WWI propeller resources
 

Looks like we need a thread to put all the other odds and ends threads, photos, and webpages about modeling WWI propellers. It would be nice to have them all in one place.

Here are a few of the RCU threads on the topic:

http://www.rcuniverse.com/forum/m_66..._2/key_/tm.htm
http://www.rcuniverse.com/forum/m_23...tm.htm#2310030
http://www.rcuniverse.com/forum/m_35...tm.htm#3542372

And here are a couple of reference sites:

http://www.aeroclocks.com/Prop_pages/2060.htm
http://www.woodenpropeller.com/

And the Fokker Team Schorndorf's wooden propeller replica:

http://www.collectors-edition.de/Sal...ex_english.htm

RE: WWI propeller resources
 

Clark industries quite a range from 10" to 12 feet!

http://www.clarkindustries.on.ca/

RE: WWI propeller resources
 

Well, I wasn't a complete slacker during the holidays. Since I was away from my workshop and my Snipe I spent some time thinking about the "next" project which will be a prototype of the CDScaleDesign 1:6 scale Albatros CI. I looked over the plans as they stand at the moment and figured that I might as well start at the very front -- so I started working on a scale static propeller.

First, I put on my researcher cap and started pouring over the photos in the datafile. One thing became immediately clear: There were several different propellers used on the Albatros CI during it's lengthy service life. The most common was a flat-bladed prop with rounded tips. The other had a curved leading edge and a straight (offset) trailing edge. I'll probably end up doing both just for the fun of it.

But the prop that really caught my eye in the datafile was a wonderful laminated prop with great curving striations. Actually almost all WWI props were laminated but not always with different woods. Thanks to some very knowledgeable assistence from Bob Gardner (who's in the process of writing an e-book on WWI German propellers) over on the Wooden Propeller Forum, we were well on the way of identifying the laminated prop in the photo.

In order to carve a static prop I needed three things: 1) an accurate front view 2) and accurate profile and 3) a diameter. I first tried to just calculate the diameter from measurements off the 1/48 scale drawings in the datafile. But what I really wanted was a documented number. As I was looking again through the datafile I noticed a WWI era original 3-view drawing with German notations. This had various dimensions but not an obvious one for the propeller diameter. But then I noticed a table of informtion at the bottom of the drawings. This was all in German and it turns out this information is not given anywhere else in the datafile. And there in very teeny neat WWI German handwriiting was the information on the diameters of the propeller (2850cm) and the blade width and the pitch and the RPM details (n=1400). And it also stated "Reschke Holz" so back I went to the Wood Propeller Forum.

Reschke turns out to be the manufacturer of the flat-bladed variety and Bob (from the UK) provided a close-up of the manufacturer's decal and a great photo of the full Reschke prop. But I was still missing the side view. And we hadn't yet identified the laminated prop.

The key to identifying WWI props is usually the decals and the shape. At least four different German propeller manufacturers used the Patee Cross decal usually in addition to a comany logo. Bob was able to identify the itty-bitty second decal in the datafile image as belonging to the company Integral. But I still didn't have either the front or side view. Then I looked through the the Albatros BII datafile and, lo and behold, there on the drawings were front and side views of FOUR different German props: Reschke, Schwarz, Germania, and Garuda. The outline of the Germania prop looked pretty much like the laminated prop I was interested in. So I scanned that, rotated and resized it, and overlayed in on the photo and BINGO: A perfect match!

So now I had what I needed.

**Note: Be careful using photos of propellers for outlines as the photos were almost certainly taking at a slight angle. The result is that the two blades might not be exactly equal even if it looks right. The best approach is to used just half of the photo and then copy and flip the image to make a perfectly symmetrical image. This is what I've done on the image of the Reschke prop.

RE: WWI propeller resources
 

So on to modeling the prop. The first step was to create the laminations. There appear to be 5 laminations (dark-light-dark-light-dark) so for a scale thickness I needed 5 sheets of 3/16 hardwood. I went with three sheets of mahogany and two of basswood because that's what was available in the hobby shop (in Southern Cal). After appliying liberal amounts of Titebond I clamps them together and let them dry overnight.

But then it was time to fly back to the Japan so the laminationed wood was stuffed into my suitcase. Once back in the Japan, I printed out the final propeller outlines (actually I had to split the image in two to fit on my A4 paper), I sprayed the wood with 3M spray glue and stuck on the drawing.

