Application of printed fabrics.

[Taz]

WF2- First you see what happens and then you figure out what caused it. The photos say it happens, so why did it happen? One of my photos shows a Dr.I with the rib tapes on the port lower wing very clearly darkened and visible, but not on the starboard wing. Why? The difference is the port wing gets the majority of the blow-back from the rotary engine. Why else would the rib tapes be darker unless they were absorbing oil? They were painted the same color as the bottom of the wing after doping, but became darker over time. The rib tapes even got darker on the port middle wing.

Dr.I 558/17 crashed by Fritz Rumey.

Taz
Terry Phillips

Dr.I 558 17 WN 2228 Fritz Rumey Ex von Hippel Jasta 5 Crash May 1918 Forum.jpg

[StephenLawson]

It is understandable that the burned oil / exhaust collected on the painted Dr.I wing surface even around the minute' ridges and edges of the overpainted tapes but the areas or ridges appear to be only effected on their surfaces. With the printed fabrics there was only the dope to protect it. But it should be uniform across the surface. Stains from condensation within the wing envelope will be uneven.

Here is another view of the Canadian held Fok. D.VII(Alb.) 6810/18

[StephenLawson]

WWI Modelers Page/gallery/ Fok. D.VII
The more I look at all of the photos of this machine the more I am thinking that the rib tapes are upper surface colours. Though the struts here seem to be recently painted.

[Flug Werke]

With green, blue, purple, deep blue and yellow/brown they're definitely topside tapes. No doubt about it.

[MicroSculpt]

I have not seen the Knowlton D.VII in person. So, I'm only reacting to the image I'm seeing.

The tapes do seem to be consistently darker on the under surface. Are they as dark on the upper surface?

Could the tapes be applied recently with new printed lozenge material?

Just an errant thought.

Tom

[greatwarpilot]

Two points on 6810/18 in Knowlton.

Stephen - The struts were painted, as best I can tell, in 1963.

Tom - The fabric repairs that were done on the aircraft, also in 1963, are fairly obvious today. I believe it is for the following reason. When this new material was applied, the fabric was 'artificially aged' so that it matched the original fairly well. Over the past 45 years, the original fabric has continued to fade/discolour at a faster rate than the 'new' material. Thus, especially in photographs, the new material stands out like a sore thumb.

I cannot find any locations where the RCAF applied tapes to the aircraft, even when they repaired an area that technically called for the reapplication of rib or edge tapes (upper surface of the inboard port lower wing around the step, or the upper side of the Lower starboard wing tip as examples).

In case visual inspection of the aircraft might help solve this debate, I hope to be in Knowlton some time in the next 2-3 weeks. I was last there in February, but it was a tad cold to spend any length of time with the machine.

An aside, prompted by WF2's comments:

Over the last two weeks, I applied Vintage Aero Fabric lozenge sample pieces to a chunk of replica D.VII wing (LH wing tip bow + two ribs inboard = as much as I could get covered with the samples on hand). I was using ceconite, attached with Super Seam Fabric Cement and then hand brushed the requisite layers of Randolph Nitrate and Burtyrate (clear) dope. Using these modern methods, I tend to agree with WF2 that the tapes are fairly well encapsulated into the dope.

On the other side of that coin, I'm well aware that wartime German practices weren't exactly equivalent to the modern Randoph procedures manual. As I understand it (please correct me if I'm a little off here) original methods relied upon only nitrate based dope, and generally involved the application of far less dope. I seem to recall that the Butyrate layers in today's process are what seal the fabric against aviation fuel. The absence of this layer in wartime German doping practices may well have allowed fuel (and oil?) to permeate the dope, even if tapes were encapsulated within it.

In many respects, I think that we're better off replying on excellent photos like the ones Stephen and Taz have provided - in terms of visually assessing the darkness of lozenge material/tapes - compared to 6810. The airplane is an immaculate reference for many things, but its fabric is getting a little tired at this point. It is truly invaluable for certain things (how it was sewn, laced, tapes applied, etc), but I've compared the colour of its exterior fabric with unfaded/protected original lozenge and the two are worlds apart at this point.

In my article I'm going to explain in detail what the RCAF mechanics did to this aircraft's fabric (and why). Hopefully that information will raise a few eyebrows, and be of use to discussions like this one about the aircraft's current appearance versus the way it looked in 1918 (P.S. - It will include a number of pre-restoration photos, and mid-restoration photos that most people have probably not seen before).

Cheers,

[greatwarpilot]

Originally Posted by Roadhog

I could not pay grad students to have done this level of scholarly work for me. Scott

Scott,

Um... at the moment I happen to be a grad student. I can pretty much guarantee that if I was being paid for this kind of work, it would allow me to dedicate more time to it and afford me greater access to the necessary sources (which, alas, always seem to involve travel).

Cheers,

[Flug Werke]

Greatwarpilot, nitrate dopes were the only game in town until around 1950 when butyrate dopes came on the scene. Any original WW1 fabric will be doped with nitrate not butyrate.

Nitrate dope is soluble in aviation fuel, butyrate is not. No matter how well encapsulated fabric is in nitrate dope, if you regularly expose the surface to oily fuel it will soak in.

How many layers were originally applied is something that is hard to answer if you weren't there at the time methinks. I've seen a number of examples now where respected scholars in the aviation field claim that things always happen in a particular way and yet there is clear evidence to be found on an airframe that it aint so. (and equally that the UK Air Ministry or the German WW1 equivalent issues a directive that everything is to be done in a particular manner and yet the evidence to be found on the airframes proves that this was not adhered to)

[greatwarpilot]

Flug Werke,

Thanks for confirming my somewhat hesitant comments about the relatively solubility of nitrate vs butyrate in aviation fuel.

I'm certainly in agreement that be it Brit or German, there are almost always examples (and reasons) to illustrate that things were not always done one way or another.

Cheers,

[Dan_San_Abbott]

Gentlemen:
1. Steve, you could not have picked a worst example. It has be very poorly treated. in their efforts to repair this machine, they could not have been done it, more poorly, if they were amateurs.
2. Tell me which lozenge is blue, forget about the rest, they are all screwed up from whatever "they" doped, varnished, shellacked or whatever. All the colors are altered. There should be light blue, pale green, ochre, pink and reddish violet. (This is a simple description of the colors.)
3. Further more, the fabric is stained as are the tapes from water, it could include a case of mildew under the ribtapes.
4. The colors in the rib tapes match the fabric colors.
5. The leading edge fabric seams are covered with tape.
Blue skies,
Dan-San