RE: wood props

RE: wood props
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RE: wood props - 4/13/2007 4:00:16 AM

daven

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From: Andover, MN, USA
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My guess, is that you are reading the gauge right. I like to turn it upside down, and slowly move the prop back and forth and even out the distance (gap) between the prop and the bar.

The 7.4 x 8's can vary. I don't have any plastic props with me, just my gauge, so you'll have to get them from someone else. I've seen up to a full pitch number difference between props, between 7.5 - 8.5 at station 7 is not unusual.

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Post #: 126

RE: wood props - 4/13/2007 4:30:54 AM

iamtom

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From: Cincinnati, OH, USA
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Dave,
There have been a lot of props made of beech wood,usually much larger props. I would not run these. Maple is the wood of choice as it is very close ,generally strait grain and has the strength charachteristics we require. From my experience props are made of quarter sawn maple. Logs are cut in many ways. Flat sawn is where a log is just cut in a paralell fashion from one side to the other to make board. Quarter sawn means the log is cut into quarters which run thru the center of the log in both directions. The best board would be the one running straight thru the center with the growth rings going vertically from top to bottom of the wide surface.
This is desirable for the best strength and stability. The front surface of a fine guitar and the sound board of a piano are both made of quarter sawn spruce. For our props we look for this charachtaristic. So when you look at a board or a prop blank the best situation is to find ones where the growth rings of the wood run from the front of the blade to the back. If there is a lot of ,what's called "figuring" it is more likely to be flat cut where the rings are going flatter to the blade or from le to te. A proper propeller will have a very strait clean side and the other will look checkered, were small fleck occur. This is just due to cutting the blade in reverse on the other side. In chosing premade blanks you would prefer to have as littledisturbance in the grain patternas possible, meaning, few waves or sudden changes in direction from the main axis. Obvious exclusions like the one Gary mentioned are big no no's. As I said befor wood is an imperfect medium but will suprize you with its strength. The woodies thend to unload differently than the plastic props once at speed. All props will act different. The only way to be sucessful at this game is to fly each one and not be tied to RPM, pitch or any fixed length. You can have two props made as best you can the same and more likely than not one will be the hero and one the dud. I've had a lot of dud's. Some of them can be fixed with a little caress and some just ain't gonna make the cut. When they work they can really work. Anyway, just my two cents.
Tom

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Post #: 127

RE: wood props - 4/13/2007 1:20:20 PM

Super Splatter

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Joined: 3/21/2006
From: , MN, USA
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I wish I had the patience to spend that much time on a prop, but after watching a wood prop come out of a CNC machine in 5 minutes, I can’t seem to make it worth it in my head.

I burnt out on QM15

The conversation on grain takes a whole new twist if you make one bladed props. I guess a wood prop will always have some sort of compromise in terms of which blade will have the better grain characteristics.

I’ve seen a system that uses a customized hub that will accept two bladed props to form one prop when it is all bolted together. So then you have the grain running the right way on both sides.

Wish I had a CNC,

(in reply to iamtom)

Post #: 128

RE: wood props - 4/13/2007 1:49:41 PM

daven

Posts: 6911
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From: Andover, MN, USA
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I have a couple of those Jesse, and ran them in Apopka last year. Jeryl was playing with them in Phoenix this spring also. I think the potential is there, just needs some tweaking.

I took a good look at the Zinger 8.5" x 7 - 8.5 s' that I bought a week or so ago. These props are nearly identical to Darrol's blanks. I put them on the pitch gauge at several stations and they are near identicle. The hub of Darrols is a little beefier but the shape and pitch are the same. I wonder if this was the basis of his blank??

