1/18 scale Bölkow Bo-102 Helitrainer scratchbuild model

[Guest]

CHAPTER IV - Landing pad & supporting base construction

Having obtained a number of information data & pictures about the structure and functioning details of the Bölkow Bö-102 Helitrainer, I have concluded, that this training aid could be found in various versions. In most photographs, a solid land-fixed construction is visible, consisting of a system based on 4 sliding legs, stretched around, ensuring secure support. Nevertheless, both diagrams & photographs show that this was not the only version, as there were some Bö-102s which were based on inflatable rubber pads to float on water or wheeled bases which enabled transport of the device in different places, even into a hangar. Careful observation of the individual photographs and archive material showed that there are too many differences between these Bö-102s. Therefore, taking under account that only 18 were produced, I do not think too much to assume that each one of them was completely different from each other.

[Guest]

For my 1/18 scale project, I chose to recreate the wheeled version, which seemed to me as more interesting than others. As you can see in the following pictures, the landing pad & supporting base was built by styrene plastic, sprue, metal wire and glued with CA super glue and Humbrol liquid polysterine glue.

[Guest]

When it looked OK to me, it was sprayed over with Humbrol acrylic primer to spot any mistakes and be ready for final paint. Each part was fit tested to ensure that anything can be combined together as one piece.

[Guest]

It's an absolute pleasure to watch scratchbuilding at this level. What an amazing original and innovative model you are creating, many thanks again for taking the time to share this build with us.

[Guest]

CHAPTER V - Fuel tank canisters construction

Once sprayed with the Humbrol acrylic grey primer the model’s constructed pieces so far, I thought it would be a good idea to use the spray cap in a productive way to construct two identical fuel tank canisters. The reason I chose to use this, is that the cup is made of a quite flexible polyamide material and the Miliput standard epoxy putty could hardly stack onto it.

Using styrene, I split the cap cylinder’s inner area into 4 quadrants. The space of two of these quadrants, would be used as molds, filled with Miliput standard epoxy putty. To ensure that the epoxy putty would be easily removed after the polymerization, a generous coat of baby oil was applied on the contact surfaces. Johnson's baby oil or similar, is well know to anybody who have children in house. If you are not a father yet, ask your sweet girlfriend - all girlfriends have a tiny baby oil bottle in their cosmetics drawer, especially the beautiful and those who pay particular attention to their beauty & appearance. If you don't have a girlfriend, close this web page at once, shut down your PC/laptop and get your feet out of house to meet one! Scale modeling is nice & productive hobby, but feeling a beautiful female next to you, is much better. Thin layers of vaseline based mixtures can be also used instead of baby oil to apply with a soft brush as a segregative material between the styrene side walls and epoxy putty.

For those who feel like pioneers and might want to go one step further, you can also use aviation oil.

Aluminum foil was placed underneath to avoid spilling the cut surface and to prevent the epoxy material to stick to the green cutting surface.

When the cap cylinder, was filled with epoxy putty and had enough time to polymerize and get solid rock, it was slightly pressed and the epoxy cast removed easily. That’s the reason why it would be nice for the cylinder to be made of flexible polyamide material.

With this simple and easy way, two identical pieces with the exact same curvature and volumetric dimensions, were built in just a few minutes. These twin epoxy parts, can be now used as a base to shape into the Bö-102 fuel tanks. Having measured the desired dimensions, the two identical epoxy blocks were cut the same length. Few epoxy overcast remains that were left, were also removed during cutting process.

Remember that epoxy materials are dangerous when breath or shallow and could result skin, eyes or lungs severe problems or even cancer when used for long period with no precaution measures. Always keep in mind, that a powerful vacuum system to suck away the epoxy dust should be used all time to keep the workbench area clean while sanding or milling epoxy or resin materials. Using an issued breathing mask and a pair of surgery latex gloves to prevent dust contact with lungs and fingers while sanding or milling epoxy, is also an important matter that you should seriously take care of! My recommendation is to also wear an overall working suit (as I do) to keep your clothes dust free while sanding epoxy. Some people might find it too much, but I wouldn't like to bring epoxy dust & grains from my workbench into living room and my beloved.

