Refurbishing the Snoopy pilot's seat

Torstai 7.11.2024 - Tuesday Club member

Suomeksi

The pilot’s seat of the Snoopy experimental aircraft, built by the brothers Hietanen from Turku, at the end of the 1960s, was moulded along the times. In the first version, the seat frame had a curved back support and a back rest of plywood, covered with fabric. Later the back rest became rectangular with an inset for the pilot’s parachute. The material of the back rest was changed at the same time from plywood to aluminium. With the inset in the back rest, the distance between the pilot and the control column could be increased, because the Snoopy’s seat isn’t adjustable. The parachute backpack worked as a padding for the pilot’s back.

Photo by Esko Keskinen.

The seat of the Snoopy, a donation to the Finnish Aviation Museum a few years back, consists of the back plate, side plates the shaped bottom plate and the case at the rear of the back rest. These parts have been riveted with pop-rivets to the steel tubes of the seat frame. A plywood plate, with a canvas-covered padding, attached with screws to the cockpit frame, forms the seat.

After tens of years in storage the Snoopy’s seat steel tube frame was rusty, like the fuselage frame, the aluminium parts of the seat were dirty and oxidized grey. The plywood seat plate with its padding had totally vanished.

To restore the seat, we started by detaching the aluminium parts fastened to the seat frame. They were detached by drilling away the pop-rivets that had fastened the aluminium parts to the frame.

After that we disassembled the seat frame of tubular structure, to be refurbished. We had our work cut out for us in doing that. We had to use a jack and a plastic mallet, before we were able to detach the frame parts from each other, because they were joined together with rust.

After separating the frame tubes, they were cleaned from rust to be painted in their original appearance. We did the cleaning by hand, using sandpaper of various grits and abrasive pads. We also did the same to clean the Snoopy’s fuselage frame tubes.

Because we’ll use Isotrol-lacquer to prime the seat frame, the tubes need not be sanded into clean metal. It suffices that the surface rust has been removed and that the surface of tubes feels smooth to touch. An Isotrol paint of the original shade will be painted on the Isotrol primer.

The dirty aluminium parts of the seat were cleaned with Fairy Power Spray agent. The Power Spray is a very efficient detergent for dirt and grease. You spray the agent on the surface of the part to be cleaned and leave it work for a few minutes.

After that the parts will be dried with a cloth or rinsed with water. In doing so we had the aluminium seat parts looking quite different, compared to when we detached them from the seat frame. The aluminium parts will still be buffed out before fastening them back to the restored and refitted seat frame.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Matti Liuskallio.

Cleaning the parts of the Snoopy?s Continental engine

Perjantai 1.11.2024 - Tuesday Club member

Suomeksi

As soon as parts had been detached from the Continental A 65 engine that we had received for the Snoopy (OH-XEA), originating from a plane destroyed in an accident, they were cleaned. Besides being physically damaged, the engine had also burnt. Unfortunately, many of its devices had been destroyed useless, so the missing parts also had to be searched for.

Photo by Erkki Rossi.

Small metal parts with little or no damage were cleaned from rust by bathing them 24 hours in 33 % solution of phosphoric acid. For example, the propeller hub, detached from the engine and dismantled into its parts, was all immersed into phosphoric acid.

When the acid starts working, foam will be forming on its surface. After a day and night, those propeller hub parts were taken out and carefully dried with fabric. As a result, the parts are rust-free, with dark grey clean surface. Even as such, the parts are fully usable.

However, we decided to blow the propeller hub parts with glass bead blasting to bright metal, to make them appear as brand new. One might ask, why not blast them straight away as rusty. We chose this approach to avoid contaminating of the glass blast media with rust enriching into it.

For aluminum engine parts with dirty surface, we chose another procedure. Aluminum parts that were dirty or blackened after burning, such as magnetos, were first cleaned of dirt and thereafter their surfaces glass bead blasted. Before the blasting, holes in the magnetos were plugged with wooden plugs to prevent the blast media from penetrating into the magneto. With the blasting, the magnetos got clean surfaces. Finally, the clean surfaces were treated with a solution of Sinol and water to prevent the oxidization of the surface.

Oily and dirty parts were initially washed in a basin dedicated to cleaning engine parts, with a handy brush that feeds washing liquid through a hose.

The washed parts were dried with pressurized air, aluminum parts then possibly treated with glass bead blasting and Sinol-water solution. This method was chosen e.g. for the aluminium distributor head cover.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Hannu Mononen.

Preliminary steps for covering the Ressu (Snoopy) fuselage frame

Sunnuntai 27.10.2024 - Tuesday Club member

Suomeksi

The fuselage of the Snoopy experimental aircraft (OH-XEA) was covered with fabric. When Aviation Museum Society Finland received the Snoopy two years ago, the fuselage was totally stripped of covering fabric. Therefore, the fuselage will be covered at the Tuesday Club as it originally was. Luckily we have some good photographs of the Snoopy at our disposal to guide us with the covering. So to work.

The whole fuselage frame of steel tube has been cleaned of rust during the autumn, given a layer of lacquer and finally painted with red Isotrol- paint. These jobs have been necessary for starting the work on the fuselage frame. These include the installing of the long wooden battens along the sides and upper surfaces of the fuselage frame and the partial covering of the fuselage frame steel tubes with fabric strip.

Metal brackets with 10 mm slots have been welded to the structure of both sides and the upper surface. Thin wooden battens have been fastened to these brackets along the whole of the rear fuselage. The purpose of the battens is to keep the covering canvas separated from the fuselage frame trusswork. Otherwise the metal would start to “eat” into the canvas, especially when rusting.

In order to prevent direct contact between the canvas and the longitudinal steel tubes at the upper and lower corners of the fuselage frame, cloth strip had been tied around the tubes. There were still remains of these strips left in the tail and vertical stabilizer of the Snoopy.

Next we started making the long protecting wooden battens. We found suitable material to make the battens at the restoration workshop’s woodware storage at the Finnish Aviation Museum. The battens were cut to measure and shaped to fit the brackets. At fitting the battens the brackets were squeezed tight to them. The batten was locked into place with small nails. Finally the battens that were fastened to the brackets, were protected with nitrocellulose lacquer.

Along with making the battens, we started covering the steel tubes of the fuselage frame with 20 mm wide cotton strip or tape. We bought that from Eurokangas. When the shop assistant queried what we needed it for, we said that it was used for covering a museum aircraft. The assistant was surprised but interested, so we briefed her in more detail about the purpose of the fabric strip. We must have been the first customer of this sort.

The ribbon was wound around the fuselage tubes to form a solid surface of fabric around the tubes. We wound the fabric strip to overlap the edge by about 5 mm. The stripping thus became solid, without any metal surface being visible. On the lower surface of the fuselage, without the wooden batten, we wound the strip on the lower part trusswork as well.

All the strip-covered surfaces were finally treated with nitrocellulose lacquer, which simultaneously glues the strip onto the tubes and later functions as an adhesive surface for the canvas covering. The covering canvas is tightened with that very same nitrocellulose lacquer.

Photos by Lassi Karivalo.

Translation by Matti Liuskallio.

The surface treatment of Snoopy?s fuselage framework

Perjantai 25.10.2024 - Tuesday Club member

Suomeksi

The fuselage framework of the experimental aircraft OH-XEA “Snoopy”, currently being restored  by the Tuesday Club of Aviation Museum Society Finland, was without its fabric covering when the Society received its ownership. When and why the fabric covering had been stripped off, is not known. Anyway, Snoopy had been stored without its covering for a long time, as its fuselage framework, welded of 13 mm steel tube, was in such thick rust.

The first stage of restoring the fuselage framework was to clean it from rust. Cleaning the steel tubes until clear metal appears is however unnecessary, as removing the superficial rust will suffice. When the tube surface feels very smooth to your fingers, it is clean enough. For the purpose, we used sandpapers of various grades as well as scrubber sponge. The grinding dust was wiped away carefully with rags of fabric and solution mixed of Sinol spirits and water.

