Myrsky's wing root walkway

Lauantai 26.9.2020 - Tuesday Club member

At the wing root of VL Myrsky II, on both sides of the fuselage, on the wing’s plywood covering there is a strengthening strip of plywood. This makes it possible to walk on the wing when doing maintenance work. Very often these strengthened strips, which allow stepping on the wing, are clearly visible from the wing surface or painted black at least. However, this is not the case in the Myrsky, where these plywood strips have the same black and green paint scheme as the upper side of the wing.


Upper photo: The photo archive of the Finnish Air Force Museum.

On the Myrsky drawings these strengthening plywood strips are called “step plates”. They are fastened on the wing’s plywood covering with glue and screws. The aluminium wing root fairings, which protect the connection of the fuselage and the wing, are fastened onto the fuselage side edge of the step plates with flange nuts and screws.


The step plates for the Myrsky’s wings are being made at the Tuesday Club. The semi-finished plates were cut from 2 mm thick plywood according to the original drawing. The actual plywood covering of the wing is 4 mm thick at the wing root. The step plates for the port and starboard wing are mirror images. The position of the fastening screws and wing root fairing flange nuts were marked on one of the step plates, following the original drawing. The pencil marks were highlighted with a metal punch. The punch markings will make it easier to drill the holes into their exact positions.


After this the mirror image step plates were placed accurately on top of each other and fastened with pieces of double-sided tape. In this way the holes for the screws can be drilled simultaneously on both plates and exactly in the same position on the plates. The holes for the fastening screws were drilled with a 3 mm drill bit.



For the flange nuts on the wing root fairings, holes for the nuts had to be made on the edge of the step plate. These holes must match the shape and size of the flange nut and be slightly oval-shaped because the nut is sunk through the step plate, all the way to the level of the wing surface.


First three holes were drilled into the plywood with a 3 mm drill bit, these holes help when the oval hole is made into the step plate. The small holes were used when making the holes larger with a column-type drill, using drill bits of two different sizes. The work continued by shaping the holes into their correct size and shape with a chisel and a file.



The following phase will be to fit the step plates into their places on the top surface of the port and starboard wing and to fasten them with glue and screws. The step plate has already been preliminarily fitted to the root of the starboard wing.

Photos: Except separately otherwise mentioned, Lassi Karivalo.

Translation: Erja Reinikainen.

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

Myrsky MY-5's fuselage frame was taken to sandblasting and painting

Keskiviikko 16.9.2020 - Tuesday Club member

The earlier blogs describe how  the Myrsky MY-5’s rusted fuselage frame will be straightened, sandblasted and painted before it can be used for the wing test assembly of Myrsky MY-14.


The text in the box: Original paint under the bracket.

The MY-5 fuselage frame has been fastened on a sturdy metal frame, the assembly jig, outside the restoration space at the Finnish Aviation Museum. It has been straightened on the jig and the remaining parts and equipment have been dismantled. Most of these are different band-shaped fastening brackets. The fuselage frame was cut behind the cockpit, so that it became easier to handle and it can be brought into the museum’s restoration space for the test assembly of the MY-14 wing. Later the fuselage frame parts will be welded together so that it will be the whole Myrsky MY-5 fuselage frame.


The fastening brackets, which were still attached on the MY-5 fuselage frame, are important when the original paint and its tint are being investigated. When the brackets were unfastened, some well-preserved original paint of the fuselage frame was revealed. The painted surface has been protected from rusting, hidden under the brackets.


The original paint surface was cleaned by grinding it lightly, so that the tint of the paint became even more intensified. On both sides of the cleaned painted area a paint test was made, using two different shades of grey Isotrol paint (linseed oil alkyd paint). This was necessary so that the team could choose the appropriate tint of the undercoat paint for the fuselage frame. The tints of the tested grey paint were RAL 7005 ja RAL 7042.


On Tuesday, September 15th, the shortened MY-5 fuselage frame was loaded on a trailer, using a stacker. The frame will be taken to Auto- ja Teollisuusmaalaamo Oy, a paint workshop in Vantaa. The Tuesday Club team tried also to fit the rusted engine frame on the trailer, but it wasn’t possible. The engine frame will be transported to the paint workshop later.


At Auto- ja Teollisuusmaalaamo Oy the fuselage frame will be sandblasted and painted with undercoat paint. When the sandblasting has been done, the clean metal surfaces will be covered with clear varnish, which protects the frame from rusting. The grey Isotrol undercoat paint will be applied on top of the varnish. The MY-5 fuselage frame, with its undercoat paint, will return to the Finnish Aviation Museum in a couple of weeks.

Photos: Lassi Karivalo.

Translation: Erja Reinikainen.

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

City of Vantaa politicians visit Finnish Aviation Museum and learn about aircraft restoration

Maanantai 7.9.2020 - Tuesday Club member

City of Vantaa politicians visited the Finnish Aviation Museum for “practical training” as a part of the Politician’s museum internship campaign, coordinated by the Finnish Museums Association. The politicians who visited the museum were city council member Minna Räsänen (sdp), member of parliament, city council chairman Sari Multala (kok) and member of parliament, city council member Jussi Saramo (vas). Räsänen and Multala were present at the museum, Saramo attended via remote access.

As a part of the “practical training”, the cooperation of the museum and Aviation Museum Society was introduced to the guests. The Tuesday Club volunteers’ work was illustrated in the museum’s restoration space, although the Tuesday Club has officially been terminated because of the corona virus pandemic.


From left to right: Pia Illikainen, Minna Räsänen ja Matti Patteri.

In the restoration space museum Intendent Matias Laitinen told the guests about the volunteers’ role at the Aviation Museum. Tuesday Club project manager Lassi Karivalo introduced the aircraft restoration activities of the Tuesday Club. The leader of the VL Myrsky II (MY-14) restoration project Matti Patteri introduced the history of domestic aircraft industry and explained how museum aircraft, and more specifically the Myrsky, are restored in practice. The Myrsky project was launched in 2013 and up to now the restoration team has spent about 30 000 working hours. Most of the work has been done by volunteers. The Myrsky restoration also includes cooperation with vocational colleges, e.g. Vantaa Vocational College Varia and Tavastia Vocational College in Hämeenlinna, and naturally work contribution from the Aviation Museum staff. The visitors learned that the main motivating factors for the volunteers’ participation are the sense of community, the good team spirit and the interesting work items.


From left to right: Sari Multala and Matti Patteri.

Due to the corona virus pandemic situation, the museum’s volunteer activity has been terminated since March. In the future the working procedures will have to be reorganized. A large volunteers’ gathering can’t be organized yet, and not for some time – and in the social aspect this is very unfortunate. During the corona virus time the Aviation Museum Society has arranged for its members, and to all who are interested, remote access to presentations about aviation history. The museum has produced videos and audio tours with its partners. However, by now everybody is very eager to get back to work and to meet the volunteer friends at the museum. The aim is to relaunch the Tuesday Club activities in October, at some extent. The corona virus situation in Finland will define whether this is possible or not.

Photos: Mia Kunnaskari.

Translation: Erja Reinikainen.

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

Undercoat painting of MY-14?s horizontal stabilizer

Perjantai 28.8.2020 - Tuesday Club member

Before the painting work, the port and starboard halves of the VL Myrsky II’s (MY-14) horizontal stabilizer were fastened on an assembly jig, made of square steel tube. On the jig the stabilizer can be turned around as needed in the various phases of the surface treatment process.


The seams of the plywood covering on the horizontal stabilizer had been spackled and ground smooth before starting the undercoat painting work. The plywood surfaces were washed, using a water-Sinol-solution, containing 50% of water and 50% of Sinol. This is a normal procedure for removing grease from the surfaces before painting. After the wash, the surfaces were dried with a heat blower and sanded three times, with 240 abrasive paper.


Photo: Jouni Ripatti.

The MY-14’s horizontal stabilizer will be painted in several phases. First an undercoat paint is spread on the plywood surface, and the actual paint is applied after this. There will be several layers of both paints. The undercoat paint and the actual surface paint are both alkyd paints, as were the original paints when the Myrsky fighters were being built in the 1940’s at the State Aircraft Factory (VL) in Tampere.


