Frog and PM 1/72 Fokker D.XXI
KIT #:  (Frog) F.223, (Air Lines) 3902, (PM) PM-201
PRICE: Frog and Air Lines: About $3.00. PM: $4.00 to $8.00
DECALS: One option each?
REVIEWER: Brian R. Baker
NOTES: PM Kit is currently available.  Frog kit is available at swap meets. Old kits, but can be built in several variants.


 The Fokker D.XXI was one of those classic fighters of World War II that, had other circumstances prevailed, might have been better known.  It was originally envisioned as the Dutch East Indies Air Force standard fighter, but it wound up being the primary fighter in the defense of the Netherlands against the Luftwaffe in 1940.  A small number were exported to Denmark, and the type was being manufactured by the Spanish Republicans at the end of the Civil War, although only one example is thought to have been completed.  The Finnish Air Force was the largest user of the type, and after the initial Dutch-produced examples were delivered, more were produced by the Finnish State Aircraft Factory.  This article will briefly outline the variations in the production models, and the steps required to accurately model these in 1/72 scale using the two currently available kits, the original British Frog issue and the currently available Turkish Pioneer/PM kit. Each kit has its advantages and disadvantages, but both can be made into acceptable models with a little effort and a creative vocabulary.

 Developmental History

 The original prototype D.XXI appeared in 1936 powered by a Bristol Mercury radial engine.  The plane was equipped with a smooth cowling, with no protruding rocker arm covers.  Two scoops were located underneath and immediately behind the cowling.  No guns or gunsight were fitted, and there was no pitot tube on the wing. There was no radio mast or antenna.  The aircraft was painted a dark green overall, with tail stripes on the rudder and the number “FD-322” in white on the fuselage sides immediately behind the tri-color roundel, which had the traditional orange center.

 The first production models for the Dutch Army Air Force were nearly identical to the prototype, with only detail differences.  They were originally delivered in a light tan, dark green, and dark brown camouflage on top, and dark brown underneath. Large white numbers appeared ahead of the national markings on the fuselage, and a white “Fokker” logo was painted on the vertical stabilizer.   Only one scoop appeared underneath the cowling.  Radio masts were not on the airplanes at first, but eventually they were fitted as radios became available.  A pitot tube appeared on the left wing. A long telescopic gunsight was fitted ahead of the windshield, and two guns were installed in each wing, with landing lights fitting flush between the guns.  A few airplanes had only two guns in the wings, with two in the fuselage firing through the propeller arc.  The horizontal stabilizers were braced by a solid strut underneath, and a flying wire above.  External hinges appeared on upper surface of the horizontal stabilizers only on the Dutch aircraft, as they don’t show in photos of any other D.XXI’s.  A total of 36 was produced, with the last being delivered  in 1939.  In October, 1939, the markings were changed, with the roundels being replaced by large orange triangles outlined in black.  The rudders were entirely orange, with black outlines.  These markings were used until most of the Dutch aircraft were destroyed during the German invasion. At least one airworthy D.XXI survived and was flight tested by the Luftwaffe. It flew in original Dutch camouflage with Luftwaffe markings.

 The Danish export versions were similar to the Dutch models with a few changes.  Only one scoop was located under the cowling.  The first two aircraft were apparently delivered in overall silver with no armament or gunsights.  The landing light was in a small fairing on the right wing, and small “bumps” on the cowling covered the protruding rocker arm covers on the engine.  The elevator hinges were no longer there.  Eight aircraft were built under license in Denmark, and some of these were fitted with two  20 mm. Madsen cannons in fairings under the wings outboard of the landing gear.  The Danish production models  were camouflaged in an irregular pattern of light brown and medium green over pale blue undersurfaces, and had typical Danish red and white roundels, and it can be assumed that the original Dutch built examples were later  painted to this standard.   These  airplanes were  apparently captured intact by the Germans, although their subsequent use is unknown.