Not grinding the fuselage framework until clear metal shows is because for priming the tubes for their surface paint, we use the clear Isotrol lacquer (Klarlack Grund). This lacquer penetrates through possible rust to the surface of the tube, stopping the rusting process. The surface can then be painted directly on the lacquer.

After the whole fuselage framework was cleaned from surface rust, we then treated it by a thin coat of Isotrol, covering fully the steel tubes and other metal parts and giving the tubes a nice shiny surface.

After the lacquer had dried, the fuselage framework was painted with Isoqaurd Panzer, an alkyd oil paint for metal. Originally in the 1960’s, the fuselage framework had been painted with red Ferrex anti-rust paint, still visible as residues in the tubes. Simulating the red Ferrex, the Isoquard paint was tuned to the same tone of red. An exception was the landing gear that was painted with black Isoquard, according to its original black paint.

The fuselage framework surface treatment is now done.  The restoration work of Snoopy’s fuselage will next proceed with the cockpit, as well as measures priming the fabric covering of the fuselage.

Photos by Lassi Karivalo.

Translation by Hannu Mononen.

Making the engine cowlings for the Snoopy started with cardboard templates

Maanantai 30.9.2024 - Tuesday Club member

Suomeksi

OH-XEA Ressu (Snoopy) experimental aircraft from the 1960s that we are restoring, was equipped with a Continental A 65 engine. To replace the Snoopy’s lost engine we received, as a donation, a similar engine. The engine cowlings have vanished during the decades as well. So they’ll have to be made anew.

Photo by Esko Keskinen.

From the photographs we have at our disposal the size and form of the cowlings come out very well. The cowling is two partite. The larger, upper cowling, covers the engine from above and the smaller one covers the front part of the engine. The cowlings have been made of sheet aluminium, so that’s what we’ll be using too, utilizing 1 mm thick aluminium sheet. The fact that the original cowling rack fastened to the engine, has survived, will facilitate the making of the cowlings.

The constructing of the cowlings was started by cleaning the rusty cowling rack and painting it with black Isotrol paint. Black, because the original black paint was still faintly to be seen. The freshly painted rack was fastened to the Continental engine donated to us. The first phase to make the cowlings proper, was to make patterns or templates out of cardboard to fit above the rack. According to the cardboard templates aluminium blanks will be cut to be moulded to their final form.

Making the templates was started with the upper cowling. The template was made out two pieces of cardboard cut from a roll. First the tentatively cut left-hand side was fastened to the pegs in the protective rack. After that the same procedure was repeated with the right-hand piece of the template, after which the left and right-hand halves of the template were taped together. The united template of the cowling was modified by cutting and taping extra pieces to reach the final shape of the Snoopy’s cowling.

At this stage the making of the cowling template, covering the front end of the engine, was commenced. A piece of cardboard cut from the roll was bent against the front of the engine. The piece was gradually cut to form and the cardboard was attached to the pegs in the rack. By cutting suitable extra pieces of cardboard to the front cowling it was united with the upper cowling.

Thus, like a patchwork quilt, the cardboard template was built around the Snoopy’s Continental engine prior to making the aluminium cowling. The next stage will be to transform the shape of the cardboard template into aluminium sheets.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Matti Liuskallio.

Continental A 65-8 engine for Ressu "Snoopy"

Sunnuntai 29.9.2024 - Tuesday Club member

Suomeksi

The OH-XEA “ Snoopy” experimental aircraft, built by the Hietanen brothers from Turku in the 1960s, now under restoration at the Tuesday Club, had a Continental A 65 engine. Before the Snoopy it was in the Piper Cub aircraft of the Turku Flying Club. The engine on the Snoopy hasn’t survived, and there is no knowledge about its fate. So we started to ask around whether a surplus engine was to be found somewhere. We could do with quite a dilapidated engine, since we weren’t restoring the Snoopy to an airworthy condition.

Photo by Esko Keskinen (1969).

Our query was successful, as we were offered the Continental A 65-8 engine of the PIK-11 “Tumppu” (OH-YMD) single-seat sport aircraft that had crashed in Mikkeli on 7 August 1999. The engine was damaged and burned in the accident. However, it could be refurbished to look externally intact, to be attached to the nose of Snoopy.

The miserable condition of the engine had been worsened by its exposure of several years to the mercy of the weather, thus having heavily rusted through. To start he refurbishment of this engine in the Tuesday Club, we fetched it from Tampere in the boot of a Skoda Octavia.  

Our purpose is neither to repair the Continental engine into working condition nor to restore the airworthiness of Snoopy. To refurbish the engine, we will dismantle it to pieces as fully as possible, then after cleaning and fixing those, the engine will be re-assembled and attached to the nose of Snoopy.

All parts of this damaged Continental are not remaining, as some of them were destroyed in the crash. However, we hope to find or to get substitute parts for the missing ones later on. We also welcome any parts rejected in repairing and servicing Continental engines.

Dismantling of the engine was started outdoors at the Finnish Aviation Museum by detaching the badly damaged engine mount and the lower oil sump, which were still attached to the engine. At the hub of the propeller, the burnt propeller stem remained. After the nuts of the hub bolts were loosened, the propeller torso could be detached.

Next the remaining left-hand side exhaust pipe, spark plugs, both magnetos attached to the timing gear cover, the cover itself and the sprockets under it were removed. The lid of the oil pump under the timing gear cover was opened and the pump sprockets were taken out to be cleaned.

Photo by Esko Rossi.

Dismantling the engine was continued at the Museum’s restoration shop. The engine was fastened to a trestle, where the engine could be turned around its longitudinal axis, like in a barbeque. This greatly helped the handling of the engine. Now we detached the valve rods of the rocker arms and thereafter the rocker axles, after which the rocker arms came off the cylinder head. It became clear that the valves didn’t budge an inch. We tried to make them move and loosen them by dissolving with antirust agents.

Also the propeller hub was stuck firmly to the crankshaft. To dislodge the hub for cleaning, we applied various antirust and lubricant agents, but the propeller hub just wouldn’t budge. We gave some time for the antirust agent to work and finally managed to get the propeller hub out with a puller.

Only the cylinders remained in the engine block. We wanted to get them unfastened, too, to facilitate blasting their surfaces clean when separated. We were increasingly worried whether the pistons inside were rusted too tightly onto the walls for the cylinders to be taken loose. Well, we can at least give them a go, as they say, and that’s what we decided to do.

We turned the nuts on the mounting pins open and tried if the pistons would budge. No go. We then poured white spirit into the cylinders through the plug holes, to see if it would squeeze between the pistons and cylinder walls, and mobilize the stuck pistons enough to detach the cylinders. So far, we haven’t succeeded in this, “but we shall never surrender” to quote Sir Winston Churchill.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Matti Liuskallio.

The Myrsky Group of Tuesday Club completes its job

Maanantai 23.9.2024 - Tuesday Club member

Suomeksi

The eleven-year project of the Myrsky Group, to restore the aircraft registered as MY-14 of the WW2 fighter VL Myrsky II, has been brought to its conclusion. The restoration project was started in the autumn of 2013. In concrete terms, the Myrsky Group of the Tuesday Club and the Finnish Air Force Museum shared responsibility of carrying out the restoration, the latter concentrating in restoring the fuselage.

Generally, we talk about the restoration of the Myrsky, but there is also good reason to call it renewed production, as most of the Myrsky with its mixed construction had to be entirely built anew, based on the original drawings of the aircraft. This is how the construction of, among others the wood-structured wing, the vertical and horizontal stabilizers, the rudder, and the aluminum NACA ring, wing root fairings, engine cowlings, and air ducts of the oil cooler were produced.

The largest single original part in the restored Myrsky is the fuselage framework of the MY-14. It defined to identify the project as restoration of the Myrsky MY-14. There are other original metal parts of Myrsky as well, but most of even them had to be manufactured.