Right photo: Jouni Ripatti.

The undercoat paint, which is used for the plywood surfaces of the MY-14 under restoration, is TEMALAC AB 70 alkyd paint which contains aluminium flakes. The shade of the paint is RAL 90006, white aluminium. The aluminium flakes will fill the grain structure on the plywood surface, which will make the plywood surface smooth and sealed when it is ground and honed.


Photo: Heikki Kaakinen.

Now the upper and lower surfaces of the horizontal stabilizer have been painted once with the undercoat paint containing aluminium flakes. For the first layer the paint was made thinner, using Ruiskuohenne 1032, and the paintwork was done with a polyester roller (mini paint roller). The roller produced a very even layer. When the paint had dried, the surfaces were ground smooth for the second layer. The next undercoat paint layer will be done using paint, which is not thinned, and which is slightly darker in colour than the first layer. The darker shade will show clearly which areas have been painted for the second time and which haven’t. If a third layer of undercoat paint is needed, it will be darker than the second one.


An unexpected break in the painting work appeared, when the darker shade of TEMALAC AB 70 undercoat paint wasn’t available due to holidays. The Tuesday Club team will have to wait for the mixing and delivery of the darker paint before continuing the undercoat painting work on the horizontal stabilizer.


The MY-14’s horizontal stabilizer will eventually be painted according to the standard paint scheme of the Finnish Air Force in the 1940s: the upper surface will have a green and black pattern and the lower surface will be painted light blue.

Photos (expect otherwise separately mentioned): Lassi Karivalo

Translation: Erja Reinikainen

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

About Myrsky MY-14 oil cooler, wing root fairings, landing gear doors and MY-5 fuselage frame

Maanantai 24.8.2020 - Tuesday Club member

When the VL Myrsky II (MY-14) port wing half covering was being finished in the restoration space of the Finnish Aviation Museum, also other Myrsky-project items were under work.


Before the Corona virus pandemic interrupted the work, the Tuesday Club team had completed most of the engine’s oil cooler supply and exhaust air duct parts. They have been made from 1 mm thick aluminium plate. Now it was time to start building, according to the original drawing, the airflow control device into the supply air duct. The control device consists of a circular frame, inside which there are three flaps, which move on their axles. The air flow into the oil cooler can be controlled continuously with these flaps. The air flow control is done from the cockpit.


The parts needed for the air flow control device were cut from 1 mm thick aluminium plate, using a laser cutter, at ProLaser Oy. Holes for the rivets, which are needed in the assembly work, were drilled on the semi-finished control flaps. The parts of the air flow control device were also chromated to prevent corrosion.


The assembly work of the oil cooler control device was started at the circular frame. When the round frame had reached its final shape, the ends of the axles of the three control flaps were riveted on the frame. There is a slot on the end of the axle, into which the edge of the aluminium flap fits. The three flap plates fitted perfectly on the axle slots. The following phase will be to rivet an aluminium profile on the flaps, which locks the flaps on the axles.



Some metal work has been needed when making the aluminium fairings, which cover the connecting point of the Myrsky’s fuselage and wing. The work was started on the fairing which covers the wing’s leading edge and the fuselage. The complicated fairing shape consists of three pieces of aluminium plate, which are welded together. The preliminary fairing parts were cut from 1 mm thick aluminium plate. A wooden last was made for shaping the aluminium sheets into the desired shape. Two lasts are needed, one for the starboard wing and the other for the port wing. The preliminary fairing parts were shaped into their final shape at Flanco Oy, using the last. The shaped fairing parts were welded together at GA Telesis Engine Services Oy.



The work on the landing gear enclosure doors of the test wing has also continued, including the door fastened on the wheel hub and the oleo strut door. The doors had been nearly finished already in March. The remaining aluminium profile stiffeners were riveted on the inner surface of the doors. The doors were now ready to be installed. The bulging parts or the “bumps” on the outside of the oleo strut door have also been welded into place. These bumps are needed for the landing gear retraction fork which is fastened on the oleo. These bumps have also been welded on the preliminary oleo door plates of the actual Myrsky wing’s landing gear. However, the actual wing doors have not been chromated yet and their stiffeners have not been fastened.


The Myrsky MY-5 fuselage frame, which was brought from Tikkakoski, has also been under work. The parts, which were still fastened to the frame, have been unfastened and now the frame is “clean” for sandblasting. The fuselage frame will be sandblasted at Auto- ja Teollisuusmaalaamo Oy, where it will also be painted grey.


A pile of different kinds of brackets and parts was dismantled from the MY-5 fuselage frame. Some of the parts had to be unfastened with some violence, using an angle grinder for the work, because the badly rusted fastening bolts couldn’t be opened. The rust will be removed, and the parts will be painted. All the parts will be needed when the MY-5 fuselage frame is restored to be the exhibition fuselage, which illustrates the structure of the Myrsky fighter. The 2,5-meter test wing, built during the Myrsky project for testing the wing construction procedure, will eventually be fastened to the MY-5 fuselage.

Before that, the MY-5 fuselage frame will be used for test assembling and fitting the Myrsky MY-14 wings. In the fitting phase the MY-5 fuselage frame will be lowered on the MY-14 wing, built by the Tuesday Club team. The wing will be locked onto the fuselage with the four wing attachment brackets or bolsters. The wing parts will be fastened with steel plates and the whole wing can be test fitted in about a month’s time.

Photos: Lassi Karivalo.

Translation: Erja Reinikainen.

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

MY-14´s port wing half is covered with plywood

Sunnuntai 9.8.2020 - Tuesday Club member

The work on VL Myrsky II (MY-14) is continuing at the Tuesday Club, but not at full speed yet, though. Work is being done e.g. on the plywood covering of the starboard wing leading edge and trailing edge, and the sides of the flap cavity. The engine area is also under construction: the air supply duct is being fitted into the opening in the NACA-ring, the cowling under the engine is being built and the gills controlling the air flow through the air duct on the oil cooler are being installed. However, the main emphasis is in getting the port wing plywood covering to the same situation with the starboard wing. The work is almost ready.


The leading edge of the port wing is now almost covered with plywood. The strips of plywood covering the leading edge were first soaked in water so that they could be bent around the tapering leading edge. When the plywood had dried into shape, it was glued on the leading edge. The seams of the plywood were spackled and honed smooth. Only small areas around the pitot-tube and at the wing tips have not been covered.



Right photo: Heikki Kaakinen.

The trailing edge area on the upper surface of the wing, between the rear spar and the trailing edge, has also been covered with plywood. First the plywood sheets of the trailing edge area were cut into the accurate size, then covered with protective varnish on the inside and then fitted into place. When the plywood sheets had settled into their places and their bevelled edges met correctly, the sheets were glued into place. Before the inner parts of the wing were permanently covered from sight, the Tuesday Club members who were involved in the work, wrote their names on the inside of the wing as a greeting for the future generations.


Left photo: Heikki Kaakinen.


The gluing of the plywood sheets on the upper surface of the trailing edge was secured by fastening pieces of plywood on the wing ribs and the connecting battens with a staple gun. The permanent gluing of the plywood on the trailing edge batten was ensured by fastening a long row of clamps on the edge. When the glue had dried, the clamps and the stapled pieces of plywood were removed. The marks of the staples that were left on the plywood surface and the seams of the plywood sheets were spackled and honed smooth.


It was a difficult task to fasten a 10-centimeter strip of plywood onto the upper edge of the flap cavity on the port wing. A similar, but narrower strip, has already been fastened on the lower edge of the flap cavity. These strips will form an aerodynamic compartment to the front of the flap space. The leading edge of the flap will sink into this space.


Photos: Heikki Kaakinen.



The port wing covering work had now reached the phase where the starboard wing already was. The surface work, i.e. smoothing and honing which are needed before the painting of the plywood surfaces, can now be started. Some painting has already been done: the open inner areas on the top surfaces of the wing roots on both wings have been painted with grey alkyd paint. These open areas at the wing root will not be covered with plywood, because the areas will be left under the Myrsky fuselage when it is lowered on the wings.

