I get to buy a new Prop

shep · Post by **shep** » Wed Mar 11, 2009 22:31

Just had my prop looked at the Prop Shop in Troutdale, OR and it had been filed down beyond limts. I am rebuilding an 11cc Chief that will have a C-85-12F with the O-200 crank STC.

My understanding is that the O-200 crank gives a little bit better low end torque. My manual indicates: 72">prop diameter>70" and a normal pitch of 44. It seems that McCauley Props are more popular (I want to stay Metal). I also have heard that longer props are more efficient (Keep your prop as long as you can as long as you can - double entendre at is best) Any suggestions for the pitch for a CM71xx or CM72xx? Anyone using a stroked C-85?

Paul Agaliotis · Post by **Paul Agaliotis** » Thu Mar 12, 2009 08:05

shep,
I have a 70/38 on one airplane with a stock C85 and could use a couple more inches of pitch or an inch in length. I would like to try a 71/40. These little engines need to be up at the top of the RPM range to make the rated power. Any prop that can achieve this will work. I was told that when you get rated RPM with the highest manifold pressure this is the correct prop. I have never had enough props available to test this theory.
Is your old propeller cracked or just too narrow? I could be interested in it for a project I have.
Paul

shep · Post by **shep** » Thu Mar 12, 2009 10:58

I was told by the previous owner that the prop did not run "smooth" but never tested it. He was flying the plane with a wooden prop. I hauled the purchase back in a U-Haul and immediately began to take it apart. The blade thickness on the last station toward the tips is too thin. The prop arc and balance were not checked. We were going to show the prop at the next EAA meeting as the measurement marks are still on it but after that I do not have any big plans for the prop.

Paul Agaliotis · Post by **Paul Agaliotis** » Thu Mar 12, 2009 12:30

Shep,
I would be interested in the propeller. I have a 1930's small bi-plane called a Westfall Sport. I am going to power it with an A65 crankcase with O200 crank and cylinders. This prop could be a good starting point. If you need a wall hanger I have one.
Paul

Dennis · Post by **Dennis** » Thu Mar 12, 2009 13:11

Shep,

A friend recently bought a prop shops inventory of "out of limits" blades. He has a device which uses lasers to mark the stations and measure the width and thickness. Bottom line, he found a number of blades that were still in limits. They had been incorrectly measured. The "old" method is to measure the stations from a reference point. That reference point is different for different props. How good is the technician at identifying and getting right on the reference point and how good is he at measuring and marking the stations. Once the stations are marked, how good is the technician at using a vernier caliper to measure the width and thickness at each station. Did he zero it before starting?

I guess what I am saying is that there are several oportunities for error and you might want to get a second opinion before scrapping a prop.

Dennis

shep · Post by **shep** » Thu Mar 12, 2009 15:01

Dennis;

The shop wrote the service limits and actual blade thickness on all the stations on the prop.
Only the outer stations are out of limits and you can tell it has been filed down by running your fingers along the blade.

Paul;

I considered making a wall hanger out of it but think the effort would be better spent on a retired wooden prop. What'ch got?

Paul Agaliotis · Post by **Paul Agaliotis** » Thu Mar 12, 2009 15:46

I think there is a Lewis prop around. There is a Fahlin that has a broken tip. And some others Flotorp with a gazillion laminates plus some old aluminum stuff. If you have anything in mind I should be able to supply something that would suit your fancy.
Paul

Nathan K. Hammond · Post by **Nathan K. Hammond** » Fri Mar 13, 2009 01:07

I'm running a CM7146 and really like it. A 7144 would be nice if operating at higher DA/elevations or out of short strips. What's your typical mission/conditions?

The nice advantage of a new prop is a better blade profile. There was 3/8" difference in cord between my old CM7445 and the new CM7146; And I think it made a BIG difference.

I'm not sure McCauley makes a 72 inch prop; they might have to cut down a 76 inch. Be sure to price both a 71" and 72", there may be a serious price difference. And re-pitching was included when I got mine.

nkh

shep · Post by **shep** » Sat Mar 14, 2009 19:37

Paul:

You're welcome to the prop although it makes me nervous that it is not certified. The forum needs you around! Why don't I send it to you and you decide if it is useable for your purpose.

If you're ok with the prop after you have inspected it you could send me an old wood prop.
I found a picture of a lewis prop on the web - it looked to made out of a dark wood ?walnut?

Paul Agaliotis · Post by **Paul Agaliotis** » Mon Mar 16, 2009 08:04

Shep,
That's fine. I 'll find a nice one for your wall.
I don't know if the Lewis is walnut. It is a little darker. If I can locate the blade decals I'll refinish it so it makes a nice display. I'll let you know what I find.
Don't worry about the non-certified status of your prop. I'm not prone to doing foolish things. Before I would think of using it a complete check will be required. I like to make my flights a round trip with no surprises or Adrenalin.
Paul Agaliotis
2060 E. San Martin
San Martin, CA 95046

gusc · Post by **gusc** » Mon Mar 16, 2009 23:55

I have one of those old Lewis dark colored props too. It came on the A75 on my first Champ in '76 but wouldn't turn anywhere near the proper static requirements so I bought a new Sensenich.

I think Sensenich will OH these props but not sure. I think they contract the wood prop out anyway.

I know the plant moved to FL in about '97 because they OH my Stinson prop then. They do beautiful work.

shep · Post by **shep** » Thu Mar 26, 2009 13:38

Paul;

Finally am going to get some time to ship the prop. Any suggestions on how to package?
I was thinking about either wrapping it in bubble wrap or putting lag bolts with plastic tubing thru the hub holes into a 2x6. I can finish the lewis prop although I would some appreciate guidance

Scott Heppler

jc pacquin · Post by **jc pacquin** » Thu Mar 26, 2009 13:41

I do it this way: Plumbing store, buy length of PVC pipe a little longer than prop, caps for both ends. Bubble wrap prop put inside, screw caps on, ship.jp

Paul Agaliotis · Post by **Paul Agaliotis** » Thu Mar 26, 2009 14:28

Scott,
Either methods will work but you need to control the prop from sliding against the ends of the container. It will beat the tips up real bad.
Paul

shep · Post by **shep** » Sun Mar 29, 2009 14:16

Paul:

I just finished building a crate around the prop and will ship tomorrow via FedEx Ground unless you prefer a different shipper.

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I get to buy a new Prop

I get to buy a new Prop

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