The original plan was to transport those parts of the Myrsky that were built by the Tuesday Club at the Finnish Aviation Museum in Vantaa, to the Finnish Air Force Museum at Tikkakoski already in June 2024, to receive their surface painting. Some of the parts were sent as planned, but mostly the transport was delayed until the autumn, as everything wasn’t ready yet by June.

Photos by Lassi Karivalo.

The packing of the remaining parts of the Myrsky for transfer to Tikkakoski was started in August. The packaged parts were tied onto pallets that could then easily be moved by forklift onto the platform of the transport lorry. The wings were not packaged, but instead fixed onto wheeled transport frames that proved handy in moving around each heavy wing, weighing over 200 kilograms. Specific braces were tailored for the wings, to enable stacking them on top of each other on the lorry platform. This stacking procedure was tested in advance before the transport in the restoration workshop of the Finnish Aviation Museum, separating the wings and laying them on top of each other, like they would be travelling during the actual transit.

Photos by Lassi Karivalo

On Wednesday, 18 September, a lorry of the Defence Forces with its trailer arrived at the Finnish Aviation Museum to fetch the parts of the Myrsky to Tikkakoski. The loading of the parts began. Each wing was loaded (with ailerons, flaps, landing gear, wheels, and wheel well doors packed separately), parts of the tailplane (vertical and horizontal stabilizers and the respective rudder and elevators), the oil cooler (with air intake and exhaust air ducts), the aluminum wing root fairings, and a great number of small parts. Previously the NACA ring, the lower engine cowling, air duct and air horn had been already delivered to Tikkakoski.

After all the Myrsky parts had been loaded either on the platform or the trailer of the lorry, the journey to Tikkakoski commenced. After arrival at the destination, the freight was moved inside the FAF Museum.  

Even though the Myrsky project has now been completed for the part of the Tuesday Club, the whole restoration project is by no means over yet. At Tikkakoski, the parts of Myrsky with primer painting will be getting their surface paint of green / black camouflage pattern, national insignia, and the identification code of the aircraft. This task is already underway. Would one dare to say that the Myrsky MY-14 will be assembled on display at the FAF Museum still during this year, as there have been so many failed predictions?

The restoration project of Myrsky is one of the most extensive restorations ever in Finland, of aircraft used by the Finnish Air Force. The working hours used for the project speak for themselves. By mid-September 2004 the restoration of the Myrsky MY-14 during eleven years had taken working time as follows, with numbers rounded. Total work input: 40,000 hours. To this total, the Myrsky Group of the Tuesday Club had contributed 28,000 hrs. The share of the FAF Museum is 9,000 hrs. Outside the project, either paid or donated work amounts to 3,000 hrs. Based on the numbers, the Myrsky Group of the Tuesday Club has produced most, i.e. 70% of the restoration effort of the Myrsky.

However, there will be more working hours waiting for the Finnish Air Force Museum to accrue to the total amount at stake for the Myrsky restoration. Those will be coming from the surface painting of Myrsky, presently underway, as well as from the final assembly for display at the Finnish Air Force Museum.

Photos by Jouni Ripatti except if otherwise mentioned.

Translation by Hannu Mononen.

The Link Trainer wings ready to be delivered to the Karelian Aviation Museum

Maanantai 9.9.2024 - Tuesday Club member

Suomeksi

The Karelian Aviation Museum, situated in Lappeenranta, asked the Tuesday Club to restore the wings of a Link Trainer (LT) in their collection. Partly broken and wing covering torn the wings were brought to the Finnish Aviation Museum at the end of 2023 and the work could be started. The progress of the wing restoration has been followed in earlier Tuesday Club blogs.

Our aim was to complete the restoration work at the end of May, before closing the Tuesday Club’s spring season 2024 but the top coating of the wings was left unfinished. So the painting continued in August after the Club’s autumn season had started. Presently the wing paintings are concluded.

Left hand side photo: Kimmo Marttinen.

The wing covering fabric, which we had tightened to drum top tightness with NC-Speed nitro cellulose lacquer, was painted with Isotrol oil paint. The paint was tinted similar to the original beige tone (tint TVT Q609). The painting was executed with a paint brush and the Isotrol-paint had an excellent coverage from the first layer on. Furthermore, the paint formed an even and smooth surface, so a second application of paint was unnecessary. Someone at the Tuesday Club cut in saying: ”My word. It’s like factory work!”

When both wings had been painted, the earlier restored ailerons were assembled in them. It’s a bit peculiar that this Link Trainer has ailerons in the wings, but no mechanism to transact the joystick’s movements to the ailerons. There are Link Trainers with moving ailerons. There are also Link Trainers with only a piece of board instead of a canvas covered wing.

The aileron is fastened to the wing with two traditional hinges. During the restoration the screw holes had remained under the covering. The places of the hinges could be defined by photos, which were taken before restoration to define the status of the wings. The places of the hinges were marked on both wings with masking tape.

The ailerons were attached one by one to their own wings. Each hinge was placed on the marking tape on the aileron and the middle screw hole was marked on the tape. Traditional groove head screws were used. A screw hole was bored on the mark with a thin bit and the screw was screwed on. After this the marking tapes could be removed.

With both hinges had been fastened in the aileron with its middle screw, the aileron was placed in place beside the wing so that the other halves of the hinges were now resting against the wing. The place of the middle screw was marked on the wing, after which the middle screws were screwed on. The aileron was now fastened in the wing.

The next step was to check that the aileron was fastened in the right position. When that was verified, all the hinge screws were screwed to place. Installing the ailerons was now completed. The last phase in the restoration was to paint the brackets in the wing beige. These brackets are needed to fasten the wing to the Link Trainer fuselage.

The restoration of the wings was now completed and they were ready to be delivered to the Karelian Aviation Museum in Lappeenranta. The tail boom stabilizers of the Karelian Aviation Museum’s Mil Mi-8 (HS-4), which we had finished in the spring, will go with the same delivery with the Link Trainer’s wings.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Matti Liuskallio.

Assembling the Myrsky wing root fairings and the oil cooler

Maanantai 15.7.2024 - Tuesday Club member

Suomeksi

Apart from the Myrsky-project other activities of the Tuesday Club are on hold for the summer break. So the parts of the OH-XEA “Ressu”, Caudron C.59 (CA-50), Valmet Tuuli III (TL-1) and the Link Trainer, heaped in the former Aviation Museum coffee room, can wait for the work to continue halfway through August, when the autumn season 2024 for the Tuesday Club will commence.

The project members of the Myrsky restoration team at the Tuesday Club have toiled “day in and day out” to finish and assemble the wing root fairings covering the wing/fuselage seam and the oil cooler, with its intake and exhaust air horns. Both these projects have taken more time than planned, so the Myrsky II (MY-14) roll-out, planned for the beginning of August, will be delayed. The summer holiday season both at the Finnish Air Force Museum and at Patria industries have affected in the delay.

Oval-shaped openings and a flapped hatch were made to the lower surface of both the right and left-hand side wing root fairings. The narrow oval openings are for cooling the wing root fairings, which for their part cool down the engine oil cooler, sheltered by the fairings. The edges of the openings cut to the aluminium plate were strengthened with a 1 mm thick aluminium strip.  The strips were fastened with rivets.

The wing root fairing edges were likewise strengthened with aluminium strips on both fairings. That way the fairings stay better in form and are easier to handle when they are more rigid. The strips were riveted to the wing root fairings with countersunk rivets.
In addition to the abovementioned ventilation openings, an opening was cut to the right-hand side wing root fairing, for the horn for the exhaust air from the oil cooler. The exhaust air will be conducted through the opening in the fairing onto the lower surface of the wing. The edges of the opening for the exhaust air horn were strengthened with 1 mm thick aluminium strips.

Photo by Heikki Kaakinen

When the openings in the right-hand side wing root fairing were ready, the fairing was fitted in place. After that, the end of the horn for the exhaust air could be pushed into the opening in the fairing and fasten the other end of the horn to the oil cooler. It was noted that the exhaust air horn fitted its opening just like it should.