Photos (expect if separately otherwise mentioned): Lassi Karivalo

Translation: Erja Reinikainen

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

About the fuselage frame of VL Myrsky MY-5

Tiistai 4.8.2020 - Tuesday Club member

When the restoration project of VL Myrsky was launched, three damaged Myrsky fuselage frames were available at the Finnish Air Force Museum in Tikkakoski. The rear section has been violently cut away from all three fuselage frames. The least damaged fuselage frame of MY-14 was chosen for the restoration project. This is how the project became the restoration project of the VL Myrsky MY-14 fighter. The MY-14 fuselage rear section, which has been cut off, has disappeared and therefore the rear section of MY-9 was chosen to be connected to the MY-14 fuselage frame. Also a fourth Myrsky fuselage frame (MY-10) exists, in a private collection, and there have been negotiations about purchasing it for the Myrsky project.


The MY-14 fuselage with its engine and control equipment is mainly restored at the Finnish Air Force Museum in Tikkakoski. The main task of the Aviation Museum Society’s Tuesday Club is to build in Vantaa in co-operation with the Finnish Aviation Museum the other parts of the fighter, such as the wings with all their equipment, the parts of the tail and to build the parts for the nose, e.g. the front engine cowling, NACA-ring and the engine cowlings on the sides.


Photo: Jorma Laakkonen.

The restoration project started in 2013 and the development of the project has been followed all the time on homepages of the Aviation Museum Society and Myrsky Project, and also in yearly journals. In Tikkakoski the restoration of MY-14 fuselage is already quite far. In Vantaa the Tuesday Club has prepared the tail parts and the wings to the point where their surfaces can be honed smooth and painted. The aim is that the restored – but static – MY-14 can be placed on display during the year 2021.


The second best Myrsky fuselage from Tikkakoski, i.e. MY-5, was also taken into the restoration project with its separate rear fuselage and engine mounting. The MY-5 fuselage frame has its own important role in the Myrsky restoration project. Some useful parts have been dismantled from the fuselage frame and repaired in Tikkakoski for the needs of the MY-14 fuselage frame restoration. On the other hand, the fuselage frame of the MY-5 will be used by the Tuesday Club for the fitting of Myrsky’s wings. The wing positioning and fastening will be tested on the fuselage frame by the Tuesday Club before the wings are sent to Tikkakoski to be installed on the fuselage of MY-14.


Additionally, an even bigger role has been planned for the MY-5 fuselage frame. It will be used to build a demo-fuselage of the Myrsky-fighter to illustrate the metal and wood structure of the aircraft. The 2.5-meter piece of the starboard test wing and the 1-meter piece of the port test wing will be fastened on the fuselage frame. Before building the actual wings, the test wings have been built to test the methods how to build the complicated root of the wing with the landing gear and how to lock the wing halves to each other with steel plates.


The rear fuselage of MY-5, brought from Tikkakoski to Vantaa to the Finnish Aviation Museum, has already been used in the Myrsky-project. The badly rusted rear fuselage frame was straightened in a jig, specially made for the purpose, and sandblasted and painted, using grey alkyd paint. After this the rear fuselage has been used by the Tuesday Club to fit and support the horizontal and vertical stabilizers when they are being built.


The fuselage frame and engine mounting of MY-5 were brought from Tikkakoski to the Finnish Aviation Museum in Vantaa on July 21st, 2020. The MY-5 fuselage was transported by the Myrsky-project’s PR-man, on his holiday trip to Ostrobothnia. On Friday 10.7 on his way there he took the trailer and “some Myrsky items” to Tikkakoski. On Tuesday 14.7 a group of Tuesday Club members travelled to Tikkakoski and moved, with some assistance from the Air Force Museum, the MY-5 fuselage frame and engine mounting on the trailer to wait for the transportation. The unusual load travelled successfully to the Finnish Aviation Museum on 21.7. Fortunately, the traffic was rather quiet and it wasn’t raining.



When the fuselage frame was outside the museum, the cargo straps were unfastened. Then the MY-5 fuselage was lifted from the trailer with a forklift and placed on the ground to wait for cleaning and repair. The badly rusted and partly bent and damaged fuselage frame will be straightened and cleaned by sandblasting, straightened and repaired, and then painted grey. Behind the cockpit some frame pipes have been bent and some are even missing.



Left photo: Heikki Kaakinen.

The assembly jig, which was made from square steel pipe for the straightening of MY-14’s fuselage frame, was re-assembled and modified for the MY-5 work. The jig was fastened on the four brackets by the cockpit on the MY-5 fuselage. These brackets are used for fastening the wings with four fastening bolsters on the wings.


Photo: Heikki Kaakinen.


The MY-5 fuselage frame, now fastened on the assembly jig, will be measured carefully and straightened. The places of some parts or their fastening brackets will be defined and photographed before they are dismantled for cleaning. Also the rusty engine mounting, brought from Tikkakoski, will be cleaned by sandblasting and painted.


When the fuselage frame has been cleaned and painted, the rear fuselage frame (which has already been restored earlier) will be welded to it. Then the MY-5 fuselage frame will be ready to serve as the fitting frame or assembly jig for the MY-14 wings, and later as the basis of the Myrsky demo fuselage. The MY-5 demo fuselage will be restored so that the structures remain visible in the way they were left visible when building the short test wings. The restoration of this demo fuselage is not the main priority at the moment, the work will be started when the restoration of the MY-14 has been completed.

Photos (except if separately otherwise mentioned): Lassi Karivalo

Translation: Erja Reinikainen.

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

Stiffeners are fastened on Myrsky?s wheel and oleo compartment doors

Tiistai 14.4.2020 - Member of Tuesday Club


The VL Myrsky (MY-14) is being restored and its parts around the wheel well, including the outer door of the wheel well, the door of the oleo compartment and the door stiffeners were sent to be chromated. When they came back from the chromating process, it was time to fasten the stiffeners on the doors. Chromate bathing means that the aluminum plate is treated with acid solutions containing chromates and a thin inorganic film is formed on the surface of the aluminum with the components of the surfacing bath liquid. This surfacing protects the aluminum plate from oxidization. In the chromate process the Myrsky’s landing gear doors and their parts got a beautiful golden hue on the surface.


First the stiffening battens were fastened on the landing gear oleo compartment door. The battens have top hat profile. This means that the square batten is open at the bottom and it has sleeves bent to the sides. The sleeves have holes for riveting the stiffening batten on the edges of the door.



The holes for the rivets had already been drilled earlier on the oleo compartment door and on the stiffening battens. The rivet holes on the edges of the door had also been beveled for flat head rivets. The stiffening battens were riveted on the lower side of the door. The work was started by fastening the battens into place with a couple of pins which were pushed through the rivet holes. Before riveting the battens the oleo compartment door was assembled into place and the team made sure that it fitted properly in its place also with the stiffening battens.


Then the battens were riveted on to the inner side of the door, rivet by rivet, using the riveting gun. The riveting gun is faster and more practical than using a hammer for the riveting work. When all the stiffening battens had been fastened on the oleo compartment door, the work on the stiffeners for the door on the wheel hub was started.


The oval stiffening plate on the outside of the outer door of the wheel well was fastened on the wheel hub with four machine screws. Then the places for the rivet holes were marked on the edges of the stiffening plate. The oval plate is fastened on the door with rivets. A prick was used for marking the location of the holes. A temporary screw was fastened to both ends of the oval plate so that the stiffening plate could be pressed tightly on the slightly convex door. The screws keep the stiffening plate in its place on the door while the rivet holes are being drilled.



The holes were drilled using a vertical drill and beveled with a beveling drill bit. Then the stiffening plate was riveted on the door, from the inside of the door, using a riveting gun.



Then the box shaped stiffeners were preliminarily placed on the inner side of the outer wheel well door. There are stiffeners on both sides of the door and one at the bottom edge. The stiffeners are riveted by their outer edge on the supporting frame around the inner edge of the door, made of square steel tube, and by their hems on  the door. The supporting frame of steel tube was not chromated but painted with grey Isotrol paint to prevent it from rust.



