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CNC Prop


MadMan

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Has anyone ever done an "apples to apples", CNC vs cast propeller comparison (same pitch and dia.)? I read ACME's and OJ's propaganda on the advantages of CNC, but are these actually seen in the real world?

I've never used a CNC, only old school cast.

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It would seem to me that CNC machining and casting are simply two ways to arrive at a finshed prop. If the finished specs are the same, prop should behave identically. I supposed a lot depends on the quality of each process, but I would rather have a properly cast prop than a poorly CNC'd one.

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@Madman: Yes and yes. In my case an improvement in acceleration and elimination of cavitation. They tend to also be very smooth, but that can vary and easily change if you hit something with any prop.

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CNC props typically have much more surface area than a cast equivalent. You'll find most go one pitch down (13x12 CNC vs. 13x13 cast) and have much improved hole shot pulling power and nearly identical top speed.

In short, yes they do what they say.

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I had a stainless 4-blade that was built to similar specs (pitch and diameter, cup may have been slightly different) as the original 3-blade CNC prop on my 2002 Sunsetter. All the comments above hold true even comparing those 2 props. The 4-blade stainless ended up going in my back up kit.

In total I have 5 props (2 stainless and 3 CNC) all of the CNC props have less felt vibration than the best running stainless prop I have.

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Hydrofoils that are made by CNC are always much stronger than cast foils. These props are probably still made of Nibral so I doubt they will be all that strong, but maybe there is a difference.

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dont know if its still true "for props" but most lost wax casting parts often still require a CNC to finish them to spec as they are somewhat rough.

CNC from a solid extruded block would yield a stronger prop than casting which could have tiny amounts or some porosity to it,

castings were a cheap way for volume production but now a days everything is small with lots of options sizes pitches diameters and being able to make a prop on the fly or tweak it with a simple programming code is a lot easier than re-tooling a new mold for a casting.

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