 The Spanish Republicans began manufacturing the D.XXI in Spain during the latter stages of the Spanish Civil War, and it is believed that only one aircraft was completed before the plant was overrun by Franco’s Nationalists.  This plane used a Russian  M-25 engine, the type used on the Polikarpov fighters, and also featured a Messier undercarriage.  No photos of the plane are known to exist, although a color drawings exists on the Wings Palette website.  Apparently, only the prototype survived, but its ultimate fate is unknown.

 The major user of the Fokker D.XXI was the Finnish  Air Force, which received 7 Dutch-produced D.XXI’s after 1937.  Later,  93 were produced by the Finnish State Aircraft Factory at Tampere. The Dutch models were virtually identical to the Dutch production models except for the following changes.  A small venturi tube appears on the left side of the fuselage about even with the main spar. Landing lights were included, similar to those used on the Danish versions.  Navigation lights were in small fairings on the wingtips, with small handles immediately behind them for ground handling. No guns or gunsights were fitted, but these were later added by the Finns.  Two scoops are located under the fuselage, and a pitot tube is located on the wing leading edge just outboard of the left landing gear.  Some aircraft were flown with Finnish designed skis, which used most of the normal landing gear struts.  A shorter but slightly thicker gunsight was located in the position ahead of the cockpit on some aircraft, but later, some of these were replaced by German Revi sights. 

 Finnish production models also involved a few changes.  A small glass panel was installed behind the cockpit canopy, and this is hard to detect on most photos. A radio mast protruded from the top of the cockpit, with a small post on the top of the vertical stabilizer mounting the other end of the LF aerial.

All Finnish models had a “V” strut bracing the horizontal stabilizers.  Original Dutch-produced aircraft were delivered in a brown camouflage over silver undersides, but these were soon repainted in a single dark green camouflage with light blue undersides similar to RLM 65.  Later, irregular patterns of black were added, forming the familiar black and green over light blue usually associated with the Finnish aircraft. Yellow theater markings were added once the German invasion began in 1941, and the results were some very colorful airplanes.  The Profile publication shows a drawing of a snow camouflaged D.XXI on skis, but I find it significant that there is no photo or reference to a snow-camouflaged D.XXI in the Finnish book, leading me to assume that the planes carried the black and green colors all year around, even when they were operated on skis.

When the supply of British Bristol Mercury engines began to run short,  some aircraft were manufactured or rebuilt using 80  1,050 hp. Pratt and Whitney R-1535 radial engines that had been obtained from Sweden in 1940.  This represented a power increase from the 760 hp. Mercury engines, and resulted in a few changes in the airframes. The most obvious is the canopy, which was extended back almost to the leading edge of the vertical stabilizer, adding four frames to the structure.  Another change was the rudder, which was enlarged due to the power increase. These new rudders had balances ahead of the hinges at the top of the unit.  However, some Mercury powered examples also had this new rudder, so check your photos for this detail.  The cowling was approximately the same length, but due to the smaller frontal area of the Wasp engine, it was slightly narrower.  Of course, the American engine turned in an opposite direction to the British, so a new prop had to be used, and slight changes in the aerodynamic settings of the tail surfaces had to be made, but these would not be visible in photos.  The scoop under the fuselage was entirely different. The same skis were used, and markings remained essentially the same.

 One experimental prototype, powered by a Wasp engine, was built and flown using a retractable landing gear similar to that used on the Fiat G.50, and this involved considerable redesign to the wing center section.  Only one was completed, and it was later reconverted back to original configuration, but there are plenty of drawings and photos available for this aircraft. Another  five examples were produced in 1944 using 920 hp. Bristol Pegasus X engines, but I have not seen photos of this variant, which must have look very much like the Wasp powered aircraft except for opposite propeller rotation.

