Windshields for the Kurki cockpit and cabin

Sunnuntai 11.12.2016 - Member of Tuesday Club

Suomeksi.

The aluminium-framed windshields of the I.V.L.K.1 Kurki cockpit and passenger-cabin can be folded down forward to make covering the open cockpit and passenger-cabin with a tarpaulin against rain easier.  The vertical frames are at the edges and in the middle of the wind-shields, which are each additionally supported by three triangular support frames. In 1920ies manner the windshields themselves are made of celluloid. The bottom frames of the windshields which also acts as hinges have been formed with a groove into which the 2 mm thick celluloid has been riveted.

Many decades of storage has led to almost total destruction of the celluloid sheets, leaving only minor parts in the grooves of the frames. Only three of the triangular support-frames, two middle and one edge-support, have survived and of the frames along the edges of the windshields only a short piece remains. Thus the windshields have to be almost completely rebuilt.

The work was begun by removing the windshields from the frame. The cockpit windshield hinged frame was fastened to the fuselage with screws and was easily removed but the windshield of the passenger-cabin had been fastened with small bolts through the fuselage cover-plywood. Removing the corroded bolts was an arduous undertaking. The rivets holding the remains of the celluloid windows to the bottom parts of the windshield-frame were drilled out so that the small parts of celluloid still remaining could be removed. The frame-parts were thoroughly cleaned and then painted using silver-coloured Isotrol. As the original type of celluloid-plate is no longer available the new windshields will be made out of 2 mm thick polycarbonate plate.

The three missing triangular windscreen support-frames were made using the remaining triangular end-support frame as a template. The frames were cut out of 1.5 mm thick aluminium-plate then bended and finally lightening holes were drilled into them.

Templates for making the windshield “glazing” were made of plywood and these templates will also be used when installing the triangular windscreen-support frames and when trying out the installation of the “gazing” in the hinged bottom-frames.

The templates will also be useful when making the bent aluminium edge-frames for the windscreens and in making sure they will fit correctly to the “glazing”.

First photo: The foto archive of the Finnish Aviation Museum, others: Lassi Karivalo.

The conservation of the Kurki fuselage reaching its final leg

Torstai 1.12.2016 - Member of Tuesday Club

The conservation of the fuselage of the I.V.L K.1. Kurki fuselage is soon on final. A lot of work has been done on cleaning the corroded steel part, on refurbishing the landing gear, mending damages of the fuselage surfaces and painting them, repairing the stabilizer and elevators, refurbishing the cockpit and passenger cabin and equipping the engine-mount.

The ski-equipped steel-tube landing gear was taken apart so that the corroded parts could be more easily cleaned. The cleaning was done both using different polishing-grinders as well as using elbow-grease and different grades of abrasives. The cleaned parts were first varnished using clear Isotrol-varnish and then re-varnished using Isotrol that had been tinted black. The landing-gear skies are wooden whit sheet-metal covered bottoms and sides. The sheet-metal parts were given the same treatment as the other metal-parts of the landing-gear whereas the wooden parts were treated with a mixture consisting of 1/3 pit-tar, 1/3 turpentine and 1/3 boiled line-seed oil. The landing –gear is ready to be fitted to the front fuselage.

The damages to the fabric- and plywood surfaces of the fuselage have been repaired and painted. The painting was done using the original painting procedures. The paint was prepared using nitrocellulose varnish into which colour pigments were mixed. For the silver colour of the fuselage aluminium-bronze pigment was used and for the national insignia ultramarine blue pigment was use for the swastika and a mixture of titanium-white and zinc-white pigmentfor the white background roundel. For a good result the painting was repeated a number of times with rub-downs in between.

The decayed wooden tip-parts of the elevators had to be totally re-built and in addition to this some holes elsewhere in the plywood covering had to be repaired. One third of the covering of the upper surface and more than half of that of the lower surface of the left elevator had to be renewed. On the right elevator the complete upper surface covering had to be renewed. On the stabilizer a couple of largish decayed areas of the plywood-surface as well as some minor holes had to be mended. Before putting the new surface plywood parts in place their future inner surfaces were properly varnished. Eri-Keeper Plus adhesive for wood was used to glue the plywood pieces in place in addition to which the repairs were strengthened in the original way by using brass screws and nails.

The areas of the elevators and stabilizer repaired using plywood were first varnished a number of times using clear Le Tonkinois varnish with rub-downs before the application of the next varnish-layer. After this a mixture clear Le Tonkinois varnish mixed with aluminium-bronze pigment in a ratio of 9 parts of aluminium-bronze to 36 parts  of varnish. To finish off the new bright surface and to protect it against moisture, it was given a protective top-layer of clear Le Tonkinois varnish giving it a slightly greenish hue of silver.

