OJ Uses Advanced Prop Design Techniques

[Jesus_Freak]

Just wanted you all to be aware of the great effort Eric at OJ is applying in order bring you all the best prop on the market. He and I have embarked on a series of studies to optimize his proven design. No, this is not a paid advertisement....just an FYI. Take it for what it is worth. Below is a sample of some results showing, in short, the movement of water around one of his designs.

[Jim@BAWS]

Looks more like a piece or pretty cool artwork

Glad you are helping Eric out...good guy to work with

Jim@BAWS

[CruisinGA]

CFD is pretty cool stuff...

So the real question is, will it make me jump higher and land more back rolls?

[thatsmrmastercraft]

I'm thinking 50 more RPM and one more MPH.

[87MCProstar]

i feel like an idiot, what does that diagram mean?

[slickwater1]

It appears to me that it is showing differentiated amounts of pressure applied through out the water column. with blues and greens being little to no pressure applied "resistance" and reds being significant amount of force being applied to the water. basically showing how the prop works as it is propelling the boat. I am not an engineer but this is what I gather.

[Sidewinder]

Jesus_Freak,

Thanks for the pic. Really interesting. I'd be curious to see a 3 vs 4 blade comparison or a 3 blade smooth vs 3 blade with cnc marks on it like this...
https://is30.eporia.com/company_58/610147.jpg

I've always been curious to know more about the pros/cons of a smooth prop vs a prop with the cnc marks... I would think that the cnc prop would have tremendous bite when new, but would based on the number of "edges" on the blade it would cavitate once it was nicked by a small impact (ie. a small stick that you didn't see floating in the water) or older / tarnished.

Anyway, I recently came across the following site and thought I'd post it for those who are interested. The info is more to do with cavitation on commercial shipping, but there are some interesting pictures and video...
http://www.erocav.de/
Go to main results and also facilities -> hsva -> propellers and cavitation
Here are a few pics...

[Jesus_Freak]

Originally Posted by CruisinGA

So the real question is, will it make me jump higher and land more back rolls?

Not for a fixed boat speed, hull, and weight distribution.

Originally Posted by 87MCProstar

i feel like an idiot, what does that diagram mean?

Too long of a story; the purpose was only to notify you all that he is working on it. I can say that the colors here indicate the speed of the water. Red is faster than blue. Again, short version.

Originally Posted by slickwater1

It appears to me that it is showing differentiated amounts of pressure applied through out the water column. with blues and greens being little to no pressure applied "resistance" and reds being significant amount of force being applied to the water. basically showing how the prop works as it is propelling the boat.

Absolutely not, but great guess.

Originally Posted by Sidewinder

…I've always been curious to know more about the pros/cons of a smooth prop vs a prop with the cnc marks... I would think that the cnc prop would have tremendous bite when new, but would based on the number of "edges" on the blade it would cavitate once it was nicked by a small impact (ie. a small stick that you didn't see floating in the water) or older / tarnished....

Interesting question. I would need to separate out the blade stresses between the pressure integral and viscous integral to see how much the surface roughness plays a role in the thrust generation. I had not thought of that. I don’t think, however, that the potential for cavitation will be greatly influenced by the surface roughness. Cavitation occurs near the leading and trailing edges where the slip velocity is the greatest (pressure lowest by the overly-simple-but-often-useful Bernoulli relationship). Are you thinking that the CNC prop is easier to nick?

[mccobmd]

I don't know what he's saying but I'm trying to stay with him.

[Skywalker]

Originally Posted by Jesus_Freak

Just wanted you all to be aware of the great effort Eric at OJ is applying in order bring you all the best prop on the market. He and I have embarked on a series of studies to optimize his proven design. No, this is not a paid advertisement....just an FYI. Take it for what it is worth. Below is a sample of some results showing, in short, the movement of water around one of his designs.

It just mean that OJ props make the water pretty!