The riveting of the box-shaped stiffeners was not started before the Tuesday Club activities were terminated due to the Corona virus pandemic. The stiffeners were riveted on the oleo door but the stiffeners on the outer door of the wheel well are still under work. The landing gear of the test wing will have to wait until the work continues after the virus epidemic is over.

Photos: Lassi Karivalo

Translation: Erja Reinikainen

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

Wheel well and oleo doors for Myrsky are made

Tiistai 7.4.2020 - Member of Tuesday Club


Retractable landing gear was common already in WW2 fighters and VL Myrsky is not an exception. At the root of Myrsky’s wing there is an enclosure for pulling in the landing gear. The enclosure consists of a wheel well for the wheel and a compartment for the oleo (the shock strut of the landing gear). One half of the wheel well opening is covered by the inner door, made of aluminum plates, also called “daisy cutters”. The door is fastened on the inner edge of the wheel well with hinges. This door is opened automatically by a spring lever when the landing gear is taken out and it is closed by the wheel when the landing gear is taken in.


The other half of the wheel well is covered by the outer door, which is made of aluminum plate and fastened on the wheel hub, it is a pair for the “daisy cutter”. The oleo enclosure door is made of aluminum plate as well and it is fastened angel on the oleo. These two doors on the landing gear are overlapping at a distance of about 20 cm and they slide against each other when the landing gear oleo is flexing. The wheel is fastened by its axle on the “piston rod” which moves inside the oleo. The landing gear can’t have one solid door fastened on the wheel and oleo because this would disturb the vertical flexing movement of the wheel.

The Tuesday Club team made first the inner doors for MY-14 wheel wells on the test wing and the actual wings. Then the construction of the outer doors and the oleo doors was started. The team decided to make the doors for the test wing first.


A laser cutter was used when cutting the semi-finished shape of the oleo door from 1.5 mm aluminum plate according to Myrsky’s original drawing. At the same time a hole was cut into the plate where the retraction mechanism fork connects to the oleo. Holes were drilled along the edges of the door where stiffening battens will be riveted.




A small canopy is needed to cover the hole where the retraction mechanism fork connects to the oleo. A metal mould was made first and the canopy was pressed against it from aluminum plate. The canopies were made for the test wing and for the actual wings. The canopy was welded onto the edges of the hole on the door. After this the pre-cut door was fitted into place into the oleo opening and fastened on the temporary plywood brackets on the oleo. Eventually the door will be riveted on the brackets which are welded onto the oleo.




The semi-finished shape of the outer wheel well door was also cut from 1.5 mm aluminum plate with a laser cutter. The door is fastened on the wheel hub with four 6 mm flat head machine screws. The holes on the door for the screws have to be exactly in the right position to meet the threaded holes on the wheel hub. The positioning was done by placing a positioning plate with sharp-pointed markers on the wheel hub. A marker was also placed in the middle of the hub. Then the door was positioned carefully into the wheel well and the plate surface was tapped against the marker points. Now there were clear marks on the lower side of the plate for drilling the holes for the screws. The marker marks were strengthened with a spike before making the holes with a vertical drilling machine.




The door fastened on the wheel hub has an oval-shaped stiffening plate on the outside. It was cut from aluminum plate. The stiffening plate is fastened on the door with the four machine screws which fasten the door on the wheel hub. Holes were made on the oval stiffening plate and the edges were beveled. The stiffening plate will also be riveted on the door by its edges. The outer wheel well door was fastened on the wheel hub with the oval stiffening plate attached. Now the test wing landing gear had both doors in place for the first time. They are well visible when the landing gear of the test wing is taken out.


There will be stiffeners and supporting battens on the inner surface of the outer door in the wheel well. A supporting frame made of rectangular steel tube will be fastened on the edge of the door. The lower part of the door will have box construction strengtheners made of aluminum plate.


Pre-cut strengtheners for the inner surface of the wheel well door were cut from aluminum plate with the laser. They were modified to be fitted and fastened into place. Also the stiffeners for the oleo door are now ready.

The stiffeners will not be riveted on the doors before the half ready doors and the stiffeners have been chromated. The chromate treatment will prevent the aluminum plate from oxidizing and it will be done by an outside supplier.

Photos: Lassi Karivalo

Translation: Erja Reinikainen

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

Ribbons of Caudron's horizontal stabilizer frame

Maanantai 30.3.2020 - Member of Tuesday Club


The horizontal stabilizer frame of Caudron C.59 (CA-50) had bent during the years and it had to be dismantled and straightened. The restoration work was finished in early February – as described in an earlier blog – and the frame was now ready for covering. Before the actual covering with fabric, ribbons or strips of fabric were fastened on the ribs of the stabilizer and its leading edge. The fabric covering will be fastened by sewing on these ribbons.


Before starting to install the ribbons on the horizontal stabilizer, the Tuesday Club team studied carefully the pictures taken of the dismantling phase, the dismantling report and the pieces of fabric covering, which still had some original ribbons attached. Based on these sources the team could see clearly how the stabilizer frame of the CA-50 had been covered and how the ribbons under the covering had been fastened.



The leading edge of the horizontal stabilizer had been tightly covered with a 50 mm wide strip of fabric. The trailing edge and the end battens on the stabilizer didn’t have any ribbons around them. The ribs had 15 mm wide ribbons around them: first a ribbon had been tied along the upper and lower edge of each rib and then it had been tied on the rib, using another 15 mm wide ribbon which was spun around the rib. The leading end of the ribbon used for spinning had been fastened on the leading edge with tacks and the far end fastened on the rib root. 


The stabilizer ribs had also been connected to each other at the middle, using a 30 mm wide ribbon with its ends fastened on the end battens of the stabilizer. The ribbon connecting the ribs had been woven through the ribs so that it ran under every other rib and over every other. The ribbon ran weaving over and under the ribs between the end battens.



The Tuesday Club team started the ribbon work on the restored horizontal stabilizer frame on the plywood ribs. The leading end of the ribbon was fastened on the leading edge with two tack nails, on the rib position. Then the ribbon was pulled along the upper edge of the rib as far as the trailing edge, around it and along the lower edge of the rib back to the leading edge. There the end of the ribbon was fastened on the starting point with another tack. The same procedure with the ribbon was followed when working all eight plywood ribs.



The following phase was to fasten the ribbons on the ribs into place by spinning another ribbon around each rib. Based on the pictures taken of the cover dismantling, the leading edge of the spinning ribbon was nailed with two tacks on the lower side of the trailing edge batten, where it met the ribbon running along the rib. Then the ribbon was tied diagonally around the rib, with 3 cm wide spaces between each round. At the other end of the rib the ribbon was fastened on the strengthening piece of plywood at the root of the rib. When the eight normal ribs on the stabilizer had been spun, the same principle was used when spinning the three solid wood ribs, which support the stabilizer structure.




When the ribs had been spun with ribbon, the 30 mm wide strip of fabric connecting the ribs was fastened. The leading end of the wide ribbon was fastened with four tack nails onto the inner side of the port end batten, following the original installation. Then the ribbon was spun a couple of times around the end batten before weaving it over and under every other rib until the starboard end batten. Also the location of the ribbon was checked so that it ran halfway along the ribs. The ribbon was locked into place with a tack on the starboard end batten. Then the ribbon was woven in a similar manner back to the port end batten and fastened on it with three tack nails. Finally the ribbon was nailed onto each rib’s upper and lower batten.


The ribbons on the horizontal stablilizer’s leading edge of the Caudron C.59 were not installed before the Tuesday Club’s activities were interrupted due to the corona virus pandemic.

Photos: Lassi Karivalo

Translation: Erja Reinikainen

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Caudron C.59, CA-50

Other than restoration activities in Tuesday Club

Maanantai 23.3.2020 - Member of Tuesday Club


The Tuesday Club of the Finnish Aviation Museum Society is mainly connected to restoring and repairing old aircraft and placing them on display in the aviation museums. Mainly this is naturally true, but the Tuesday Club is involved in various other activities which support the functions of the Aviation Museum or the Aviation Museum Society. This blog introduces some examples of these activities.

Legs for large display monitors

The Aviation Museum Society purchased six large display monitors, second-hand but functioning, to be used in different in public events connected to aviation. The bargain didn’t include legs which are needed when the display is standing on a table. Therefore the Tuesday Club team was given the task to make two legs for each display.


