, damaged and partly rotten plywood on the inside of the lower surface of the wing could be seen. Especially in the area between the backmost spar and the trailing edge the veneer of the plywood board had come apart. The top veneer was also cracked and frayed. The whole plywood board was soft and buckled. In unfavorable storage conditions humidity had taken its toll.


The first idea was to dismantle the damaged covering of the lower surface of the wing. However, the Tuesday club team decided to try and save the covering by using repairing conservation, which meant by trying to fix the plywood board with glue.


The team debated whether to use epoxy glue or to experiment with Casco Outdoor glue diluted with water. The fixing of the plywood was started in the area between the first two ribs of the trailing edge. The area was cleaned and the cracks in the topmost layer / veneer of the plywood were lifted by using the tip of a screwdriver, in order to make space for the glue under the top veneer. Then the diluted wood glue was spread on the plywood, making sure that it went also under the separated material layers.


When the glue had been applied, a layer of bakery paper was placed on top of the glued area in order to prevent the compression plate from sticking onto the glued plywood surface. A supporting plate and a layer of bakery paper were placed also on the other side of the plywood. The glued area was then pressed tightly between the plates by using several clamps.


After a couple of days the clamps were removed. The former soft and frayed plywood had adhered into hard and intact plywood surface. This method will be used to fix all the rotten and decayed covering plywood areas between the backmost spar and the trailing edge.


When the damaged plywood covers of the lower surface of the wing and the rotten ribs have been repaired, it is time to begin with the new covering on the upper surface where the old plywood has been dismantled.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, I.V.L. K.1 Kurki

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.


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.


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.


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.


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.


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.


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

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