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Nick_Karatzides

1/18 scale Flettner Fl-282 V21 Kolibri scratchbuild model

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If the assembly sequence would follow the instructions by-the-book, the two battery packs should be placed on appropriate brackets located on either side of the transmission unit as shown in the picture from the kit manual. Since the original building idea requires to setup the 1/18 scale Kolibri model in such way to look like under maintenance (or refueling) procedure with all the hatches & sliding panels opened or removed, I decided to deviate just a little from the schedule and do something different: To unplug the batteries and place them somewhere else - possibly on some wooden box or the previously mentioned wooden ladder, one of these unrelated to the helicopter structure additional parts which were designed & 3D printed to be used as part of a diorama scene.

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CHAPTER VIII - Crew seats & front fuselage cover assembly

Each one of the 1/18 scale Flettner 282 V21 kits contains two crew seats for the pilot and for the rearwards facing observer. The observer’s seat consists of two perforated plywood boards, one for the bottom part fixed on a retractable bracket and one for the backrest fixed on frame rails. Cushions are placed over bottom part & backrest plywood boards to provide comfort. On the other hand, the pilot’s seat consists of a (similar cushion covered perforated plywood board) bottom part only, since he rests his back-pack type parachute against the front fuselage cover.

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Having just painted the perforated plywood boards and being quite pleased with the outcome, I decided (once again) to deviate from the instructions and skip the cushions installation - after all, the reddish varnished look on plywood boards seems to make a fine contrast with the overall RLM 71 Dunkelgrün FS 34079 and breaks the green monotony.

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Those who have followed this thread from the start, will remember that the front fuselage cover had already been covered with an overall dark undercoat and later gradually airbrushed with RLM 71 Dunkelgrün FS 34079 to achieve proper gradations of light. The front fuselage cover patiently awaited the tubular frame painting completion, in order to come the turn to be properly installed. The part carefully dragged in place along the frame tubes, until reached down on the pilot’s seat & secured in place with a drop of cyanoacrylate super glue.

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The first two production model kits under 1/18 scale, were 3D designed such way to have the seatbelts & buckles embossed on the crew seat cushions - a tactic that later altered, since customers mostly prefered to add their own harness or leave the miniature helicopter free of straps webbing. For this reason, the seatbelts shown into following pictures were built from 2.5mm to 3.5mm wide masking tape and photoetched set by Eduard, under 1/20 scale. The seatbelts later got some brownish & khaki paint - so as to make sharp & nice looking contrast against the reddish varnished plywood seatboards and the overall RLM 71 Dunkelgrün FS 34079 painted airframe cover.

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CHAPTER IX - Rear fuselage section assembly

The rear fuselage section on real Flettner 282 helicopter was made of doped fabric covering over the steel and wooden frame. Those who have followed this thread from the start, will remember that the rear fuselage section had already been covered with an overall black / dark brown undercoat and then gradually lighten the surfaces to replicate the way that sunlight hits on large objects, following the Francois Verlinden’s old-fashioned way (which was re-introduced and become popular around the scale modelling community, by its new "modulation" name). The dark undercoat, gradually airbrushed with RLM 71 Dunkelgrün FS 34079 to achieve proper gradations of light, trying to balance between realism factor and artistic expression. IMHO modulation effect does not accurately replicate the reality, but it looks so artistically attractive and becomes easily accepted by our visual subconscious. Custom made water slide decals applied and later everything washed by brushing “Winter Streaking Grime” AK014 filter available by AK Interactive, until the desired colour density is achieved.

As described into pages #25 to #27 of the ultra-detailed “1/18 Fl-282 V21 kit building instructions” manual (which can be found HERE as a downloadable PDF format file), the rear fuselage cover part carefully dragged along the miniature's wooden frame, until reached down on the transmission pivots & secured in place with a drop of cyanoacrylate super glue.

 

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On 11/4/2016 at 6:07 PM, Nick_Karatzides said:
A year passed since April 11th 2015. A day like today and the whole World seems so empty when you miss your other half.