 After the Finns were compelled to agree to an armistice with the Russians in 1944, the D.XXI’s were used alongside their  Bf-109G’s to drive the remaining German forces from the country,  and soon after, the D.XXI was no longer used as a fighter. Postwar, the D.XXI’s soldiered on until 1949, and the last were not disposed of until 1952. These were mainly Mercury and Wasp-powered types, and aside from the removal of the yellow theater markings, the small blue and white roundel replaced the original Finnish swastikas, which of course, pre-dated the German use of the symbol by many years.  Some of these aircraft carried small cylindrical air filters under the cowlings, and most had the wheel pants removed, exposing the wheels. The D.XXI’s service life extended through almost 15 years, and it is believed that at least two survive. In addition, at least one North American Harvard Mk. IV has been modified to look like a D.XXI for movie purposes, and this will make a most interesting subject for a model.


The Frog D.XXI Kit

Frog first issued their D.XXI kit in the 1960’s, and for many years, this was the only kit available of this type. Featuring the typical detached control surfaces, the pilot seat was the standard “all purpose Frog seat” mounted on a stub in the cockpit. There was no instrument panel or any other cockpit detail.  The propeller is accurately shaped, and the Bristol Mercury engine is adequate.  The cowling has no rocker arm covers, so it is correct only for the Dutch built variant. There is no exhaust stack, which should be located on the lower right side of the cowling.  The landing gear is too short, and incorrectly shaped, but the wheel pants can be corrected by judicious sanding down.  There is no provision for the rear window panel.  Also, although the canopy is accurate, the rollover pylon behind the pilot’s seat is shown as lines on the canopy glass, whereas the structure is actually inside of the cockpit.  The elevator hinges on the Dutch model are missing, and the gunsight is only for the Dutch version.  The radio mast must be scratchbuilt.  The rudder shape is not entirely correct, especially in the upper hinge line. The tailwheel appears to be a little small, but it is useable. 

The Pioneer/PM Kit

At first, this kit looks to be infinitely superior to the old Frog kit, but after building these side-by-side, I’m not so sure.  The outline is reasonably accurate, although I have the impression that the rudder is just a bit too short in chord.  All control surfaces are molded into the airframe, and these are marked by thin raised panel lines, making them all but invisible once the paint is on.  This is NOT a copy of the Frog kit, although the kits do have a few parts that are almost interchangeable.  The engine looks like the Frog engine, but it is slightly bigger, as is the cowling.  The prop, however, is slightly undersized, and has no hub, just blades protruding from the crankshaft. I replaced mine with a Frog unit. As on the Frog, there is no exhaust stack, so this has to be scratchbuilt. There is a floor and pilot seat, but no other cockpit detail.  The interior is a little rough, with casting marks in the cockpit area that should be trimmed off.  The molding of the wings leaves something to be desired, and these need trimming down to achieve the correct shape.  The fuselage has some rough areas, especially ahead of the windshield, and there are some sink marks behind the cockpit.  The fit of the wings and tail unit to the fuselage is not as good as that of the Frog, and some filling will be required to correct this. The rudder appears to be a little small, and the hinge line at the top doesn’t look right, but I didn’t bother to correct this minor detail.

One good feature of this kit is the landing gear, as the wheel pants and skis and both provided.  Both are accurate, and the extras can be used to correct the Frog kit. However, the skis, especially on the bottom, need some filler, as they don’t line up completely.  They do, however, attain the proper angle for when the airplane is sitting on the ground. If you are going to model the airplane in flight, you’ll have to cut the skis off and reposition them.  Check photos for proper angles.  There is, of course, no rear cockpit bracing, and this needs to be scratchbuilt from plastic rod.  Use a small section of flat strip for the top, as this is correct. Also, be careful in attaching the wings, as they will want to assume too great a dihedral angle. 


Frog Kit:

Assembly is fairly simple.  Once the cockpit is detailed and joined, the seams need to be filled in, and there is considerable work in the belly section, as this is one of the old kits that had the slot for a stand.

