Angle of Incidence marking on Fok DVII

[Jeff Brooks]

Hi all,

I am interested in learning more about the angle of incidence marking that are painted on the bottom of the wings of the Fokker DVII (near the trailing edge.) Are there any folks out there versed on these markings?

As I have been studying the wings to make the spars, and I find that some plans have the spars constructed to keep the angle of incidence at 0 deg along the wing, while others allow the tip of the wing to rise up.

The angle of incidence markings on the bottom wing seem to indicate that the bottom wing spars allowed the leading edge of the airfoil to twist upward as it moves outward to the wingtip. While the markings on the top wing seem to indicate the angle of incidence stays at 0 deg on the whole wing.

Are these markings all the same from one DVII to another, or were they aircraft specific like the weight tables on the port side?

Were the wings constructed differently from factory to factory, or possibly a change during a production run?

I am hoping, that as I become more familiar with the angle of incidence markings, I might gain some insight as to how the spars were constructed.

Jeff

[Dan_San_Abbott]

Jeff:
I have that data, I'll look it up and get back to you.
Blue skies,
Dan-San

[Jeff Brooks]

Dan-San, I was hoping you would see this, thanks

[Dan_San_Abbott]

Hi Jeff:
Here is the data on incidence markings for the Fok.D.VII wings.
Upper wing, lower surface, in board of rib tapes, of ribs r an l, 4, 6, 8, and 10 in from the trailing edge and at the aileron spar on rib 10, about 30 mm, in white numeral 30mm high in white 0 with the degree symbol.
Lower wing, upper surface, inboard of rib tapes, of ribs r and l: 2, 1.0; 4, 1.1;
7, 1.3; 10, 1.5; in white. the numeral 1 is 30mm high, the decimal number is 15mm high.
Blue skies,
Dan-San

[Jeff Brooks]

Thanks Dan-san,

Were these angles of incidence always the same number from one DVII to another? Are you aware of any DVII's where the markings showed a different number on the angle of incidence marking?

It seems to me, that the method of construction for the wing spars are advertised right there on the wing.

To be consistent with the angle of incidence markings, both spars on the bottom wing would have straight edges on the top, inboard sides in order to cause the angle to change.
While on the top wing, the front spar would have to have a droop in it to get the angle of incidence to stay at a constant 0 degrees.

[Dan_San_Abbott]

Hi Jeff:
Those number are consistant for all Fokker D.VII aircraft. the Fokker Spar drawings I would assume were the derterminant. Albatros and OAW received a sample aircraft, complete set of drawigs and jig drawings. That is whycomponents can be mixed. The Albatros built Fok.D.VII that was at Chalais Meudon 1972 had components from Fokker and OAW and all fit.
Blue skies,
Dan-San

[Jeff Brooks]

Thanks Dan San!
Very Helpful!!

[Dan_San_Abbott]

Jeff:
I logged into Achim's site last night on the Aeroforum and was reading the posts on the wing incidence. I do not believe the incidence was measured on the mean chord line, but on the lower surface of the wing. For example the the bottom surface of the upper wing is parallel to the aircraft center-line which is zero incidence. The lower wing I feel quite sure is measured the same way, on the bottom surface, but with 1 degree positive at the root and 1.5 degrees positive at the interplane strut.
From my studies, no one at that time, measured incidence through the mean chord line.
Blue skies,
Dan-San

[Jeff Brooks]

Dan-San,
As I have been preparing to build my wings, I have many different sets of plans that I review. Sometimes I think this causes most of the problems, as you can have too many choces!

Anyway, I have drawn up a bunch of diagrams that illistrate what I am trying to figure out.

[Jeff Brooks]

The 5mm described would be different for the top wing.

Now If I follow the angle of incidence markings, I would tend to think the top wing had a slight droop in the front spar to keep the angle of incidence (along the bottom edge of the airfoil) at 0 degrees.
While the bottom wing would have a straight edge on both spars, causing teh twist upward consistant with the markings.