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Home In English In English Piotr Mazurek - MU-2 Scratch build.

Piotr Mazurek - MU-2 Scratch build.


I have been passionate about hydroplanes ever since I remember. I’ve got many models of II World War seaplanes and more are pouring in. Usually as I enter a model shop or browse an auction site I ask for specific models. However this time I did it other way round – I asked the seller to show me all he’s got on floats. I was more than amused when he gave me vintage Po-2 kit made by ABC Modelfarb...

I have been passionate about hydroplanes ever since I remember. I’ve got many models of II World War seaplanes and more are pouring in. Usually as I enter a model shop or browse an auction site I ask for specific models. However this time I did it other way round – I asked the seller to show me all he’s got on floats. I was more than amused when he gave me vintage Po-2 kit made by ABC Modelfarb. I had no idea that Po-2 had its “floated” twin brother, so I purchased it with no hesitation.


Back at home I had the chance to have a careful look on the sprues. I did not expect Trumpeter quality and sink marks (1) nor flash (2) did not deter me. More worrying was the total lack of any float struts. The manufacturer simply put a blob of plastic to stick on the floats instead of their struts (3). When my Russian colleague equipped me in essential reference material it turned up that single float version varied a lot from ordinary Po-2. Modified nose covered most of Shvestov M-11 engine, additionally rudder and elevator lines were hidden in the fuselage to protect from waves splattered by central float. Just to mention few changes implemented to the airframe. Unfortunately the model I bought does not represent any of it. The final decision to scratch build was made when I compared fuselage halves with 1:72 drawings. And since I made my mind to make it with my own materials and invention – I decided to build version with two floats


Careful analyze of gathered reference materials such as blueprints, drawings and pictures is the key to successful scratch build. Good reference will be an essential aid when acquiring proper materials. The more detailed the reference is, the more detail one can pack in his model. Planning ahead will surely simplify the build. It would help avoiding mistakes like gluing the fuselage halves before inserting the interior.




Update 26.10.2010

I have started this project some time ago but there wasn’t much to show until now. The build proceeded from basis of fuselage structure. Most details could be reproduced thanks to the blueprints I got. The details will be visible through the opened service hatches.


Next I took a careful look at the photo etched parts I bought for this model. I knew from the beginning that I wouldn’t use some of them. It applies to parts which 1:1 equivalents have round cross section (like seat baskets which are made from steel rods) or those which can’t be duly represented by PE parts due to their thickness. Moreover the PE frets are dedicated for kit which I have previously rejected. Particular parts are designed to ease their assembly – often affecting the proper scale. That’s why the PE rudder pedals are etched in near to 1:48 scale, and control sticks clamps reflect their thickness, which in case of ABC Modelfarb kit are much oversized. The first PE part that I chose not to use was the cockpit floor. I had to make several slots in the new floor but unfortunately my tools couldn’t stand the task. So the actual work on this part started form creating required tools. The oval openings were made with aid of flatten injection needle and filed hobby knife was used to punch the edge slots.


I planned to build the fuselage from the bottom upwards. The idea is to reduce the risk of damaging ready assembly while adding new parts.



In the meanwhile I changed a bit the concept of creating the fuselage formers. Previously I wanted to make them same as in original – form individual pieces. But later on I thought that one piece sections can strengthen the construction and will allow more accurate assembly.


Update 13.11.2010

The works on this project have advanced and now the structure of the rear fuselage is completed. The fuselage rigging additionally strengthened this part of assembly. All the rigging is made of elastic thread ripped up from a cheap sock. Sadly the haberdasheries in Torun offer nylon thread only. These are less elastic and more difficult to glue with CA glue. Another important advantage of the thread I have used is possibility of regulating its thickness by stretching. Additionally if needed individual fibers can be separated. The staples of crossing lines are made of stripes of adhesive paper. Few stripes were laid next to each other and cut with one crossing cut to give staples of the same length. The glue of adhesive paper allowed initial setting of each staple which then were finally set with CA glue. At first I did not make the spinal rigging, trusting that this would allow access to the fuselage chamber and ease mounting the trimmer lines. However after careful study of reference materials and confronting it with the opinion of experts it turned out that the particular aircraft was not equipped in trimmers.



Next I dealt with fuselage structure of the fuel tank and cockpit compartments. Initially I thought I would use the PE parts. In concern of proper dimensions the PE fret contains doubled framework parts. Gluing them together should give the accurate thickness. Unfortunately comparing it to the drawing showed unacceptable difference.