The team decided to make T-shaped legs from metal tube. The legs could be installed into the holes in the lower edge of the display and unfastened after use. The team acquired rectangular metal tube with suitable dimensions and cut it into pieces which will be welded together to form the T-shaped leg. For each display two tube pieces were needed for the horizontal legs and two pieces for the vertical supports. A total of two dozen tube pieces were cut for the six displays.


The 12 T-shaped legs were welded in the welding space outside the Finnish Aviation Museum. The welded seams and the ends of the tubes were ground smooth and then painted black. Finally the square tube ends of the legs were plugged using black plastic plugs. Now all six displays had their legs ready and they can be used in the different aviation events.

Extending the guard railing of the stairs

Visitor safety is important for the Finnish Aviation Museum. When inspecting the safety issues, a shortcoming was noticed on the stairs leading to the balcony of the I Hall. The guard railing of the stairs was shorter than the staircase. This may be dangerous for the visitor when the railing suddenly ends and there are still more stairs to walk. The museum decided to build extensions to the railings.


For the  new railings the Tuesday Club team acquired stainless steel tube, which is strong enough and has a glossy polished surface which doesn’t need additional polishing. The tube will be connected to the existing railing tube using a lapped joint.


The lapped joint is made by cutting away the lower part of the tube at a length of about 30 cm. The open curved end of the railing tube can be pressed tightly on the original handrail and fastened with brackets on the vertical balustrade. The joint of the stainless steel tube on the original handrail will be made first on one railing to test how it works. When the joint has reached the desired form and appearance, the other three railing extensions can be made according to the model and using serial production process. The first joint is already in the testing phase.


The extended handrails will naturally need their own vertical balustrades. The balustrades will be made from ordinary steel tube which was cut into four pieces. Fastening plates were welded onto the lower end of each balustrade tube. Fastening brackets for the handrail will be welded to the upper ends of the tubes.


Now the guard railing extension project is at the phase where the joint of the extended handrail and the existing handrail is finalized and the balustrade tubes are made. However, the corona virus pandemic interrupted the Tuesday Club activities at the Aviation Museum and the work will be continued when the pandemic is over.

Paint tests

The Tuesday Club is working on the restoration of the VL Myrsky II (MY-14) fighter and the Caudron C.59 advanced trainer plane and the rotor blades of the SM-1 helicopter (HK-1) are being repaired. Each project is now reaching the painting phase. The exact paint type and colour originally used on the Caudron and the helicopter rotor blades are not known. Also the fabric-covered parts of the Myrsky will require paint tests. The test is not only about paints but also different kinds of cotton and linen fabrics will be tested how they fit the needs. The Tuesday Club team decided to make a dozen wooden frames, covered with fabric, for testing the paints and different kinds of fabrics and for choosing their combination.


Suitable batten material was found in the wood storage of the restoration space and it was cut to measure. The battens were connected to form frames of 50x50 cm. The frames were covered with four different kinds of cotton fabric and a linen fabric. On some frames the fabric was properly sewn, as it would be when covering an airplane with fabric. On other frames the fabric was fastened using a stapler.


When the frames were ready, the fabric was tightened using nitrocellulose varnish. The fabric has to be tightened before the paint tests. The fabric has to be covered with the shrinking dope several times before it is tight enough. The shrinking procedure is started with thinned varnish (50% varnish, 50% thinner) and finished with plain varnish.


The shrinking process was left unfinished when the corona virus pandemic interrupted the Tuesday Club activities. Hopefully the pandemic is soon over and the team can return to their normal routines.

Photos: Lassi Karivalo, translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Tuesday Club

Metal trestles for Junkers 50A Junior and repairing of Junnu's model

Keskiviikko 18.3.2020 - Member of Tuesday Club


The Junkers 50A Junior was on display at the Helsinki-Vantaa airport for many years, but it was returned to the Finnish Aviation Museum about a year ago because of the refurbishment works in the airport terminal. This aircraft is the famous OH-ABB, registered on 6.3.1931 by Väinö Bremer, who flew several long distance flights on this plane. In 1932 one of his flights reached from Finland all the way to Cape Town in South Africa and back.


So far Bremer’s Junkers has been in storage at the Finnish Aviation Museum and hidden from the public. Now the “Junnu” has been placed on display in the II Hall of the museum. At the moment the museum is closed because of the corona virus epidemic, but the plane can be admired later. The plane was moved and assembled by the museum’s hot air balloon volunteers together with the museum staff.


The Junkers is standing in the II Hall on its landing gear wheels with its full weight, so the Tuesday Club team decided to make metal supports under the landing gear wheel axles. This is a normal procedure for aircraft which are on display in aviation museums. When the metal trestles bear the weight of the plane, the tires won’t be damaged when the plane stands on display for many years.


The Tuesday Club team was surprised to find half-finished metal trestles in the corner of the restoration space in the Finnish Aviation Museum. These trestles could be modified to fit the Junkers 50A Junior. The trestles were covered with rust and the surfaces needed to be cleaned. The tube-shaped adjusting spars inside the trestles had to be modified to fit the new purpose. The trestles were sprayed with black varnish paint.



The team took the modified metal trestles to the II Hall in the Finnish Aviation Museum and managed to lift the Junkers so that the trestles could be installed under the wheel supports on both sides.


The Tuesday Club team had also another task concerning Junkers Junior. A model of the Junkers OH-ABB has been on display in the II Hall of the Finnish Aviation Museum. Its skin is made of corrugated cardboard to imitate the real corrugated metal sheet covering of the Junkers. The scale of the model was actually defined by the size of the “waves” of the corrugated cardboard.



The engine of the model had been damaged during the years and it had come loose and also the cylinders and some parts had broken. The Tuesday Club team repaired the engine and fastened it back into place.


The model was taken back into II Hall and placed beside the real Junkers 50A Junior (OH-ABB). Now the model and real aircraft are side by side, on display, with a pilot sitting in the cockpit.

Photos: Lassi Karivalo

Translation: Erja Reinikainen

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Tuesday Club, Junkers 50A Junior, OH-ABB

Horizontal stabilizer's frame of Caudron is repaired

Keskiviikko 4.3.2020 - Member of Tuesday Club


The restoration work on Caudron C.59 advanced trainer’s wooden horizontal stabilizer frame has involved a lot of work and after about six months it is finally ready. The starting point in the restoration work was that the stabilizer’s covering was rotten and broken and had to be replaced. It turned out that the whole frame of the stabilizer was bent and its ribs were rotten. The Tuesday Club team decided to dismantle the whole structure and rebuild most of the ribs, and straighten the bent battens on the leading and trailing edge.




The restoration work on the various parts of the horizontal stabilizer was completed in the beginning of this year. The ribs have been repaired, the bracing wires have been cleaned and painted and the battens on the leading and trailing edge have been straightened. On one rib the half-rotten plywood waist could be fixed with glue, but on the rest of the ribs the plywood waist had to be replaced. Before assembling the horizontal stabilizer the holes, which make the rib lighter, were made even larger to match the size on the original rib holes. This work was done using a vertical rotary tiller.



The assembly work was started by fitting the repaired plywood ribs preliminarily into their places between the leading and trailing edge battens. Some adjustment was needed on the ends of the upper and lower battens on the ribs before they fitted tightly into their places. After the fitting, the fastening of the ribs was started, beginning on the leading edge.



The ends of the upper and lower battens on each rib were pushed into the fishtail joint notches on the leading edge. Then the rib batten ends were fastened on the leading edge batten, using 3x16 mm countersunk brass screws. First a preliminary hole was made, using a thin drill piece, to prevent the batten ends from splitting. In addition to the plywood ribs, also three solid wood ribs were fastened on the leading edge batten. The fasteners for the bracing wires were fastened between the wooden ribs and the leading edge batten. The bracing wires, still attached on the fasteners, were left loose.


The Tuesday Club team didn’t use any glue when fastening the ribs and assembling the horizontal stabilizer. When dismantling the Caudron’s horizontal stabilizer, the team found out that the stabilizer has been originally built in France at the Caudron factory without any glue.