Work has also been done on the cockpit. The cockpits plywood surfaces have been cleaned of grit and mould using a solution of denatured alcohol (Sinol) and water. During late summer the control-column and ancillary devices were removed, cleaned and painted using black Isotrol –varnish. The pedals were treated in the same way. The removed and reconditioned parts have now been re-installed. The control wires have been cleaned.

The engine-mounts still lack the end plate for attaching the engine as well as its aluminium side and top cover-plates. Their fabrication is ongoing.

Where can we get wing-struts for the Kurki?

Sunnuntai 27.11.2016 - Member of Tuesday Club

Suomeksi.

Even though the fitting of the wings to the I.V.L.K.1. Kurki is still months away the issue of the wing-struts has already popped up. Without them, fitting the wings will not happen.

In the late 1940ies the I.V.L.K.1. Kurki, like many other planes de-commissioned in the 1920ies and -30ies ended up being stored in an old war-time hangar at Vesivehmaa airfield. Later this hangar became the Päijänne-Tavastia Aviation Museum. When taking the Kurki for conservation we got the fuselage and the wings but only two out of six wing-struts, that presumable were from the Kurki. Presumably, because we’ll really know if, when we start fitting the wing to the fuselage.

No drawings of the Kurki wing-struts are available, but based on comparison of dimensions of the struts in pictures taken of the plane and those of the available wing-struts, the Tuesday-Club members have concluded that one is the front strut of the right wing and the other the mid strut of the left wing.

When considering the issue of the wing-struts and taking a close look at photographs of the I.V.L. C 24 and I.V.L. C 25 fighters designed and built at the Air Force Aircraft Factory at Suomenlinna we concluded that their wing-strut arrangement was similar to that on the Kurki. This was especially true for that on the I.V.L. C 25. Thus it is possible, that the wing-struts of these planes, that only reached the prototype stage and were taken out of use already in 1925, could well have been used on the Kurki built a couple of years later.

It also came to our minds, that when the I.V.K C 24 was restored “around” the rather damaged fuselage, could it be possible that wing-struts fit for the Kurki had been used in this project? To check this, personnel of the Finnish Air Force Museum took a close look at the disassembled I.V.L. C 24 stored at Tikkakoski, However, its wing-struts turned out to be carved out of “common 2 by 4rs”, so no answer there.

So at the moment we have but two damaged wing-struts that we presume belong to the Kurki. Our next steps will be to repair the damage on the plywood cover parts of the struts and to clean the corroded metal parts and finish of the work by varnishing the repaired plywood surfaces and cleaned metal parts using aluminium-bronze varnish. We will also make drawings to enable us to re-create the missing wing-struts and build them. Inspecting the damaged parts has shown us, that the load-carrying part of the strut is a steel tube of 2” diameter, with a leading edge shaped from solid wood and a trailing part built using wooden wing-ribs and a trailing rib. The whole wing-strut has then been covered using plywood.

We assume, that the wing-struts on both sides are mirror images of each other, but otherwise similar. Thus we can use the two existing struts as reliable models when building their pairs. Building the missing rear struts though, is a bit of a problem, because the only source we have for their design are the photographs taken of the Kurki. We can start designing and making them using the existing struts as basic models, but they can only be finished once the wings of the Kurki have been conserved and the wing has been fitted to the fuselage supported by the front- and centre wing-struts.

SZ-25 unveiled in Kauhava

Lauantai 1.10.2016 - Member of Tuesday Club

The on June 2015 started Focke-Wulf Fw 44 Stieglitz (SZ-25) renovation project at Tuesday Club got a worthy ending on 29th of September. On that day happened the ceremonial inauguration of the newest showcase at Kauhava Aircraft Park. SZ-25 was placed in this showcase together with VL Pyry (PY-1). The third trainer in the same showcase will eventually be Valmet Vinka when Finnish Air Force renounces the use of this type.

SZ-25’s wings had been transported to Tikkakoski for interim storage already during spring, while its fuselage stayed at Finnish Aviation Museum to be finalised by Tuesday Club.

The last phase of renovation was making of missing locking parts for propeller by turning. Also exhaust tubs for cylinders had to be made. This was outsourced. Matching exhaust tubs, exhaust manifold and exhaust tube under the fuselage turned out to be difficult. However, finally all parts fell together and the fuselage was ready to be transported to Kauhava.

Transportation was done on 13th of September by Finnish Army. Their truck arrived at Aviation Museum and SZ-25’s fuselage was hoisted into truck and secured with cargo straps. The propeller was moved separately and attached into a transport pallet. Also SZ- 25’s wings were transported to Kauhava from Tikkakoski. A dozen strong group of Tuesday Club members traveled two days later to Kauhava to assemble SZ-25 inside the gorgeous, newly built showcase.

Even while we started working immediately after arriving, there were things to do also on the next day. It took seven hours for us to assemble SZ-25 plus wash both Stieglitz and Pyry.