Basic fit is very good, and the wings line up at the correct dihedral angle.  The tailplane lines up easily, and the control  surfaces can be mounted securely before painting.  If you’re doing the Dutch version, it would be wise to paint  the rudder before installing it, as it requires tricolor stripes or the typical orange rudder markings used in 1940.  The landing gear needs to be reworked, with new struts and reshaped wheel pants. The Frog kit doesn’t include the skis, so if you want to do that version, you’ll need the PM kit or some scratchbuilding skills.  The engine needs some detailing, but it fits into the cowling snugly.  The prop can be attached to the engine before the cowling is attached to the fuselage.  Be sure to scratchbuild the exhaust stack, as this is not included in either kit.  A piece of round sprue works fine here if you heat one end and bend it before trimming it off. Also, check the tailplane bracing struts.  Some airplanes had only one strut, while others had two.  The kit provides a single strut only, so this may need to be added.  Check photos for the plane you are modeling.  In general, the Dutch planes had one strut, while the Finnish built examples had the “vee’ struts. This goes for the Pioneer kit also.

 The canopy fit is very good, and you can actually see some of the cockpit detail inside.  Be sure to add the correct gunsight.  Also, add elevator hinges on the Dutch version.  Painting is no problem, and there are a lot of color schemes to choose from.  Just be sure to check photos first, as there are a lot of detail differences.

  PM/Pioneer D.XXI

 Once the cockpit is detailed to your satisfaction, the canopy can be attached.  This canopy is almost opaque, and not much can be seen inside. I suppose that smoothing it down with toothpaste, a very mild abrasive, might help, but I didn’t bother.  Again, there is no provision for the rear window panel, so this needs to be added using glass or a decal of some kind. 

 All in all, this makes up into a pretty nice little model of the Fokker D.XXI, but it is quite a bit of work to get things right.  You’ll need a lot of putty and some spare parts,  but I was satisfied with the results.  The landing gear is probably the best feature as compared with the Frog kit, especially since both the ski and wheel gear are included, and the extras can be used on a Frog kit, saving some work.

 Converting Either Kit to the P.W. R-1535 Wasp Powered Version

 This conversion makes up into the last production model, done in Finland because of a shortage of Bristol Mercury engines later in the war.  The main changes are, of course, the engine and propeller, along with the enlarged rudder and extended canopy.  The retractable gear prototype was built from this model also, making a large variety of conversions possible from this model.

 The engine and cowling require replacement, and an ideal unit is the extra cowling from an old Hasegawa A6M2 Zero kit.  Three cowlings and two engines are provided in this kit, and the earlier A6M2 cowling is ideal.  Be sure to replace the prop also, as it rotates in the opposite direction as compared with the British engine.  The rudder has to be scratchbuilt, and has a small balance protruding forward from the top.  Also, this model had “vee” struts bracing the horizontal stabilizers, so these also need to be built from plastic rod.

 The canopy provides the major problem with this conversion. I made a vacuform mold and made several canopies, using a wooden form and adding the bracing with thin strips of masking tape.  I cut down the rear fuselage aft of the cockpit so that the canopy would fit, and superglued it in place.  It is not a difficult conversion, but it can be a little tricky to get everything to fit right.   


These are both pretty decent little kits, and can be made into acceptable models with a little work.  If a newer kit is available, it will probably be much more expensive, so don’t throw away or trade off the old ones.  They still make up into nice models, and the price is right.


There isn’t a lot of material available on the D.XXI, but some useful sources include the old Profile Publication No. 63 from the sixties and a number of ‘Fighters of the world” books, which contain  some basic information.    The Squadron “Finnish Air Force” paperback has some good color information.  The best source, although it is published only in Finnish, is the paperback  by Keskinen, Stenman, and Niska, “Fokker DXXI”, which contains a wealth of photos and drawings, including some color.  Even with the language difficulties for English readers, there is enough useful information to make this worth getting, even though it is dated 1977.  The photos and drawings are outstanding.

Brian R. Baker

March 2011

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