Fokker FG-2 - Congrès 2017 Vauville

[bocorvin]

Hello everyone, I am Vincent de Bode from Holland. I can speak and understand French and German, but writing it, is difficult for me. English is easier, but it is still a foreign language for me, so excuse my mistakes.

I liked to join Congres Vauville 2017 very much, so I was looking for a suitable glider.
Rob, who is a Fokker fan showed me a picture of the FG-2 and I thought; that can't be to difficult. (mistake!)
It will be built scale 1 : 5 with a wingspan of 2.4 meters ( its a biplane, quite voluminous)
We tried to get a proper set of plans, but till now we didn't succeed. I am quite sure when it is finished, the drawings show up .

I hesitated a lot where to put this story, in "Constructions détaillées en Photo" or "Constructions Métalliques".
About 70% of the fuselage is steel tube, combined with wood. The horizontal and vertical tailplanes are also from steel tube, so I put it in "Constructions Métalliques".


When looking at different photo's and (very short) video's (all on the net) I discovered he made a lot of changes on the plane. I started to read a lot about Anthony Fokker to get an idea how he constructed aircraft. It was great fun and I even discovered I was at the same secondary school (a lot earlier) and I even recognised the old fysics classroom on the movie of his live.

Next story is a mostly guesswork combined with facts and analysing photo's and video's.

Fokker went to the Wasserkuppe in 1922 with two gliders, the FG-1 single seater and the FG-2 double seater. A reporter writes that they were build in 10 days!!! The wings are in one piece, here on a transport craddle on a truck. Also visible the internal nose construction with the skid.



Anthony Fokker with the FG-1



And the FG-2. On top of the rear centre vertical strut is the pully for the wing warping.











One of the drawings I found, which showed ailerons!



I guess he had control problems partly because the plane had a very short tailboom (I discovered that much later) First change was enlarging the vertical tailplane.
Another drawing I found, with enlarged vertical tailplane, but the tailboom not correct.








I think the tailboom was far too short, on one video it looks he is not very good in control, tries to land , but stays in the air, people are a bit running away. On most photo's someone is lifting the tail, or they put with a pole under it, it is a bit hidden, look carefully!
Maybe also the cg was to far aft???
So they made a longer tailboom, added a tube frame to stiffen the tubes, made the nose longer and changed the steel tube/ canvas streamline nacelle. (I read a story from him that they changed a prototype of one of his fighters in one night, made the fuselage longer).

One of the best photo's I found.



I was looking for the ailerons on this photo, I couldn't find them....





I think he flew succesfully with this configuration. but I found again another photo, with ailerons!
I guess this was done later, I didn't find a photo with ailerons and flying
but is a very informative picture.



I tried to make a drawing, it's a lot of guess work. It helped to see how his planes where made of wood and steel , bolted together and lots of wire.
The wing looks very transparant, so I have to make "nervures aux baguettes". Rob came up with the idea to make the wings in three parts. One short piece connected to the fuselage and two outer parts demountable for transport.



On the drawing I made(it is more a scetch) red is steel tube, green is wood, blue the wing and canvas.
Back to the ailerons (or lack of them) Fokker had a lot of experience with wing warping and obviously this plane had it.
The front girders with the struts and cross rigging, combined with rigging to the nose and tail should made it rigid. Rigging in green.


The rear girder was only attached in one point (the rear strut, it had 3 struts in the middle instead of 4). On top of the rear strut is a pully and at the bottom of this strut must be a connection to the torsion tube of the control , which is under the wing. In the model comes a big servo, about the same as the Willy Farner from Fréderic. His building story is very helpfull!
Because the rear girder is resting on one point there should be no bending in the rear girder when the wings are warped.


The photo in the beginning of this article from the FG-1 gives an idea of the controls.
So, this was a lot of puzzling, I can now start building.
I think I am going to make all the ribs this summer, Adri is going to CNC a aluminium jig to make the ribs in, something like 80!
All info is welcome!
to be continued, Vincent

[VincentB]

Bonjour Vincent

Ha chouette enfin un nouveau projet qui se concrétise pour Vauville

Pour les biplans, triplans... je me demande si on aurait pas pu réduire l'envergure à 2m, ça fait déjà une belle taille, enfin ça dépend aussi de l'échelle. A 2m ça ferait au 1/6e c'est encore bien pour les détails.
Donc si ça t'arrange de construire plus petit... Mais bon si tu as déjà les plans tracés et tout prévu, fais comme tu veux

[Wolfgang]

next projekt is starting

[bocorvin]

Merci Vincent et Wolfgang pour les comments!

About the scale, yes it's getting pretty big, I think it's worth a try, hopefully it will fly more steady and I was already mentally prepared

Vincent.