When all the ribs had been fastened on the leading edge batten at one end, the work on the trailing edge could be started. The first step was to fasten the end of each rib into its notch in the trailing edge batten. Three cargo straps were tightened around the horizontal stabilizer to keep it in shape when fastening all nine plywood ribs and three wooden ribs into place.


When all ends of the upper and lower rib battens had been fastened on the trailing edge with fishtail joints, the battens were secured using brass screws. The solid wood ribs with the bracing wires were also fastened on the trailing edge. Now the crossing bracing wires could be slipped through the lightening holes on the plywood ribs. The last step in the assembly work was to fasten the end strips of the port and starboard end of the horizontal stabilizer onto the joints at the ends of the leading edge and trailing edge battens. Now the assembly work had been completed.


At this point the bracing wires of the horizontal stabilizer could be preliminarily tightened. The work was started by removing remaining old wire strips from the turnbuckles and cleaning the threads on the turnbuckles. Then the crossing wires were tightened using the turnbuckle. The final tightening of the bracing wires will be done before the stabilizer covering work is started.


The horizontal stabilizer had been assembled and the bracing wires preliminarily tightened, so the supporting cargo straps could be removed. When this had been done, the team noticed that the port rear corner of the stabilizer was a couple of millimetres above the table surface. When assembling the stabilizer frame, the team didn’t use any glue, so it was natural that the uncovered stabilizer will bend a little. The team managed to straighten the frame manually so that it rested evenly on the table surface.



After the assembly, the horizontal stabilizer frame was varnished using protective clear Le Tonkinois varnish. The varnish is a mixture of linseed oil varnish and China wood oil. The Tuesday Club team didn’t use varnish tinted red, as it would normally have done when varnishing a new wooden frame. Clear varnish was chosen because the team wanted to preserve some of the still remaining original red protecting varnish which had been applied on the horizontal stabilizer frame at the Caudron factory in the 1920s. Now the horizontal stabilizer is ready to be covered.

Photos: Lassi Karivalo

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Caudron C.59, CA-50

Fabric covering of Caudron's port wing is patched

Keskiviikko 19.2.2020 - Member of Tuesday Club


By the end of January all holes and tears on the Caudron C.59 (CA-50) aircraft’s lower port wing have been mended. The edges of each tear were first sewn together and then a patch for each hole was cut from cotton fabric. The edges of each patch were unravelled in the manner used in the 1920s. The frayed edges help the patch to fasten tightly on the repaired area when the fabric is varnished.


The patches on the upper side of the port wing were glued first. Nitrocellulose varnish was used for the gluing work. This kind of varnish is used also for tightening upholstery fabrics. It is necessary to wear effective protective masks during the varnishing work and there can’t be other ongoing activities in the restoration space of the Finnish Aviation Museum when varnishing is being done.



Before gluing the patches, each damaged area was surrounded with protective tape. The tape limits the work area and stops the gluing lacquer from seeping into the fabric covering outside the patching area. When all patch areas had been taped, a thing sheet of protecting plastic was spread on the wing. The plastic protects the fabric covering outside the work area when all the holes around the wing area are being varnished. A hole was cut in the plastic at each taped area. The edges of the protecting sheet were taped on the tape surrounding each work area. The wing was now well protected for the varnishing work.



Half a dozen Tuesday Club members started gluing the patches on the wing. X-Speed nitrocellulose varnish was used. The first phase was to varnish the patches soaking wet while they rested on a sheet of corrugated cardboard. Then the areas surrounded with tape were varnished. The patches were not immediately moved into their places. It took about five minutes before the lacquer became drier and gluey. After a short while the patches were moved and pressed onto their corresponding repair areas.  Another layer of lacquer was applied, and the brush was used to straighten the frayed edges of each patch.


When all the patches had been fastened, the protecting sheet of plastic and the tapes around the work areas were removed. The Tuesday Club team used the gentle blue type of painter’s tape around the work areas, but it was noticed that the tapes have to be removed immediately after the varnishing is ready. If the tape stays on the old fabric for more than an hour, the tape may stick too tightly on the original painted fabric and when the tape is unfastened, it will leave a mark or, in the worst case, the original painted surface will be damaged.



When the 34 patches on the upper surface of the port wing had been glued into place, the same procedures were done on the 32 patches on the lower side of the wing. Now the 66 holes on the lower port wing had been patched.




When the patches had dried, the surfaces were honed smooth and varnished again. The varnishing and honing was repeated four times. Now the patches are ready to be painted, using paint which matches the original paint on the wing. The painting will not be done before the work on the lower starboard wing has reached the same phase.

Photos: Lassi Karivalo.

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Caudron C.59, CA-50

Tuesday Club has started its 31th year with many activities

Maanantai 10.2.2020 - Member of Tuesday Club



In the beginning of the year it is appropriate to summarise the activities of the Tuesday Club in the previous year. In the summer the Tuesday Club team finalized the restoration of the I.V.L. K.1. Kurki aircraft, after three years of work. The Kurki was assembled and placed on display at the Päijänne-Tavastia Aviation Museum in Vesivehmaa. As the Kurki-project had come to an end, a new project could be started: Caudron C.59 (CA-59) will be restored for display. The restoration of the VL Myrsky II (MY-14) was started six years ago and the Tuesday Club team worked on it in 2019 as well. The fourth project in the Tuesday Club was to repair the two broken rotor blades of the SM-1 helicopter. Also some additional minor tasks were given to the Tuesday Club team and the year was rather loaded with work. Over 7 000 work hours were done during the year. The team has continued with the ongoing tasks in the beginning of this year.

Repairs of Caudron’s fabric-covered wings


The main tasks at the moment in the Caudron C.59 advanced trainer plane restoration project are the repairs of the holes and tears in the fabric covering on the lower wings. This is not a minor project, because there were 66 holes to mend on the lower port wing and about 50 on the starboard wing. It is very sad to see how badly the Caudron’s wings have been treated during the 90 years of storage.



The holes and tears on the lower port wing have already been repaired. The edges of the tears were connected with stitches and a fabric patch was glued on the sewn area. Nitrocellulose varnish was used for gluing the patches and it smoothed the repaired fabric when shrinking. Historical values have to be considered when the holes on Caudron’s wings are repaired. If the fabric covering of the wing had been damaged with over 50 holes when the aircraft was still in use, the whole wing would have been covered with new fabric. At the moment the Tuesday Club is working on the lower starboard wing. The fabric surfaces were cleaned and then the repairs of the holes could be started. In addition to the work on the wings, the repair of the horizontal stabilizer is going on. The horizontal stabilizer had to be dismantled to repair the damages and now it is being re-assembled.

SM-1 helicopter’s rotor blades were repaired


The repair work on the PZL SM-1SZ (HK-1) helicopter’s rotor blades was started a year ago. Now all the damaged areas have been repaired, i.e. covered with new fabric and treated with shrinking varnish. The damaged areas were located in the fabric-covered areas of the blades. Now the new fabric areas have been smoothed using nitrocellulose varnish and are waiting to be painted. When the original paint type and colours have been defined, the new fabric areas can be painted. The upper surface of the blade will be painted dark green and the lower side will be pale blue.


Myrsky’s restoration work continues for one more year

The aim is to complete the restoration of Myrsky MY-14 in March 2021 when the aircraft will be placed on display. The schedule is tight, but the restoration teams are working hard in the Tuesday Club and in the Finnish Air Force Museum in Tikkakoski.




In the Tuesday Club the main emphasis is on the restoration of the two wing halves. Both wings are under construction in the restoration space at the Finnish Aviation Museum. The leading edge of the starboard wing has been almost covered with new plywood and the trailing edge area on the upper surface will be covered soon. The starboard wing will soon be ready for the surface preparations, which are needed before painting. The work on the port wing is about one month behind the starboard wing. There is still some work needed on the port wing before the flap compartment on the trailing edge is ready, the flap is completed and the leading edge is covered with new plywood.



Photos: Lassi Karivalo

Translation: Erja Reinikainen.

The repairs of the Caudron’s fabric-covered wings

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Tuesday Club

Repairing tears in Caudron's (CA-50) fabric covering

Maanantai 30.12.2019 - Member of Tuesday Club



Caudron C.59. Photo: Wikipedia.