Renovating SZ-25 was an acceptable work for Tuesday Club. It was even more meaningful because while working we knew that this aircraft will be placed in an appropriate exhibition place. This new showcase includes even dehumidification equipment. It is sad that most of aircraft we renovate end up in storage areas or somewhere else than in actual aviation museums. This is because Finnish aviation museums are too crowded already now.

It was heart warming to experience how serious was the attitude of the Air Force Academy Guild towards the preservation and presentation of Air Force aviation heritage. This new showcase built by Guild and our good co-operation between Guild and Tuesday Club is an example of this. And now the showcase glows with its bright lights like a jewel in Kauhava’s night.

This photo: Timo Telen. Others: Lassi Karivalo.

MY-14's tail repairs, part four

Lauantai 1.10.2016 - Reino Myllymäki

We had an almost intact VL Myrsky II’s tail wheel. The only missing part was axle and it was made at Air Force Museum from piece of solid 20mm steel tube.

Tail wheel rim is made from Elektron-metal which is a trademark for a range of magnesium alloys. Same goes for brake shields of main wheels. These parts were badly corroded and thus tiresome to dismantle. Paint was worn out and bearings stuck.

Both outer and inner tires turned out to be useless. Obviously corroding of rim had eaten rubber at rims edge. Inner tire had been patched up several times (!) and was no more usable.

The rim was dismantled into parts and new holes were drilled into retaining ring of bearing for tool. Clogs of retaining ring were left as is. Rim halves and bolts were blasted with glass beads, primed with Isotrol Klarlack and finished with Isotrol color tone RAL 7005.

Bearing was replaced with a SKF 6304 bearing with new mounting nuts. Tires were replaced with commercial 12 by 4 inch inner and outer tires. Air valve had to be lenghtened with a stub of brass tube soldered in place.

Isn’t it good looking now!

MY-14's tail repairs, part three

Keskiviikko 28.9.2016 - Reino Myllymäki

Even after MY-9 empennage was attached into MY-14 fuselage frame, there remained things to fix at Tikkakoski.

Tail wheel assembly was missing support tubes and some existing ones were eaten by rust. They had to be renewed. Tubes coming in from fuselage corners were good up to the original joint but even they had to be straightened.

Replacement tubes were taken from MY-9 as possible but also new tubing was used. Original tubes included wall thicknesses down to as thin as 0.5 mm, but all new ones were of 1 mm wall thickness. Axle bushings were made of new commercial quality tube.

Further there were things to fix at tail wheel assembly’s upper supports and attachments. All six pipes leading there were either missing, broken or twisted. Replacements were again found from MY-9, but bushings and supporting lugs for retracting mechanism had to be made from new material according to drawings.

Again all needed welding was done with TIG welding, partly by Rauno Pylväläinen from Patria and partly by Antti Lappalainen from Finnish Air Force Museum.

MY-14's tail repairs, part two

Sunnuntai 25.9.2016 - Reino Myllymäki

Tuesday Club’s Matti Patteri made an assembly jig for joining of MY-14 fuselage and MY-9 empennage. Joining was done at Finnish Air Force Museum in Tikkakoski. Damaged tubes were straightened and cut where necessary. New pipes were taken from MY-9 fuselage as needed.

Assembly and straightening was made as close to drawings as possible. Pipes were bended with the help of welding torch to align them exactly right. Also supporting wedges made of laminated wood were helpful during alignment.

Tube to tube joints were strengthened with sleeves. Corner joints where tube endings were shaped remained without extra support, unless there were original support flanges.

Myrsky’s fuselage is a welded frame made of chrome-molybdenum alloy steel tubes. Welding method was gas welding with unalloyed wire. By the time when Myrsky series was built, arch welding was just making its first steps at the State Aircraft Factory. Here it was decided to use TIG welding, which was done by Rauno Pylväläinen from Patria.

Welding was done in two phases. When the fuselage and tail assembly were fixed into jig, some points could not be welded. For those last remaining points the fuselage was moved into a rotating platform.

After welding, the tubes were first coated with phosphoric acid, then primed with Isotrol Klarlack and finished with Isotrol color tone RAL 7005.

MY-14's tail repairs, part one

Torstai 22.9.2016 - Reino Myllymäki

There was three VL Myrsky II fuselages available and the least damaged of them (MY-14) was chosen as the basis for renovation. The least damaged meant here something far from being intact. All three fuselages (MY-5, MY-9 and MY-14) had been damaged in crashes in front of tailplane. They all had been transported to Valmet Kuorevesi factory to be rebuilt but they ended after war as surplus at a gravel entrepreneur’s back lot in Jämsä.

The empennage of MY-14 is totally missing as it was crushed by MY-41 smashing into it at Pori Airport. Tail assembly for renovation was detached from MY-9’s fuselage.

While MY-9’s tail assembly was rusted all over, it was still sound enough to be sand blown. Inner core of tubing was actually well preserved and tubes contained even some of the original anti-corrosion oil.