The first step was to cut out the outline with the Ryobi 9" band saw that I picked up with "Christmas money." Yes, I hauled it all the way back to Japan with me! :D Man, is that one sweet little power tool for $99! It cut through the laminations like a hot knife through foam. Doing this with my scroll saw would have been a tough job.

Next I used my cheapy Harbor Freight 1" belt sander to sand the rough cut piece to the outlines.

Then, I flipped the piece on it's side, and drew on the profile using the drawing as a template.

Then I used the bandsaw to do a rough cut to that profile (which is conveniently flat on the back).

Next, I used a sanding bar to fine-tune the profile which reveals bands of the different colored wood.

After that, I marked out the curves for the laminations as per the photo and added marks to guide my cutting.

Then it's whittling time! First I carved down the back side of the blade. This face is mostly flat.

Next, I used the sanding bar to shape the front of the blades, The wood was actually quite easy to same. I knew I had the right curves when the laminations started to look like the photo. There's still a lot of fine-tuning to be done as well as finishing and making a hub but I've enjoyed all the research and carving and it was a fun little Xmas project.

RE: WWI propeller resources
 

BTW, if I had gotten the profile wrong, the bands of the laminations would have worked out all wrong. Actually based on some eye-ball photometry I had worked out what "must be" the profile in order for the laminations to appear the way they do in the photo. It was really satisfying to find that the profile from the datafile matched my "imagined" profile almost exactly.

RE: WWI propeller resources
 

So am I the only person here interested in carving props?

RE: WWI propeller resources
 

No way! This is an amazing thread. Please keep it up.

RE: WWI propeller resources
 

It was a surprise to me how the geometry of the propeller blades produced completely different patterns in the laminations on the front vs. the reverse. The pattern on the back of the blade reflects that fact that this side is essentially flat with an essentially equal angle through all the laminations. The pattern on the front reveals how the blade has an airfoil curved surface which is much flatter towards the tips and very steep (and thick) towards the hub.

This prop would have been designed to spin at about 1400 rpm. It's quite thick compared to the props we use on our RC models -- something on the order of a 18 inch prop with a pitch of 15-16.

I'll add also that carving the prop is not at all hard. Once you get your head around the ways things curve (e.g. which is the leading edge and which the trailing edge) the actual carving follows very natural lines. Whittling and sanding the wood seemed like the most natural and intuitive thing in the world. Actually the different colored laminations actually help in this regard since the pattern revealed during sanding can serve as a guide. The lines should curve smoothly. I didn't really have any idea what the reverse would look like but I noticed that once I had sanded the surface flat I got more or less equal bands.

Rough sanding was easily accomplished with an aluminum sanding bar -- followed by some 80 grit sandpaper wrapped around a 1" dowel section. I was also surprised by how easily the "hardwood" sands. The 80 grit paper cut right through it. In fact, I didn't use anything but sanding to shape the front of the blades. Besides, it was also fun to see sawdust in another color besides "balsa!" :D

RE: WWI propeller resources
 

Chris, can you provide a translation for the German term "Bremleisting?" The table lists the "Bremleistung" of the 170PS Argus as Pi = 180 PS. For the non-German speakers among us "PS" is the appreviation for "Pferdestaerke" (horsepower).

RE: WWI propeller resources
 

Could it be Bremsleistung?

RE: WWI propeller resources
 

Oops. Apparently "Bremleistung" is something completely different from "Bremsleistung." Both get quite a number of Google hits. I've found a translation of "Bremsleistung" as "engine braking" but that means nothing to my non-engineering brain:

http://www-aix.gsi.de/~wolle/TELEKOL.../abb5_f10.html

RE: WWI propeller resources
 

I think the Bremleistung(en for plural) you found with Google are all typos, mostly the texts refer to brake discs, brakes in German is Bremse. Obviously it should be Bremsleistung, which roughly means power reduction (loss) through mechanical parts and/or friction etc.

RE: WWI propeller resources
 

Hmm...I think you're right. That's 139 hits for "Bremleistung" and 123,000 for Bremsleistung. It would sure help us language learners if you Germans could learn how to spell korektly. :D

OK, so what would Bremsleistung mean in terms of an aircraft engine? And why would it be a relevant specification? This box of the table provides the information Pi=180PS and n=1400 umdr/min ("umdrehungen"/rotations per minute).