Left hand side photo by photo archive of Finnish Aviation Museum.

Next in turn was the making of the cover for the space for the mouthpiece of the intake air horn. The mouthpiece of the horn is situated in the leading edge of the wing in an area limited by two ribs and the front spar. Cooling air for the oil cooler is taken through an opening in the wing’s leading edge. The horn for the oil cooler intake air is for the most part located under the left-hand side wing root fairing, but the mouthpiece of the intake air horn reaches outside the fairing edge.

Photos by Heikki Kaakinen.

When the intake air horn for the oil cooler and the left-hand side wing root fairing had been installed once again, we checked once more that the air intake horn’s mouthpiece was exactly flush with the wing’s leading edge. Now we could start to make the cover for the space for the mouthpiece of the air intake horn. The space will be covered with a shield made of aluminium sheet, with an opening for the air intake horn. The shield will be fastened to the wing ribs and the edge of the front spar.

The blank for the shield was cut from 1 mm thick aluminium sheet. The blank was bent to match the leading edge shape. After that an opening for the air intake horn for the oil cooler was made. The half-ready shield was fitted to its place. It was observed to sit well. The edges of the opening of the shield were bent inwards by forcing.

Photo by Jorma Laakkonen.

The aluminium shield covering the mouth of the oil cooler intake air horn will be fastened at its edges with screws and flange nuts to the wing ribs and the wing spar. On the fairing side the right-hand edge of the shield remains in between the stem fairing and the metal wing rib, i.e. it will be fastened to its place simultaneously with the edge of wing root fairing. Holes for screws were drilled at the edges of the shield. The holes were strengthened with “crickets” or brass strengthening rings.

Photo by Heikki Kaakinen.

The shield was now ready to be test-fitted together with the left-hand side wing root fairing. So the shield was screwed at its edges with a few screws to the leading edge rib and the front spar’s upper and lower edges. After this the left-hand side wing root fairing, next to the oil cooler, was fitted to place. The outer edge of the fairing curved snugly over the air intake horn’s mouthpiece shield’s edge. Assembling the wing root fairing and the shield needs only some fine adjustment.

When the fittings of the oil cooler air intake and exhaust air horns, wing root fairings and the air intake horn mouthpiece shield are ready, the aluminium parts that haven’t been chromated will be taken to Patria Industries for yellow chromating. The chromating will take place at the beginning of August.

By now it’s clear that the preplanned roll-out event of the MY-14 Myrsky fighter will be postponed. But, as they say, it’s worth while waiting for something good.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Matti Liuskallio.

The right-hand side wingtip of Caravelle III "Bluebird" is delivered to Turku

Sunnuntai 26.5.2024 - Tuesday Club member

Suomeksi

The Caravelle III "Bluebird" (OH-LEA), on display in Turku, has until now been without the wing tip piece of its right-hand side wing. For about a year, the wingtip has been under repair and parts of it have been rebuilt at the Tuesday Club, working at Finnish Aviation Museum. The leading edge of the wingtip had been destroyed while the Caravelle, in SAS colours at the time and carrying registration SE-DAF, stood by the edge of Arlanda airport for decades. Probably some airport vehicle had bumped into the aircraft.

The repair work of the right-hand wingtip section was completed at the Tuesday Club, but it wasn’t taken to Turku until now. The wingtip was transported from Finnish Aviation Museum in Vantaa to Turku airport, to be assembled on “Bluebird’s” wing. The wingtip section is too large to be transported in an ordinary passenger car. It was packed properly and loaded on the Aviation Museum yard on a trailer. The journey towards Turku could begin.

The vehicle was welcomed at Turku airport by the Caravelle Turku restoration team. The team unloaded the wingtip from the trailer and carried it under Caravelle’s right-hand side wing to wait for assembly.

Right-hand photo by Reijo Siirtola.

Now all Caravelle work allocated to the Tuesday Club have been completed. The work included repairing the nose bulkhead edge and the damaged radome, refurbishing and painting the wall panels of the flight deck and the corridor leading to the flight deck, repairing the glare shield above the flight deck instrument panel, building the frame for the navigation light on the right-hand wingtip and preparing the navigation light globes by 3D-printing.

Photo by Ismo Matinlauri.

Furthermore, in 2022 we built stands for supporting the Caravelle’s fuselage and wings during the transportation from Arlanda to the former shipyard hall in the Pansio harbour area in Turku. We also restored the Caravelle III towbar, brought from Arlanda, which was in poor condition. The towbar is already in place, fastened on “Bluebird’s” nose wheel.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Erja Reinikainen.

Caudron C.59 advanced trainer; covering of the horizontal stabilizer

Tiistai 14.5.2024 - Tuesday Club member

Suomeksi

Caudron C.59 was an advanced trainer used by the Finnish Air Force in the 1920s. The restoration of the individual aircraft CA-50 was commenced at the Tuesday Club in 2019. The work has advanced in stages. After the Finnish Aviation Museum acquired from abroad cotton fabric designated to covering aircraft, we could start covering the horizontal stabilizer of the Caudron, which had been waiting for some time. We had earlier refurbished the Caudron’s horizontal stabilizer, which had been in very poor condition, by taking it apart and reassembling it for covering.

Prior to the covering, it was decided to lacquer with nitro cellulose lacquer the fabric strip covering, wound around the leading edge of the stabilizer. It was made of 50 mm wide linen band according to the original. By lacquering the band covering, the gluing of the covering fabric will be enhanced on the surface of the leading edge of the stabilizer.

Photo by Jukka Köresaar.

The linen band covering wound on the leading edge of the horizontal stabilizer was lacquered with 75% nitrocellulose lacquer. As lacquer we used NC Speed nitrocellulose lacquer, and it was tinted red with iron oxide powder. After the lacquer had dried, the edges of the linen band had, as we expected, risen as well as the fabric fuzz. So the band covering was sanded smooth, and another layer of lacquer was applied. Even after the re-lacquering, the leading edge band was uneven and the band had to be sanded once more, after which it was lacquered with 100% nitrocellulose lacquer. So the linen band wound around the leading edge had been smoothed, and we could start covering the horizontal stabilizer.

The width of the horizontal stabilizer is 60 cm and its length 120 cm, so a 130 cm wide piece was cut from the 140 cm wide cotton fabric. This way the fabric has enough working allowance to work both in length and width way. The fabric was wound around the stabilizer, which was laid the table, so that the lapels of the fabric reached past the horizontal stabilizer’s trailing edge. We meant to make a bag out of the fabric, which would be open at the trailing edge.

To achieve this, at both ends of the stabilizer the lapels were joined with pins. The lapels were then sewn together with a sewing machine, along the line of the pins. So the fabric was formed to be a bag, open at the trailing edge. When the ends had been sewn, the fabric was turned inside out, leaving the sewing seams of the lapels inside the fabric bag.

The fabric bag, open at the trailing edge, was drawn on the horizonal stabilizer. The sewing of the fabric was very successful, because the fabric bag had become tight, or rather “skin-tight” on the horizontal stabilizer. Now it was time to sew together the still open trailing edge fabric lapels. For the sewing extra parts of the lapels were cut off, so that the lapels met at the outer edge of the trailing edge batten.

To keep the lapels of the fabric in place when they were sewn together, the fabric was fastened with staples from a stapler at the side of the trailing edge batten. The lapels of the fabric were sewn together with a thin double yarn cotton thread. As a needle we used a curved needle, which was handy for this kind of sewing.

Photo by Antti Laukkanen.

The sewing of the covering fabric lapels was done so that the seam formed a continuous serrated shape. When the lapels had been sewn, the covering fabric formed a closed bag over the horizontal stabilizer.

Photo by Antti Laukkanen.

The next phase in the work was the water-tightening of the fabric. The stabilizer covering fabric was soaked with boiled, but cooled water, and was left to dry. With water-tightening, the fabric is pre-tightened, because when dried the covering fabric has already tightened a few percent on the stabilizer.

Photo by Antti Laukkanen.