So I have no other choice than to make it from scratch. I have started from portside as this part of cockpit requires more details. This way I have access through starboard which for now will be left open.


Before I took care of starboard I decided to replace rudder pedals with more delicate ones – made up to the freshest idea. Then the right side framework was completed similarly to the left side.



Update 22.12.2010

The next step is to fill the cockpit chamber with those elements that wouldn’t fit after installing the turtle deck. It is high time to make the seats. Although Part PE fret contains seat baskets and their upholstery but they are close to quarter inch scale. Maybe it was done on purpose to ease the assembly. However, in my opinion ambitious modeling cannot compromise the accurate scale for ease of construction. Besides, the PE parts do not match the drawings I collected.


I’ve started with making little jigs in order to simplify the construction of two identical seat baskets. The jigs allowed easy tweaking and cutting particular elements to desired length as well as aligning all pieces in a similar manner. Rule number one in scratch building is dry fitting and comparing against greater assembly. In this case I made sure that the structure complied with drawings in plan and side view.



Painting the fuselage structure and permanent fixing of seats was exciting and awaited moment. In the meantime the baskets got additional detail in the form of simple height regulation. The upholstery is made of black PVC film with seams embossed with a panel line embossing tool. The harnesses consist of PE parts combined with precut stripes of masking tape.




Next I focused on the cockpit cover. I thought the PE part would be too thin and decided to replace it with 0,3 mm thick equivalent made of PVC rigid film. The sequence of tasks has been carefully planned. First, I clamped the PE part to PVC plate using a strong adhesive tape. I decided to cut out the cockpit openings first and trim the outer edges at the end. A bigger piece allows for better grip during filing. Moreover, it is easier to trim the outer edge leaving 1 mm to the cockpit opening edge than to open a hole so that its edge is 1 mm from the outer edge. The instrument panels are PE parts. The cockpit back walls behind pilots’ heads are also PE parts but sandwiched with styrene pieces.



Update 16.01.2011

Initially I planned to plunge mould the turtle deck in thin PVC film. But then I thought it might be too fragile and could suffer damage during further assembly. Therefore I decided to use post-beer scrap. I rolled a piece of sheet aluminum on 12 mm drill bit. Next I printed on adhesive paper the unwound surface of turtle board and stuck it to aluminum roll as cutting guide. Cockpit back walls behind pilots’ heads were previously sandwiched with sandwiched with styrene pieces to allow more contact surface with the covering. The other segments of fuselage spine were made in same manner. All these parts were made with their internal structure because in the end the last panel will be removed revealing fuselage interior.




Next step was to make vertical and horizontal stabilizer along with elevator and rudder fin. All these were made of 2 mm styrene sheet. First I cut the outlines with a bandsaw. Then I drilled a hole for tail light in rudder’s edge. Last I sanded all pieces to the desired shape.



The linen fabric was strenghten on the ribs with additional stripes of material. To imitate this I’ve masked off the surfaces living gaps in spots where the stripes should go. Next I applied few generous layers of flat black. After removing the masks I sprayed another layer of grey primer.


Happy with the effect I started work on the fuel tank. Original one is welded of sheet metal pieces pressed to shape. The front and back of it has a characteristic pleat all around the edge. I wanted my fuel tank to have that feature as well. Therefore I sculpted the general shape out of few thick styrene pieces glued together. After obtaining correct shape I wrapped it around with 0,1 mm PVC film and secured with CA glue. Next I trimmed off the excess material leaving that specific pleat all around the tank. Narrow stripes of masking tape made the base for fuel tank clamp which is a PE part.


Update 27.02.2011

The next stage in assembly was covering the fuselage. I made it using 0.1 mm PVC film. Side and bottom pieces were repeatedly dry fitted to the fuselage in order to ensure the best fit.


Then several openings had to be made. I used a brass rod to prepare punches for piercing the fuselage step and the ground service grab handles. After few trials on different bases varying in hardness I could handle these new tools sure enough to have a go on the fuselage parts.

Having the internal faces painted I could fix the parts to the skeleton. In this point I’d like to emphasize the need of proper planning long before the actual action. With the fuselage structure still under construction I decided to make the lower wing of two solid pieces from a thick styrene sheet. Due to the relatively heavy weight I had to figure out a sound fixing. That’s why I replaced two pieces of cockpit floor frame with new ones having sockets for wing roots. These parts were made of 0.8 mm injection needle and Milliput. When the putty hardened I filed it to the proper shape obtaining 0.5 mm channel along the longitudinal axis. Now I had to remember to drill 0.5 mm holes in the fuselage skin. Having the left side fixed to the fuselage frame I could drive the drill bit through the channel and open the hole from inside.