…if you are still reading the WIP article so far, you are a proud father already or you have a beautiful girlfriend to spend your money faster than you earn it.

[Guest]

Hi mate, this is just amazing to see. Awesome work.

Cheers

Kresten

[yak face]

Hi nick , your scratchbuilding is amazing , and educational too! Superb work , and i love the fact that its using everyday materials too, keep it up ,looking forward to seeing the end result , cheers tony

[Guest]

The twin epoxy blocks got trimmed and sanded gradually to shape into the desired form and look realistic Helitrainer fuel tanks into scale. Later, few thin layers of liquid scale modelling filler applied over the epoxy to smooth out small imperfections and be seen as a comprehensive outcome.

[Guest]

Each fuel tank, is placed on metal plate / receiver base and secured in place by hoops and tensioners, as seen into the following picture.

In order to reproduce, these metal plate / receiver bases, I tried vacuum forming. Because I was planning to use smaller wooden frame to secure the styrene (the pieces to be vacuum formed are small and there is no need to spend big styrene sheet), I had to close the outer holes on the hardboard high-density fibreboard plate. To do so, I cut a plastic bag in shape and covered as required the desired area.

The twin fuel tanks, wedged halfway into plasticine and placed on the vacuum former plate to form the fuel tanks receivers.

I pinned a styrene plastic sheet on the wooden frame, insert it into the preheated electric oven as described before and as soon as I noticed that the plastic got warm enough and started drooping down, I removed it from the oven and thrown the sheet on the vacuum former plate, while the vacuum cleaner was already plugged & switched on. This procedure may take some practice and sometimes a mould tips over or the plastic won’t form properly over the mould (folding around edges). This is also the part where I should warn you that you can burn your fingers - I highly recommend Nomex Aramid flame resistant MilSpec gloves, which I personally use for the job. I buy large plastic styrene 50x30cm sheets for €0.5 to €1.5 each (depending width), not the more expensive styrene by Evergreen. When an attempt fails, I usually throw the sheet back in the oven and start again. Once you have the machine, you can make all kinds of things. You can make a lot of aircraft wings, airframe, panels etc out of a sheet like that. You can make the master moulds from balsa wood, epoxy, polyester etc and the parts you make depend on how accurate the master moulds are. The moulds must be as accurate and detailed as necessary to achieve the results you are after.

The plastic nicely formed around the fuel tanks moulds and here is how it looks like.

Using a new #11 stainless steel surgical blade, I removed the formed pieces from the styrene sheet. The yellow stuff appears in the picture, is plasticine surplus - the plasticine used to secure the twin epoxy tanks on the vacuum former plate and caged into vacuum formed plastic sheet. Later, these two receiver bases will be sanded as required and some details such as securing hoops and tensioners to keep the twin fuel tanks in place will be added.

[Guest]

Some additional details were added to the fuel tank canisters. The left side fuel tank, was placed on the receiver base and strapped with hoops & tensioners to keep in place, while the right side fuel tank is to be placed on the ground, with the filler cap opened, simulating maintenance procedure.

[Guest]

CHAPTER VI - Main rotor blade & transmission components construction

The rotor blade is made of styrene sheet softened in boiling water to stretch 'n' turn in a way to look realistic. I also tried soft and careful sanding on the blade's leading edge to be shaped as realistic as it should be. The transmission shaft components and minor details also made of styrene, sprue and metal wire bond together with CA super glue. Everything was sprayed with Humbrol light grey primer when ready to paint.

[Guest]

CHAPTER VII - Applying paint, wash & weather effects

Model parts were washed with liquid soap and warm water to disappear leaving oil traces, fingertips etc and then sprayed with Humbrol light grey primer.