Wishing to remember this day and honor her sweet & loving memory, last week Anyuta 3D decided to make an offer for few fellow modelers & skilled craftsmen by sending a limited number of coupons. During last week, few hand-picked forum members, specialy selected talented & promising modelers, received (or about to receive) their own 3D printed 1/18 scale Flettner Fl-282 Kolibri cutaway model kits. By the time these lines are written, the parcels are on their way to modelers postal addresses.

Considering that approx 75 cubic centimeters of “FUD” (Frosted Ultra Detail) plastic material are needed to produce all the 40+ individual parts of each 1/18 scale Flettner 282 cutaway model kit and Shapeways factory is charging $3.49 per cubic centimeter plus $5 for handling fee per model (which explains the $270 price under normal conditions), I think that it was a great oportunity. I wish that it could be possible to get a lower price but as said before, Shapeways factory does the production and sets the price - not me. I wish modelers, could buy 3D products in lower prices but I guess that we are not responsible about this, are we? After all, the multi-hundred USD worth coupons, paid by my own budget, just to be possible to get these kits built by fellow modelers too, honoring her loving memory. Something to be remembered for.

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Steering of the Fl-282 was achieved by a combination of the rudder and differential collective pitch change on the two rotors, but only the rudder could give steering during autorotation since collective pitch was then ineffective (another reason for the large rudder area). Rudder fin (of very generous area), was made of wood and covered by fabric, with max 40° deflection left or right. This large area was necessary because much of it was ineffective due to the poor aerodynamic shape of the fuselage causing rearwards flow separation and turbulence. The vertical stabilizer and the elevators were also made of wood, with plywood leading edge and fabric covering, bolted to fuselage frame.

As described into pages #29 to #32 of the ultra-detailed “1/18 Fl-282 V21 kit building instructions” manual (which can be found HERE as a downloadable PDF format file), the rudder fin’s slots should be aligned onto horizontal stabilizer's hinges as shown on the following pictures. I tried dry fit testing before the final gluing & part secured in place by adding a drop of cyanoacrylate superglue. Since the rudder fin can be instaled turned (with max 40° deflection left or right), the servo bars should be inserted into slots & placed as required. Notice that if the rudder fin is tilted left or right or neutral, the rudder pedals at cockpit area & nose wheel, should be also positioned accordingly.

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The two horizontial elevator fins should be installed by inserting the 1.4 mm Ø pins through side openings of rear fuselage section as shown on pictures and securing in place with a drop of cyanoacrylate superglue. Keep in mind that if the horizontial elevator fins are placed tilted up or down or neutral, the cyclic / KG.13 control stick at cockpit area, should be also positioned accordingly.

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Under normal conditions, each helicopter’s registration ID was duplicated under elevator fins. After all, there are many photographic evidences certifying this feature, just like the following picture showing the CJ-SK registered Fl-282 V17 helicopter, crashed at Travemünde on April 13rd 1944, while test pilot FliegerStabsingenieur (Luftwaffe Major) Gerhard Geike was attempting a “diving nose-down and then pulling back” technique landing.

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However, there is a rare photograph of the already mentioned CJ-SN registered Fl-282 V20 helicopter assigned to Staffel 1/196 at Pillau AB as found & captured by the British Army, that clearly shows registration missing under the elevator fins. Luckily, the picture taken before helicopter been brutally disassembled, doped fabric ripped away & removed from fuselage, clipped rotor blades cut off & never seen again since that day and remaining framework wreckage with upper rotor transmission parts transferred back to UK as a War trophy and ended up as souvenirs.

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CHAPTER X - Parallel build challenge? Accepted

When I started this project almost two years ago, I had in mind to also present the “cutaway” model kit version step-by-step WIP, as soon as the “full fuselage” model kit building would have been completed. Actually, both versions already built multiple times as commision work for collectors (for example click HERE to see both versions frames placed side-by-side, while painting process) and I only had to write the text and later attach the pictures shot during assembling & painting process.

Considering that over 130+ model kits of both versions sold since Anyuta 3D produced the very first 3D printed V6 version kit under 1/18 scale on early 2014 and due to the fact that the V21 cutaway version became quite popular the last few days, I am now thinking to change a little the basic plan and let the cutaway version step-by-step building edit into the full fuselage version WIP and present them both as a parallel project into a single forum thread.