Constant checking against drawings was necessary to prevent a fuselage twist.


Having the fuselage covered from all sides I discovered that few spots required some minor corrections. All the imperfections were quickly fixed with small amounts of putty. I also had to drill the holes for the spars in the skin. This time the drill bit was driven through the left side (the picture shows opening of the drilled hole).


I sprayed all over the fuselage with a grey primer to detect possible surface imperfections. Having made sure that no further filling was needed I was able to start fixing the PE parts. Contrary to the interior PART pieces which were useless – the exterior ones are excellent and deserve to be recommended. There is only one fuselage part that requires modification. The element No. 60 has got round edges while it should be rectangular. This minor inaccuracy was easily fixed with a few gentle rubs of a file.


To finish the fuselage I only had to make fuel tank and belly covers. The PART PE fret contains fuel caps cover, which needs to be pressed to shape. The task required tools which I made of an old brush stick and a piece of aluminum tag. Having only one go on the brass PE bit I had to practice handling my new tools first. I tried it on some scrap aluminum pieces of different thickness. A piece from a beer can made for the rest of the panel. The bottom cover did not require any press forming but I had to make inspection flaps of the rolls guiding aileron lines (there are such bits in PART PE fret, but the quantity provided is only enough for wings).



The last thing to do was to paint the fuselage with the final colour. I decided to fix the horizontal stabilizer after it would be painted. Once it was done I fixed the elevator. Properly planned painting sequence made the job so easy, that rudder, horizontal stabilizer, elevator and covering panels were painted free hand without any masking. Spraying Sidolux and applying decals was only a formality…




Update 18.06.2011

It’s high time that my model gets the undercarriage. I had to think over how to make the floats and how to fit them correctly to the fuselage. First of all I made my mind on the method which I would use to make the floats. Next I chose the strut measuring method in order to calculate correct struts’ length and eventually provide accurate geometry of the undercarriage.

I thought the best way to make the floats would be the method, which paper modelers use for the ship model hulls. Additionally, to ease the job I chose to make one master and mould resin copies. But first I had to draw simplified theoretic lines based on front and side view drawings.


Next I printed the drawings on adhesive paper and applied it on styrene sheet. After all the pieces were cut out I could fix the float skeleton.


Empty spaces between float ribs were filled in with plumbing epoxy filler and after setting the excess was filed down. I had to be extra careful and change the abrasive grade - as soon as the white polystyrene ribs appeared the float only needed polishing.


To ensure the desired smoothness I covered the float with grey primer. After correcting some minor imperfections I could fix the details such as the cleat fixture and the lath walkway. The laths layout is the only difference between the left and the right floats because of the snatches leaving space for draining holes. I have intentionally omitted them in my float. The purpose was to create an universal master that could be used to mould both floats. Then the idea was to modify the resin mouldings so that they would differ as the original ones.



Now it is enough to mount the masters on the moulding block and prepare the silicone form. Unfortunately, I have not any vacuum pump, so my mouldings – both silicone and resin – are poor due to air bubbles trapped inside them. Expecting such problems I fixed the master in such a way that possible bubbles would make their way to the bottom sides of the floats.


As I thought the bottom sides were studded with tiny holes caused by trapped air bubbles. But due to fairly flat surfaces these were easy to fill. Applying yet another layer of grey primer proved that no further filling was required.

It’s time to start working on struts. I followed the method presented on The Aerodrome forum.


Briefly: “In the front view, draw a vertical line A-C that goes through the point where the landing gear strut meets the axle (in my case it is the horizontal tube joining the floats). Using a pair of compasses, draw an arc B-C with A as the center with the arc going through the point where the landing gear meets the fuselage and extending to the A-C line. Draw a horizontal line H-J that goes through the point where the arc crosses the vertical line. Extend this line H-J over to the side view. If the two views do not line up, measure the distance on the A-C line from A to where the arc crosses the A-C line. Transfer this distance to the side view vertically from the A point. On the side view draw two vertical lines D-E and F-G each line crossing the point where the landing gear attaches to the fuselage”*.