The proper tightening of the covering fabric to resemble a drum head, will be made with nitrocellulose lacquer.  Before tightening the covering the fabric needs to be sewn on the stabilizer ribs. The sewing will be done by following the original 1920s Caudron stabilizer sewing method. This way of sewing was documented, when the decayed covering fabric was stripped off the Caudron’s stabilizer. According to that, the covering fabric was sewn onto the fabric strips, which were fastened to the stabilizer ribs, with tacking interval of about 3 cm. The fabric strip was for its part tied to the rib’s surface with an edging ribbon. We had done similarly, when refurbishing the stabilizer.

The places of the stitches were marked at each rib on the surface of the covering fabric, using a thin template made of plywood. The stitching places of the sewing needle were marked on the fabric surface with a thin felt pen, through the template holes. Using a curved needle and double yarn thin sewing thread, the covering fabric was sewn stitch by stitch to the edging ribbons that ran along the ribs. A regular space between the stitches made it possible that the needle occasionally pierced the edging ribbon which tied the fabric strip to the rib. When the sewing had been done, the staples could be removed from the fabric surface.

The covering fabric was now sewn to the horizontal stabilizers’ ribs, both on the upper and the bottom surface, so it’s time to move on the next phase of the covering. There the horizontal stabilizer’s covering fabric will be tightened to drum head tightness with nitrocellulose lacquer. As lacquer we use NC Speed nitro cellulose lacquer. Applying the lacquer is started with 25 % thinned lacquer, and from there in stages to the full 100% nitrocellulose lacquer.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Matti Liuskallio.

Covering of Ressu's (Snoopy) rudder

Maanantai 6.5.2024 - Tuesday Club member

Suomeksi

When the preliminary tasks concerning the covering of the experimental aircraft Hietanen OH-XEA rudder had been done, the proper covering could be commenced. The rudder covering is done with cotton fabric meant for covering aircraft. The covering will be done the same way it had originally been done in the 1960s.

The covering got started by setting the metal-framed rudder on the fabric, which was spread on the table. The edge of the fabric was wrapped around the right-hand side metal tube of the leading edge and sewed onto it.  The sewing was done with thin cotton thread, using a suitable curved or hooked needle.

After the fabric had been sewn to the leading edge right-hand tube, the rudder was turned over on the table, so that the metal frame of the rudder was left under the fabric. The fabric that was attached to the right-hand leading edge, was drawn over the leading edge and left-hand side to the trailing edge the of the rudder, where the lapel of the fabric was left hanging over the table edge.

A metal bar was attached to the hem of the fabric hanging over the table edge. With the aid of the bar the fabric, resting on the left-hand side of the rudder, was tightened. At the top and bottom edges of the rudder the lapels of the fabric were tightened with small clamps to the edge of the table. When the fabric was tightened this way, the water tightening of the fabric was started. The fabric was soaked through with boiled water. When drying, the fabric shrinks a little. The proper tightening of the covering fabric will be done after the water tightening with nitrocellulose lacquer.

The tightening lacquering of aircraft covering fabrics is carried out in a process with several phases. The tightening lacquering is started with a 25 % thinned nitrocellulose lacquer. From that the process continues with intermittent sanding to 50, 75,100 -% nitro lacquer. After each phase the fabric is sanded free of the fuzz brought to the surface by the lacquer. From phase to phase the covering fabric will shrink more and more. The end result is a covering fabric tight as a drum head. The sufficient degree of tightening is easy to verify by tapping the surface. It’s customary to pigment or colour red the lacquer with iron oxide powder. This will help to recognize which area has been dealt with the lacquer and which not.

When the water-soaked fabric on the left-hand side of Ressu’s rudder had dried, 25 % thinned NC-Speed nitrocellulose lacquer was applied on the surface of the fabric. As a thinner NC-Speeds’s own Thinner-8 was used. The lacquer was tinted red with red iron oxide powder. After the lacquer had dried, the weights were detached and the rudder was turned around, after which the unlacquered side of covering fabric was drawn tightly under the right-hand side of the rudder. The lapel of the fabric was sewn to the leading edge of the right-hand side metal tube, i.e. the same, where the lapel of the fabric had been sewn in the first place. The covering fabric was now around the rudder like a bag.

Now the right-hand side fabric of the rudder in its turn was water-soaked. After that this side, too, was lacquered with 25% NC-Speed tightening lacquer. After the lacquer had been dried, the rudder’s lower edge, triangular shaped in cross section, was covered by sewing the lapels of the fabric onto the tubes in the rudder’s lower edge.

The tightening of the covering fabric continued with applying a second layer of 25 % lacquer on the rudder surfaces. Because the fabric didn’t start to tighten in the manner we had hoped, the rudder was lacquered a third time over with 25% lacquer. From this point on we advanced in stages to three times applied 50% and twice applied 75% NC Speed lacquering. In this manner a sufficient level of tightness was achieved, so that the fabric strips protecting the stiches of the covering fabric at the edges of the rudder can be fastened. The protecting strips will be glued to the leading, upper, and bottom edges of the rudder. No strip will be needed at the trailing edge because there’s no seam in the fabric there. Of course we could glue a strip there, too, because it would make it more resilient.

The protective strips were cut off the same covering fabric with which the rudder was covered.

The cutting was done with serrated zig-zag scissors. The serrated edge of the protective strip will stick better to its base, i.e. the lacquered surface of the covering fabric compared to the straight edge.

The protective strips were glued to the rudder with 75% nitrocellulose lacquer. First the area of the protective strip was lacquered, after which the strip was pressed onto the wet lacquer. The strip was applied with lacquer so that it became thoroughly soaked with lacquer. The strip was pressed against is base and brushing away air pockets or bubbles from under the strip. At the same time it was made certain that the serrated edges were tightly glued to the surface of the covering fabric.

After the strips had dried, their surfaces were sanded smooth paying attention especially to the serrated edges. The lacquering and sanding were repeated three times, after which the protective strips and especially their serrated edges were worked so smooth, that feeling with your finger gave you no sensation of the strip edge on the surface of the covering fabric.

After fastening the protective strips, the whole rudder was lacquered once with 100% nitrocellulose NC Speed lacquer. The covering fabric of the rudder had now reached the stage where it was as tight as a drum head and thus ready for painting. According to Ressu’s original colour scheme it will be light bluish grey.

Photos by Lassi Karivalo.

Translation by Matti Liuskallio.

Caravelle right-hand wingtip is finalized with the navigation light globe

Lauantai 27.4.2024 - Tuesday Club member

Suomeksi

When the new leading edge had been built to replace the destroyed right-hand side wingtip leading edge on the Caravelle III (OH-LEA Bluebird), we could begin the installation of the navigation light globe into its place on the leading edge.

We don’t have the original navigation light globe because it has been destroyed together with the wingtip. We could not find a globe as a spare part either, so we had to make one. We chose to do this by 3D-printing. We used the partly broken navigation light globe from the left wing as a model. A new globe was printed for the right wing and also for the left wing navigation light.

The new navigation light globe was installed on the OH-LEA Bluebird’s left-hand wing earlier in the summer of 2023. The right- hand wing, however, had to wait until March 2024 for its new globe to be put already in early into place after the new leading edge of the destroyed wingtip had been finished.

The 3D-printed navigation light globe is made of stiff plastic, and in the beginning it didn’t fit properly into place. We heated the globe with a hot air blower so that it could be moulded to fit into its mounting on the wingtip. The globe was fastened tentatively on the edges of the mounting with a couple of screws. This was necessary for holding the globe in place while making the fastening frame. The globe is fastened on the aluminium edge of its mounting with a frame. The frame has holes for screws, and it presses tightly against the sides of the globe, and the screws in the frame holes are tightened through the globe edge into the aluminium edge underneath.

Diverging from the original solution, we decided to make the fastening frame for the globe from two parts. This made it easier to build the frame. Nevertheless, the frame we made will cover the most part of the navigation globe edge. A connecting piece will be needed on the top of the globe to connect the ends of the frame.