The Caudron C.59 (CA-59) airplane, which is under restoration at the Tuesday Club, has several holes and tears in its fabric covering. The damage has happened during the 90 years of storage. All damages in the fabric covering will be patched using fabric patches, following original procedures.


There are several methods to repair the tears on the fabric covering. A thin strip of plywood can be glued under the fabric to support the tear and the edges of the tear are glued on this supporting piece of wood. A covering fabric patch is placed on top. If the damage covers a large area on the fabric covering, the damaged material can be removed and replaced with new fabric. This method can be used e.g. between wing ribs. In this blog we concentrate on how the tears and holes on Caudron’s fabric were repaired by sewing and using fabric patches on top of the stitched area.


First the edges of the tear will have to be stitched against each other, or at least as close to each other as possible, by tightening the stitching thread. Then a covering fabric patch is glued on the tear. Small punctured holes can be covered with a patch without stitching first. The edges of the tear are stitched using a curved upholstery needle and thin linen thread.




Before the edges of the tear were stitched, a narrow strip of linen was glued under the edges to support the frayed covering fabric. The old fabric is so thin that it would be frayed even more when the edges are pulled together with the stitching thread. When the stitching progressed, the edges of the tear were pulled closer to one another by tightening the thread. Usually the original covering fabric has shrunk during the years and it is impossible to connect the edges of the tear.



Then and now.

After the stitching, the fabric in the repair area remains somewhat loose and wrinkled, in spite of tightening the stitching thread. Additional tightening can be done with a heat blower. The heat from the blower melted the old lacquered surface of the 1920s’ covering fabric and it became a little bit loose. When the lacquer cooled down, it shrunk, and tightened also the stitched area. Heat treatment is a useful method to tighten the stitched area before gluing a fabric patch on the damaged area. The fabric patches were glued on the stitched areas and punctured holes using traditional nitrocellulose lacquer. On Caudron’s patches Tikkurila Oy Dicco lacquer was used.



Suitable patch pieces were cut from cotton fabric. The edges of each patch were frayed manually before gluing so that the patch would fasten tightly on the repaired area. The fraying was done by unravelling the warp threads along 3-5 mm around the patch edges. This method was used already in the 1920s’, the edges on the strengthening fabric strips on the Caudron’s wing ribs have been unravelled in this manner. Nowadays special scissors are used when cutting the saw-toothed edges of a fabric patch or a fabric strip before gluing.



The damaged area on the original fabric was surrounded with protective tape, which was placed around the area before gluing the patch. It is necessary to limit the work area and to keep the gluing lacquer in the patching area, preventing it from seeping outside the area. The work area was buffed rough before gluing. The buffed dust and the grease on the fabric surface was removed using water-Sinol solution. Then nitrocellulose lacquer was spread on the work area and on the fabric patch, which was placed on a piece of cardboard. The patch was lacquered soaking wet.



It took about five minutes before the lacquer became drier and gluey. The fabric patch was carefully placed on the stitched work area. Another layer of lacquer was applied, and the brush was used to straighten the frayed edges of the patch. After about ten minutes the protecting tapes were removed, and the patching was ready.



The Tuesday Club team noticed that leaving the protecting tape on the work area for a longer time will cause problems. A “gentle type” of painter’s tape was used but the problem could be seen. The tape may stick too tightly on the original painted fabric and when the tape is unfastened, some original paint will peel off with the tape.


About two dozen holes and tears on Caudron’s port lower wing and tailplane and fin have been repaired, using the method described above. About a dozen holes still need patching. And there is more work ahead when the tears and holes on the starboard lower wing and both upper wings are repaired.

Photos: Lassi Karivalo

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Caudron C.59, CA-50

Experimenting dry plywood covering for leading edge on Myrsky's starboard wing

Tiistai 10.12.2019 - Member of Tuesday Club


The restoration work of VL Myrsky II (MY-14) has progressed well during the autumn and the plywood covering on the starboard wing has been completed, excluding the leading edge. The plywood work on the leading edge has had to wait that the work on the port wing, which is being built alongside, reaches the point where the trailing edge is under construction. This is when the two wings under construction in the restoration space of the Finnish Aviation Museum change places. The wings will be moved from their first work platform on to the other platform. This is necessary in order to have enough working space around the wing to complete the port wing’s trailing edge and the starboard wing’s leading edge.



The leading edge of Myrsky’s wing consists of plywood ribs and supporting battens between the ribs. The leading edge is covered with 1,5 mm thick plywood. One sheet of plywood covers the surface of four rib-gaps. Four joining plywood sheets are needed to cover the whole leading edge, which is about five meters long. The plywood sheets are joined on a rib, using a scarf joint.


The challenge in the plywood covering of the leading edge is to bend the plywood sheet around the tapering leading edge. If the profile of the leading edge is very pointed, bending the dry plywood sheet around the edge will cause tears and cracks on the outer surface of the plywood. To prevent the plywood from cracking, the sheet is usually moistened or sometimes the wet plywood is fastened on a last, which models the leading edge. The plywood sheet will dry on the last and form a trough, which can be installed on the leading edge.


The Tuesday Club team wanted, however, to make an experiment and bend the dry thin 1.5 mm plywood sheet on the leading edge. The leading edge profile on Myrsky’s wing is not very pointed. For the experiment steel bands were made from 1 mm thick steel plate, they were cut 10 mm wide. The bands are used for pressing the plywood sheet evenly against the leading edge ribs. A steel band was made for each rib on the leading edge, corresponding the length of the leading edge profile. The bands were placed on each rib.


A tightening clamp was made at the upper end of each band, with a wing nut for tightening the band against the plywood. At the tightening clamp the ends of the band are bent to an angle of 90 degrees for the wing nut joint. The lower end of the band is fastened with a screw on the front spar on the lower side of the wing. The upper end of the band (with the tightening clamp) is fastened on the upper side of the wing on the wing spar.


The dry bending of the plywood covering was experimented without any gluing along the distance of four rib-gaps. The bands were fastened on their places on the five ribs, with the tightening clamps still open. A piece of plywood was cut from the 1.5 mm thick plywood sheet, matching the area of the four rib-gaps. The edges of the plywood sheet were bevelled so that the adjacent sheet can be joined with a scarf joint.




When the preparations for the experiment had been made, the plywood sheet was fitted, lower edge first, between the leading edge ribs and the tightening bands so that it reached the front spar on the lower side of the wing. Then the plywood sheet was pressed against the ribs, using the bands. When the sheet was in place, the clamps were tightened with the wing nuts. Now the plywood sheet was tightly pressed against the ribs.



The Tuesday Club team was annoyed when a crack in the plywood veneer sheet was noticed at the tip of the leading edge. This means that the experiment failed: dry plywood can’t be used when covering the leading edge on Myrsky’s wing. The 1,5 mm thick plywood sheet has to be moistened on its outer surface before it is pressed and tightened with clamps against the leading edge ribs.

Photos: Lassi Karivalo

Translation: Erja Reinikainen.

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

Repairing Caudron C.59 front cockpit's windscreen

Perjantai 6.12.2019 - Member of Tuesday Club


On Friday, October 11th some of the Caudron’s (CA-50) fuselage parts were dismantled in Vesivehmaa and brought to the Tuesday Club’s workspace. These items included the damaged aluminium frame of the front cockpit’s windscreen. The windscreen had been fastened on the plywood covering of the fuselage with seven bolts. The bolt nuts were easy to unfasten, but it was a challenge to unfasten the windscreen frame from the plywood, because the bolts were covered with a heavy layer of rust. A screwdriver was used as a lever between the windscreen frame and the plywood covering and finally the rusty bolts could be manoeuvred through the plywood.


The windscreen frame, originally made from thin aluminium sheet, had been badly bent and partly damaged. However, it can be straightened and repaired, and it can be installed back on the Caudron’s fuselage. There were fragments of the original windscreen still attached to the frame. The Tuesday Club team concluded that the windscreen had been made of celluloid, typically used in 1920’s airplanes. The celluloid window has been fastened with rivets between the windscreen frame and the aluminium profiles around the window.


