Building a Prop

[DanH]

Ya'll are entirely too kind. I appreciate the compliments; thank you very much.

A little perspective; years ago, most homebuilders had to carve a prop so it's nothing new or exotic. Like those guys, I didn't have a choice; there really wasn't anyplace to buy one. And I think you might be surprised how many other builders with similar experiences lurk on this very forum. I recall threads about "other projects" and "other airplanes"; there is some very cool stuff going on out there.

Just for fun, here's a photo of the thing that turns the airscrew:

[Ted Johns]

Dan, cool woodworking project!

For some reason my mind flashed back to a state fair long ago. I chatted with a guy who carved big (6' +) wooden bears. One of his tools was this 4.5" angle grinder attachment that looked like a 4.5" circle of chain saw chain. He said it was very controllable. I've seen 'em for sale, but never needed one. Might be a faster way to rough in the prop, compared to hammer and chisel. However, the chisel doesn't remove as much meat from your hand when you're careless!

It sure is a pretty piece of work. I'd have a tough time with the decision to clear coat vs wrap with glas myself!

Congrats,
T.J.

[DanH]

Postscript.

I just came up from the shop. Tonight's project was to dig out my old pendulum prop balancer and check static balance before I went any further.

Straight from the template table, end-to-end balance was out by 1.3 grams......a single AN4-960 washer laid on the tip.

Unbelievable. I'm a happy camper.

[Brian Vickers]

Dan,
Is the static balancer you are using an item that can be purchased somewhere? Did you make it yourself? I have searched around for such a tool but have not found anything on-line or at ACS, etc. What are prop makers using for basic static balancing?

Nice going on your prop project. I am a wood worker more that a rivet bucker so maple on the nose looks good to me.

[elippse]

Originally Posted by Brian Vickers

Dan,
Is the static balancer you are using an item that can be purchased somewhere? Did you make it yourself? I have searched around for such a tool but have not found anything on-line or at ACS, etc.

Check Contact! magazine for the article that shows how to make an extremely sensitive prop balancer; www.contactmagazine.com

[DanH]

<<Is the static balancer you are using an item that can be purchased somewhere?>>

Well, not this brand:



I love old aviation tools and make a point of giving them a good home. This Flottrop balancer was purchased new by my local FBO in 1957. I've rebuilt it, and I'll pass it on someday.

Operating principle is simple. You mount the prop on cones, centering the balancer, then adjust the acme nuts to raise or lower the CG of the prop as compared to the pivot in the center of the balancer shaft. Sensitivity increases as you raise the prop in relation to the pivot. "Real sensitive" has the prop CG about 1/4" lower than the pivot. Add or subtract weight as necessary so the brass disk on the cable is perfectly centered on the shaft.

Out of balance:



In balance:



Here's the guts of the assembly:



And the whole kit:

[enielsen]

Amazing and it sounds like you're having fun too! Kudos!

[DanH]

Any dynamic balance guys here? I'd love to have a real-world check.

I spent some time carefully checking static balance ths evening. Converting to a term I think is universal in the balancing business, I have unbalances of:

61.5 gram-inches spanwise (ie, 1.5 grams @ 41 inch radius)

92 gram-inches transverse (across the hub, 35 grams @ 2.625" radius)

Are these low values in the balancing world? I see references to maximums of up to 400 gram-inches in dynamic balance literature, but what values do you commonly find when you're out there balancing in the field?

[gmcjetpilot]

I love it, old school, with hand tools Dan? Wow! It's not like you put it in some CNC machine, you did it the way they did it way back when, with a saw and chisel! Neat looking prop and airfoil. Nice radial. The fit and finish is nice.

For any that want to get into it, you could get one of these Prop Duplicators:
http://www.wood-carver.com/gemini.html

The gemini site also has articles and http://www.wood-carver.com/store.html like glue for blanks.

Here is a software program for props
http://user.tninet.se/~trz012v/JCPro...llerDesign.htm

Never got into wood working except in middle school wood shop. I got an "A". I loved it. I like Norm on PBS New Yankee wood working shop. He has a special tool for every operation. If you think building RV's requires special tools, we have nothing on wood workers.

[DanH]

Originally Posted by gmcjetpilot

I love it, old school, with hand tools Dan? Wow! It's not like you put it in some CNC machine, you did it the way they did it way back when, with a saw and chisel! Neat looking prop and airfoil. Nice radial. The fit and finish is nice.

For any that want to get into it, you could get one of these Prop Duplicators:
http://www.wood-carver.com/gemini.html

Well, to be fair, a chisel yes, but a power saw, sanders, etc. And I am gonna build a CNC propeller machine eventually, given the ready availability of prop software that outputs XYZ blade coordinates. After all, this is 2008.

My duplicator is similar to a Pro model Gemini, but with increased arm stiffness....and it can be purchased for less since I'm now done with it.