When the globe had been fastened with a couple of screws, broad paper tape was fastened on its edge. The shape of the globe frame was drawn on the tape. Based on the drawn line, a model for the frame was made of cardboard. The model was taped on a 1 mm thick aluminium sheet, which had already been pre-cut into the frame shape. After this we began to modify the sheet with a cutter to match the shape of the cardboard model.

The aluminium frame was test-fitted into place and modified several times. Gradually the frame reached its final shape and it rested against the lower edge of the globe as §planned. When the desired shape had been reached, the blue plastic film which had protected the aluminium surface was removed from the frame.

A strip of paper tape was fastened on the surface of the finalized fastening frame for marking the location of the fastening screws at regular intervals with a pencil. Holes for the fastening screws were drilled at the marked locations, then the screws were fastened one by one. This made the navigation light globe press into its place between the fastening frame and the edge of the globe mounting. Now the navigation light globe on the right-hand side wingtip was in place.   

The last phase was to make the 5 cm connecting piece between the fastening frame ends on the top of the navigation light globe. First a cardboard model was made of the connecting piece. The connecting piece was cut and moulded from aluminium sheet, following the model. When the blue plastic covering had been removed from its surface, the connecting piece was fastened between the fastening frame ends, using two screws with washers. Finally the screws were tightened.

Under the globe, out of sight, is the socket for the navigation light bulb and its green glass globe. The socket was lathed from aluminium and installed into place at the Tuesday Club. The Caravelle’s right-hand side wingtip is ready for housing a powered navigation light, if there is need for it at some point.    

Now the Caravelle Bluebird’s right-hand side wingtip had been completed. Re-constructing the destroyed leading edge took a whole year. The wingtip can be delivered to Turku to be assembled on the Caravelle Bluebird, which is on display near the passenger terminal at Turku airport.

Photos by Lassi Karivalo.

Translation by Erja Reinikainen.

The Ressu (Snoopy) rudder covering preliminary work assignments

Sunnuntai 21.4.2024 - Tuesday Club member

Suomeksi

The IMY Tuesday club has continued its work with the Snoopy (Ressu).

Planned and built by the Hietanen Brothers from Turku, the mixed structure experimental aircraft Ressu from the 1960s is next in line for the rudder’s canvas covered steel tube structure to be restored.

For the restoration the rudder was detached from the fuselage. The fabric covering was in a fragile shape, and the paint finish of the canvas badly crackeled. On the left-hand side the covering is fairly intact, but on the right-hand side a large piece of covering is missing on the lower edge. From this unexpected opening it could be seen that the covering canvas had been sewn onto the rudder frame outer tubes only, but not onto the cross tubes. The outer ring metal tubes had been covered with 20 mm wide cotton edging ribbon, by winding it the tightly along the tube.  This was a common way to avoid the covering fabric to be attached to form a direct contact with metal. The fabric, that was sewn to the metal structure, had been tightened drum tight with nitrocellulose lacquer, after which the surface had received a light blue coat of paint. Finally the rudder had been treated with red speed stripes, a black number 2 and a bird figure.

Because the Ressu’s rudder covering fabric was in a bad shape and partly broken, we decided to cover it completely anew, complying the old manner of doing it, however. The old covering fabric had to be detached from the steel frame of the rudder by cutting it off with a knife, because the fabric had glued itself tightly to the edging ribbons around the tubes. After detaching the covering fabric, the edge ribbons around the metal tubes were also removed.

The red stripes of the rudder’s covering fabric and the left-hand side black number two and the right-hand side black bird were copied on transparent rice paper. After that the bird and the number were transferred onto sturdy cardboard to wait for the final transfer of these symbols onto black contact plastic, and their fixing onto the surface of the new covering fabric.

The work with the rudder’s metal structure was continued with doing away with the rust on the tube surfaces. Luckily the tubes weren’t badly rusted or corroded. The rust was sanded off with sanding paper, however, so that the tubes weren’t ground to pure metal. The transparent Isotrol-lacquer can be applied as primer even though the surface is still a bit rusty. The shielding cover of the Isotrol- lacquer will stop the rusting process. During the sanding it had been noticed that the rudder had originally been painted red. The paint had most probably been the red Ferrex, used widely in the 1960s to stop rusting.

The rudder frame structure was primed thinly with the transparent Isotrol -lacquer. Owing to the lacquer, the tube surfaces came out beautifully clear and the red paint applied on the surfaces rose up even more gloriously. After a light buffing, a layer of red Isotol paint was applied on the bright Isotrol lacquer, emulating the original red surface paint.

When the rudder frame had dried, we started to cover the steel tubes by winding 20 mm wide cotton edging ribbon around the steel tubes. Thus we’ll prevent, according to the original concept, the covering fabric being in direct contact with the surface of the steel tubes. By hurrying slowly we managed to wrap the cotton ribbon around the outer tubes of the frame. Ressu’s rudder in now ready to begin the fabric covering proper.

Photos by Lassi Karivalo.

Translation by Matti Liuskallio.

Ressu's fuselage frame moved from Lemu to Vantaa

Tiistai 9.4.2024 - Tuesday Club member

Suomeksi

On Thursday April 4th, the Tuesday Club task force set off towards Lemu in the Turku region to fetch the OH-XEA “Ressu” (“Snoopy”) fuselage frame to Finnish Aviation Museum to be restored by the Tuesday Club. The OH-XEA is an experimental aircraft, designed and built in the late 1960s by brothers Hietanen, Esko and Ari. Since last autumn we have been working on the restoration of Ressu’s horizontal stabilizer, elevator, rudder, and wing struts. This work will be ready soon and we could pick up the Ressu’s fuselage frame from Lemu to be restored.

The Ressu fuselage, stripped entirely of its fabric covering, has been stored in the hall of Martti Mattila, an aviation enthusiast from Lemu. Last autumn we fetched the Ressu’s wings and tail parts from the same place. On our way to Lemu we made a detour via Turku Airport, to Caravelle “Bluebird”, which is on display there. In Helsinki we had picked up a Super Caravelle First-Class double seat frame, which we left to the Caravelle. The aim is to build four rows of seats in the “Bluebird” cabin and an adapted group of First-Class seats. From the Airport we continued to Lemu, where we arrived soon after noon.

Photo by Martti Mattila.

Martti Mattila had already prepared the Ressu fuselage frame for pick up by fastening two wheels with pneumatic tyres, borrowed from a ride-on lawn mower, on the ends of the landing gear axle and by moving the fuselage frame outside the hall. Due to the wheels the fuselage frame was easy to move. The lawn mower wheels are exactly the suitable size for Ressu. Before the fuselage fame was moved next to the trailer to be loaded, the pick-up team posed for a group photo.

Photo by Matti Kainulainen.

When the rather light fuselage frame was lifted on the trailer, we noticed that the landing gear with its wheels was too wide to fit inside the trailer sides. We solved the problem by unfastening the wheels and the landing gear fitted just nicely inside the trailer sides, and the fuselage frame rested on the trailer floor on its wheel flanges.

Photo by Matti Kainulainen.

We fastened the fuselage frame on the trailer with the nose of the aircraft facing forward. The trailer we had at our disposal was long enough to hold almost the whole length of the Ressu’s fuselage frame. The tail reached just slightly over the tailgate. The fuselage frame was secured tightly on the trailer, front and aft, using cargo straps. We topped up our cargo by adding a security banner on the tail. We also loaded the rest of the Ressu stuff from Mattila’s hall, such as the cockpit plexiglass windows and the seat belts. Many thanks to Martti Mattila for accommodating Ressu and its parts in his hall since last June.

Photo by Matti Kainulainen.

We spent some time with Martti Mattila, listening to him talking about his ongoing aircraft engine project. Based on what we heard, we can say that Mattila is a person with multiple skills when it comes to aircraft engines and aircraft in general. He has designed and built an aircraft and he also owns an airworthy engine-Lerche.

