FTS Projects

[AchimEngels]

Hello Langdon!

I was wondering about this myself.

I think the inset sketch in the Flight drawing just reffers to the rib that has the "stack padding" attached to.

However, the Factory drawings as you already mentioned shows the sandwiched rib cap strip design.

What do you think?

Achim

[Langdon]

I think the rib immediately behind that enlargement is a normal rib and it shows the rienforced piece on the nose but it doesn't show the stacking pad. Many American replica Dr.Is have this reinforcement which is wrong on that aircraft but possibly they got this from the D.VII? Certainly the D.VIII has its capstrips the way you have done yours but these came later.
The Swiss D.VII manual, page 10 & 11 show that the ribs were done the way it is shown in the Flight artical so if that was a Fokker built wing then this is certainly the way it was done. Curious about the original technical drawings though!

Langdon

[AchimEngels]

I would really love if there was a filling piece in the nose, since the radii required to bend the cap strip around is very tight on the D.VII, especially towards the wing tip.

I know what you talk about the the rib next to the one of the filling protection padding in the flight sketch, but this just shows a vertical line which is doubtless intented to show the filling piece, but no real proof in my eye that it was actually done that way.

I prefer to go with the actual Fokker factory wing drawing which shows a filling piece only at the rip with the metal padding, while all others show the nose without this. In addition we have the factory drawing for the ribs itself which show it that way, too.

The Canadian Fokker built D.VII preserved at the National Aviation Museum at Ottawa shows it also done this way. Of course one could argue that this in turn is a later built model.

When I place a decision of how things have been done I use my classification of source documents as a major guide.

Original factory drawings and images are classified with the letter "A", while drawings, sketches and articles based on such sources classified as "A" are classified as "B".

In this case the "Flight" article is a "B" class source, since it could provide errors and missenterpretations made by the author. I agree that this article might serve as a evidence to the fact that early D.VII´s have been built different.

Actually I do not see a reason for this, since the same article also shows another sketch with the rib flanges tacked to the sides of the webs. There is no real reason to not bend them around as on the E.V/D.VIII.

Apart from this the Fokker Factory drawings for the upper and lower wings are dated very early and show the sandwiched rib types anyway.

I am quite satisfied with the factory drawing as classified source "A" to work from, as long as no contemporary photograph turns up that shows it done different.

Ther could of course also be another explaination. While the wing rib was originally designed with the rib cap strips sandwiching the webs in between and beeing bent all the way around the nose, the Perzina company decided not to go through this trouble and just built the wing different.

This however is again just guessing....

Dave Watts, what are your thoughts on this very interesting question?

I have seen an image publishes in DR. Volker Koos` small book on Fokker showing a D.VII production wing with the cap strips all bend around the nose as well. I have to ask him for a copy of it or at least for permission to post it here.

Achim

[Langdon]

Hi Achim,

I can understand you being a little perplexed by the contradictory evidence but it seems to make sense that there would be a nose filler piece. You mention that you have experienced a 50% failure rate when bending the nose section of the rib contour, this must mean that the other 50% are close to failure as well which doesn't seem good to me.

If you look at the D.VII nose section of the rib compared with the D.VIII you can see it has a sharper leading edge than the round nose D.VIII. I have seen a photo of a D.VII - I do not know if it was Fokker built though - that had a round nose and a leading edge stringer like the D.VIII and it had the one piece rib cap strip but it had a distinctly round nose (this is a surviving example, maybe its the one in Canada under restoration?).

I understand your grading of your sources upon their perceived reliability but in this case I think the amount of material supporting a nose filler piece outways the Fokker technical drawings reliability. The British Ministry of Munitions report (see sketch page 23 of Windsock datafile Fokker D.VII Anthology I), the Flight report as well as the Swiss D.VII manual all show this leading edge piece, your own experience with bending the material described in the drawing also adds proof to the case that it was not practical to bend the capstrips around the ribs, particularly the out-board ones. Possibly the Fokker draftsmen conceived the idea of the one piece rib contour but it was not practical in reality so the Perzina workers made a modification?

Certainly the rib-caps were sandwiched onto the rib-webs and nailed.

Langdon

[AchimEngels]

Langdon,

may be you are right. Maybe not.

If I take the Flight report for instance for very good, than I should build the wing spar main longerons of only two laminations, since this is shown there, although we know for certain it was made from much more laminations.

I rather more see the reason for my first experiment failures in the way I do it. This is one of the techniques that mighjt require some more experience than I have. I have tried another method now and the failure sudenly reduced to one out of ten which for sure can be contributed to a poor grain in this piece.

Your point of assuming the engineer designed something that in practical life was not executable sounds good to me, but on the other hand they had experience in 6 years of wing building.

My opinion is rather more that Fokker developed his planes in trail and error procedure. As far as we know there have never been made exact working drawings before the planes were built, but rather more vice versa. Prototype planes have always been made from rough layouts (Basic technical drawings as we know from the V.2 and V.3) and only after they proofed reliable exact working drawings of all the details have been made.

Of course your ideas go around in my head as well....

Achim

[Langdon]

Hi,

Yes I agree, if it were just the Flight report I would be sceptical as they certainly made mistakes, but generally they were correct. In this case though they are confirmed by another two independent sources (MoM & Swiss drawings).

Fokker did have experience with many other wings but the D.VII was the first production aircraft with the new sandwich type rib cap-strips.

When dealing with Fokker drawings (particularly the E.V fuselage drawing) I have found mistakes. They were not always correct either.

Anyway I hope I have helped.

Langdon

[AchimEngels]

Sure! Any critisism is welcome and might lead me to new paths!

The Swiss drawings can hardly be held as a refference for a Fokker built airplane since it certainly shows a different design in many respects.

Since the all around going cap srips are the original design technology and I now have found out that it is not really a big deal to get it done, I will do it that way. In case there turns up any document that really proofes me wrong, I will have to make new ribs the other way.

Both options have their very good resaons and should be considered. Perhaps I should build one wing this way and the other one the other way around. This would leave me with a 50/50 chance of being correct.

Wulffo, if you are still listening, please contact me on that issue!

Wulffo´s airscrew was pre carved on the upper side yesterday. I hope to also pre finish the back to day, so that the profiles can be worked out starting on Friday.

[Langdon]

Hey it was never meant as critisism I was debating the evidence after you after you asked for coments on your other thread.

Sure the Swiss drawings vary from the Fokker wartime production D.VII in some respects but my point is that if you took this information on its own you could easily disregard it as another Swiss change to the Fokker design but when you look and see three independant sources showing the same feature it has to be considered as very strong evidence.

Good luck with however you decide to do it, I will not bother you further with this detail as you have obviously fully considered the information. I respect your work and what you are doing and look forward to your further progress.

Langdon

[AchimEngels]

As I said:

Both options have their very good reasons and should be considered...

Thanks for any input like this.

Please continue to "bother" me, since I really apreciate your opinion. As I said offline I consider your "Critisism" as positive and constructive, not as negative.

Wulffo´s new Axial airscrew comes along very nice!



Enjoy!

Achim

[AchimEngels]

This is Tom.

Tom was a pilot for decates and loves to help me sometimes. In the beginning he was one of my frequent visitors.


Here he is working out the profile sections of Wulffo´airscrew.


Here are some of the profiles with the templates in place.


And here another shot without the templates.

Enjoy!

Achim