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Post #: 129

RE: wood props - 4/13/2007 2:28:55 PM

iamtom

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From: Cincinnati, OH, USA
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Super,
I wish I new the secret to getting a prop off a CNC machine in 5 minuites. In my mind thats not possible. I'm in the buisiness. CNC not prop. There is much more to it than just having a CNC machine. Get one then what do you cut??? To design and build the geometry for a propeller is quite a feat. Fred and his Brother Otto are the masters of this.
Dave, you are on the right track with the Zinger 8X7's etc. Grunk has been usine these blanks for a while and made som unusual shapes out of them and done pretty well. Can't remember which race but he turned a 1.01 with it. He did not touch the back side of the blade and all the work was on the plan view and the front only. Again no 2 are alike. Finding blanks and working then is far more possible than starting from scratch. We will also be at the Ft Lauderdale race and along with RR and a couple of refreshments, no tellin what can come up.
Tom

(in reply to daven)

Post #: 130

RE: wood props - 4/13/2007 2:50:51 PM

daven

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From: Andover, MN, USA
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Jesse, the quickest I've seen Dave CNC a prop is about 20-30 minutes (10 - 15 minutes per blade). But many, many hours go into programming the machine and zeroing the machine on the block. I was up to Daves new house a little before Christmas and watched him cut a couple of the single bladed winger wangers. Believe it or not, he starts with the block upright, and the cutting starts at the tip of the blade and spirals down the block to the hub. He has to be very carefull (hence machine slowdown) at the tip because the wood gets quite thin and it vibrates under the pressure of the cutting bit. Pretty amazing to watch, but even after it is cut, the blank needs some finishing.

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Post #: 131

RE: wood props - 4/13/2007 4:55:26 PM

Ed Smith

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From: Brantford, ON, CANADA
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quote:

.....................along with RR and a couple of refreshments, no tellin what can come up.
Tom

After too many refreshments I know exactly what comes up!

Ed S

(in reply to iamtom)

Post #: 132

RE: wood props - 4/13/2007 4:58:31 PM

diggs_74

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From: Emerald, WI, USA
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quote:

ORIGINAL: Ed Smith

quote:

.....................along with RR and a couple of refreshments, no tellin what can come up.
Tom

After too many refreshments I know exactly what comes up!

Ed S

.... All the refreshments!!

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Post #: 133

RE: wood props - 4/13/2007 6:01:30 PM

Super Splatter

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what me and Daven are talking about is Jeryl Smith's dad , Dave Smith, we had a club meeting at his place where he showed off the process a couple years ago.

He had a jig to hold the blank , the CNC would run it's course, he'd flip the prop over and hit the button again, it would run it course and wall-la one nearly perfect prop.

practically nano-seconds compared to my struggles, black props for this cowboy

(in reply to Ed Smith)

Post #: 134

RE: wood props - 4/15/2007 2:55:57 AM

Super Splatter

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From: , MN, USA
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Wow man, it's not winter today. I got a chance to shake off the rust. Got a to fly my Miss Foxy Lady, it's like 6 years old, it's got the nice wing.

Lee jumped at the chance to let me try one of his props, it tached up to 23,800. I opened it a 1/4 turn and let it fly.

Mmmm.... yes, Quarter 40... too much fun.

First landing, no big deal, I brought his prop home safe.

But I'm chasing a buzz or flutter, so I took it home. I have better wheels and a plan for a slightly floppy rudder to deal with.

That prop will chew up the competition, flew fast. Make me one, remember to leave some meat on for tuning

(in reply to Super Splatter)

Post #: 135

RE: wood props - 4/15/2007 3:19:22 AM

daven

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From: Andover, MN, USA
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Is that the purple / yellow plane you got from Ron Jess? I always thought that was a sharp looking plane. Glad to hear Lee got a prop going good.

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Post #: 136

RE: wood props - 4/15/2007 4:32:34 AM

HighPlains

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When we made a Rev-Up prop, is took about 1 second to cut one side of a prop blade. Part of the secret is the shaper head was running around 20,000 rpm on about a 3" diameter, the other was the angle of the cutter blades was very different from typical wood working cutters. To keep the prop blade from chattering, you need to support it on the backside, as well as bend it slightly so that it is "sprung" (the side being cut is in compression slightly).

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RE: wood props - 4/16/2007 12:32:18 AM

diggs_74

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Thanks for the "that a boy" Jess.. It was a great day for flying.. Now I just have to try and duplicate the prop.. That will be fun I bet..

So far that's 1 out of 3 that works..

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RE: wood props - 4/18/2007 1:49:08 PM

daven

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From: Andover, MN, USA
Status: online

Maybe this is a stupid question, but has anyone had an issue taking carved wooden props on a plane in their carry on luggage? Must look dangerous in the x-ray machine.

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Dave Norman

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(in reply to diggs_74)

Post #: 139