After removing all parts which could be detached without cutting, the rest of assembly was cut from MY-9 fuselage at original welding seams. Then it was sent to be sand blown and primed at an automotive and industrial paint shop in Vantaa.

After receiving the tail assembly back to our workshop we went on by doing necessary welding to prepare assembly ready for new stabilizators, rudder and elevator. These were manufactured by Tuesday Club and Vocational College Varia. Some bearing brackets had to shifted because MY-9 had not been built according to drawings. Obviously jigs were not made before MT-14 was assembled. Tail assembly had to be modified to match those newly built parts which were made according to drawings. 

Kurki landing gear under restoration

Torstai 7.7.2016 - Member of Tuesday Club

Suomeksi

VL K.1 Kurki’s maiden flight started from sea ice near Suomenlinna, south of Helsinki, on 20th of March 1927. Most of trial flights were made with ski under gear but wheels were also tried. Kurki was found to be an inferior airplane and it was stored soon after trial flights the same year.

Kurki’s landing gear is typical for its time. It has a steel frame and a suspension with braided sandum rubber cords. Our research shows that steel frame had originally a black lacquer finish. Wooden skis show remnants of tar, and also Kurki’s procurement documents mention tar. It is unlikely that tar was used for anything else but for treatment of wooden skis.

After storage of 89 years, landing gear has suffered lots of damage just like the whole plane. All metal parts are badly rusty, tar has evaporated from skis and sandum rubber cords are broken.

As the first step, the whole landing gear was removed from Kurki’s fuselage. Then it was dismantled to make restoration of various parts easier. It was decided to clean rusty metal parts by mechanical sanding. We did not aim to reach clean metal surface but to remove most of rust before priming with clear Isotrol Klarlack Grund lacquer.

This primer is covered with glossy black Isotrol Finish lacquer to get a finish which looks like the original black finish of landing gear’s metal parts. Isotrol system is designed to penetrate rust and form a barrier against further rusting process.

We honed metal parts manually with sanding paper and also with brushes on pneumatic drill. With good weather this dusty work was done outside in front of our workshop. Also  wooden parts of skis were cleaned similarly for further treatment with tar.

Honed metal parts were first primed with clear Isotrol Grund. As we had expected, clear lacquer brought out remnants of original black finish on steel pipes.

When primer had dried, we went on with painting metal parts with black Isotrol Finish. Wooden skis are still waiting to be covered with tar.

Myrsky?s spinner got its attachment parts

Perjantai 17.6.2016 - Member of Tuesday Club

For restoration of VL Myrsky II, serial MY-14, we have the original spinner. But this spinner is empty inside and lacking all parts to attach it over propeller hub. Thus we needed to make front and rear bulkheads. Front bulkhead comes inside spinner and rear bulkhead comes behind propeller and is attached to spinner's rear edge.

Propeller must be removed first to get rear bulkhead around propeller shaft. It is secured with a collar attached to propeller hub. With propeller installed, front bulkhead is attached to propeller hub. Spinner is now attached over hub to both bulkheads.

Both bulkheads were spun from a metal sheet according to Myrsky’s blueprint. We made an adjustable mold for spinning. With an adjustable mold we could spin both bulkheads which have different diameters. Front bulkhead is naturally the smaller one.

We made 3 inch lightening holes into rear bulkhead with a punch press. By using a suitable punch and die those holes got also nice strengthening flanges.

Now we are at a point where we have bulkheads which are ready to be installed for spinner attachment.

Tuesday Club ready for summer break

Maanantai 6.6.2016 - Member of Tuesday Club

Tuesday Club's spring season was a busy one as a whole. Work was carried out on restoring and conserving several museum aircraft: Valmet Vihuri II, VL Myrsky II, Focke-Wulff Stieglitz, Valmet Tuuli III and VL K.1 Kurki. Most hours were spent on Myrsky II and Kurki. For Tuesday Club's work balance, it was positive that Kurki’s conservation could be started. This blog explains in summary the activities of Tuesday Club’s spring season 2016.

Although our spring season ended at the end of May and starts again in mid-August,
Finnish Aviation Museum’s restoration shop will not quiet down totally. Myrsky project progresses during summer months and it is possible to work also on other projects.

Valmet Vihuri II (VH-25): Building of cockpit module went on with making a floor which separates cockpit from the wheeled transport chassis on which the cockpit sits. Oxygen system’s piping is now installed into both front and rear cockpit. Seat belts for rear seat are ready. Luggage container, made of fabric and situated behind the rear seat, is advancing and also a chute for signal pistol is in the makes.

