I am realizing my desire finally to build scale WWI aircraft. What I have noticed is the complete lack of scale propellers. People build gorgeous models and are left to sticking a prop with Topflite or Powerpoint or whatever on the blade. I realize there are many diff types of props that were used in the "Great War" but sometihng that had a laminated look and some curvature would be great when you look at what's being used now. I'm sure these shapes could be made more efficient utilizing modern aerodynamics. Maybe it's me but it seems like there is a hole here that could be filled.

Are there scale working (not static) props available for early aircraft?

Clarks in Canada has several types of early scale props. Not sure of their website but i'm sure they have one.

Gotta love the internet... thanks.. i took a look but no pics .. http://www.clarkindustries.on.ca

Here's just what you need:

http://www.rcuniverse.com/forum/m_67...tm.htm#6738262


But you need to keep in mind that WWI engines only generated around 1,500-2,000 RPM and because of this they used props that were much larger and with much higher pitch than we can use with with our 4-stroke engines (let alone 2-strokes). For example, the Saito 72 in my Snipe can reasonably turn a 14/5 prop. But a scale sized prop for the Snipe would be more like an 18/11.

So really all we can do it make a nice dummy prop for static display and pick a flying prop for its suitability to the engine. The exception to this would be systems that use a belt drive or the RCV SP engines that because of their novel design can spin a larger prop.

There are some nice scale prop kits that you build yourself available here: http://www.manzanolaser.com/id49.html , but they are for electrics only.

Very interesting! The one thing I haven't figured out how to do yet is to create the proper stepped forms to create the basic shape of the prop. I just end up laminating a large slab and then cutting away the extra. But this is not only wasteful of wood but, in terms of wooden propeller technology produces a weaker prop because the grain isn't ideally aligned (lengthwise) in each layer.

WWI era props used between 5 and 8 layers. In most cases slightly different woods were alternated for better strength but only rarely did that result in the strongely striated props we modelers love so. In fact, this seems to have been primarily a feature of German prop manufacturers.

BTW, Von-J's link provides a nice link to an RC-Groups thread on carving scale propellers:

http://www.rcgroups.com/forums/showthread.php?t=541181

You should also realize that there is no such thing as a generic scale propeller. Each WWI propeller was designed with one specific engine in mind. Thus what was scale on one aircraft would not be scale on another. In general, the more curvy and "asymmetrical" prop designs went with early engines with limited horsepower. As engines became more powerful, propeller designs moved more toward the shape of a Zinger prop. For example, the shape of a Zinger looks pretty scale on a Fokker DVII (though it would still be too small for scale diameter and with too little pitch). That same Zinger would look decidedly un-scale on an Fokker EIII.

Looking for static prop/spinner for the GS TF 85" P-51. I know they are out there somewhere, hidden amongst the millions of doo-dads that one has to go on a quest for, but can anyone produce a short cut? Thanks!

Now I'm sure the diagram below contains all the information I'd need to create the stepped (pre-shaped) layers for this propeller but I can't for the life of me figure out how I'd go from these views to the shapes for each later.

Can anyone with better drafting skills (or a sharper mind for geometry) explain how I'd do this?

OK, it's very straight forward, but rather difficult to write down in plain English so...
I just happen to have a full sized propeller from a Sopwith Camel laying on the floor next to my computer so I've grabbed a couple of shots to chew over.

A quick look at your diagram shows at the top, a side view of the prop, similar to the first picture.
You'll notice that the trailing edge is straight. Actually flat and the leading edge curves downwards along the whole length of the prop.

Next on the diagram is a top view, same as the second picture. Again see how the trailing edge is totally straight and flat against the floor.
The third picture, taken from a slight angle hopefully explains more.

What you have at the bottom of your diagram are sections through the props cord at the given points.
ie the small one on the left is the airfoil section at the tip cord an so on. Remembers these are sections through the prop viewed end on.
You'll notice that as you cut the prop the trailing edge remains flat as indicated in the diagram and the pictures.

