# Prop makers?

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#### lr27

##### Well-Known Member
I couldn't either. If you're going to use one of these, you'd better make sure there is some way to get a lot of air moving over the engine. The usual test clubs have short, wide, steeply pitched blades to do this.

##### Well-Known Member
Anyone have a link to the Eiffel club props? I'm getting no where with google.....:ermm:
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.

Shannon.

Edit: I might have the wrong end of the stick here and have the wrong idea of what you are after?

#### pictsidhe

##### Well-Known Member
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.

View attachment Eiffelclub.xls

##### Well-Known Member
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.
Thanks for jogging my memory.. I raise you the version I picked up from somewhere....

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#### lr27

That f!@#$%^& insignificant tower in Paris keeps getting in the way of my web searches on this subject. ;-) #### Tiger Tim ##### Well-Known Member There used to be one of those Aeromatic props with just one wooden blade. That way you wouldn't have to make identical blades! http://www.rexresearch.com/unibladeprop/onebladeprop.htm Those put a weird asymmetric load on your crank shaft that at the very least can wallow out your front main bearing. IIRC the Cub that was flying with an Everel prop a couple years ago was wrecked over that very reason. #### pictsidhe ##### Well-Known Member That f!@#$%^& insignificant tower in Paris keeps getting in the way of my web searches on this subject. ;-)
eiffel propeller -tower

#### blane.c

##### Well-Known Member
HBA Supporter
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.
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There used to be one of those Aeromatic props with just one wooden blade. That way you wouldn't have to make identical blades!
View attachment 74581
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.
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NACA TN-212 discusses designing and making wood props. Go to the NTRS server and search for "Simplified propeller design for low-powered airplanes".

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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.

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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.
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?

#### TFF

##### Well-Known Member
The blade is balanced side to side but it has asymmetrical thrust loading so it needs a teetering hub bearing like the Cub prop mentioned.

#### BBerson

##### Light Plane Philosopher
HBA Supporter
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.

#### pictsidhe

##### Well-Known Member
Aircraft Propeller Design by Fred Weick, the NACA 212 guy. There's also a print on demand available in abebooks.

Hovey's prop book is on a VJ24W owner's website, along with one by Shubert.

The folding single blade props fixes some issues that they have. I wouldn't want to use a fixed single blader myself.

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#### lr27

##### Well-Known Member
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.
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?

#### BBerson

##### Light Plane Philosopher
HBA Supporter
What percentage of performance degradation do you think you could detect?
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. #### Bill-Higdon ##### Well-Known Member Composite single balde props would probably be OK, the Everel prop had a problem of keeping it in balance as the wood adsorbed and lost mosture #### lr27 ##### Well-Known Member 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.
If a motorglider isn't a glider, what do you call a good glider or sailplane that's able to launch itself?

#### BBerson

##### Light Plane Philosopher
HBA Supporter
There are only motorgliders or pure gliders. Pure gliders don't launch themselves.

#### pictsidhe

##### Well-Known Member
Some footlaunchers are glaring at you, BB.

#### lr27

##### Well-Known Member
There are only motorgliders or pure gliders. Pure gliders don't launch themselves.
Snob! I won't let you ride in the S-10! ;-)