Fokker F.VIIa

[Stunthenk]

Looking for a successor for my Koolhoven FK.43 models, the Fokker F.VII came to mind. This aircraft was first designed and built in 1923 as a larger successor to the F.II. It retained some design features of the previous model. After a small number had been built the design was altered; a more efficient wing with integrated ailerons, a simpler U/C and a longer fuselage. Later, in 1925 Tony Fokker wanted to expand his bussiness in the US and entered the Ford Reliability Tour. His US agent, Noorduijn, told him that US airlines wanted a multi engined plane for safety reasons, so the original single 400 hp Gnome-Rhone engine was exchanged for three 200 HP Wright J-4 engines. In this configuration, the F.VII 3M the type was a huge success. The - 3m was not a successor to the single engined model as multi- and single engined examples were built side by side. Each F.VII received the attachment points for the wing mounted engines. Some started with three motors but were converted to a single powerplant later in their lives. The designations a and b were introduced during the period when F.VII's were built with the b signifying the longer span wing achieved by inserting an untapered center section.
Well, that is quite enough history. I wanted a rubber powered model, so it was to be a single engined example. And I needed a decent 3-view to start with. This was found on the internet. As a bonus, an original F.VIIa survives in a museum in this country. This is construction number 5054, delivered to Denmark. This plane happily survived WW II and was bought by KLM and Fokker in 1953 and presented to the aviation museum in Schiphol aerodrome. I had the 3-view enlarged at a local copy shop, to 33 cm for possible use for a peanut model, and tot 51 cm. for an F4D model. It was then simply a matter of adding my own construction to the enlarged 3-view and the ususal mods of slightly larger tail surfaces, higher U/C for a decent size prop and a slight dihedral.

[TheLurker]

... a slight dihedral.

I'm struck by how like the Ryan M-1, M-2 & NYP it looks and I wonder if you might be able to do without dihedral?

Looking forward to seeing this come together.

[Stunthenk]

The big difference between the Koolhoven FK.43 and the Fokker F.VII compared with the Ryan NYP is the wing, both in plan view and in section. The NYP has a parallel wing with the same section from tip to tip (I do have that correct, don't I? ) while the Dutch designs feature tapered wings in planform and in thickness towards the tips. The F.VII wing has a vertical center line with zero dihedral so it actually has an anhedral on the top surface and a dihedral on the bottom. I considered to make the top surface straight, resulting in a center line dihedral of 5 mm at the tip (I might still change my mind and do that for scale appearance) but for now I have drawn the center line to have 10 mm dihedral at the tip resulting in a dihedral on the top surface too. The Koolhoven FK.43 has a straight upper wing surface with dihedral on the center line. My larger FK.43 model flies fine in this configuration. But I changed this to some dihedral on the smaller model.

[THB]

Great to see this one in the works... I have something similar in mind... so look forward to your progress
Tim

[Stunthenk]

I decided to start with the fuselage - the complicated part. I first built a fuselage side from 3/32 sq. balsa, with 3/32 x 1/16 uprights. The uprights in the cabin area are diagonal and can be seen through the windows so needed to be placed carafully. I then decided that the stringers along the fuse sides were not prominent enough to put them over the uprights so I let in pieces of 1/16 x 3/32; a tedious job at best with a less than neat result. After removing the structure from the plan I decided it was too clunky and started again, this time with 1,5 x 1,5 mm basswood longerons and 1,5 x 1,5 balsa uprights. Looking closely at pictures of the real thing I thought that adding the stringers to the outside would be justified but they needed to be thin so I used 1 x 1 mm basswood for these. I also changed the structure around the cockpit a bit, trying for a better scale effect.
One problem remained, however; on my 3-view the lines of the nose were drawn as rounded, both in side- and plan view. This did not match with the pictures I had, but I could not get a clear view. So it was off to Aviodrome museum near Lelystad, nice 40 mile ride on my 1974 Moto Guzzi 750S, truly combining need with pleasure! Close inspection of the real F.VIIa showed all straight lines on the nose, with only some sheet alu streamlining on the bottom giving a rounded effect. But I found another significant item I had not seen on any plan or sketch, and had not noticed before on photographs: the fuselage sides at the cockpit area have a triangular section that cants inward! Probably to allow the pilots to look rearwards through the open side windows. At the museum there is also an exhibit of a crashed F.VIII that was retrieved from a desert sometime, and the rusted bare steel tubing displayed the same feature. So back home the fuselage sides were modified once more and could finally be built into a basic structure.

[Stunthenk]

Here are the final pictures belonging to my previous post.

[billdennis747]

For stringers like those, which barely show through the covering, I use fine carbon rod. And you you won't accidentally squeeze and break them.