[bocorvin]

Bonjour a tous,
Quite suddenly I started with the ribs. I thought to make them of battens 2 mm X 3mm spruce with gusset plates from 0.8 mm ply and a nose section from 3 mm ply. Adri had some spare time and so he could CNC the jigs for the ribs. One of the easy things on the FG-2 is that the wings are straight, so alle the ribs are mor or less the same. So it was a good idea to make a jig. At that time (I made a stupid error) I thought I needed 80 ribs, later I accidentely discovered I needed 140!
We first thought of milling them out of aluminium, but after some thouhts and discussions we got the advice to make them of Delrin, a kind of plastic which looks and feels the same as nylon, but is much better for milling. At a local shop I could buy a piece of 10 X 100 cm and Adri started milling. Before he started I tried to glue a piece of wood on the Delrin with cyano and indeed it didn't stick at all! He proposed to make the jig 2mm deep, so the ribs will protrude 1mm, good for sanding and get it out of the jig.

He also made small nose section from 3mm ply

Some battens needed a bit of sanding to get in the jig



aftre fitting in all the battens and gluing on the gusset plates ther was a tense moment, will it come out? to my relief after twisting and bending the jig a bit, it came out easily



On the background all the milled pieces, gusset plates and nose sections, at tis moment for 80 ribs. in total I need 710 halfround and 1120 quarter round gusset plates.

The aluminium jig is for making th tailpiece, and Adri milled two jigs, for left and right ribs (the gusset plates are only on one side) I two days I made some 20 ribs and now my hands are a bit tired!





I am amazed how strong the ribs are! Only 120 to go....
To be continued.

[VincentB]

C'est une très bonne idée le moule en Delrin quand toutes les nervures sont les mêmes. Paolo Severin perce le moule afin de démouler encore plus facilement les nervures, voir sur son site http://www.paoloseverin.it/techno/ribs/page41.html

[GARCIA]

Oui c'est une bonne idée ce moule. Travail très propre

[bocorvin]

Bonjour a tous,

First I continued with the ribs and I tried to speed things a bit up. I wanted to have it finished before the holydays. I made an adjustable jig to cut all the vertical and diagonal trusses to the correct lenght.

I slowly realised the amount of work! All these bits have to be glued!

This is how I cut the diagonals.



Some of the top and bottom battens had to be sanded down to fit into the jig. This is my favorite sanding block, 10mm balsa with self adhesive sandingpaper.

With all the battens in the jig I sanded the surface flat

. One drop of gap filling cyano and directly I put the gusset plate on his position.



and pressed it on for 15 seconds. (Yes its not the same gusset plate.) It seems to me that, after some time, it became harder to get the ribs out of the jig. Luckily Vincent pointed me at the jigs of Paolo Severin who had made holes in the jig to tap the ribs out. That exactly what I did (thankyou Vincent!)



That went much better! So I made the last 50 to 60 ribs this way

The last one Adri calculated it, 3784 actions!






Now I only have to build the plane...
In the meantime I did some more research and I contacted the Aviodrome Collectiebeheer. They quickly answered me and mailed a plan!
Wonderful! With handwritten text, very good.
From Aviodrome, Collectiebeheer;

This drawing had some very interesting measures, the height (which I had almost correctly got from the fotographs) and a different wingspan, (11.20 m instead of 12 m). They also gave me the name of Hans Disma, who has a archive. I mailed him and he send me the same plan and some very interesting stuff. First a German article which mentioned the same wingspan (11.20 m) and also a description of the qualities of the plane; they thought that it was more a floater, not very suitable for soaring, due to the low wingload.
From the archive of Hans Disma;


In this article the spacing of the main spars in the wing was mentioned (55cm), we had estimated that correct! The other thing he send was a wunderful and very informative picture.
From the archive of Hans Disma

This is a gem! There are so much details; I think it was taken at the Wasserkuppe, the FG 2 standing on some crates on the left someone is taken off the cloth of one rudder, I guess to enlarge it, Anthony Fokker with another man and two woman is changing the nacelle. This looks like the first modification, enlarged vertical stabilizer, still a short tailboom and the nacelle hanging over the trailingedge of the wing. Later the nacelle is moved forward and the tailboom lenghtened. This picture gives a very good image of the wing and I detected internal crossbracing. Also good visible is the thickness of the spars and I think I drawed them to bulky. In the model (and already in made the ribs!) they were planned for 8mm thick, and I think they should be something like 4mm. It means that the apertures in the ribs are to big. Luckily you only will see it when you look into the wing.
The thing that worries me a bit are the planned joints in the wing, but it's very impractical to make the wings in one piece. Something to breed on!

To be continued,

Vincent.

[Johannes]

Toller Bericht
Bitte weiter so

Johannes

[sebastian92]

marvelous technic for building !

[bocorvin]

Thanks Sebastian for the compliments und danke Johannes fur die
It is always very encouraging!

Vincent.

[CHAUSSEBOURG]

Vincent, I like your ribs. Wonderful!

[Johannes]

Hallo Vincent,
was für ein Profil hast Du genommen?
Ich brauche noch eine Idee für mein Stehaufchen

Johannes

[bocorvin]

Hallo Johannes,

Ich habe nur die abbildung der Rippen:


Die Nahme kommt doch spater, , all die Locher gehoren naturlich nicht dabei

Vincent

[bocorvin]

Hallo Johannes,
Rob hat es gefunden, das profil ist: Eppler E174.