All the struts are made of injection needles with fuse wire glued inside. Protruding wire made excellent locating pins which were glued in sockets previously drilled in fuselage frame. The photoetched caps for draining holes and water rudders are often ommited in mass production kits – all the more my model could not lack them.


With painted and fitted floats the model resembles a seaplane:


* Source: The Aerodrome forum.


The next step of the assembly was preparation of the flight surfaces. They were made of 6 mm polystyrene sheet. First I have printed on adhesive paper the blueprints in top and bottom views for top and bottom wing respectively. Next I cut out the templates, applied them on polystyrene sheet and with use of band saw I have cut the outlines of each wing. To simplify the further work I cut the bottom wings as one piece.


After cutting off I could start to shape the leading and trailing edge. In order to achieve the required angle of the upper wing I cut two grooves on the underneath surface of its center plane. These cuts allowed me to bend the wings upwards. A stripe of polystyrene acquired from a SIM card holder was used to fill the grooves, which have spread even wider after bending. The hard plastic that filled these gaps also prevented the wings to lower down.


Next I separated the bottom wings and cut away the ailerons. The wing root surfaces were trimmed to angle that gives them the required raise. It was also a good moment to add the fittings of the lower wings. I have marked four points that correspond to the sockets I prepared in the fuselage. Then the holes were fitted with short lengths of 0,5 mm injection needle in order to provide locating pins and a solid support. Once the ailerons received the final shape I have applied the imitations of the strengthening tapes similarly to the way I did it on the tail surfaces.


Now the flight surfaces were ready to be given the photo etched details. Generally the PART fret designed for this model is very good and is essential for genuine look of the wings. However I have one objection in regard of the landing light. Simply the angle of the leading edge of the light is wrong. Hence I had to make the casing myself. The required element was made of aluminum sheet acquired from a drink can. The tricky thing was to make the glass and the reflective part of the landing light. Of course I could use the film supplied together with the PE fret but for better results I recommend finding a zirconia of a proper size. Then it is enough to linish its cut and polish the glass surface. This way the landing light is equipped with factory made reflective piece.


The wing tips' supports were made of wire and their fixings are PE elements. Next I had to paint the wings and apply the decals.



I started to assemble the wings by fixing the lower wing. Then I could fix the control cables of the rudder, elevator and water rudders. All the cables were made of a rubber thread that can be separated into individual fibers. Each cable consists of few such fibers which were colored black right after separating from the thread.


Next I dealt with the struts. All of them were made of injection needles. I used 0,8 mm needles for the outer struts and 0,6 mm ones for the fuselage struts. In order to use the material with minimal loss I burned the plastic ends down. After cleaning it was enough to cut off the required lengths and press the struts in a vice. I have faced some complications during installation of struts and fixing of the upper wing but the reason was my narrow experience. The rigging of the wings chamber was made of the same elastic fibers I used for control cables. I did not drill any holes because the rigging was attached to the fixtures. To ease gluing the rigging in place I have prepared required lengths and fitted each end with about 2 mm long pieces of fishing line. Aside of imitating the turnbuckles, these were really helpful for gripping the ends of the thread.


In the last article in this series I will describe the build of the engine and its cowling.


Update 21.12.2011

This is the last part of the series of articles describing the build of the Polikarpov MU-2 model. A few years ago I would have not believed that I would ever build a model airplane from scratch. Now I have realised that I won’t be able to build out-of-box models anymore. But let’s get to the point…

The final stage of the construction was probably the most attractive part of my model – the engine. During the preparation of this project I have planned that all inspection panels will be removed and due to the fact that all the engine covers are removable – I had a lot of work to do.

The first step was to prepare a mould for thermo-forming of the panels. The Milliput is excellent for such purposes. To make the panels I have initially used a thermo shrinking sleeve for isolating and organizing of wires.


But it turned out that after shrinking such a material is too thick and flexible. The PVC shrink film used for example to secure wine cork in wine bottles would be much better. However, I could not get such an unprocessed material, so all the panels were made of PVC for deep thermoforming. The difference between these films is that the PVC film stretches under pressure while the other one shrinks, wrapping around the mould and adjusting to its shape. Application of the shrink film is much more convenient because it only requires mounting on a mould and watching as it shrinks under the influence of temperature to fit the shape of the mould. Unfortunately, I had to use the thermoforming film. Taking care not to get burnt I held each piece of the film with bulldog clips and heated it up. Once the film was soft I pressed it firmly against the mould. In this way I made all the panels one by one.