VL Myrsky II (MY-14): All wing ribs are ready. Same goes for frames which will be attached around the steel tube skeleton of fuselage. Work on aileron ribs is in progress. Wing spars are half done. The brakes in Myrsky’s original wheels have been renovated. Also done is the mould for engines’s cauldron plate which is out-sourced. We are building a test wing which will be used to try the strength of wing structure and also the installation of various equipment and mechanisms. Wing spars for test wing are ready and we have tested matching of ribs and installation of steel support structure of landing gear.

Focke-Wulf Stieglitz (SZ-25): Restoration of fuselage is finished. Work done during spring season  was a new cowling around the engine mount and equipping the engine ready to be installed. Wednesday Club was responsible for renovating the engine and they also installed it. The engine was left incomplete as some equipment is missing. We are still waiting for exhaust manifold and exhaust pipe to be installed as the outsourced exhaust pipe is not ready. Also propeller is waiting for installation as propeller’s locking hex bolt with its cap have not yet been turned. SZ-25’s fuselage and wings, which we have already renovated, will be transported to Kauhava where this aircraft assembled this autumn as a memorial in a showcase.

Valmet Tuuli III (TL-1): The first part of Tuuli III’s restoration was started late 2015 and finished by the end of May. We prepared its fuselage ready to be painted at Hämeenlinna Vocational Collage Tavastia. Within reason, all parts and equipment from the fuselage, including cockpit, were stripped off. Then the fuselage was transported to Hämeenlinna, where similarly stripped wings have been waiting since February. The re-painted wings and fuselage will return back to Tuesday Club only at the end of this year. Then we start re-equipping and assembling the aircraft to be exhibited. Alongside our work, Aviation Museum’s Wednesday Club has been renovating Tuuli III:s Continental engine.

VL K.1 Kurki: As a new project we started repairing and restoring Kurki. It is an aircraft prototype which was built at State Aircraft Factory in 1927 and never progressed further. A suitable slot for Kurki emerged after Tuuli III’s fuselage left to Tavastia. Its fuselage was transported from Tavastia-Häme Aviation Museum in April. Also wings will be restored at Tuesday Club after we have finished the fuselage and it is returned back to its museum at Vesivehmaa. So far we have done patching of more than 30 holes and damages in Kurki’s fabric skin. Also we have repaired its horizontal stabilizer and elevator.

Tuesday Club’s smaller deeds remain many times without mentioning. One of those is making of trivets for Aviation Museum Society. They sell them with their logo and are a wanted item.These trivets are made of plywood which is bended into the shape of Polikarpov I-16 fighter’s plan view.

Repairing fabric skinning of Kurki fuselage - more work than we thought

Keskiviikko 25.5.2016 - Member of Tuesday Club

Suomeksi

Kurki fuselage had more damaged fabric skinning than expected. Well, that’s how it usually goes with museum airplanes which have been in storage for a long time. Hopes and reality do not always coincide.

Backwards from cockpit, there were some 15 holes, tears and other damaged spots in fabric. Fuselage’s underside fabric had one severe tear, half a dozen holes and also rotten areas around metal brackets of landing gear. Plywood skinning of front fuselage had just a few damages.

Small holes and damages were repaired with fabric patches. We cut suitable patches from aircraft grade linen with zig-zag scissors. Surroundings of holes were sanded as wide as corresponding patches were. Each fabric patch was glued over the hole with varnish, which was applied both on damaged fabric and the patch. We let the varnish to settle a while before the patch was pressed over the hole. More varnish was applied over the patch, while ensuring that serrated edges of the patch are glued into the fabric below. Varnish was let to dry before the area was sanded and re-varnished. This was repeated a few times until we had a tightened patch ready to be painted with aluminum dope.

Larger damages, like teared fabric, demanded another procedure. In these cases we glued a supporting, 1 mm thick veneer inside of fabric skin. We used Eri Keeper Plus wood glue. While glueing, the edges of torn hole were stretched in along veneer. Then tears were glued into veneer  with Casco contact adhesive. When glue was dry, the repaired area was sanded smooth and it was covered with a fabric patch like above.

The whole length of fuselage underside has fabric skinning. Below cockpit there was a nasty transverse rupture. The whole width of fuselage was cut open. Also there were half a dozen holes.

We decided to repair the rupture by gluing the edges of the hole into a fuselage frame which was nearly in the middle of the hole. A contact glue is necessary here because the fabric must be stretched and an immediate adhesion is needed.

One edge was easy to glue, but the opposite edge was too far from the frame. We glued a strip of fabric along this edge which made it possible cover the gap and thus stretch and glue the fabric into the frame. Finally, varnish applied over the joint to stretch the fabric.

Remaining holes were covered with patches like above. I felt like an old-time car mechanic when I was lying on my back under the fuselage repairing those holes.

There should be footboards!

Tiistai 24.5.2016 - Reino Myllymäki

Suomeksi

There are two footboards on the floor of the cockpit of the VL Myrsky. The supporting structure of the footboard is made from birch plywood and pine strips and the sliding surface from aluminium sheet.