RE: WWI propeller resources
 

An engine would be much more powerful if it wouldn't lose energy through mechanical motion and friction etc. I'm assuming it 'pays' 180ps when it produces 170. Does this mean it would have 350 if it didn't pay that price? Makes sence to me, but this is not my fortè, I'm a construction engineer [8D]

RE: WWI propeller resources
 

Well, I guess I can take solice in the fact that even a native speaker might be unsure about this word. Back on topic, here's the pattern I've made for the hub(s). I can already imagine that this is going to be quite a nightmare even with a drill press. Maybe I should just make them out of ply and then paint (or cover with aluminum tape).

RE: WWI propeller resources
 

I love watching all the things you make keep it up!

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clearly, I have too much time on my hands. [sm=52_52.gif]

RE: WWI propeller resources
 

Hey Don, your prop looks great! Your hub will be fine just make sure the bit doesn't "walk". I use a punch to mark the center of the hole which keeps the bit from walking. I don't know why I am telling you this because you probably know. Oh well, just my two cents worth. Good luck with this project.

RE: WWI propeller resources
 

Actually what I should probably do is drill all the holes first (using the drawing as a guide glued to the metal/ply) before going to the effort to cut it out. Even with the center punch I've still had problems with holes being micro-millimeters out of position which in such a tight pattern can cause problems. I had this problem with the hub on the prop I made for my Snipe. I ended out "evening out" some of the holes with a rat-tail file.

Actually, come to think of it, the pattern I posted isn't even the hub for the Mercedes 180 -- it the pattern I used on the Snipe prop! [:@] That hub has 17 hole to drill but the image I have of the hub on for the Mercedes has two circles of lightening holes for a total of 25 holes!

RE: WWI propeller resources
 

Don, beautiful work!

FA[8D]

RE: WWI propeller resources
 

An interesting question is this: WHY would the original designers have added such elaborate "lightening" holes at all? I mean, why bother to lighten this prop retention plate at all? What why would saving some pound or two of weight UP FRONT matter? Certainly these hub plates would have been difficult to manufacture and would have to be properly balanced. So why bother? In the world of RC WWI modeling, we almost always need MORE weight up front. We can even by "heavy hubs" for planes like the Cub or the Corsair.

Why would WWI engine designer's have wanted to save weight? Perhaps it had to do with minimizing the "total propeller weight" -- but given that this metal flange is closely centered on the drive shaft it's impact would seem to be minimal. Folks back then WERE however concerned with engine weight. In fact, airplanes look the way they do precisely because engines were "too darn heavy" so designed had to extend these weird appendages "out the back" to balance the dang thing. I remember reading about Anthony Fokker solving a CG problem on one of his prototypes by having his technicians weld a couple more inches of length into the tail tubing.

So were the "lightening holes" in the prop retention plate (what I've been calling the "hub") actually about "saving weight up front" so not to need to add additional weight on the tail? This sounds crazy from an RC perspective but then we have these darn "underweight and overpowered" model engines to work with.

Anyway, it's an interesting question to ponder as I drill the 25 holes in the Mercedes 180 "hub." [sm=50_50.gif]

RE: WWI propeller resources
 

BTW, I never intended this thread to be "mine" but rather started it as a resource for any and all interested in modeling WWI propellers. I realize that it's a bit of a niche area since this primarily applied to static display props. Still it's possible to apply much of what we learn here to a carefully made flying prop as well. For example, this one that I did for my Snipe.

So, anyway, please feel free to join in on the fun (or the madness)! [sm=bananahead.gif]

RE: WWI propeller resources
 

Hi Don,

What do you think of these propellers?

http://foto.modelbouwforum.nl/albums...P1010002~0.JPG

These are 30x12 hand carved flying propellers! The right one tend to be used on a 1/3 scale Mick Reeves Camel with ZG62 and Reeves reduction gear, and the left one on a 1/3 scale Fokker D-VII with the same gear.

The planes and prop's are from Ralf Strutter, he ordered the prop's by a guy here in Holland who made them on demand. More info [link=http://www.modelbouwforum.nl/forums/showthread.php?t=47870&page=11]HERE[/link] and [link=http://www.modelbouwforum.nl/forums/showthread.php?t=36144&page=15]HERE[/link] on the dutch forum.

Teus

RE: WWI propeller resources
 

Don,
beautiful work with that prop! amazing,
I have to admit that I just order my props here:

[link=http://www.modellbau-schlundt.de/]oldtimer props[/link]

Is a bit easier,:)

Frank

RE: WWI propeller resources
 

SWEEEEET!!! [8D] If I ever decide to build that big I'll definitely look into the gear drive!

BTW, you just gotta love a model big enough to paint the markings with a paint roller! :D