Vincent

[Walter]

Hi Vincent,

...very interesting project - I will follow!

3784 actions.... and nobody can see this after covering....

So - I would suggest - make one ore two more for demonstration...

...hope to meet you in vauville



Walter

[bocorvin]

Hi Walter,

Thanks for the . Luckily you can see the ribs at the "Expo fuselage!", but the main reason is the translucentcy of the wings, with massive ribs they would look very different (I think )

Vincent

[Mad Doc]

Hallo Vincent!!!!
Endlich habe ich es geschafft mir Deinen Bericht anzusehen, was für eine schöne Arbeit!!!
Ich bin sehr gespannt auf Deinen weiteren Fortschritt, liebe Grüße,

Christian

[bocorvin]

Hello everyone,

Back from Polsa and our holyday I started again with the wings.
I liked to make the wingspars thinner, 4mm instead of the 8mm as planned, with internal crossbracing, as I discovered on the photo (with the FG 2 on crates). First I made a full size drawing of the wing.


I made mainspars from 4 X 4 mm with a ply webb and vertical from 3 X 2mm.




When I got them finished they appeared to be very flimsy. I can imagine, that combined with the crossbracing it would be just strong enough, but very vulnerable. In the end I decided to go back to a bigger spar. Because the wing must not be stiff in torsion, I opted for 4 X 8 mm top and bottom with a single 1 mm ply webb.

This was much better! I also choosed to have the wing divided, in one piece is too impractical. As wing joiner for the main spar I took a steel strip 10 X 1 mm and for the rear spar a 3 mm steel rod. In the centre part of the wing are a lot of attachments; on top the struts with fuselage, and at the bottom the landing skid. I took M 4 bolts bedded in epoxy with filler and some carbon reinforcement. I greased the M 4 bolts a bit, so I could take them out when the epoxy was set.







(The balsa at the ends is just to prevent the epoxy for flowing out, it can be taken away easily.)



All the stuff needed for the wings..

The central lower part of the wing.

Putting all the ribs on the spars, a very quick job compared with making of the ribs itself!

One wing! To my big relief it was in horizontal plane sufficient stiff and stiff enough (for a biplane) vertically.

Moment of truth: the wing is easily warped!

Next thing is the upper wing.
To be continued.
Vincent.

[VincentB]

Encore un sacré travail de fait, bravo Vincent

[michel]

belle structure, c'est quoi comme profil ?

Michel

[bocorvin]

Merci Vincent et Michel pour les comments encouragieus!
Le profil est Eppler E174.
The weight of the wings at this moment is 640 grams, I think the whole plane will be about 3000 to 3500 gramms. Gives a wingload of 22- 26 gr/dm.

Vincent

[bocorvin]

Hello everyone,

Erstens, Christian , danke fur dir kommentar, es war schon lange da, befor wir zu hause waren, Ich war vergessen darauf zu reagieren.

This week I assembled the top wing,




I'will make the internal crossbracing only cosmetic, because I made the girders a bit heavier.



Top and bottom wing together;




Laminated the wingtips out of two 2mm X 3mm spruce .


Both wings



Now I am going to finish the wings and start with the fuselage.

To be continued.

[Frédéric]

Salut Vincent !

C'est magnifique ! Très joli travail !


Amicalement
Frédéric

[michel]

Magnifique structure,

Michel

[bocorvin]

Merci Frederic et Michel! It is very encouraging
I am waiting for the tubes and puzzling about the fuselage, how did Fokker connect the wood with the tubes etc?

Vincent.

[VincentB]

Que fais tu exactement en tube? tout le fuselage avec les haubans des ailes et les poutres arrières qui maintiennent l'empennage? ou seulement la partie avant du fuselage qui est entoilée?

[bocorvin]

Bonjour Vincent,
Excuse moi, je continue en Anglais, the tailboom, horizontal and vertical stabilizers, wing struts, struts for the skid and the tubing to support the skin of the nacelle are of tube.
The " A " which you can see on the view from above on my plans is from wood, but I think it is interconnected with metal fastenings. In the coming week I am going to visit the "Aviodrome " (a museum) to have a close look of the Fokker Spin (spider) which is displayed there. The Spin is also a bit of hybrid construction, timber with metal. I hope that I understand a bit more of his , don't know how to say, construction pattern? just the way he worked with wood & metal. I ordered the tubes at "tubos capilares", very nice service, hope to get them on short notice.

Vincent.

[VincentB]

Pour des connexions tubes/bois, tu peux braser une tôle de 1mm et boulonner. Le bois peut aussi rentrer dans un tube si ce n'est pas une partie soumise à des efforts.

[bocorvin]

Je ne comprends pas, helas, je ne connais pas le mot "boulonner".
On one of the photo's you can see (guess) how support tubes are fastened to the skid, it looks a bit like this.
The tubes are silver soldered to the "U "plate.


The bolt is M2 , that would be M10 true scale. I guess he connected those quite big timber parts with metal plates and bolts. Its only educated guessing

Vincent