MPM 1/72 Curtiss-Wright CW-21B Interceptor



I still have to write a proper introduction, but I couldn't resist adding this piece of highly interesting information about the CW-21 that I found here. I had always thought that the CW-21 was quite inferior to the A6M Zero that the Japanese flew when they invaded the Dutch East-Indies, and that this explained the very limited success of the Demon/Interceptor. But former Flying Tigers pilot Erik Shilling notes: "I have flown a CW-21, an aircraft built by Curtiss Wright in 1938 that's empty weight was 3150 lbs which was 10 mph faster than the Zero, could out climb the Zero by more than 2500 fpm, and 100 mph faster in a dive faster and had a higher role rate as well. Why didn't the military buy it. Just dumb I guess." So, the tiny CW-21B was a quite capable fighter! Erik Shilling was one of the pilots of the small number of CW-21's that were delivered to China, but all crashed en route. Another snippet: the CW-21 is now usually called Demon, but that name only surfaced after the war, and mistakingly based on an abbreviation of 'demonstrator' for the first CW-21. A publicity photo from 1939 reports: 'The new plane, called the CW21 Interceptor Fighter, climbs ...'. The short version, Interceptor, was also (apparently) used by ML-KNIL.



The 1/72 MPM model

The CW-21B is a typical MPM limited run kit. The parts are relatively thick, some minor mould damage is apparent (pits, dents, parts of the mould broken off), but overall it is very buildable. The canopy is quite thin, but not completely smooth. A small photo-etch fret contains mainly cockpit parts. The decals look good to me, and give the builder a set of ML-KNIL markings (with enough numbers for every CW-21B used), and a Japanese captured example (see MIP article or this page). A build report by Caz Dalton on his homepage, unfortunately no longer available, reported that the white decals are opaque (enough?), MPM nevertheless provides a double set. The orange parts however were translucent, and the white line showed through. Alternatives are available, as listed below.

I started building my MPM kit without worrying too much about the model's accuracy. After some time I got a better grip on the CW-21B, and slowly started to see some more errors. Here's an attempt at listing the kit's problems:

I think that correcting these errors is quite manageable, and it will be fun to do (I like doing some work of my own to a model). On the other hand, the Beechnut model could be a better starting point. Henk Jan Donker's analysis of other CW-21B models added some other areas that need checking, such as the cockpit size and location.

Fellow IPMS-NL modeller Han Krol has completed the MPM CW-21B and reported the following problems:

A discussion with fellow IPMS-NL modeller Huub van Dijk yielded further ideas. I had noted that the real aircraft had joints of overlapping sheet aluminium. I thought it would make a highly interesting model if this could be portrayed in 1/72, but I lacked an idea how to realise this. While discussing this aspect of the CW-21B, Huub suggested that strips of thin card could be glued on the model (covering the engraved panel lines), perhaps sanded a little thinner, and putty used to build up skin thickness. I think this could work very nicely. Ideally it should be combined with some subtle 'stressed skin' simulation. But perhaps this a few steps too many at once ..

On the newsgroup rec.models.scale, Jim Maas posted the following interesting points:



Construction

Instead of focusing on the details, I first want my models to have the correct overall shape. This often leads to long delays because it takes a lot of effort to study and correct. The MPM CW-21B has a few problem areas. First and most obvious is the fuselage shape between the front of the cowling and the cockpit. The model has an almost continuous taper between these points, whereas the Beechnut (right) and Rareplanes have a definite kink. The MPM model need to be corrected here. Note that I reduced the thickness of the cockpit sides with a factor of three or so.
Here I tried to photograph the same area of the Rareplanes fuselage, still on the sheet. The kink is clearly visible.
The second shape problem is the fuselage shape below and behind the cockpit. MPM included part of the wing root fairing in the fuselage shape, and made it too square. Shown here is a comparison of the MPM and Beechnut models.
The photo shows the same area of the MPM and Rareplanes models. I'm not so sure that the wing root fairing of the Rareplanes model is correct.

I worked on two areas so far. The model lacks wheel wells. I decided to add walls, although I don't have references to prove that the real thing had them. The cutaway drawing does show walls, but only if that drawing was made in the Curtiss factory, and not 40 years later, it can be considered a reliable source. I started with of with bending some 1 mm thick plastic card strips of 4 mm width around a pencil. I found a pen with a slightly smaller diameter than the wheel well opening, and used this as a stop to glue the curved strip millimeter by millimeter to the lower wing surface, using super glue. This process required four hands, but I had only two at hand. Next the straight sides were added. Some filler had to be employed at the lower wing - strip connection. And then came the process of fitting the new (oversized) walls to the upper wing surface. Step by step more material was removed from the strips, until it fitted snugly. In the middle I had to add a little filler. Then I removed just a little more, in order to be able to cover the wheel wells with 0.1 mm plastic card. This is necessary because the upper wing halves only cover part of the wells, and a crude piece is supposed to be used in the center. Even though this process is written down in a few sentences, it took quite a few hours in reality. The job is not yet done, because I want to add some stiffeners and details.

I later test-fitted the wheels in the wheel wells, and was very surprised when I noted that I could probably fit two wheels in each wheel well! This is largely caused by the 50% too thick wing, as I found out later. But changing the wing thickness involves large modifications, and is rather useless.

Next came the cockpit. As shown above, I thinned the walls with a factor of three or so, allow the construction of a more realistic cockpit interior later. The next step in the construction of the cockpit was to fill the lower sides of the cockpit walls, because MPM's wing root fairings created an opening there. Milliput was employed as a filler here. I will probably skip most of Eduard's photo-etch, and build the details with plastic strips, in order get a more three-dimensional interior.



