The plywood covering of OH-XEA Ressu is under repair

Perjantai 1.12.2023 - Tuesday Club member

Suomeksi

Ressu’s restoration has progressed well in the Finnish Aviation Museum’s restoration workshop. The left wing, ailerons, vertical stabilizer, rudder, horizontal stabilizer, wing struts and tail wheel assembly are all now under work. Maybe we should actually be talking about repairs, because Ressu is mainly in good condition – except the fuselage and vertical stabilizer. Therefore we mainly concentrate on repairing the damages in the plywood covering.

The aim in repairing the damages in Ressu’s plywood covering is to save as much of the original plywood as possible. Where a blow has damaged the covering and the plywood is still a strip which is in one piece, we aim to repair the damage by gluing the strip back into place, using a supporting piece of new plywood. However, if the damage is an open hole, the plywood is shattered, or there is a piece of plywood missing, we will patch the damaged area with new plywood. The latter repairing method is introduced in this blog, using the repair of the damaged plywood covering on the elevator as an example. In all cases the glued seams of the patches are spackled and sanded, and the patched area is painted to the original hue of the painted surface so that the damaged area can hardly be noticed.

The plywood covering of Ressu’s elevator had one larger damaged area to be repaired. The damaged area is located on the elevator’s left-hand end, in the trailing edge side corner. Here the plywood covering has been broken on the elevator’s upper side and on its end. The plywood has broken in several places and parts of the covering are missing. We decided to patch the whole damaged area with new plywood.

First we removed the broken pieces of the covering plywood at the damaged point on the upper surface. Then we drew a rectangle around the damaged area and cut the plywood off along its edges, using a Dremel circular saw blade. This is how we created an opening for the patch on the upper surface. In a similar manner we cut a rectangular opening around the damaged area on the elevator’s end. Now the whole damaged area had been opened for patching.

The next step was to fasten supporting strips on the edges of the opening. The plywood patch will be supported by these strips when it is glued to cover the opening. Some of the supporting strips were glued with strengthening nails to the structure of the elevator. A strip was fastened also on the area where the patches on the elevators upper surface and on its end meet, i.e. at the upper edge of the elevator’s end.

Photo by Antti Hietala.

One of the supporting strips was glued on the underside of the plywood edge so that a little less than one centimetre of the strip was left outside the plywood covering’s edge. Before gluing, the old varnish was sanded away from the underside area of the plywood covering which was to be glued. The supporting strip was glued on the edge of the plywood covering and pressed tight on the plywood with small plastic clamps. The glue we used was Casco Outdoor wood glue.

 

Furthermore, a longitudinal supporting strip was fastened across the opening on the upper side. This strip is needed to support the plywood patch on the opening and make it slightly curved so that it follows the gently curving profile of the elevator’s upper surface.

When the supporting strips had been fastened, patch pieces of 1 mm aircraft plywood were cut for the openings on the upper side and the elevator’s end. The patches were fitted into place, shaping their edges until the patch edges pressed tightly against the sides of the opening.

Photo by Matti Kainulainen.

First the plywood patch was glued into place on the elevator’s end. The upper edge of the patch was pressed against the supporting strip with small clamps and the glued seam on the lower edge was secured with some small nails.

Photo by Matti Kainulainen.

Then the larger patch on the upper surface was glued into place. On the elevator’s leading edge side, the glue seam of the plywood patch could be pressed tight with ordinary clamps. A piece of plywood was placed between the clamps and the glue seam to distribute the pressure evenly on the seam. On the other side of the opening a metal weight was placed on the glued seam to press the plywood patch against the supporting strip.

The gluing of both plywood patches went well. The patch seams were spackled using Plastic Padding’s two-component Chemical Wood. The spackled seams and the whole newly patched area will be sanded before painting. The plywood patches will be painted later, together with several other plywood patches on Ressu’s surfaces.

Photos by Lassi Karivalo except if otherwise separately mentioned.

Translation by Erja Reinikainen.

The restoration of OH-XEA Ressu has been started

Tiistai 21.11.2023 - Tuesday Club member

Suomeksi

As told in the previous blog, the parts of the OH-XEA, designed and built in the 1960s by the Hietanen brothers from Turku, will be restored by the Tuesday Club. The aircraft was nicknamed Ressu. Its wings, horizontal stabilizer, elevator, rudder, tail wheel assembly, wing struts and fuel tank have been brought to the Finnish Aviation Museum. We will concentrate on the restoration of its fuselage frame later. When the condition assessment and the restoration plan of the Ressu’s parts brought to the Museum had been completed, it was time to set to work.

The restoration of the wings was started by cleaning the plywood surfaces, painted blue. Both wings were brought to the restoration workshop of the Finnish Aviation Museum. We started the cleaning of the painted wing surfaces with a well-tried method: a magic sponge. Naturally the worst dust was first vacuumed off. The aileron was unfastened to be washed separately. The dust in the joint of the aileron and the wing was brushed off with a paint brush and vacuumed clean.