It was time to head back to Vantaa and the Finnish Aviation Museum, where we arrived late in the afternoon. On the museum yard we unfastened the cargo straps from Ressu’s fuselage frame and reassembled the wheels on the landing gear. Then we lifted the fuselage frame from the trailer on the asphalt-covered museum yard and pushed it on its wheels in front of the restoration workshop. As the Ressu’s fuselage frame will remain outside for the time being, we wrapped a tarpaulin around it to protect it from rain.

The Ressu’s fuselage frame is now ready to face the restoration procedure of the Tuesday Club. The first actual work item will be to clean the rusty frame tubes of the fuselage frame, stripped of its fabric covering. Then the tubes will be painted with protective Isotrol paint.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Erja Reinikainen.

The Caravelle right-hand wingtip leading edge is completed

Keskiviikko 27.3.2024 - Tuesday Club member

Suomeksi

Owned by Aviation Museum Society Finland and now on display at Turku Airport, the Caravelle lll (OH-LEA Sinilintu, Bluebird) has had its damaged right-hand wingtip leading edge restoration completed. The wingtip in the Caravelle is a separate entity, which can be detached from the wing. For the sake of simplicity, I’ll use the term wingtip for this structure in the future.

The last task in building the new leading edge for the wingtip was to rivet the edges of the upper and lower covering sheets to the centre line of the leading edge. The edges of the covering sheets meet at the centreline of the leading edge. Otherwise the covering sheets of the new wingtip had already been riveted in the wingtip structure.

To be able to rivet the covering sheet edges on the leading edge centreline, the sheet edges were tightened against the leading edge using a cargo strap, tied around the wingtip. After this, rivet holes were drilled at both ends of the sheets and the edges were riveted on the centre line with pop rivets.

It was noticed that a gap of 1-4 mm was left between the edges. The edges of the sheets therefore didn’t reach each other to form a butt joint. It was decided to cover the gap with an aluminium covering strip, running along the leading edge centre line.

To make the covering strip, an 8 cm wide and 40 cm long aluminium strip was cut out of 1 mm thick aluminium sheet to conceal the seam between the covering sheets. The aluminium strip was shaped to the curved form of the leading edge by shaping it against a suitable size iron tube. The concealing strip was arduous to shape because the wingtip leading edge slopes to various directions. The strip was, therefore, moulded phase by phase, fitting it to place at times. Thus the concealing strip was made to press tightly against the leading edge ridge.

Now the blue plastic films protecting the aluminium sheet could be removed and start the riveting of the covering strip. For the riveting the covering strip was tightened to place at both ends with a cargo strap. Masking tape was applied to both ends of the covering strip to mark the places of the pop rivets. The places were marked on the surface of the tape at even spaces with a compass and pencil, and the holes for the rivets were drilled accordingly.

We discussed what would be the best order to rivet the covering strip, so that it would best confirm to the shape of the wingtip leading edge. We ended up in starting the riveting from the rear end of the covering strip, proceeding rivet by rivet towards the wingtip. In doing so, the covering strip riveted itself tightly to the wingtip leading edge. Finally, the edges of the covering strip were tapped with a hammer and a piece of wood to press it still more tightly to the underlying surface of the covering material.

The demanding task of rebuilding the destroyed wingtip leading edge of the Caravelle III was now ready. Let’s not forget the fitting of the 3D-printed navigation lamp cover to its place in the leading edge tip.

Photos by Lassi Karivalo.

Translation by Matti Liuskallio.

Covering the Link Trainer ailerons

Maanantai 18.3.2024 - Tuesday Club member

Suomeksi

The wing refurbishing of the South-Karelian Aviation Museum’s Link Trainer has moved on to the covering stage.  At first we set on to covering the ailerons. One aileron was original and the other built at the Aviation Museum Society’s Tuesday Club to replace the missing aileron. Stripped of its covering, the repaired original aileron and the rebuilt aileron were covered with a special cotton fabric for covering, bought from Switzerland at Craftlab.

The covering was commenced by setting the aileron on the covering fabric and drawing the shape of the aileron on the fabric with a felt pen. The fabric was cut with a wide margin, taking into consideration the actual space for working. The fabric was folded around the aileron, so that the lapels met at the trailing edge. The lapels were fastened together with wig pins, at the same time tightening the fabric on the aileron. T-headed and long wig pins are very handy for this purpose. The pins were acquired from a Chinese on-line shop.

After the lapels of the covering fabric had been fastened to each other with pins, we were facing with tightening the fabric with water. Water tightening is the first phase to make the covering fabric tight. In the process the warp and weft already shrink somewhat, i.e. the fabric pre-tightens around the aileron. For water tightening the water was boiled. By boiling the water it will be disinfected, so that organic impurities won’t infect the fabric, which could cause the fabric to mould. Well, in this case the boiling wouldn’t have been necessary, because we aren’t dealing here with an airworthy device. After the water had cooled down, the fabric was thoroughly soaked.

After the fabric had dried, the proper tightening was commenced. It will be done with nitrocellulose lacquer, which causes the fabric to become as tight as a drumhead. As a lacquer we used NC-Speed nitrocellulose lacquer and as thinner Ohenne 8. Red iron oxide was mixed into the tightening lacquer as a pigment. It is customary to colour the tightening lacquer, so that you can keep track of which areas have been dealt with and which haven’t.

25 % lacquer.

50 % lacquer.

The tightening coats of lacquer for the covering fabric will be applied in phases by starting with diluted lacquer and ending up with undiluted lacquer. The Link Trainer’s ailerons were applied at first with two layers of 25% lacquer, followed by two applications of 50% lacquer, one application of 75% lacquer and to finish it all an application of undiluted nitrocellulose lacquer. The lacquered surfaces were sanded between applications for the fuzz, which was stood up by the lacquer.

After the application of 50% lacquer, the fastening pins of the covering fabric were removed. At the same time the extra fabric lapels’ surplus to the trailing edge were cut off with a Stanley knife. This was possible, because the covering fabric was glued firmly enough to the trailing edge of the aileron, the ribs, and other parts of the aileron structure. The trailing edge will be sanded smooth, and a serrated cotton strip will be glued to it to strengthen it.

75 % lacquer.

In this connection it must be noted that in case of an airworthy aircraft, the covering fabric would have been sewn to the ribs of the aileron, the same way as the fabric would have been sewn to the wing ribs. In not covering the ailerons and the wings we decided to cut corners, so in this case skip sewing the fabric to the ribs. This had been the case with the damaged covering fabric we stripped off the wings.

The tightening lacquer for one aileron is ready and waiting for to be painted beige. The other aileron will receive a few more applications of lacquer, before its fabric will be as tight as a drumhead.

Photos by Lassi Karivalo.

Translation by Matti Liuskallio.

Damages in the Ressu (Snoopy) plywood covering repaired

Tiistai 12.3.2024 - Tuesday Club member

Suomeksi

The restoration of the experimental aircraft (OH-XEA) “Ressu” has so far concentrated on the work with repairing the holes and damages in the plywood covering of the wing halves, ailerons, horizontal stabilizer, and the elevator. This job has now been finished as far as patching goes.

There were about twenty holes and damaged areas in the plywood covering. Part of them being tiny pinpricks, but some were damages measuring tens of centimetres. As patching material, 0,9 mm aircraft plywood was used. To patch small holes, Ressu’s original plywood with a coating of paint was used. We obtained it in connection with clearing the large damaged areas in the wing.

In patching the holes in the Ressu plywood covering, we followed the same proven method throughout. In this blog the patching of a largish damage on the lower surface of the left-hand wing will be presented as an example.

A hole, or an area of a larger damage, was sawn open to a square or rectangular shape. In sawing, a “Kugihiki”, or a so-called Japanese saw was used, which is an excellent tool for sawing thin plywood. Supporting battens were glued under the sawn edges, so that about 1 cm protruded from the inside of the opening. The plywood patch to cover the opening will be glued on these supporting battens.