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As you all understand, the “cutaway” version is actually based on the previously released “full fuselage” model kit, but more than 50% of parts should be CAD designed from the start in order to achieve best results. Although both versions are accurate miniatures of the Kolibri V21 helicopter under 1/18 scale, each one follows different assembling methodology. During the CAD phase, the individual kit parts designed in such way to be as easy as possible for the average modeler to build the model. To do so, the total number of tiny parts reduced (as possible) and different components combined into one part only. IMHO, building something from scratch is not so difficult - after all, we all tried some scratch once in a while. On the other hand, designing a helicopter model from scratch, exploding it into 60+ parts and make each one of them possible to get re-assembled & combined all together in order to create a miniature, is not a piece-of-cake. Speaking of a “cutaway”, the design difficulty factor gets multiplied.

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If you download the 102-page "full fuselage" and the 67-page "cutaway" PDF formated building instructions manuals, you'll notice the building process differencies on the first pages. Both versions have exact same dimensions when models fully built, but each assembling process differs a little. For example, as shown into following picture:

  • The "full fuselage" version kit is equiped with four full-length rotor blades (measuring approx 28 cm long each), but the "cutaway" version has the short / chopped rotor blade parts (marked into red ellipse), to simulate the Kolibri found by British Army and now preserved by Midland Air Museum, in cutaway condition.
  • The "full fuselage" version's main tubular frame is a little shorter (marked into red circle in following picture) than the normal-length “cutaway’ version's tubular frame. This is because the "full fuselage" version's rear fuselage cover part (which simulates the doped fabric covering over the steel & wooden frame and moreover has the vertical stabilizer attached on) should be dragged along the miniature's wooden frame, until reached down on the transmission pivots. So, as you understand, few milimeters of empty space are needed to ensure the appropriate contact.
  • The "full fuselage" version's main tubular frame is equiped with a "sleeve" (marked into purple ellipse in following picture) over the front tubular frame. Actually this is a bracket made of wood to support avionics & radio either side of the pilot at cockpit area. This "sleeve" part as well as some others like eg batteries, avionics & radio, 25 litres cylindrical fuel tanks mounted externally on both sides of the pilot, seat cushions etc are also missing from the "cutaway" version.
  • The undercarriage support (marked into blue ellipse in following picture) is different on each version. Although both versions will show the same on this undercarriage support area when models are buit, the “full fuselage” version's main tubular frame is missing this part, since it is already attached on the rear fuselage cover part.

 

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  • The vertical stabilizer of the “cutaway” version kit is offered as a separate part, which should be glued on the wooden frame. On the other hand, on “full fuselage” version kit, the vertical stabilizer is already attached on rear fuselage cover and offered as combined items.

 

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After studing the available reference (few hundreds of pics, blueprints, slides & negatives, videos, technical data and original Luftwaffe's text documents) kindly offered from a variety of sources such as Deutsches museum flugwerft schleißheim, Hubschraubermuseum Bückeburg, Midland air museum, a fellow modeler from Germany whose grandfather was a worker in the Anton Flettner Flugzeugbau GmbH factory at the time when the helicopters manufactured, Mr. Steve Coates author of the "Helicopters of the Third Reich" book and ofcourse Mr. Google (modeler's best friend), the already existing CAD digital file converted to Kolibri cutaway. Now, the model is ready to be forwarded to the 3D replicator and become an actual physical object under 1/18 scale, within short time.

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Approx 50% of the components are copied & pasted from the already existing full fuselage version and (lucky me) I did not had to design everything from the start. For example, the complex of intermeshing rotor gearbox, the 7-cylinders radial engine, the 24° angled rotor heads etc. On the other hand, all the “wooden frame” parts such as the vertical stabilizer, the rudder fin, the horizontial elevator fins and rear fuselage frame details, were CAD designed from the start. Ofcourse, the cutaway version was also built with all included truss-type welded tubes and drive shaft rods with universal joints attached on frame. IMHO, that was mostly preferred because all basic parts should be accurately pre-installed in place without any glue, putty, sanding etc.