The repair work was started by unfastening the four aluminium profiles that surrounded the window. All rivets that had connected the windscreen frame and the surrounding profiles were unfastened using a spike. The original windscreen celluloid fragments were also removed. The bent windscreen frame was carefully hammered into its original shape. The aluminium profiles were also straightened. Then the new windscreen could be made.


The original windscreen windows had been made of 1 mm thick celluloid plate. Such material isn’t available anymore, so a modern polycarbonate plate in the corresponding thickness was used.



First a thin flexible piece of plywood was placed on the windscreen frame and the window shape was drawn on it. The pattern was used to cut the new window from the polycarbonate plate. The new window was cut a couple of centimetres larger than the pattern, in order to have enough material to shape the plate into the correct measurements. The polycarbonate plate was fitted into the windscreen frame, shaping it gradually. When the new window fitted properly between the frame and the surrounding profiles, preparations for the riveting were started.




The polycarbonate window was fastened between the frame and the surrounding profiles using strong clamps. Then the holes for the rivets were drilled through the plate, positioning them at the original rivet holes in the windscreen frame. When each hole had been drilled, a cleko-fastener was placed in it, using pliers. The cleko-fasterers were used to ensure that the window stayed in place and the rivet holes were in the correct positions. Hole by hole, the edge of the windscreen was fastened with clekos.



The polycarbonate window was riveted onto the frame, hole by hole, removing each cleko-fastener and putting a 1,5 mm long aluminium rivet into each hole. A compressed air hammer and a traditional hammer were used to hammer the rivets into place. When the riveting was ready, the Caudron C.59’s front cockpit window was ready. A protecting film still covers the window on both sides, the films will be removed when the windscreen has been installed into its place on the Caudron’s fuselage. The paint on the windscreen frame is worn and damaged, but the decisions about the surfacing of the frame will be made later.



The windscreen of the rear cockpit has been lost. At first the Tuesday Club team thought that the rear cockpit’s windscreen could be built using the front cockpit’s windscreen as a model. When the team studied the surface and the marks of the Caudron’s fuselage in Vesivehmaa more closely, it was discovered that obviously the rear windscreen had been significantly different from the one in front. Therefore it was decided that the rear cockpit’s windscreen won’t be made before the Caudron’s fuselage is moved from Vesivehmaa into the restoration space at the Finnish Aviation Museum. This will probably take place in 2021.

Photos: Lassi Karivalo.

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Caudron C.59, CA-50

Caudron C.59's horizontal stabilizer is straightened

Tiistai 19.11.2019 - Member of Tuesday Club


During the 90 years of storage, the Caudron’s horizontal stabilizer has bent badly and it is also otherwise in such poor condition that it had to be dismantled for the restoration work. During the dismantling it became clear that the reason for the bending was the batten on the leading edge. The batten on the trailing edge was also slightly bent. Both battens had to be straightened before re-installing the stabilizer parts and the fabric covering. The team decided to try and straighten the battens by making them thoroughly wet and then fastening them on a level table top to dry and straighten.



Some flexible ventilation duct was found in the storage of the Finnish Aviation Museum and this duct was used to make a container for soaking the leading and trailing edge battens. A four meters long piece of duct was needed for the battens which are nearly three meters long. When the battens had been placed inside the duct, the ends of the duct were bent upwards and the duct “tub” was filled with water. The team estimated that it would take about a week for the battens to get thoroughly soaked when they were submerged in water.



The battens were taken out from their bath after a week, and it seemed that both battens had already straightened by themselves. Obviously wood returns to its original shape when it is thoroughly soaked, in this case to the shape which had been made for the horizontal stabilizer. However, the leading edge and trailing edge battens were fastened on a heavy table surface using clamps. There the battens could dry and hopefully regain their correct shape.


After another week the clamps were unfastened, and the team found out that the battens were dry and almost straight. The thinner trailing edge batten was completely dry but the leading edge batten felt damp and it was still a little bent. The team re-fastened the leading edge batten on the table with the damp side upwards.

In the following week the batten was unfastened and the whole horizontal stablizer frame (leading and trailing edge battens and the end battens) was assembled and placed on the table. The team noticed that the leading edge batten was still slightly bent and the whole frame rose 3 cm up from the table top at its starboard rear corner instead of being flat against the table top.


The team decided to soak the leading and trailing edge battens for another week. Also the end battens were placed in the tub because they were a couple of centimeters bent inwards. After a week the battens were taken from the tub and this time they were fastened on the table as a frame. In the assembly work the leading edge batten was pushed straight using wedges. The aim was that when the leading edge batten dries when assembled in the frame, it would not bend back into its previous shape.


Another week went by and the frame was unfastened. The team noticed that again the frame was not flat but the rear corner of the frame rose slightly from the table top. The leading edge batten was still damp on the side which had been against the table. Therefore the leading edge batten was fastened on the table once more and left to dry for two weeks.


After two weeks the horizontal stablizer’s leading edge batten was unfastened and the trailing edge batten and the end battens were assembled. The team was delighted to see that the frame rested flat on the table – the leading edge batten wasn’t bent any more. Now the repaired ribs could be preliminarily tested between the leading and trailing edge battens. The Tuesday Club team had worked hard to return the battens to their original shape and succeeded.

Photos: Lassi Karivalo

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Caudron C.59, CA-50

Parts of Caudron C.59 were transported from Vesivehmaa

Maanantai 4.11.2019 - Member of Tuesday Club


The Tuesday Club has been working on the Caudron c.59’s (CA-50) horizontal stabilizer, both elevators, the wing struts and one lower wing. As there is no major work to be done on these parts of the plane, the team decided to go and fetch some more parts of the Caudron’s fuselage, which is still in the Päijänne-Tavastia Aviation Museum at Vesivehmaa. The Vesivehmaa museum was visited by about ten Tuesday Club members.



As soon as the team arrived in Vesivehmaa, the work was started and the vertical stabilizer, rudder and the bracing wires were unfastened and carried into the car in no time. All the parts fitted well into the spacious boot of the Skoda Octavia.


It took much longer to dismantle the wing struts which were on top of the front fuselage. Each strut bracing had rusted badly. CRC was used to unfasten the rusty bolts and fortunately the team managed to unfasten without damages all the bolts, three on each strut. Also the bracing wires fastened on the bracings were taken along. Furthermore, the aluminum sheet cowling on the engine mounting, the front cockpit seat and the badly damaged windscreen frame were dismantled to be taken to the Tuesday Club work space.


Left photo: Ari Aho.

The engine cowling came off easily, as did the front cockpit seat, fastened on the frame with four bolts. More effort was needed to unfasten the damaged front windscreen frame. The frame had been fastened through the plywood covering using eight bolts, which had rusted badly. The nuts below the plywood covering were easy to unfasten, but to maneuver the rusty bolts through the plywood and the frame was challenging. The frame is very bent and there are still some remains of the original celluloid plexiglass on it.

There are still several other pieced to be dismantled from the Caudron’s cockpit, e.g. the rear cockpit seat, the control column and the rudder pedals, but more time is needed to do all this.


While the rest of the team was working on the Caudron, a couple of Tuesday Club members installed the securing pins on the bolts of the I.V.L.K.1 Kurki landing gear and wing struts. The Kurki restoration work has been completed and the plane was returned to the Vesivehmaa hall in June.


The following parts of the Caudron C.59 (CA-59) were dismantled and transported from Vesivehmaa to the Tuesday Club hall:

  • the tailfin
  • the rudder
  • bracing wires of the tailfin
  • all four wing struts of the upper wing which were fastened on the front fuselage
  • bracing wires on the wing struts
  • front cockpit seat
  • bent frame of the front cockpit windscreen
  • engine cowling


When the team returned to the Aviation Museum in Vantaa, all items were carefully labelled and the smaller parts (such as the nuts and bolts of the wing struts) were stored in plastic bags to wait for cleaning.

Photos: Lassi Karivalo except one separately credited

Translation: Erja Reinikainen.

Kommentoi kirjoitusta. Avainsanat: aviation history, restoring, old aircraft, Caudron C.59, CA-50

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