[Stunthenk]

That sounds like a good idea. However, since I have none in stock, I'll have to stay with the basswood. But it makes me think that for a Peanut, you could use thread.
The next step for the F.VII fuselage was to add the U/C. I bent the main leg (the rear one) from 0,8 mm pianowire (21 gauge) and the supporting leg from 0,5. (25 gauge). The wire was bound to the crossmembers with fine silk thread and glued with medium CA; the ends were bound with fine copper wire and soldered.
The instrument panel will be hardly visible so I 'suggested' one with brown tissue on a former with the instruments indicated with a black marker using a circle template.
The nose sheeting was first made to size using a paper blank and was then cut from soft 1 mm balsa. The sheeting felt too coarse so I sanded about half the thickness off. When glueing sheeting I prefer to glue one side in  place before doing the rest. Unfortunately I damaged the sheeting in a clumsy movement so I had te make a new one. I decided to cover this on the inside with lightweight tissue for strength; that has the added advantage that it already curls. There are open windows at the rear of the cockpit; I glued lengths of thread in  place to make cutting them out easier.

[Lastwoodsman]

Fokker FV11  peanut      Aug 12 2026

Very nice build and pics Stunthenk!      You are inspiring me to get back at my stalled  30 inch Gipsy Moth ...

Lastwoodsman
Richard

[Stunthenk]

Always follow any inspiration to pull a stalled project free! If I am to be an inspiration; we are having another heatwave in North-Western Europe but I am fortunate in having a  modelling room on the ground floor - first floor for those on the other side of the Atlantic. So in stead of going out and doing usefull things I cut a set of ribs for the F.VII wing from 1 mm balsa. As I only had the section of the center rib, I 'extrapolated' the section of the other ribs. I simply took the length of each rib from the top view of the plan and the thickness from the front view, and used the front part of the plywood template of the Bill Werwage Juno plan that I cut in 1983 for the curved part. (For those who lost me here; the Werwage designs of control line aerobatics models used the so-called Detroiter construction for the wings using rib strips in stead of full ribs for lightness. A typical wing strip was 3mm balsa 6 mm high or 1,5 mm 10 mm high. It turns out that the curves or sections of those wings are very similar to the wing sections we use). The noses of the wing ribs were drawn with the use of a Burmeister set of drawing curves. As each smaller wing rib was fashioned, is was eyeballed to check if it conformed to the next larger rib and copied for a 2nd example. After all ribs had been cut, the 1,5 x 1,5 slots for the spars were cut with a small file. Next the rib noses were cut down to allow for the nose sheeting, and slots were cut for the 2,5 x 2,5 mm leading edges.  Then it was a small job to cut the TE, LE and spars from sheet and assembling the wing on the plan.

[OZPAF]

Nice careful work there Stunthenk.

A approach I have found helpful for building rectangular or straight tapered wing such as the wing you are building, is to build the wing with root and tip aerofoils shaped with blanks in the other rib positions.

Once the wing rib blanks are glued in place, the blanks are shaped with a straightedge using the root and tip ribs as templates.

The root and tip airfoils are protected with masking tape which is also used to hold the wing down.

I add the spar slots using hacksaw blades with a straightedge guide, after shaping the ribs. The hacksaw blades are pulled backwards with light pressure. Notch sanders would also work well.

John

[ramses]

Beautiful work and model Henk!

Cheers, Ramses

[Stunthenk]

Your approach sounds very well thought out, but with this Fokker wing the wing section decreases in thickness so strongly, that I thought my approach would be the only way to achieve success. With with less accute decrease in thickness and taper I have used the technique you explain myself. Another problem is the slots for the spar. As my thinnest file is 1,5 mm thick, I find it difficult to make consistent sized slots smaller than that.
Well, back to this build. After some thought I decided to lift the wingtips (at rib 6) 10 mm. This would leave the top of the wing horizontal but still show some dihedral. Perhaps a little more difficult from the aspect of stability, but better for scale appearance, I thought.
So the tips were lifted, center section spars were added, and spars and trailing edges glued together. In this form the wing was stable enough for some sanding. The TE was sanded down, and I sighted along the ribs at the LE. The hand made rib shapes were well aligned, only some detail sanding was needed to achieve a uniform section throughout the wing. A rib standing out must be sanded down, to misquote a Japanese proverd. The slots for the LE needed some more work, but after that the LE fitted nicely and was sanded down to conform to the section.
The next step was bending the tips out of thin bamboo over a soldering iron, and pinning down the wing half to fit and glue the tip. After sanding this to shape and fitting the right hand tip, some LE sheeting was sanded down from soft 1 mm sheeting to approx. half thickness. The sheeting was applied in three sections: center and both wing panels. The sheeting was first glued to the spar, and then to the LE. The center section was also sheeted on the bottom because a cut-out for the cockpit must be placed under the wing.
After a final detail sanding the wing was put on the scale; 5 grams, not unreasonable.....