For gluing the supporting battens and the plywood patches, moisture resistant Erikeeper Plus or Casco Outdoor glue for wood was used. Before gluing the support battens, the protective lacquer was ground off the edges of the underside of the covering plywood. Thus the glue sticks better on the underside of the covering plywood. The support battens were pressed onto the edges of the underside covering plywood with small clamps. Work was also in progress with other holes in the wings, simultaneously with this large opening underside the left-hand side wing.

After the glue had dried, a sheet of thin paper was fastened over the whole opening to be patched. The plywood edges of the plywood opening were “smudged” with a pencil so that it became visible on the paper, thus producing an image of the edge line of the opening. The paper was cut along the now visible opening edge in the plywood. So we had a model to cut the right size of a patch. The paper was superimposed on a sheet of plywood and, hey presto, after this model a plywood patch we needed was cut out of the sheet.

The cutout piece of plywood was fitted in place on the support battens. We marked with arrows the places where the plywood patch still needed filing at the edges, to get the patch press itself in a butt-joint manner against the edges of the opening. When the plywood was in place, glue was spread on the support battens, and the plywood was pressed against the battens.

The gluing of the plywood patch was secured by putting a sturdy plywood sheet on the patch and iron weights piled on it. At the lowest a sheet of foam rubber was placed to distribute the weight evenly.

Before laying the weights, a layer of protective plastic was spread over the patch, to prevent extra glue from seeping off the seams of the plywood patch and possibly sticking to the foam rubber sheet. When both the foam rubber sheet and the sturdy plywood sheet were in place, iron weights were piled on the plywood sheet. We noticed after the glue had dried and the weights and the plywood sheet were removed, that the plywood patch had settled very neatly in place.

Photos by Lassi Karivalo.

Translation by Matti Liuskallio.

Building of the missing Link Trainer aileron

Sunnuntai 10.3.2024 - Tuesday Club member

Suomeksi

The restoration of the Lappeenranta based Karelian Aviation Museum’s Link Trainer wings is underway at the Aviation Museum Society’s Tuesday Club. Our main work is to refurbish the wings and cover them again. Furthermore the missing aileron from the left-hand wing had to be built. As a model we used the right-hand wing aileron, which was stripped of its covering.

Photo by Kimmo Marttinen.

Photo by Lassi Karivalo.

Photo by Lassi Karivalo.

We started to build the aileron from strips of wood according to the original. However, we noticed after a few days that the finished parts of the aileron didn’t keep their form, but there were distortions. The material we used wasn’t good enough. We ended up with a solution different from the original by building the left-hand aileron mainly from plywood, which keeps its form well. The decision facilitated our work also so that the curved trailing edge tip had originally got its form from strips of wood soaked in water. Making the curved part of the aileron from plywood will be easier.

Photo by Lassi Karivalo.

We started making the aileron from the curved tip of the trailing edge. In order to get thick enough plywood to build the trailing edge tip, we glued two sheets of plywood together. After the glue had dried, a picture of the right-hand aileron’s curved trailing edge was drawn on the plywood. The plywood was sawn along the drawing line, to give us a blank for the left-hand aileron trailing edge. The blank was shaped tentatively to its form.

Next we made from plywood the left-hand aileron’s leading edge, which could be called the spar of the aileron. We sawed it from 6 mm thick plywood according to the model given by the right-hand aileron. The leading edge is not at right angles to the wing base. The correct angle (98,3 degrees) was defined from right-hand aileron’s leading edge. The left-hand aileron’s leading edge base was ground to that angle. The leading edge batten was now ready.

The necessary three triangular ribs were made of plywood according to the right-hand wing aileron ribs and angles. In the same way some thin 3 mm strip of pine was found, from which the straight stem of the trailing edge was made. The trailing edge stem will be joined according to the original model with a 5 cm long glue joint to the curved tip of the trailing edge batten.

When all the components of the aileron had been made, the construction of the aileron was started. The compilation was commenced with the leading edge and the ribs that were glued to it. As a gluing platform sturdy plywood was used, onto which a guiding piece with an angle of 93,8 was fastened. The leading edge batten was fastened with clamps to the guide piece and its sturdy platform.

First the aileron’s root rib was glued into place and after that the two other ribs. The gluing was secured with two screws. The aileron had already got its basic form.

The trailing edge of the aileron was still missing. First the straight thin stem of the trailing edge, which was shaped from a batten of wood, was glued to the ribs. Last to go to place was the curved tip of the trailing edge. At the same time the tip and stem were joined at the rib with a glue joint. The rib also strengthens the glue joint.  Because the curved tip of the trailing edge had only been tentatively ground, the tip was ground to final form after the glue had dried.

The missing aileron of the Link Trainer was structurally finished. The aileron will be covered and painted in accordance with the covering of the Link Trainer wings.

Photos by Pauli Jokimies except if otherwise mentioned.

Translation by Matti Liuskallio.

Restoration of the Ressu (Snoopy) experimental aircraft?s wing struts and building the missing one

Lauantai 17.2.2024 - Tuesday Club member

Suomeksi

The restoration of the Ressu aircraft’s wing struts is completed. The aircraft was designed and built by the brothers Hietanen from Turku in the 1960s. Originally registered OH-HEA, the aircraft was registered as an experimental aircraft with the registration OH-XEA in 1969.

The wing halves of the high-wing Ressu are supported with two wing struts fastened to the fuselage lower edge. The front strut has been made of 50 mm and the rear strut of 20 mm thick steel tube. Both the front struts have remained, but only one of the rear struts. These three struts had been in storage inside the bare fuselage frame, which had no covering. The rusty struts were restored yellow according to the original paint scheme and the missing strut was built.

The restoration of the struts was started by taking them to be sand blasted at Taximo Oy in the Tattarisuo area in Helsinki. The sandblasted struts were dealt with a transparent anti-rust Isotrol-lacquer immediately after the sandblasting. The struts were primed with light grey Isotrol-paint of the shade RAL 7005. The light grey primer worked well for the yellow finishing paint of the struts.

As the yellow finishing paint we used at first the Tikkurila UNICA outdoor furniture paint with RAL 1023 as the shade. The yellow paint had poor coverage, which we knew in advance. To replace the UNICA, a corresponding yellow Isotrol paint of the similar shade was chosen for the second coat of paint. The yellow pigment of the Isotrol paint has a better coverage, which was noted when painting the struts. They were painted with the yellow Isotrol three times over, so

To make the missing rear strut, a 2,5 m long 22 mm thick steel tube was bought from Starkki hardware store. As a model for the building, a wing rear strut has survived. At both ends of the rear strut there’s a fixed bracket plate, with holes in it to fasten the strut to a bracket in the wing and the fuselage.

When we examined the photographs of Ressu at our disposal, we noticed that the lower end of the rear strut had been adjustable and not fixed, as was the case with the rear strut at our disposal. At the lower end of the strut can be seen a fork-like bracket with a threaded spindle. It was evident that the lower end of the rear strut had been changed to a fixed bracket. We decided to make the missing rear strut lower end adjustable, to correspond to the wing strut in the photograph. For this purpose we received a wing strut adjustable head used in a Super Cub.

The building of the missing wing rear strut was started by cutting the steel tube to the measure of the rear strut. First we made the lower end of the rear strut. We welded a suitable nut, which fitted the threaded spindle of the lower end of the tube and screwed the bracket in place.

We made the wing rear strut top end a fixed one, according to the strut we had at our disposal. The end of the tube was sawn at an acute angle. After that the bracket halves for both sides were cut out of 2 mm metal plate to be welded in place. They were welded to the top sides of the tube. After welding, the bracket was ground to its final shape. When a hole had been drilled for the strut fastening bolt, the new strut was structurally finished.

The new wing strut was primed with light grey Isotrol paint, the same way as the three original ones had earlier been dealt with. After the primer had dried it received a coat of yellow Isotrol paint. Thus we had restored the two original front wing struts and a rear strut of the Ressu-aircraft and built the missing wing rear strut

Photos by Lassi Karivalo.

Translation by Matti Liuskallio.