After cutting out all the elements were completed with frames, hinges and oil tank cap. Once the paint job was finished I have checked the finished parts against the drawings and noticed that I forgot to make the air intake on the bottom panel.


To prepare the intake I needed another mould. Once I have thermo-formed the new part I have cut out an opening in the bottom panel and joined the parts together. Addition of a few photoetched elements helped me to obtain the desired effect.


Then I left the finished panels safely secured and began assembling the photoetched PART engine.


Actually the PART engine contains only the elements of the cylinders and a few parts to detail the engine body, so the kit part is required. Unfortunately, it turned out that the part from the ABC Modelfarb kit is not to 72nd scale and all cylinders were matching the size. Again I had no other choice then to reject it. I was in a fix… I could either build the engine from scratch or use an aftermarket upgrade kit. The colleagues from a Russian model forum gave me a couple of suggestions concerning resin kits as well as the ELF extruded detail set. I must admit the pictures which I found on the Internet were not encouraging…


… But I decided to take this chance because the number of parts in this set exceeded the number of components in resin kits. In addition the ELF kit contains parts for the back of the engine body, so even if I decided to build from scratch I could at least base on some ELF kit parts. When the parcel finally arrived I was surprised with the quality of the parts extruded in rigid plastic. Interestingly, the kit even contains a metal propeller axle as well as a propeller mounting pad punched from aluminum sheet. My only objections concerned the back of the engine body and the exhaust pipes, which are not a faithful representation of the original. But these parts could be easily replaced with scratch built ones.


I have started from removing the faulty elements from the rear part of the engine. Next, I have added some photoetched bits to detail the engine body.


Then I cut off the imitations of the cylinder valves. The valves in this type were covered with metal cups protecting them from water splashes. These coverings had to be made from scratch. I have removed the valve imitations to allow for an easy installation of these covers. Moreover, I planned to leave two cylinders uncovered and to scratch build their valves with more detail. After painting I have applied a decal imitating the manufacture plate and started working on the valves.


Next, I have formed the valve covers. I have sculpted one of them in Milliput and the rest was copied using a silicone mould and resin.


All the cables and wires of the engine were made of painted artificial hairs. The correct wiring of the engine required a bit of patience but only after the completion of this work I allowed myself to move to the next stage.


This was to fill the space inside the engine mounting. The engine mount was already done when I wrote the previous part of this article. Now I have painted it and fixed the rigging at the bottom of the structure. I have intentionally omitted the rigging on the top of the engine mount to allow for an easy access and trouble-free installation of engine components. The first part to be fixed in this space was the oil tank with its mounting and plumbing. I made it of thick polystyrene, an injection needle and PE straps.


Then I only had to attach the previously prepared elements, add the engine wires and complete the rigging on the top of the structure. The last stage of the engine assembly was preparation of the correct exhaust tubes. In my model they are mostly made of injection needles, so it was not very difficult to make the angle trimmed exhausts and yet they look like the original ones. However the one, which lets the fumes out of two combustion chambers, required a bit more attention. Its shape reminds deer horns and it took me a while to form the desired shape. The ends with circular cross sections are made of two pieces of an injection needle. I have rolled two stripes of paper and glued a piece of injection needle at each end. After impregnating the paper pieces with a CA glue I could work on it with a file and gave it the final shape.


The final touches were made by adding the door-like engine side covers and installing the wing tip position lights made of clear colour plastic. The propeller was the last element I made. I had to carve it from scratch as the kit part was useless.


I am very pleased that I managed to finish this model. I believe that as I persistently formed it bit by bit – it also had an influence on me. My aim was to create a detailed scale replica. This concept has been defined clearly enough, so I knew exactly whether the achieved effect met my expectations or not. I was able to judge that basing on all drawings and pictures of the aircraft replica. So now I cannot imagine building any model without a proper documentation. I have never tried to build such a model before and I only could admire those modellers who used to do such miracles. Today I am convinced that ambitious model making is within everyone's grasp. You just have to decide firmly that every subsequent model has to be better. That is why I will not be able to make any model with no modifications - simply my crossbar is now put higher that that. This model let me see what I could do. Now, being aware not only of my capabilities, but also of mistakes, I have learned what I should still improve.

I would like to thank my colleagues whose advice, remarks and help made it possible to create this model.

Vyacheslav Demchenko, Wojtek Fajga, Radosław Jurczyk, Yuriy Tsytselskyy, Andrzej Ziober


Text and photos: Piotr Mazurek