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  #751  
Old 10-02-2009, 01:51 PM
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Miss Rita Miss Rita is offline
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I always wondered about those ACME props......why the ribs?
I wonder too. Maybe Acme knows something I don't. Maybe the ribs hold the water better, channel the flow across the blade so that the flow is more laminar, keep the water from spilling off the outer edge of the blade. Everything I've read says that the machined CNC props are superior to smooth polished props.

Last edited by Miss Rita; 10-02-2009 at 02:46 PM.
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  #752  
Old 10-02-2009, 01:56 PM
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Quote:
Originally Posted by Miss Rita View Post
I always wondered about those ACME props......why the ribs?

I wonder too. Maybe Acme knows something I don't. Maybe the ribs hold the water better, channel the flow across the blade so that the flow is more laminar, keep the water from spilling off the outer edge of the blade. Everything I've read says that the machined props are superior to smooth polished props.
Eric!......can you fill us in?
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  #753  
Old 10-02-2009, 06:31 PM
TMCNo1 TMCNo1 is offline
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Quote:
Originally Posted by Miss Rita View Post
I wonder too. Maybe Acme knows something I don't. Maybe the ribs hold the water better, channel the flow across the blade so that the flow is more laminar, keep the water from spilling off the outer edge of the blade. Everything I've read says that the machined CNC props are superior to smooth polished props.

The ribs are a result of the CNC machining process, where a/the bit/bits eat away the excess metal of a cast prop to create the finished product to a consistant/blueprinted spec, one time/everytime, compared to a cast prop of days past that was ground/sanded by hand/machine with variances that did not always meet a near perfect spec and it's also a somewhat faster process.
You will also notice, a repaired CNC prop will have the smooth finish like days of old because the repairs are done by hand, much like the entire old prop manufacturing process.
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  #754  
Old 10-02-2009, 06:49 PM
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OK we know why the ridges are present. Do we know if the machined surface offers any performance advantage over a prop with a smooth or polished finish?
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  #755  
Old 10-02-2009, 07:08 PM
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OJ CNCd props have the ridges as well.

Under $500 shipped from ski-it-again for the complete OJ kit that includes prop puller and carrying case with new nut, key, cotter pin, and wrench for removing the nut. It is shipped directly from OJ and I received it 3 days after sending my order.
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  #756  
Old 10-02-2009, 07:20 PM
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Originally Posted by Chicago190 View Post
OJ CNCd props have the ridges as well.

Under $500 shipped from ski-it-again for the complete OJ kit that includes prop puller and carrying case with new nut, key, cotter pin, and wrench for removing the nut. It is shipped directly from OJ and I received it 3 days after sending my order.
The one in my pic is an OJ legend......it's not cnc'd? looks like it.....there's mill marks but not like the acme as you can see
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  #757  
Old 10-02-2009, 08:27 PM
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The one in my pic is an OJ legend......it's not cnc'd? looks like it.....there's mill marks but not like the acme as you can see
I have an XMP series prop. I think the Legends are not CNC'd. This is my prop (phone pictures):
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  #758  
Old 10-02-2009, 09:22 PM
TMCNo1 TMCNo1 is offline
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Originally Posted by Miss Rita View Post
OK we know why the ridges are present. Do we know if the machined surface offers any performance advantage over a prop with a smooth or polished finish?
According to EJ OJPROPS in a previous post, the CNC prop ridges offer no advantage or disadvantage to the props performance over the old style prop. It's just a result of the machining process as the machine is set up. The props are just more identical and in most cases, for obvious reasons require less work to balance too.
I'll continue to look for that post and edit if I find it.

Here is one interesting quote,
Quote:
Originally Posted by EJ OJPROP View Post
We have been making CNC machined props since 2002. All CNC machined propellers start as castings, just as a hand finished propeller is cast. The difference in the castings are the CNC machined parts are cast thicker in order to machine the propeller. Our hand finished props are made from CNC machined patterns that are very accurate and provide a very good net casting, allowing for minimal clean up of the part. In fact, our hand finshed props are very accurate when finished. Hand finishing a propeller is an art and takes skill to not change the face of the blade while cleaning up the part. While CNC machined props are here to stay we still offer the hand finished line of propellers.

A CNC prop will bend in an impact just as a hand finished prop will bend. The thinner the prop the easier it will bend.
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Last edited by TMCNo1; 10-02-2009 at 09:31 PM.
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  #759  
Old 10-02-2009, 10:01 PM
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Originally Posted by TMCNo1 View Post
According to EJ OJPROPS in a previous post, the CNC prop ridges offer no advantage or disadvantage to the props performance over the old style prop. It's just a result of the machining process as the machine is set up. The props are just more identical and in most cases, for obvious reasons require less work to balance too.
I'll continue to look for that post and edit if I find it.

Here is one interesting quote,
So from Eric's quote it sounds like there's not a whole lot of difference from a cnc and a cast then hand finished prop.....only the finished cnc is a little more accurate in mass production.....am I reading this right?
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  #760  
Old 10-02-2009, 10:08 PM
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Originally Posted by coz View Post
So from Eric's quote it sounds like there's not a whole lot of difference from a cnc and a cast then hand finished prop.....only the finished cnc is a little more accurate in mass production.....am I reading this right?
Apparently so.
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