CW-21B models and accessories in 1/72 scale

Six models of the CW-21B are/were available in 1/72:

           

   
The main components of the Beechnut kit. The parts are quite rough, and the wing parts have a wood print, which is kind of unique for an injection-molded kit! If you look through the roughness, a reasonably nice kit hides underneath, that is often more accurate than the MPM model.
The small components of the Beechnut kit. There's no guarantee it's complete, since I bought the kit as an unmarked bag of parts, without instructions. The limitations of the production process are quite obvious. In case your're wondering: the parts on the top right are nine cilinders and a crankcase. And I'm still wondering what slight below the center is - maybe a torque scissor for the landing gear? Most are best replaced by spares parts, or scratchbuilt. The vacformed canopy is too rough to use.
A close-up of the fuselage shows delicate riveting on the sides and what I believe a largely correct shape. The vertical tail is very thick.
The left wing shown upside down. The profile thickness looks excessive to me, similar to the MPM wings.
The Rareplanes model consists of one sheet of vacformed parts. The fuselage halves show very nice and delicate rivet detail. The wings are drowned in rivets, as if every stiffener is represented. I don't think it will look realistic.

I found the following 1/72 accessories:



CW-21B models and accessories in 1/48 scale

In 1/48 four models are/were available:

In 1/48 the following accessories are available:



CW-21B models in 1/144 scale

For completeness: in 1/144 one model is/was available:



1/72 model comparison

Below is a first comparison of the Rareplanes, Beechnut and MPM kits, put together by Henk Jan Donker. I added some comments I noted on my own MPM model. Lacking good references, it is not yet possible to say which kit is most accurate. Thee Rareplanes is the most average in dimensions of the three models.

Item

MPM Rareplanes Beechnut
Fuselage ahead of tail

extremely narrow
Wing chord (root)

1.5 mm less than others
Cockpit opening

5 mm longer than other two
Cockpit location

rear edge agrees with Rareplanes, forward edge 5 mm forward rear edge agrees with MPM, forward edge 5 mm rearward rear edge 2 mm forward of MPM, forward edge 3 mm rearward
Prop diameter

smaller than other two (see Replic review below)
Wing tip shape

more square than other two
Horizontal tail span

5 mm larger than Rareplanes 1 mm smaller than Rareplanes
Vertical tail offset to the left

not included ? ?
Wing thickness

some 20-22% thick, some 50% too much
Fuselage tapering

There's a kink in the fuselage taper, just aft of the cowling. The MPM kit has a straight taper on the left side, and a slight kink on the right side! Clear kink in the taper


CW-21 references

Below is a list of CW-21 references compiled from my own data, fellow CW-21B modeler Henk Jan Donker's data and information found on the newsgroup rec.model.scale. I only have sources number 2 to 6 and access to a library copy of number 7.

Dedicated CW-21 information:

  1. Air Enthusiast Sixteen (new series) has an extensive article, including a cutaway drawing. This appears to be the only comprehensive article on the CW-21

  2. 'Curtiss Interceptor' ML/KNIL' by Max Schep, in Modelbouw In Plastic 1987-4 (IPMS-The Netherlands). Eight page article, 8 photos, cutaway drawing, camouflage drawing, and a report on building the Rareplanes vac

  3. 'Japanse Interceptors' by Max Schep, in Modelbouw In Plastic 1988-2 (IPMS-The Netherlands). Two page article with four photos of the CW-21B in Japanese colors

  4. 'Geest uit de fles! Nederlands-Indische CW21B Demon' by Erwin Stam, in Modelbouw In Plastic 1998-2 (IPMS-The Netherlands). Single page article about the MPM kit, two photos, some camouflage comments

  5. 'Fighter A-Z: Curtiss-Wright CW-21 and CW-21B Demon' in Air International January 1977 (Vol 12 No 1). One column text with small but nice three-view drawing

  6. 'Plane Facts: Demon deviations' in Air International February 1977 (Vol 12 No 2). One and a half pages of text about the lineage of the Curtiss CW 19W / 19R / 22 / 22N / 21 / 23 / 21B

  7. 'Curtis-Wright Aircraft 1907-1947' by Peter M. Bowers, single page text, one photo, and drawings that I don't trust right away

  8. 'To join with eagles' by Murray Rubinstein and Richard Goldman (Doubleday). An illustrated history of Curtiss-Wright aircraft from 1903 to 1965. 230 pages, 326 illustrations

  9. The IPMS-NL web site has some nice photos contributed by Max Schep

  10. Skyways #38 (April 1996) has, according to Mark Schynert on the newsgroup rec.models.scale, three huge CW-21B cockpit photos, of panel and right and left cockpit sides respectively. Mark reports that although there are no notes on color, it is evident that the panel itself is black, and the cockpit walls are basically non-reflective, which implies a light gray or green - the pictures are of a factory-fresh example, and the fire extinguisher (natural metal) is very reflective

  11. Skyways #77 (January 2006 ?), article by Dan Hagedorn

  12. 'Curtiss aircraft in combat... and commerce' by Curtiss-Wright Corporation (circa 1947), with sections on the C-46 Commando, the SC2C Helldiver, the A-25 Helldiver, the P-40 Fighter, the P-36 Pursuit, the CW-21B Interceptor, the SO3C Seagull, the SOC Seagull, the O-52 Observation, the C-76 Caravan, the AT-9 Fledgling, and the SNC Falcon

Dutch books about the ML-KNIL air force with information on the CW-21:

These magazines are reported to contain some CW-21 information:

Generic fighter books with some CW-21 information:



CW-21 colors

Camouflage and color information can be found in:



Links





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