The aluminium parts of the footboards of the MY-14 were repairable. Only cleaning by oxalic acid and solvent washing agent was needed as well as protective handling by Isotrol lacquer.

But the wooden parts were in poor condition and the design drawings were lacked. By collecting the footboards' wooden parts of three aircraft (MY-5, MY-9 and MY-14) it was possible to assemble an almost complete supporting structure. By using it as a model it was possible to rebuild two new footboards from plywood and strips.

Finally, the footboards were painted by Isotrol paint. The color tone is RAL 7005. The aluminium sheets were fastened to the supporting structures by wood screws. No by original screws but fully equal.

Reino Myllymäki

Fastening bands for MY-14

Tiistai 10.5.2016 - Reino Myllymäki

Suomeksi.

VL Myrsky has a lot of fastening bands used to fasten equipments and fuselage formers to the chrome-molybden-steel-tube frame. The fastening bands were made either from 1 mm thick steelblate by pressing or from pipe stumps by welding.

The fastening bands were disassembled from the fuselage frames of MY-5, MY-9 and MY-14 at the Finnish Air Force Museum. The broken bolts were released and the twisted bands were straighten. Some bands have been fixed by welding. The condition of the bands was very variable. Some were almost ready after glass bead blasting but some were very corroded. There was original paint inside the bands.

Some fastening bands were found from the storages of the Finnish Air Force Museum and some were made by using original blanks of the State Aircraft Factory.

The bands were cleaned by glass bead blasting and phosphoric acid disposal. The Isotrol Klarlack was painted by brush for priming and Isotrol RAL 7005 was painted by air brush for paint finish.

Restoring of Kurki has started

Lauantai 7.5.2016 - Member of Tuesday Club

Suomeksi

VL K.1 Kurki aircraft was transported from Päijänne-Tavastia Aviation Museum to Finnish Aviation Museum - and Tuesday Club quickly started restoring its fuselage. At the same time began repairing of damaged skinning of horizontal stabilizer, cleaning of fuselage surfaces, removing of rudder and removing of rusty metal parts to be cleaned.

Horizontal stabilizer and elevators have lots of damaged skin. Both tips of elevators are destroyed. Stabilizer’s plywood skin has a few smaller damages and one big damage, where the plywood skin is broken for around 40 x 40 cm area on both sides of stabilizer. It looks like someone has stabbed a blunt object through the stabilizer. Repair work of stabilizer was set as the first thing to do. Tailplane was removed to make it easier.

Because of large area of damage, it has to be re-skinned. We started with stabilizer’s underside. The broken plywood skin was removed span wise over a few ribs with a utility knife. Revealed ribs were stripped of nails which were used to attach the old plywood skin. Next we glued support flanges under the edges of this new opening in plywood. They will support the new plywood skin. As the glue we used Cascol Outdoor.

We went on with cutting a fitting piece from 1,2 mm thick aircraft-grade plywood. This piece of plywood is glued to support flanges and two ribs revealed in the opening. Bonding will be ensured by nails according to original skinning method. The corresponding damage on the upper side of stabilizer is fixed similarly. Smaller skin damages of stabilizer were fixed while working over the opening.

Plywood and fabric-covered surfaces of fuselage are badly soiled as a result of almost 90 years of storage. Originally Kurki has been painted with aluminum dope which was covered by clear nitro-cellulose lacquer. Over decades the lacquer has evaporated and what is left is a dull grey paint surface. The original, clear but now yellow lacquer surface can be seen in a few spots which have been sheltered from sunlight.

Fuselage surfaces were cleaned with Wonder Sponge. The sponge was pre-soaked in clean water and afterwards the surface was dried with a cloth. Wonder Sponge is an effective and suitably gentle tool for cleaning old paint surfaces. It is as good for plywood as for fabric skinning.

Removing of rudder was tedious. Bolts in hinges between rudder and fuselage were badly stuck. Two of them could not be taken off at all. We had to remove instead those bolts which attached hinges to rudder.

Fuselage and tailplane have several metal parts, relating for example to attaching stabilizers or carrying control cables. All these metal parts are rusty and had to be removed for cleaning. Landing gear struts are also of steel and heavily covered with rust. Landing gear has to be removed and dismantled from the fuselage for cleaning and re-painting but this is already another story topic.

Instruction panel of VL Myrsky under restoration

Perjantai 6.5.2016 - Reino Myllymäki

Suomeksi

Although a lot of VL Myrsky parts are lacking, the situation of the instruction panel is better. All missing meters were found. However, the instruction panel needed repair. The conservation team of the Finnish Air Force Museum focused on it.

The instrument panel has four fastener. Three of them have been made from iron and they were corroded badly. One of them near the compass has been made from brass and it was oxidised. Some fasteners were taken from other instrument panels of VL Myrskys and in all six fasteners were blasted by glass beads and painted. The aim is that the best of the six fasteners will be installed to the MY-14

Fasteners' vibration absorbers have disappeared. A example has been found from VL Pyry. The new absorbers were manufactured from rubber seal and thin rubber plate. The used screws were original crews from the State Aircraft Factory.