When using a magic sponge no cleaning agent is used. The tools you need are the magic sponge, a soft cloth, and half a bucket of water. The painted surface of the wing is cleaned by rubbing the surface of the wing, a small area at a time, with the magic sponge dipped in water and squeezed damp. With the soft cloth in the other hand the rubbed area is wiped at short intervals. The magic sponge removes the dirt from the wing surface, and it is wiped off with the cloth, which is rinsed in the bucket. There were also splashes of red paint on Ressu’s wings. Even they could be removed with the magic sponge. The rubbing with the magic sponge does not damage the painted surface unless excessive force is used.

The plywood covered horizontal stabilizer and elevator were treated in a similar manner. We managed to get their surfaces very clean too. We were satisfied to see that after the wash the greyish blue surfaces of the wings, horizontal stabilizer and elevator were as if newly painted. We wonder whether they have been painted in the 1960s using durable Miranol enamel paint as the painted surface has been so well preserved.

For the rudder surfaces no washing was needed, but the covering fabric was removed from the metal frame of the rudder. The covering fabric needs to be completely replaced. A carpet knife was used when removing the fabric. We could see that a strip of fabric had been spun around the outer edges of the frame. This strip protects the fabric which covers the metal rudder frame. On the other hand the covering fabric can be sewn on the fabric strip, but we could not tell whether this had been the case here. The fabric strip covering the edges of the metal frame was removed with a carpet knife. The rudder’s metal frame, stripped of the covering fabric, is now ready for rust removal and the surface treatment after it.

Photos by Reino Aatsalo.

Photo by Antti Hietala.

Three of the Ressu’s four wing struts have been preserved. The struts are surprisingly heavy, so they are probably made of ordinary steel tube. The surfaces of the struts have been painted yellow but are now covered in rust. The surfaces were sandblasted clean. Then the struts were treated with Isotrol varnish which prevents rust. Now the wing struts are waiting for their final surface treatment, and they will be painted yellow as in the original paint scheme.

Photo by Lassi Karivalo.

Photos by Osmo Väisänen.

The restoration of Ressu’s sprung tail wheel assembly was started by disassembling it. Even the tail wheel had to be disassembled so that we will have access to the wheel bearings, which are totally jammed. When the four bolts on the wheel rim had been unfastened, the rusty wheel halves could be wrenched apart by force. When the bearings were visible, we sprayed a lot of rust removing chemical in them and on the rusted surfaces of the wheel rim and left them “to mature” for a week. When a week had passed, we were able to clean the wheel rim halves quite well from rust and the bearings were preliminarily working. The following task will be to repair the sprung tail assembly.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Erja Reinikainen.

The condition and damage assessment of Hietanen OH-XEA Ressu and its restoration plan

Sunnuntai 19.11.2023 - Tuesday Club member

Suomeksi

The Tuesday Club is starting the restoration of the Hietanen OH-XEA Ressu aircraft which has been stored at Lemu in the Turku area. The aircraft was built in the 1960s by Ari and Esko Hietanen from Turku. The first phase of the restoration will include the wings, horizontal stabilizer, elevator, rudder, tail wheel assembly, wing struts and fuel tank, which have been brought to the Finnish Aviation Museum from Lemu. The fuselage has no covering, but it remained at Lemu, and its turn will come later.

The first step in the renovation work is to assess the condition of the aircraft and its possible damage. Therefore we took the Ressu’s parts into the restoration workshop at the Finnish Aviation Museum and went carefully through the condition and damages of each part and made preliminary restoration plans for them.

We could see that the plywood covered surfaces of the wings, horizontal stabilizer and elevator are very dirty and have stains of red paint. The damages on the plywood covering are mainly small crushes or holes. However, on the underside of the left wing there is a large area around the registration mark where the plywood covering is badly broken. Or should we say has been intentionally broken – it certainly looks that way. The first phase in the restoration will be to clean the surfaces of the wings, horizontal stabilizer, and elevator and then to repair the damages on the plywood covering.

Ressu's rudder has metal structure and fabric covering, in similar manner as the tubular structure fuselage. The covering fabric is torn on one side of the rudder and a piece is missing.

The rusty metal frame of the rudder can be seen under the torn fabric. The metal frame will be cleaned and painted as it originally was. It seems that the frame has been painted with red Ferrex, the anti-rust paint which was commonly used in the 1960s. The red colour is visible under the rust. We will paint the frame using modern red Isotrol paint.

Finally the rudder will be covered with new fabric and painted pale blue, following the original paint scheme. Red stripes will be painted on both sides of the rudder, following the original look. Number 2 will be painted on the left side and a black bird figure on the right.

