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View Full Version : OJ Uses Advanced Prop Design Techniques


Jesus_Freak
05-25-2010, 09:41 PM
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
05-25-2010, 09:56 PM
Looks more like a piece or pretty cool artwork

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

Jim@BAWS

CruisinGA
05-25-2010, 09:57 PM
CFD is pretty cool stuff...

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

thatsmrmastercraft
05-26-2010, 12:15 AM
I'm thinking 50 more RPM and one more MPH.

87MCProstar
05-26-2010, 07:27 AM
i feel like an idiot, what does that diagram mean?

slickwater1
05-26-2010, 07:58 AM
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
05-26-2010, 12:01 PM
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
05-26-2010, 12:51 PM
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. :)

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.

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. :D

ÖI'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 donít 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
05-26-2010, 11:01 PM
:worthy::worthy::worthy: I don't know what he's saying but I'm trying to stay with him.

Skywalker
05-26-2010, 11:43 PM
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!

Ole Miss Rebels
05-26-2010, 11:59 PM
i am sure acme makes a great prop but i will never buy one. mastercraft chose oj as their oem supplier and i have had nothing but oj's on all three of my xstars ('99, '05 and '08). eric has always sspent many hours working with me on the phone or by email and made sure i got the perfect prop for my boat and use. he has allowed me to test them and return them if they weren't what i wanted. i never needed to take him up on his offer but it was there for the talking. oj is the best prop and eric is the best supplier i have ever dealt with. go oj.

JLeuck64
05-27-2010, 12:54 AM
Well there you have it... Every thing that happens in this universe can be boiled down to just two reasons...
Pressure and timing!

DooSPX
05-27-2010, 09:28 PM
JF, you never cease to amaze me. You are truly a gifted man and many ways.

thank you for all your help both technical and spiritual.

BTW, is this saying that OJ/You are coming up with a different blade design, or are you saying that the blade design that OJ is using is the best for its job for the towboats?

Jesus_Freak
05-28-2010, 01:00 PM
JF, you never cease to amaze me. You are truly a gifted man and many ways. thank you for all your help both technical and spiritual.

Well, thank you. I am honored to help in any way. In terms of "amazement", however, I need to pass 100% of that along to the only ONE who deserves it. :)

BTW, is this saying that OJ/You are coming up with a different blade design, or are you saying that the blade design that OJ is using is the best for its job for the towboats?

Excellent question. I was waiting for someone to start asking the hard questions. At this point, I can only say for sure:

A. I cannot know how a given OJ prop compares to an "equivalent" competitor version without evaluating that version. Frankly, I think this would be a great idea.

B. There is no perfect design.

Comments?

ski_king
05-28-2010, 01:07 PM
Very cool and interesting information. It is nice to see a company puting time and money into R&D.

Did you start to see those cool colors before or after your ski met your head at CSM?

bobx1
05-28-2010, 01:14 PM
i feel like an idiot, what does that diagram mean?

I did not think it was a diagram but thought it was some new type of LED light kit for your prop. I tried something similar but the cords kept getting tangled.

DooSPX
05-28-2010, 01:59 PM
JF, understood about the ONE and ONLY who deserves it. After all, HE created us.

Both major players have their own advantages and disadvantages. It would be great if you and Eric could get say the equal 3 blade and 4 blade slalom props and equal wake boat props and test them.

JF, you may have some input on my opinion... If you look at the other brands' blade design, it looks like a prop that is used on a big boat/ship, to create the MOST possible thrust per revolution of the prop compared to OJ's wide elephant type design which seems to favor the wake and feel of the skier behind the boat.
Does the above seem plausible to you?

if there is going to be a blade design change, I may have to hold off getting my OJ 454 four blade.

DooSPX
05-31-2010, 07:44 PM
Eagerly awaiting more info on here... This thread really has my attention.

Jesus_Freak
06-01-2010, 01:06 PM
Very cool and interesting information. It is nice to see a company puting time and money into R&D.

Did you start to see those cool colors before or after your ski met your head at CSM?

Before, during, and after! I also heard a ringing sound, followed by birds singing :)

I did not think it was a diagram but thought it was some new type of LED light kit for your prop. I tried something similar but the cords kept getting tangled.

Excellent! :D

JF, understood about the ONE and ONLY who deserves it. After all, HE created us.

Both major players have their own advantages and disadvantages. It would be great if you and Eric could get say the equal 3 blade and 4 blade slalom props and equal wake boat props and test them.

JF, you may have some input on my opinion... If you look at the other brands' blade design, it looks like a prop that is used on a big boat/ship, to create the MOST possible thrust per revolution of the prop compared to OJ's wide elephant type design which seems to favor the wake and feel of the skier behind the boat.
Does the above seem plausible to you?


Thank you for the comments. I probably should avoid giving my comparative opinions publically at this stage of the game. I am hoping at some point Eric is going to pipe in...

DooSPX
06-01-2010, 01:49 PM
thank you JF...
I by no means meant to put you on the spot. I am sorry about that. I do hope Eric does chime in soon.