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After digitally building the Fl-282 Kolibri cutaway 3D model using only mouse clicks, I saved it as an STL - STereoLithography format binary file and forward it on the 3D replicator to start generating the individual parts of the actual scale model. Once again, I used best available tools & plastic material and asked from Shapeways digital fabrication lab (equipped with a high-precision & high-cost “ProJet HD 3000” machine for creating custom made-to-order products), to 3D print it. The 1/18 scale Fl-282 V21 Kolibri “cutaway” model kit consists of more than 40 different 3D printed parts made of matte translucent plastic material - in fact, the kit parts are quite more, but smaller in size are interconnected on same sprue frame which is counted as one part. Kit was CAD designed and 3D produced in such way to simplify assembling process while maintaining necessary details required by the scale size. Following the instructions described into the 67-page ultra-detailed “1/18 Fl-282 V21 cutaway kit building instructions” manual (which can be found HERE as a PDF format downloadable file), the assembling process becomes easy.

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When printing is finished, the model parts are removed from the tray and placed into an oven that melts away the wax support material. Next, the models are placed into an a ultrasonic oil bath to remove any remaining wax residues, and then a ultrasonic water bath to remove any oil on the model. Final inspection and dry by hand follows for every single model part. Although the ProJet HD 3000 prints in high resolution (16 microns per layer) and can easily produce high detailed parts as small as 0.1 mm, it is better to avoid printing such small parts because they could easily get lost while washed into ultrasonic bath later, for wax residues removing. Each complete model kit takes about 5 to 7 days to get produced after order due to increased workload for 3D printed manufacturing demand in Shapeways factory.

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As soon as 3D printing process completed, the produced parts were cleaned & checked for broken parts or imperfections by Shapeways 3D printing lab specialized personnel. Later, everything carefully packed and shipped to my home address using UPS 24hrs delivery service. Once again, I was happy to hold my own custom 3D printed model kit, CAD designed with my laptop and later converted to an actual physical object, under my preferable 1/18 scale.

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Some additional parts unrelated to the helicopter structure, also 3D printed to be used later as part of a diorama scene. For example few 1/18 scale 20 litres fuel canisters, a couple of 1/18 scale 200 litres fuel drums as used by Wehrmacht, Luftwaffe & Kriegsmarine during WWII with “Kraftstoff 200L Feuergefährlich Luftwaffe” and “Kraftstoff 20 L Feuergefährlich 1941” inscriptions engraved or embossed on side, a 1/18 scale fuel hand pump and one 1/18 scale wooden 3-steps ladder as used by Luftwaffe WWII ground crews and technician personnel for ground vehicle & aircraft maintenance procedures.

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Rotary hand pump used by techical crews & maintenance personnel to transfer fuel from the 55 gallons drums to aircraft & armoured vehicles fuel tanks or into the 20 lt fuel canisters (both drums & canisters are available for sale at Anyuta 3D products catalogue). This type of manual fuel pump used by Luftwaffe & Wehrmacht during WWII. The rotary hand pump kit contains all necessary parts for assembling one fuel hand pump under 1/18 scale. Any extra diorama accessories (hose, 55 gallons fuel drum etc) are not included and should be purchased separately.

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Although 3D printed models do not differ so much from ordinary kits, the plastic material may cause surprises. Some of the kit parts may feel a little greasy and appeat slight traces of oil on their surface. As I've already described into previous pages, it is absolutely normal. After the 3D printing process was finished and the kit parts been removed from the printer tray to be washed into an ultrasonic oil bath and later an ultrasonic water bath, some oil traces escaped the clean inspection and dry by hand procedure. Parts can be easily cleaned by following one of the following methods:

  • By washing parts with water (NEVER apply water hotter than 50º C / 125º F or you'll be really sorry) & dishwasher soap and brush gently with an old soft toothbrush. Keep in mind that items are only 0.3mm to 0.5mm thin and they are very fragile. Therefore, being very carefull while washing the parts is a necessary.
  • By sinking everything into a plastic bowl filled with White Spirit and leave it there for few seconds or a couple of minutes (max) to wash oil traces. In the end the the kit won’t feel greasy anymore and show an almost complete white colour. Never use anything more "aggresive" than White Spirit. Also, AVOID stove cleaning spray and acetone nail polish remover products - both clean oil & wax but also dissolve the plastic leading to breakage and failure.
  • By using hydrosonic cleaning machine (IMHO, is the best alternative), filled with water & dishwasher soap and repeat procedure if needed. Meanwhile the water will turn cloudy - that’s the wax.