Ressu's tail assembly has metal structure and an air-filled tyre. The wheel bearings are completely stuck. We will try to repair the wheel into operating condition. The tail frame will be cleaned of rust and painted yellow, following the original paint scheme.

Ressu’s wings are supported with two wing struts, made of metal tube. Two of them are sturdier, fastened on the brackets on the wing’s front spar, and the two thinner ones are fastened on the brackets on the rear spar. We have both front struts but only one rear strut. The wing struts had been stored inside Ressu’s fuselage frame. The struts have been painted yellow but are now badly covered in rust. They will be sandblasted clean by a contractor and painted yellow as the original ones. We will make a new rear strut to replace the missing one.

The fuel tank is located at the root of the left wing, it has been lowered into place from the upper side of the wing. The fuel tank has dents, and they will be straightened. The fuel tank has had some kind of cap with a rubber seal, there are marks of it left on the wing as well as on the tank. The cap has disappeared. If we can find out what the cap has been like, we will make one. And if we can’t find what it has been like, a good alternative is to make a cap from e.g. 1,2 mm thick aircraft plywood.

The Hietanen brothers have obviously been planning to double the size of the 21-litre fuel tank. We can judge this from the fact that the wing rib next to the tank had already been removed and the wing’s plywood covering had been opened between the wing spars up to the following rib. We will, however, restore the wing structure to its original condition where there is only space between the wing root rib and the first rib for the original fuel tank. This means that the missing rib will have to be made and the opened plywood covering repaired.

Photos by Lassi Karivalo.

Translation by Erja Reinikainen.

Hietanen OH-XEA "Ressu" to be restored by the Tuesday Club

Perjantai 10.11.2023 - Tuesday Club member

Suomeksi

Last year Aviation Museum Society Finland was donated a single-seat experimental aircraft, designed and built in the 1960s by Esko and Ari Hietanen, two brothers from Turku. The aircraft was inspected and registered in the civil aircraft register on August 13th, 1969, with the registration OH-XEA. The aircraft, nicknamed Ressu (meaning Snoopy), is a high-winged, mixed structure single-seat aircraft. The tubular framed fuselage is fabric-covered. The wings, ailerons, vertical stabilizer and rudder have wooden structure and plywood covering. The rudder is tube-structured and fabric-covered.

Photo via Aviation Museum Society, Finland.

Ressu is a small aircraft. Its wingspan is 7,4 m and the fuselage is 5,5 m long. The widest part in the fuselage is the landing gear, with 1,4 m from one end of the axle to the other. In its time, Ressu had several registration marks. First it was registered as H-EA (Hietanen Esko and Ari), then OH-HEA and eventually OH-XEA when it was approved in the civil aircraft register. Ressu’s engine was Continental A 65. The aircraft was removed from the civil aircraft register on January 1st, 1973. We don’t know how many hours Ressu has flown.

Photo via Aviation Museum Society, Finland.

After the flying activity ended, Ressu was stored in several places and its fuselage was badly damaged. Today the fuselage has no traces of the fabric covering and the tubular frame is covered in heavy rust. In the cockpit there is just the pilot’s seat, control stick, pedals, and an empty instrument board. The engine, the instruments from the cockpit panel and the landing gear wheels have all disappeared during the years. Out of four wing struts only three remain. The wings were painted pale blue, the horizontal stabilizer and the elevator have been preserved quite well, there are only some damages on the plywood covering.  The fabric covering of the rudder is broken and the paint on the fabric is badly crackled. The fabric covering on the fuselage has probably been painted pale blue as the wings.

The aim is to restore Ressu at the Tuesday Club to resemble its appearance in 1969 when it was registered. This means that the plywood covered surfaces of the wings and parts of the tail will have to be cleaned and the damages repaired. After that we can consider restoring the fuselage. There the first step would be to treat the rusty fuselage before covering it with fabric. We will try to find instruments for the cockpit if we are able to find the kind of instruments Ressu had. The engine could well be a discarded and inoperative Continental A 65, if we could find one.

Photo by Elias Viitanen.

In autumn 2022 Aviation Museum Society Finland volunteers assembled Ressu in the former shipyard hall in Pansio where the Caravelle III, owned by the Society, was under restoration. Ressu was also on display at the Society’s stand in the Turku Airshow in June.

After that Ressu has been stored at Lemu, in the Turku area. From there we fetched Ressu’s wings, horizontal stabilizer, elevator, rudder, tail wheel assembly, fuel tank and wing struts, and brought them on a trailer to the Finnish Aviation Museum in Vantaa. In the Museum’s restoration workshop the Tuesday Club members have already started the restoration of Ressu’s parts. The fuselage remained at Lemu, but it will probably be taken under restoration next year. The Tuesday Club has now started Ressu’s restoration project which is estimated to take a couple of years.

Photos by Lassi Karivalo except if otherwise mentioned.

Translation by Erja Reinikainen.