destrat

Abufletcher:

Thought I would jump in on this discussion about TE drop. I wouldn't worry to much about getting that part right, and as for building wash-out into the aileron TE it is very easy! I built Dave Hurrel's Alb C-III which has plenty of wash-out. What I did was to use a dowel for the aileron LE, then cut the ribs to fit the dowel. Next you laminate up a TE figuring how high off the building board the TE is at each rib location, because the ribs are cut to fit the dowel, they just end up rotating right around falling into place. The Albi has been flying for ten years, very nice flyer.

We are all on this Pfalz craze, me included. I lost mt 1/4 scale D-IIIa last summer, and right now I'm doing a D-XII in 1/4 scale, have the tail feathers, landing gear, and top wing all framed up. Working from enlarged Dennis Bryant prints, will use the Torrence fabric again.

I'll try to upload some pic's.

jtisch

After looking around some more, I found two in-flight shots of the D-series. Both still have the droop effect even while in flight.

FokkerAce

Any chance you could post them here??? or point us to the refernce you've found?

thanx, FA[8D]

jtisch

Unfortunately, I don't have a scanner so I can't post them. There is one small photo in the Flying Scale Models issue on the Halberstadt, though. The other photo is from a collection of 3-views and magazine articles cut out and put into a file by someone(modeler, perhaps?) that I found at a used bookstore. Unfortunately I don't know which book or magazine the other photo was cut out from.

zoomzoooie

Hi, I'm back after a 2 week holiday and just caught up with the thread again.

I don't think any design or part of an aircraft would have been accidental, experimental, yes.
Jtisch has said it - "Now on the D-series, the wing still has noticeable washout towards the tip but from the third rib going inboard the trailing edge rises up to (almost) meet the lower fuselage longeron. So the "droop" is the washout towards the tip combined with again the inboard three rib area rising up again to meet the fuselage." If you study photos carefully you can see those characteristics on many of the early planes and are somewhat similar.

Both wings would have washout in the same direction, most likely around 1° positive or possibly 0° at the wingtips. The washout is to reduce wing tip stalls and adds stability.

For me, a "scale" model should be as scale as possible, including the trailing egdes and washout and of course scale airfoils, specially the Halb D. After all those are what makes the Halb a Halb. Nothing takes away from a scale model than flat bottom airfoils and other detours from scale.

I wanted to post a couple of pics of wings I did, but I'll have to try later. I don't see the attachment option.
ZZ

abufletcher

I'm not sure I'd want to go quite this far -- particularly with WWI era aircraft. Of course we can also say that some parts of aircraft are consciously designed to be the way they are, while other aspects are the consequence of those other decisions. An example of this is the scalloped TE of the Fokker aircraft. There's no design advantage to the scallop. The design decision was to use a wire TE. The scallops are a more or less accidental (or maybe "incidental") outcome of the tension and thickness of the wire and the shrinkage of the fabric.

It's only in this sense that I think the droop could be "accidental." So maybe it's just a matter of wording. If the droop exists because the wing had washout on the tip and "rose to meet the fuse" inboard, I'd say that makes the "droop" incidental (rather than designed in). On the other hand if the droop is there to increase the lift of the wing (by providing more curvature) then we can say it's designed in.

In other words I think I maybe agree with everybody.

zoomzoooie

They did some pretty wonderous engineering in the eighteen and early nineteenth century, not just aircaft. Everthing would have had to be taken into account. Ok almost everything... Someone forgot about something somewhere, hehe), I think they would have known about the results. Cause and effect

The effective appearence of the droop makes you believe there is more incidence than there really is. Too much and the thing wouldn't fly. The Halb is a hard one to study, but I've been at it off and on for 2 years, designing accurate plans as I can, redrawing countless times. My first wing ribs seemed ok at the time, but I have to redraw them since further study of the photos. Lack of techincal info makes it hard to make it accurate, but most aircraft had around 2° to 3° with some at 5°. I am going with 3° bottom and 3° top at the peek incidence ribs. This seems to look like the photos. Almost all of the ribs are different. The top wing rib from the center to the first strut bay are the same at 3°. The first aileron rib is also 3°. Since the ailerons are extened, the appearance of the slight increase in incidence of the remaining ribs is magnified. (Cause and effect ). The tip bow is 0° with the washout and this seems to look like the photos. The bottom wing root rib will be 2° and the strut bay ribs at 3°. I have to still work out the rest of the ribs to the tip on the bottom wing, but the tip will either be 1° or 0° with washout.