Three out of four bakelite signs of the main instruction panel were disappeared. Luckily the signs could be substituted by using other instruction panels of VL Myrskys. The signs were sanded and the inscriptions were cleanded. After that the inscriptions were repainted. After sanding there is paint only in the inscriptions.

The sign showed the speed limit has to be fixed by glue and a thin background plate. The signs were fastened by 2 mm round-head screws.

VL Kurki - the new project for Tuesday Club

Torstai 28.4.2016 - Member of Tuesday Club

Suomeksi

Päijänne-Tavastia Aviation Museum, close to city of Lahti, has VL K.1 Kurki among its collection of aircraft. The plane was decided to become under restoration at Tuesday Club. This was made feasible by getting Valmet Tuuli III ready to be painted at Hämeenlinna Vocational college, Tavastia. For Tuesday Club work on Tuuli III will continue after painting only closer to the end of this year.

VL K.1 Kurki (Kurki meaning Crane in Finnish) was designed and built by State Aviation Factory (in Finnish: Valtion Lentokonetehdas = VL) in 1927 and it is the penultimate still existing aircraft by this factory to be renovated. The last one will be VL E.30 Kotka (Eagle) which is also preserved damaged at Päijät-Häme museum.

The sole Kurki has been at Päijänne-Tavastia Aviation Museum since late 1940s, when Vesivehmaa airfield's wartime hangar became a collection point for previous Finnish Air Force aircraft from 1920’s and 1930’s. These were stored at various places around in Finland. Päijänne-Tavastia Aviation Museum has also the I.V.L. D.26 Haukka I which Tuesday Club restored and returned last spring.  (I.V.L. is short of Air Force Aircraft Factory which preceded VL. Haukka means Falcon.)

Kurki’s fuselage has been featured at Päijänne-Tavastia Aviation Museum without wings. This aircraft has lost parts over the years, e.g. original items are missing from cabin. Also, it has no engine. There should be a Siemens-Halske Sh.12 radial at the bow.

Photo: Tapio Heinomaa

On Tuesday, April 19, staff at Päijät-Häme museum loaded Kurki’s fuselage, horizontal stabilizer, and elevator onto Armed Forces truck. Carefully fastened they started their journey to the Finnish Aviation Museum.

Photo: Jarmo Tammisto

When arrived in, Tuesday Club members took care of unloading the cargo to our museum’s workshop. Kurki has ski undercarriage. So, it was put on dollies to make it easier to move around.

Kurki’s wings will be brought to Tuesday Club when the fuselage is finished and returned to Päijät-Häme museum. With also wings restored eventually, the aircraft would be ready to be assembled and exhibited. The problem is that Päijänne.Tavastia Aviation Museum does not have enough free space for this.

This plane needs remedial conservation. Tuesday Club starts with cleaning surfaces and goes on with repairing damaged areas. Surfaces will be re-painted only at repaired areas and maybe where original paint is badly deteriorated. Repairing and painting of repaired areas will be done using methods which are according to Kurki’s time. We have good experience with this from similar remedial conservation of the I.V.L. D.26 Haukka I. Also we will complement missing instruments and equipment and re-build flight controls functional again.

As said, Kurki is from the year 1927. Its maiden flight was in March. It was designed at State Aviation Factory by chief designer Kurt Berger and factory director Asser Järvinen. It was meant for civil aviation as a trainer and for sports or general aviation. They also offered it to the Air Force as a liaison aircraft plus as a trainer for both pilots and observers.

Kurki on ice at Suomenlinna in March 1927. Photo: Finnish Aviation Museum.

However, it was found to be missing in both technical and flight characteristics. Kurki was not stable enough in either yaw or roll. The prototype flew only 13 hours during 55 flights before further development was abandoned. In Finnish aviation history the right-angled Kurki is nick-named as ”Järvinen’s Box”.

In case not mentioned, photos: Lassi Karivalo

Propeller spinner & metal spinning

Tiistai 26.4.2016 - Reino Myllymäki

Suomeksi

A black block appeared to the restoration room of the Tuesday Club of the Aviation Museum Society at the Finnish Aviation Museum during last winter. The black block is a propeller spinner of the VL Myrsky.

Black spinner of VL Myrsky is suprising big. Photo: Reino Myllymäki

The spinner has been in a display cabinet in the heritage room at Kauhava airbase. According to the text on the spinner, it has been donated by lieutnant colonel Antti Uotila in 1998. After the sale of the airfield, the spinner has been stored at Kauhava. Finally a delegation delivered it to Vantaa from Kauhava.