[papa 695]

Nice to see you back and hope you had a good holiday looking very good and nearly there

[Guest]

Usually, there are two available options for a scale modeler, to apply paint on a model:

• Paint the individual parts first and assemble the scale model later and
  
• Assemble the scale model parts first and paint the overall built model later.

While building this Bölkow Bö-102 Helitrainer scale model project, the first option seemed as more appropriate and would make my job easy. Unfortunately, I had to follow the second option – and that was not the only bad news. Building first and painting later, would be more difficult and would take much longer, but the reason I chose first to assemble most of parts and paint later, is because most of the Bölkow Bö-102 Helitrainer scale model’s airframe consists of a tail boom structure, in which contained the Hirth 3-cylinder / 2-stroke 40hp ILO L3X375 piston engine, the transmission components, the cable wiring etc that could not be masked without causing any damage. It could be very difficult – maybe impossible - to airbrush for example the tail boom and manage to leave the interior details remain unaffected by the painting same time. Here comes the bad news: Tail boom structure would be painted by using fine brush and lot of patience to avoid leaving any brushing marks that would be clearly visible on such a big scale as the 1/18 is.

After preparing the engine’s basic elements, connecting electric cables and oil or fuel lines, I airbrushed the engine block with Life Color LC24 Matt Aluminium FS37178 acrylic paint as a base coat and apply darker enamel mixtures using the Humbrol #27001, #27002, #27003 metal cote paint and finally add some Mr Metal Color #212 Iron on the engine and let about 24hrs to dry before trying dark brown and black washes.

As I personally believe that following simple techniques and sometimes unconventional methods, result in superior effects, I usually do not use enamel or acrylic paint to wash, because I feel risky when applying the paint mixture and let it run. I prefer an easier technique that can be undone if the results are poor - that makes it the perfect technique. I use hard chalk pastels to wash (NOT oil pastels). The hard chalk pastels, looks like a teacher would use on the blackboard in school. Do not use the soft oil pastels that artist use to draw on paper. The hard chalk pastels are easy to find in a variety of colours into your local art store or maybe Wal-Mart if in US or ASDA if in UK.

To do the wash, I use an blade, a small metal or plastic container, an old toothbrush, dish washing soap and a bit of water. Begin by scraping some chalk powder from the side of the chalk pastel stick, carefully put this chalk powder into the small container and add a tiny amount of water and stir. It is important to add a tiny amount of water in order to make the mixture look like mud - not like soup! For this reason, I use a syringe to add just few drops on the hard chalk pastel powder and I stir using the old brush. Because the chalk powder doesn't mix well with the water, a drop of dish washing soap is needed to break the surface tension of the water and also acts as a “glue” to help the chalk powder stick to the model.

Once the chalk is fully dissolved into the water/soap mixture it is time to “paint” this mixture onto the model's engine. “Painting” the mixture is simple - just apply it anywhere it is needed to darken recessed detail. The mixture can be applied carelessly, because any mistakes can be completely removed and redone. Once the chalk wash dried, I rubbed off the high spots with a slightly damp dry (not wet) Q-Tip cotton swab (Kleenex papers can be also used) and I wiped the dark colour from the areas should be light & shinny. The high spots were cleaned to the bare metal finish and the low spots were left black. I did the chalk wash on the engine in under 30 minutes which makes it a very quick and effective technique.

Some of the wash mixture is re-applied and the wash being wiped completely out of the narrow points. If you follow this method, it is adviced to not rinse out the wash container till you are finished this job. You will probably be touching up certain spots a few times, so it helps if you're not mixing up a new chalk mixture each time because you kept cleaning out your container of the chalk wash mixture. As soon as I paint the electric cables, the oil or fuel lines etc, I repeated the wash process with lighter colours where needed. Using micro cotton batons found into cosmetic shop for less than 1£, I applied some brown chalk pastel powder on the engine's chrome exhaust, to make it look overheated. I repeated the weathering process until it satisfied me and finally I sprayed a Humbrol clear coat to seal the chalk powder on the engine.

[Tommy]

Outstanding work!