OK, right. I do believe its easier to understand the diagram than my terrible explanation![&o]

OK, that all sounded very non English, so maybe this helps you?
They're actually rather easy to make (dummy static props) once you get your head around the concept. All the exotic shapes just automatically appear once you start cutting and sanding.
Just make up a 6 layer laminated log. Next draw the out line of the prop (middle pic on you diagram) and band saw out the shape.
Then sand in the top slope from near the hub to the tip, then airfoil sections as indicated in the errrrr.... other drawing.
Yeap, this is sounding useful[]
Possibly the worst tech drawing of my career[&o]

David, thanks for posts, but I was actually looking for a different explanation. I've already tried my hand at carving wooden display props using a method similar to your drawings, i.e. laminate the wood, cut out an outline, cut down the profile, then carve in the curvature. I've posted a few pic of the results below (taken from the thread I linked to at the top of this discussion). I agree, by the way, that it's really quite easy and the shape emerges pretty naturally from the wood once you get your mind around the curves.

But what I was hoping for was a way to deduce the pre-cut layers as seen in the final photo below. As seen in this photo, original prop makers didn't follow the same method I used on my props. Instead they stacked pre-cut layers and then carved off the edges. This technique had two advantages: 1) it was less wasteful of wood and 2) it allowed each layer to have the wood grain running straight across the length for maximum strength.

The question is how to come up with the shape for each of the pre-cut layers. As I said, I'm sure the information for this lies buries in the views and sections somewhere but I can't figure out how to translate it into patterns for each layer.

Great looking prop you have there, by the way! [sm=thumbs_up.gif]

What you need is a go/no go gauge of each station; front and face. If you square the hub first, you can make a jig to hold the prop; cut and compare until each station is close.

I've seen examples of the section templates (one for each station) that prop carvers use to check their progress. But that still doesn't get at how to determine the outline of each flat layer (as seen in the last photo of my post above) of the prop prior to carving.

Short of A LOT of expensive trial and error, I can't figure out how to make a template for each layer.

Abu,
Google "orthographic projection". Crate

You have all the information you need along the bottom... except a decent vertical datum line, say through the hub center.
You have the horizontal reference lines/layers. You've already marked (roughly) each section with a pink pen.
These individual measurements are transposed over the plan view., one layer at a time.
The only reference point you have unfortunatly is the trailing edge... but that is a minor problem
Having said that, I can see that the airfoil section are non to accurate.
It's doable...Yet why? It's simpler the other way.

To finish Davids edited illustration:

(By the way, I notice that section 7 doesn't accurately match the plan view(?)...

Exactly, brilliant. Cheers.
That's layer one, the base layer.
Do the same for the other layers, but remember the airfoils are a bit dodgy to say the least[sm=frown.gif]

Thanks, guys! Looks like a nice little project that I can do while I'll away from my shop.

I'm not seeing this. What's wrong and will it mess up my layer outlines?

As those who've followed my Snipe build know, doing things the simple way is not my forte. Actually, I already have a more than passable display prop for my Snipe but then I found this diagram in the Bentley BRII book and I'm feeling an irresistible urge to make a second one with the proper number of layers and grain orientation. Yes, it's an obsession. But then I did spend close to a week reproducing the graphic for a manufacturer's decal on the German Integral propeller I carved for my Albatros project (using the "simple" method). [sm=bananahead.gif]

You must remember that the method explained above is based on absolute data. In other words, it's only as good the the original projections... and as stated... they look well questionable. Also, these are finished cut down and sanded sizes. You'd have to increase them some what to allow for the final shaping and sanding.
The method used in your old picture appears nothing other than an ascending stacked arrangement of progressively smaller ovals (yeap, like that sounds understandable!).
A method for saving wood obviously. No voodoo science geometry.

Also it looks like the "ol' timers" were using full-width boards on the bottom so they are only shaving down the front face and fully cutting the flatter rear face. BTW, any chance we could get some more details and/or photos of your propeller? What's the diameter? How many layers are there? Are there any markings on the hub?

I'll fix it over the week end.
PM you, I think we've Hijacked this thread enough.
Sorry to the thread starter.

What's the point of having a "scale" flying prop in a non-scale diameter? Once the prop's spinning all those pretty laminations are gone anyway.

At a contest, fly in, or at the local field, its the AAAHHH! factor. Just starting the engine with a home made prop puts you into another league. The ones who know it is too small to be scale also know physics makes it that size, and the ones who don't understand that just think its cool. Your the hero both ways. Having an APC prop on a scale plane is about as pretty as bird poop plopped on the plane.

Too true! But then a stained and "gussied up" Zinger will have pretty much the same effect. Below are a dummy prop (of scale diameter and shape) and a prettied up flying prop I made for my Snipe. However, given that the original Snipe props were painted grey almost down to the hub, I guess an all grey APC prop wouldn't look too bad. Actually, I plan to use the same 13/6 APC prop I used for all my engine break-in on the maiden.