The spinner had three work in VL Myrsky. Firstly it protected constant speed propeller hub agaist water, ice and dirt. Secondly it decreased drag. Thirdly it expanded the cooling of the radial engine. The spinner of VL Myrsky has three small blades to boost cooling. They were needed since the Twin Waso engine ran warmer in the VL Myrsky than in the Curtiss Hawk.

A hub of VLS 8002 propeller. It is a copy of Hamilton Standard Hydromatic. The semifinished hubs were acquired from Sweden. Photo: via Kalevi Keskinen.

These small cooling blades have been invented at the State Aircraft Factory along the test program of the MY-4 in 1943. The inventor has been rewarded.

Luckily the spinner of the VL Myrsky has been preserved and donated to the VL Myrsky II restoration project. Otherwise it should be made by the metallic spinning.  The project has enough lacking axially symmetric metallic parts. Antero Flander is manufacturing the pot plate at Rautalampi and the NACA ring will be probably more demanding part.

The spinner inside. The imprint of work is more rough inside. Photo: Reino Myllymäki

The metallic spinning is a work method where a disc or tube of metal is rotated at high speed and formed into an axially symmetric part. The forming tool has been made from wood. Later the tool has spinnig tip, too. In addition to metallic spinning some other methods like English wheel are needed in the manufacturing of more complex parts.

Test wing of MY-14 progresses

Lauantai 23.4.2016 - Reino Myllymäki

The production of wing ribs and fuselage formers of the MY-14 has moved to rapid stage in the VL Myrsky II restoration project. Since the wing is a quite complex structure with all inside equipment, it is deciced to build about two meter long test wing in order to test the installations and operations of inside equipments.

After the general meeting of the Aviation Museum Society on Saturday 9th April 2016 it was possible to get acquainted with the restoration project in the restoration room of the Tuesday Club at the Finnish Aviation Museum. Matti Patteri and other team members has assembled the test wing by using incomplete wing parts.

The incomplete center parts of wing ribs were joined to incomplete spars. Therefore it was easy to shape the wing. One half of the flanges and two of three waists were lacking from spars. The wing ribs that will be assembled to the test wing are surplus parts.

It is planned that the test wing will be converted to a demo wing later. The another side of the wing ribs will not be covered by plywood and the wing will be covered by polycarbonate plate instead of plywood. The demo wing will help people to understand the structure of the wooden wing of the 1940s.

Valmet Tuuli III's fuselage is transported to be painted

Lauantai 23.4.2016 - Member of Tuesday Club

Suomeksi

Valmet Tuuli III's body was transported on Friday, April 15, from Finnish Aviation Museum to Hämeenlinna Vocational Collage, Tavastia for painting. Tuuli III's wings had been transported a couple of months earlier. Tuuli III will be painted at Pintakilta in Tavastia. Students at Pintakilta (literally Surface Guild) study surface treatments aiming get professional degree in this trade.

Tuuli III’s restoration project is supervised by Finnish Aviation Museum and Pintakilta is responsible for re-painting. It means mainly removal of old, deteriorated paint and subsequent re-painting. The whole painting job is carried out as student work at Tavastia guided by teachers Jari Välkkynen and Hannu Waltzer. Pintakilta students have welcomed Tuuli III project with great interest.

Tuuli III's fuselage had already seen a lot of preparation work before it was moved to Tavastia. Aviation Museum Society’s Tuesday Club members had removed every part where removing was reasonable. This was to make Pintakilta’s work as convenient as possible.

Fuselage was really stripped-down when it left to Tavastia. It was accompanied with engine cowlings, dorsal fin, vertical stabilizer and rudder. Aviation Museum’s mechanic Antti Laukkanen had welded a metallic rack with wheels on which the fuselage was attached to make moving around and transportation easier.

Now Tuuli III’s fuselage was quite handily loaded into Tavastia’s truck and travel towards Hämeenlinna began. Also this transportation was done as student training at Tavastia. It was provided by Logistics Department students led by their teacher Timo Lahti.

When in Hämeenlinna, the fuselage was brought into Pintakilta workshop by students of this project. Again, it was supervised by Antti Laukkanen and Kimmo Snellman from Finnish Aviation Museum. Tuuli III’s fuselage was now ready for surface treatment.

Pintakilta has already started preparations for surface treatment of fuselage and wings. It has meant testing of various paint removal methods to find the most suitable one. Re-painting can’t be successful without careful removal of old paint. Students tested paint removal with Tuuli’s smaller parts like trim tabs from elevator.

First thing to do was removal of grease and then various solvents were tested starting from mild ones. Finally it was decided that in this project the most suitable solvent is Nitromors paint and varnish remover. With the right processes found, the surface treatment of Tuuli III can now proceed for real at Pintakilta. You can follow Tuuli project progressing at Pintakilta’s project page: http://tuuli3.weebly.com/

Photos: Lassi Karivalo (first) & Antti Laukkanen (other).