Fokker D.XXIII Project

[ramses]

Even though I have already posted a few times about my Fokker D.XXIII in the "What did you do aeroplane wise today?" thread, I am starting a build thread for this project.



Especially because the Fokker D.XXIII project is not finished, but is actually just beginning!

The current prototype was to test the configuration, to see if it would work with two rubber motors, and whether I could get the D.XXIII flying at all. The first test flights of the prototype give me enough confidence to continue the project. The goal is a D.XXIII suitable for indoor flying, so also with a landing gear for R.O.G. flying.





Years ago, I created a design for a 1/5 scale RC D.XXIII. This design is the basis for the 1/20 scale FF prototype. Naturally, this means a heavily lightened and simplified construction. I am using the scaled-down RC drawing as the basis for the model. So, essentially, scratchbuilding over my own design/plans.



The model will be fitted with two rubber motors of equal length and weight. An advantage of this Fokker is that the balance point of the two rubber motors lies in front of the Fokker's center of gravity. Therefore, the heavier the engines, the less nose weight is required.



I will start this build thread with the construction of the first prototype. I will soon begin with D.XXIII version 2.0, the indoor model with landing gear.



So i will first post the build of the current D.XXIII prototype.
This build thread will then continue with the new D.XXIII version 2.0 to be built.

Cheers, Ramses

[ramses]

Fokker D.XXIII Specifications:

Engine: Walter Sagitta I SR
Length: 10.2 m
Wingspan: 11.5 m
Height: 3.8 m

Specifications of this free-flight model of the Fokker D.XXXII:

Engine: Two rubber motors (& two 6" propellers)
Length: 51.0 cm
Wingspan: 57.5 cm
Height: 19.0 cm

I chose 1/20 scale for this prototype Fokker D.XXIII free-flight model.

Cheers, Ramses

[ramses]

Short video from the 'real' Fokker D.XXIII:

The 'real' Fokker D.XXIII has made 11 test flights before Germany invaded the Netherlands in may 1940. Despite the fact that the Germans were interested in the pull-push configuration and the nose wheel design, the Fokker D.XXIII was sadly scrapped during the occupation.

Cheers, Ramses

[ramses]

Start of the build of the prototype:

For the build of the D.XXIII, I had plotted some views and cross-sections of my RC model design in the scale of the FF model (1/20):



I have plotted the 'plans' in triplicate, and cut the fuselage from a second drawing:



From that, the fuselage longerons were determined and cut, transferred onto balsa, cut out, and pinned to the building board.
Then i started on the half-fuselage formers, one by one, from front to back:



The left half fuselage formers were made and glued, and a side longeron was made from a top view. The notches in the fuselage formers and longerons were made with a small file:



After gluing the left side longeron, the fuselage was stiff, and I made the right side in the same way:



Next, the recesses for the stringers in the fuselage formers were filed one by one and the stringers were glued:



This fuselage was intended as a 'mock-up' to test the installation of the two rubber motors. I used fairly hard balsa, but also kept the fuselage formers quite narrow.
The whole thing is very sturdy and the weight is now 9.9 grams; perhaps a flying mock-up model?







Cheers, Ramses

[ramses]

Next i made the two motor plugs:



Just need to install small magnets that clamp the motor plugs against the fuselage; this is currently done by friction:



Cheers, Ramses

[ramses]

Continuing with the wing:

First, the wing spars and trailing edge were pinned to the building board.



A few wingribs are made of harder balsa, the rest of softer balsa.
Here the harder balsa ribs are ready and glued into place:



Making the rest of the wing ribs:



All wing ribs in place:



Basis of the D.XXIII wing:



Had to make some infills in the fuselage where the wing will pass through the fuselage:



I covered the leading edge with very thin sanded balsa and also made the ailerons:



Cheers, Ramses

[ramses]

Continuing with the tail booms and empennage:

Instead of a flat 'plate' horizontal stabilizer, I gave it a bit of profile:



Started with the two tail booms, first determining, marking, and making the formers:



Made the recesses for the stringers with a small file and glued them onto a keel:



Rest of the stringers in place, fixed to the building board:



Made balsa covering for the top side, from a very thin sanded balsa plate.
Then glued the keel onto the thin balsa plate and wrapped it around the tail booms:



Removing the excess covering:



The two tail booms, they weigh 3.1 grams each:



Now to figure out how I'm going to attach the empennage:



Starting with the vertical stabilizer and rudder, these are also lightly profiled:



Checking the fit:



Cheers, Ramses

[ramses]

Finished the tail booms and empennage.
Weight of the parts:

The motor plugs weigh 11.8 grams together
The rest of the parts weigh 34 grams together
That gives a total weight of 45.8 grams now:







Cheers, Ramses

[ramses]

Assembling the Fokker D.XXIII:

A height-adjusted root rib (due to the slope of the fuselage surface) marked out on the infills. Cutting it out was no easy task; the fuselage formers behind it also need to be cut, taking the dihedral into account:



After some trimming and sanding, the wing fits snugly into the openings in the fuselage.
The same was done for the tail booms until everything fitted together neatly with the correct setting angles.
A "jig" was made from 5mm balsa plates to fix everything in place, along with heavy lead  batteries for alignment. Once everything was right, the whole thing was glued together; here it is just finished after gluing:



My tripod Snoopey came to inspect again...
She nudged the tail, so luckily it was approved



The Fokker D.XXIII after assembling.
By the way, the nose is also fitted with some infills on the top and bottom:



Cheers, Ramses

[ramses]

Pre covering finishing:

Finally, the transitions between fuselage/wing, tail booms/wing, and vertical stabilizer/ horizontal stabilizer were made using thin strips of paper.
This is mainly to allow the tissue to be attached to:



The Dilly Tissue laid out and a piece cut off for the Fokker:



I applied the Dilly tissue with a (blue colored) glue stick:



After the glue dried, i first mist the entire Fokker with a sprayer with water and let it dry. Then applied a first coat of a mix of approx. 10% dope, 20% banana oil, and 70% nitro thinner. Second coat 100% banana oil, and over the wings and some fuselage parts, a third coat of 100% banana oil:



Drying fixated between each layer of dope:



Cheers, Ramses

[ramses]

Choosing the colorscheme:

For the Fokker D.XXIII, I have a choice of two color schemes.
The color scheme during the first flights of the prototype in 1939, the X-4
Or the later applied "pseudo-war scheme" of the D.XXIII in 1940, the 998:



I have many historical photos of the X-4, which are useful for good scale documentation. I have only a few historical photos of the 998 version.

Since this D.XXIII is a prototype, I will use the 998 color scheme.
Should I ever want to build a competition model of the D.XXIII, I will use the X-4 scheme.

There are nice renderings of a 3D model with this 998 color scheme on the WarThunder site:


© WarThunder


© WarThunder

Cheers, Ramses

[ramses]

Paint and decals:

I made the decals for the D.XXIII in photoshop:



I have also plotted a colored 3-view in the scale of my Fokker model.
Handy for creating some details and the camouflage scheme with the airbrush later:



For this Fokker D.XXIII, I am using Tamiya XF colors (matte acrylic), in the colors XF-10, XF-11, and XF-78:



Cheers, Ramses

[ramses]

Painting the Fokker with an airbrush:

The entire Fokker was very lightly swept with 1000 grit; you can't call it sanding.
The Fokker was then wiped down with a tack cloth, and the entire underside was first sprayed with Tamiya XF-10 (brown) using the airbrush:



Next, the Tamiya XF-78 (beige) on the top and finally the Tamiya XF-11 (green) spots:



I have to touch up the camouflage a bit more and then i can continue with the decals for the Fokker D.XXIII:



Cheers, Ramses

[ramses]

Applying the self made decals:



Applied MicroSol over the decals and let dry thoroughly:



The airbrushed camouflage didn't turn out the way I wanted, but that doesn't matter for this prototype...
I'm going to do it differently when building the next D.XXIII (using stencils instead of freehand).

Let it dry overnight on the jig:



Cheers, Ramses

[ramses]

Finishing the motor plugs:

I made a small tube inside the two motor plugs, into which a small iron rod fits.
These small iron rods block the propellers after winding; the two rods are located here by the red arrows:



After winding, insert the two rods, and to launch, simply pull the two rods out.
The two motor plugs with the tubes inside, and gave the 'locking rods' a pennant:



This is how they block the propellers:



I made two small rubber motors and wound up, here is the Fokker "under tension":



And here after removing the two locking rods:





Cheers, Ramses