Fokker Axle Wings - Part 2

[Laserlloyd]

Well, I zoomed in 400% and I think I see Something in at area but the photo starts to pixelze too much. I will Post the image later.

Lloyd...

[RAGIII]

Originally Posted by Taz

Lloyd- Nice photo. Sure looks a lot barer than most photos of the axle wing bottom. Like this one of a brand new Jasta 14 Dr.I showing the jacking pads. Wonder if the pads would pop out on a higher resolution photo? That light blue paint looks awfully fresh with only a few streaks.

Taz
Terry Phillips


Attachment 8786

Taz, Just wondering if you feel the underwing cross background in the photo is consistent with CDL or is it white?
RAGIII

[Tim West]

I think you can just make out a staking pad on the right. The pad...which appears more like a blemishm, is exactly where a pad should be. So I would agree with Terry.

Rag,
I thought the same thing about the crossfield but I wasnt sure , so I took a look at some other bottom wing crossfields and I found a few that look exactly the same as in Lloyds photo......Cdl appears lighter than the blue.....if it is CDL???? I found a few pictures where the crosses appeared to have a white outline just like top wings...these where the old style crosses too. So either someone added the outline after or some fokkers had cdl crossfields inwhich the crosses were outlined at the factory. If the fields were white...we wouldnt see a white outline...but if the crossfields were cdl...to save weight or what ever ..then why outline the crosses over cdl.

hmmm, I guess I am unsure at this point. I would like hear and or see more.

[Jim Bruton]

Might the jacking pads been a field mod?

[Taz]

Rick- I think Dr.I 198/17 had CDL cross fields, like the F.Is and most Dr.Is for which photos exist. It is possible the cross field was blue tinted, but translucent, dope, like the rest of the wing bottoms, as analyzed by Alan Toelle. Note on this image, the apparent transparency and the sharp rib details. The white paint used on fuselage and upper wing crossfields was quite opaque, as was the light blue paint used on the bottom of the aircraft.

Jim- Dr.I 198/17 had just been delivered to Jasta 14 when the photo in question was taken, along with 160/17 and 192/17, for which photos also exist. The aircraft were factory fresh and had no personal or Jasta markings on them when the photos were taken. I believe the jacking pads were factory installed and present on most, if not all, Dr.Is.

Taz
Terry Phillips

Dr.I 198 17 WN 1916 Jasta 14 Ltn Werner Newly Delivered Ur.II CDL Panel.jpg

[gipsymoth236k]

Hello,

Concerning Fokker axle wing designs, I'm applying a bit of data here on Fokker axle wings that might also be of interest in this discussion:

Fokker F.I/Dr.I Triplane (early version, as the later cord dimension was shortened):

Axle Wing Cord - 800mm with axle location @ 260/540mm = 32.5% aft of L.E.

Fokker D.VII:

Axle Wing Cord - 770mm with axle location @ 270/500mm = 35.1% aft of L.E.

Fokker E.V/D.VIII:

Axle Wing Cord - 670mm (100mm shorter than D.VII) with axle location @ 225/445mm = 33.6% aft of L.E.

Therefore, the average Fokker wheel axle location is at about 33.7% of cord.

Interesting...

BTW - Most Dr.I Triplane reproductions are still being built today with an incorrect axle location inside the axle wing as being too far forward, and not even following the original 800mm cord's 260/540mm wheel axle location, thus causing a too far aft trailing edge! This causes ground contact damage to the axle wing's T.E., just like it did with the original and early F.I/Dr.I 800mm cord design. That's why Fokker shortened the Dr.I cord design in later production, to avoid trailing edge ground damage. Photos show this damage, and the various field modifications made of tubular support frames to help support the vulnerable trailing edge of the earlier 800mm cord design. Photos also clearly show the visible difference between the early and late Dr.I axle wing cord dimension designs.

Regards, Gary Sewall

[Taz]

Gary- Very interesting. What was the chord on the later Dr.I axle wings and do you have any idea at approximately what serial number the change occurred?

Any other changes noted in Dr.I production except for the three types of ailerons and the stripe of olive paint on late Dr.I rudder bottoms? Some D.VIIs had double rudder cables, but I have never seen that on a Dr.I.

Taz
Terry Phillips

[Jim Bruton]

Gary,

I have wondered about this too- I have thought the TE of the LG subwing looks too close to the ground for comfort- Just with the natural bumps you could encounter in a real world grass field or what have you. Definitely something to consider and plan for.

Thanks!

Jim

[gipsymoth236k]

Taz,

No Fokker Dr.I Triplanes had double rudder cables, but indeed some Fokker D.VII rudders did have double cables with double control horns.

I am going to hazard an educated guess to say that the later Dr.I axle wing cord was changed from the earlier 800mm design (with axle location @ 260/540mm), to that which shared the later E.V/D.VIII dimension of 670mm (with axle location @ 225/445mm). I can support this by the fact that both the Dr.I and E.V/D.VIII had the same size wheels/tires of 710 x 85mm, as well as the fact that in side profile photos, their visible geometry is identical. Regarding finding the exact Dr.I serial number where this design change took place, we can only go by the existing photographic evidence, but it is usually very easy to see which Dr.Is had the early 800mm vs late 670mm axle wings.

Concerning some of today's Dr.I homebuilts utilizing the earlier 800mm wing axle cord design, it is easy to see the previously discussed error applied by comparing the correct distance between the axle wing/wheel geometry, as in my drawing along with this original Dr.I photo, vs a sample reproduction Dr.I built with the common error of positioning the wheel axle too far forward in the axle wing. It is obvious that this Dr.I reproduction will likely suffer ground contact damage at the axle wing's trailing edge.

Regards, Gary Sewall

[Dan_San_Abbott]

Gary:
Looking at the photograph, the leading edge odge of the axle wing appears to be even with the edge of wheel rim. If that is the case, the rim outer diameter for the 710 x85 tire is 554mm in diameter/2 =277mm. with a chord of 670, (I thought it was 700mm) the axle center-line = 41.3% of chord.
with a 700 chord, the axle is at 39.5% of chord.
At some point in 1918, Idflieg required the ruder cable to be doubles as were the aileron and elevator cables had been. If you examined German aircraft ailerons you will find they they are independant of each other. If one aileron cable is severed on one side it will not affect the opposite side aileron.
In my study I found the rudder cables were duplicated beginning approximately with Fok.D.VII, serial number D.7604/18.
The other major change was adding the firewall with serial number
D.5050/18, at which time, the rear side panel was added.
merry Christmas,
Dan-San