I have an article by Michel Colomban that I translated from french hereAnyone have a link to the Eiffel club props? I'm getting no where with google.....:ermm:
Thanks for jogging my memory.. I raise you the version I picked up from somewhere....I have a spreadsheet that can calculate hp absorbed by a certain Effel prop, or calculate the size eiffel prop to absorb a certain hp.
Uh-oh, another long thread I now have to read...I have an article by Michel Colomban that I translated from french here
The quality is quite low but PM me for a better copy.
Also use "wood club dyno" in your google search and you should get more hits.
Edit: I might have the wrong end of the stick here and have the wrong idea of what you are after?
Those put a weird asymmetric load on your crank shaft that at the very least can wallow out your front main bearing. IIRC the Cub that was flying with an Everel prop a couple years ago was wrecked over that very reason.There used to be one of those Aeromatic props with just one wooden blade. That way you wouldn't have to make identical blades!
One bladed propellers have been touted to be more efficient, But there is more to consider, what is it going to do to your motor mounts and engine bearings?I've carved props for model airplanes. However, this was rubber power, and I have a rubber stripper, so it was easy to adjust the torque to match the prop and the model. I wonder if it's really necessary to have fancy machinery to carve a prop. Seems like a drawknife, plane, etc. should be sufficient if one uses enough care to make the blades close to identical. But, not having done it on a large scale, I could be completely wrong.
I also wonder why there aren't more homemade carbon fiber props. Seems like the material is so strong that they should be fairly easy to get right.
There used to be one of those Aeromatic props with just one wooden blade. That way you wouldn't have to make identical blades!
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I guess they'd be a bit heavier than a regular prop, but maybe not heavier than a variable pitch prop? The mechanism for the single blader could be quite simple, I think.
NACA TN-212 discusses designing and making wood props. Go to the NTRS server and search for "Simplified propeller design for low-powered airplanes".
There's also Simplified propellers for low speed home built aircraft by a Mr. Hovey. I think this one is on the web someplace, or used to be.
I don't know if these are correct about everything, but I know they're out there. I suspect anything by Eugene Larrabee would be correct, but may be too technical.
Seems like if they can make a feathering prop that survives a piston engine, they should be able to make a folder that does, which can probably have the bearings a little further apart. As far as counterweights go, I'm sure they can be made quite safe if the design is right. BTW, I've seen a blade break off a two bladed RC model prop like a bullet. It's a good thing that the guy who was hit on the back was wearing a heavy leather jacket. I guess it wouldn't have gone as FAR as a counterweight, but it probably went faster, at least at first. What percentage of performance degradation do you think you could detect?I saw the counterweight come off a single bladed RC model like a bullet. I wouldn't do it. Folding props have a history of problems on piston engines. I wouldn't do that either. The difference in drag of a feathered Hoffman prop at 50 kts is not detectable by me. The main advantage of the Hoffman prop is the cockpit adjustable mechanical low/high pitch settings which make takeoff possible in a heavy motorglider.
I can feather the prop or unfeather it back and forth in a second with the prop lever. No difference that I can detect.What percentage of performance degradation do you think you could detect?
If a motorglider isn't a glider, what do you call a good glider or sailplane that's able to launch itself?I can feather the prop or unfeather it back and forth in a second with the prop lever. No difference that I can detect.
I can detect the dramatic effect of the dive brake lever and see the vsi go to 2000 fpm. I can't really detect the different glide ratio of say from 25 degraded to 20 without instruments or a clock. With a motorglider who cares? It isn't a glider.
Is the feather prop worth $12k? A very narrow fixed prop could be made with some almost feathered permanent root fairing cuffs if desired, I suppose.