One note on the other planes that have the bottom root rib at the fuselage and the rest of the ribs drop below that rib is that the rear wing spar has a curve in it near the fuselage. I haven't found any evidence of this in the Halb D series photos.

Once I get some time I will post some progress pics of the my Halb with the first set of wings, which I have to be redo once I redraw the wing ribs yet again! [&:]

ZZ

abufletcher

This is getting to be quite a discussion. But, hey, I'm a prof, I love a good discussion. I'm not questioning the engineering skills of WWI designers. Aeronautical design had come a long ways since the "trail and error" craft of the last 1800's. What I was saying is the even in theory, and even today, engineers don't get to have everything the way they'd want it. Engineers make certain design decision that they think are the most important. But those decisions will have concequences. They just have to accept those consequences. So any particular aircraft looks the way it does partly because of conscious decisions by the designers and partially because of the compromises they have had to accept.

jtisch

I think the average person(here everyone is above average )underestimates the engineering that went into the AC of this era, thinking of them as being slapped together with nails and bailing wire. Considering the materials,as well as powerplants, available at the time I feel they are quite impressive. However, engineers do make mistakes or bad decisions or even poor compromises on occasion(Ever take a close look at a picture of a DC-10 in flight?).

zoomzoooie

There are also the problems associated with designs relating back to the man with the money, telling them to stay under budget, causing design shortcuts and lesser material quality.

At least we get to see the changes or corrections in the next series of the design and can compare the changes and wonder why they did or didn't do something.

I haven't been in a DC10...now I don't think I want to LOL.

Henner Trabandt

May I add something to the discussion about the "droopy"TE ? It semms to be seen only on Halberstadt-fighters D and C series. I found a book about the Halberstadt Cl IV and there are some interesting pictures. As the book isn`t available any more, I try to show tem here. In the pic 2, 3 and 4 you can see the team of the "Museum für Verkehr und Technik" (museum of traffic and technics) im Berlin, Germany building up a wing. I hope it can bee seen, that the rear spar is curved to meet the fuselage, the front spar is straight. In one pic it can be seen, that they are glueing the nose-ribs to the front spar. So the "droop" of the TE and a straight LE can go together. Pic 5 shows, that the droop did not disappear in the air.
(oh, I think my English is poor, I can read it, but writing is difficult. Hope, you understand me.)

abufletcher

Henner, very interesting photos. As you say, the rear spar does indeed appear to be curved. And this makes much more sense to me as a construction method than alterning the shape of each rib to create a droop. On the other hand getting the curve of the spar just right would have been a major hassle.

PS. Your English is mighty impressive to be able to talk about such technical things! I have a copy of German-language review of the Pfalz DIII (from Flugsport) and that's might tough going -- even though I'm just reading!

FokkerAce

I concur, and the third photo shows it even better!

FA

jtisch

I found a photo of a DV in flight on my hard drive.Not the best angle for checking out the trailing edges compared to the other two,though.

TFF

The Smithsonian has a CL.IV at the Udvar-Hazy. After seeing the droop, I see it as more of an attempt at a fillet fairing.
http://www.nasm.si.edu/research/aero...alberstadt.htm
I believe the plane in the book being restored is this plane.
Got to see it this summer.

jtisch

I kind of like the Turkish color scheme. I have four or five other planes to finish before I tackle the Halbie, though.

abufletcher

A bit more thought on the "droop." I'm now pretty much convinced of the correctness of the proposal that it's not that there was a "droop" but rather than both the tip and the wing root "rose up." The outer wing displays washout and the inboard TE rose up to meet the fuse. The droop then is just a stretch of "normal" TE in between.

Anyway, here's a rear photo of an Albatros CI and you can see the washout on the lower wing towards the tip. If there had been a similar rise inboard we would have seen the "Halberstadt droop."