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Old 04-16-2011, 08:16 AM
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MasterCraft Strut Design Flow Analysis

Some of you may have seen the work OJ and I did with prop design here or the work Larry and I did for here his FAE system. Using similar advanced methods, I have compared the typical strut design to the one MC is marketing to "clean up" the flow moving into the prop. More TMC users' discussion and background on this design can be found here.

I notified MC of my intent to do this work under our NDA, and they have not shown any interest. I was given the silent treatment. As a result, I can only share relative effects, i.e. no absolute numbers. You will find two images below. The first shows flow streamlines around the new design. The second one is a table comparing the two designs at two speeds. The values are shown in "%", while the last column is my assessment of the direction of the % change. For example, the drag coefficient on the cone design is 10% higher than without the cone. A positive change in drag coefficient would be considered "bad", in that it works to defeat the purpose of the system.

I cannot state my endorsement, or lack thereof, publically. You must consider the tabulated data. In doing so, dont worry about the title of the measure. I dont have time to explain those. Look at the % magnitude and the direction/assessment. Keep in mind that not all things shown in the table impact the final performance with the same power. Also, not every possible fluid quantity is shown in the table. These results are all I can offer at this point.
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Last edited by Jesus_Freak; 04-16-2011 at 08:19 AM.
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Old 04-16-2011, 09:16 AM
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Tells me the claim that it gives you better gas mileage is like that little doo-hickie they used to market to put inside your air cleaner. Unless the stream of water is so much better that you get that much less prop slippage.

So I guess if the wake is softer or smaller there might be something in there.

Thanks for sharing JF.
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Old 04-16-2011, 02:16 PM
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It was a pretty obvious conclusion from the start that the strut would cause more drag due to the increased area. The real question is how much is the turbulant flow reduced and if the flow to the prop is improved. This is where the improvements in fuel consumption and the wake improvements will come from. Just for clarification the 10% increase is versus the drag of the standard strut, not a 10% increase in overall drag.
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Old 04-16-2011, 02:27 PM
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Sooooooo you are cautiously optomistic?
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Old 04-16-2011, 03:02 PM
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No I saying that the research was done before the strut was put into production, what JF has posted here shows nothing in relation to the overall system of the boat, he just proved that there is an increase in drag over the standard design, no surprise there.
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Old 04-16-2011, 03:57 PM
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Quote:
Originally Posted by MIskier View Post
No I saying that the research was done before the strut was put into production, what JF has posted here shows nothing in relation to the overall system of the boat, he just proved that there is an increase in drag over the standard design, no surprise there.
If the hull has not changed on some models then the "system" is strut. Moreover, putting that strut on an older hull is what a lot of people are more interested in. If the strut doesn't offer any improvement and in fact just causes more drag then the "system" is worthless to most of us.
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Old 04-16-2011, 04:53 PM
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Quote:
Originally Posted by CantRepeat View Post
If the hull has not changed on some models then the "system" is strut. Moreover, putting that strut on an older hull is what a lot of people are more interested in. If the strut doesn't offer any improvement and in fact just causes more drag then the "system" is worthless to most of us.
If you want to look at it that way fine, but you do not have the necessary information to draw a conclusion from the data presented. You need to know if there is a reduction in cavitation and what the flow is doing at the prop. The 10% increase that JF quotes tells you nothing other than that the strut has added surface area...well no kidding! That is the problem with CFD or FEA, anyone can make a pretty picture it is having the necessary knowledge to be able to understand what is being produced that is often the problem, and why this data should not have been posted prematurely. People are likely to draw the wrong conclusions from JF post.
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Old 04-16-2011, 05:18 PM
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Quote:
Originally Posted by MIskier View Post
If you want to look at it that way fine, but you do not have the necessary information to draw a conclusion from the data presented. You need to know if there is a reduction in cavitation and what the flow is doing at the prop. The 10% increase that JF quotes tells you nothing other than that the strut has added surface area...well no kidding! That is the problem with CFD or FEA, anyone can make a pretty picture it is having the necessary knowledge to be able to understand what is being produced that is often the problem, and why this data should not have been posted prematurely. People are likely to draw the wrong conclusions from JF post.
Now you can say what should and should not be posted. Get out of here. You're starting to sound like an over the top fan boy.

He's posted more then anyone else about the strut at this point so high5 to JF!
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Old 04-16-2011, 05:33 PM
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Right so I suppose that both of you were in the meetings when this strut was being designed, know what calculations were behind it, and have worked for the engineering dept. at MC. Oh nope thats right that was me who did those things, so until you know everything I would say that the information that JF has posted does not allow people to see all of the information that he has come up with. Before you jump down my throat about posting up all the data, dont bother because I cant due to my NDA with MC, and JF would have done well to think about future work, he posted with no consent from MC...good luck getting them to want to work with you in the future.
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Old 04-16-2011, 05:59 PM
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Quote:
Originally Posted by MIskier View Post
Right so I suppose that both of you were in the meetings when this strut was being designed, know what calculations were behind it, and have worked for the engineering dept. at MC. Oh nope thats right that was me who did those things, so until you know everything I would say that the information that JF has posted does not allow people to see all of the information that he has come up with. Before you jump down my throat about posting up all the data, dont bother because I cant due to my NDA with MC, and JF would have done well to think about future work, he posted with no consent from MC...good luck getting them to want to work with you in the future.
I couldn't careless who you've work for or how important you think you are. Get over youself son.

It's not your place to say what should and should not be posted here.
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