It is of utmost importance that the model parts are properly degreased - otherwise the paint will not stick. Small remainders can be removed with a swab or toothpick. For my own 1/18 scale Kolibri cutaway model kit, I decided (since I do not have a hydrosonic cleaning machine) to wash slight oil traces on parts by sinking everything into a 2 litres plastic bowl filled with White Spirit and leave it there for a couple of minutes. Shortly after all kit parts enjoyed their bath into a White Spirit filled bowl, they were washed with liquid soap & warm water, placed on soft paper towels and allowed to dry.

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After all kit parts washed in White Spirit & water to clean the oil traces, every section of the model has been repeatedly dry fit tested to ensure that all individual parts could be later combined together as an overall built model. When looked OK to me, each part sprayed over with an undercoat mixture of 80% Life Color LC02 Matt Black and 20% Life Color LC37 Matt Burnt Umber acrylic, to prepare the surfaces for the basic paint which about to follow. Later, a  very thin coat of Life Color UA503 Light Blue acrylic paint layer applied, very diluted with Life Color’s acrylic thinner in a 30% paint to 70% thinner ratio. The darkest recesses sprayed first, gradually working my way up the frame, keeping to the lighter areas on central parts of each tubular part. Same pattern maintained throughout the entire painting process to preserve continuity with the light source and subsequent spraying sessions continued to utilize very thin Life Color UA503 Light Blue acrylic paint layers as a base to varying degrees because it is the source of the light colour.

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The tubular frame got gradually lighten with each successive layer as the painting process continued, so the second layer of paint as the medium layer of the base coat, is based upon a less diluted 50% paint to 50% thinner ratio. Then, I added just a few drops of Life Color LC01 Matt White FS37925 acrylic paint into the mixture to lighten up this stage of paint application, being very careful to always follow the established gradation pattern, untill contrast between light and dark started to become apparent.

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Wow Nick, that s simply awesome work. Also, shapeway sure makes some cool stuff. I purchased few items from the for the first time and I was fully pleased with the results. I wish I can afford a complete kit from them but bit out of my price range but I'm glad that 3D printing becoming viable asset to our hobby. ;) You keep up the good work :)

 

Mike

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CHAPTER XI - Assembling individual parts

As soon as most individual 3D printed parts on both “full fuselage” & “cutaway” scale model kit versions were already painted & weathered, everything should be combined and assembled as an overall built miniature. Having already installed the rudder fin and the two horizontial elevator fins on the “full fuselage” version model’s tail, the gear box unit was next. Following instructions described into the building manual (click HERE for the PDF formated file) through pages 33 to 37, all the four pins on gearbox unit should be simultaneously aligned onto the upper frame’s slots and same time linked downwards with engine’s transmission shaft, as shown on following pictures.

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Here is a detailed view of the correctly installed gearbox unit as seen underneath the fuselage cover. Notice that the forementioned gearbox unit is linked (marked with red circle) with previously assembled engine’s transmission through a shaft coupling.

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This is how the assembled block of rotary engine, transmission unit, cooling twin blade propeler fan, drive shaft & upper gearbox unit should look like when correctly fit into each other. Notice that tubular frame is not visible here for better example view.

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Both “full fuselage” & “cutaway” scale model kit versions are equiped with fixed non-retractable tricycle type undercarriage with a steerable nose. The tubular shaped struts & the central supporting section anchoring points aligned on proper U-shaped slots found on the lower fuselage area. Following instructions described into the building manual, the upper & lower anchoring points on each tubular landing gear strut end should be simultaneously aligned onto the tube frame’s U-shaped slot (marked with red arrows). Successful assembly of main landing gear section will positively affect process to follow - a side tilted helicopter model, would look completely unreal.

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This is how the fixed non-retractable tricycle type undercarriage frame should look like when the parts correctly installed on the fuselage frame. Everything secured in place with a drop of cyanoacrylate super glue.

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