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Jesus_Freak
04-16-2011, 07:16 AM
Some of you may have seen the work OJ and I did with prop design here (http://www.mastercraft.com/teamtalk/showthread.php?t=35593) or the work Larry and I did for here (http://www.mastercraft.com/teamtalk/showthread.php?t=40136) his FAE (http://www.freshairexhaust.com/) 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 (http://www.mastercraft.com/teamtalk/showthread.php?t=40068).

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. :)

CantRepeat
04-16-2011, 08:16 AM
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.

MIskier
04-16-2011, 01:16 PM
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.

Skipper
04-16-2011, 01:27 PM
Sooooooo you are cautiously optomistic?

MIskier
04-16-2011, 02:02 PM
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.

CantRepeat
04-16-2011, 02:57 PM
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.

MIskier
04-16-2011, 03:53 PM
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.

CantRepeat
04-16-2011, 04:18 PM
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. 8p 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!

MIskier
04-16-2011, 04:33 PM
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.

CantRepeat
04-16-2011, 04:59 PM
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.

sand2snow22
04-16-2011, 05:06 PM
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.

X 2. I don't think he'll have affiliation with MC if he keeps this up :confused:

DooSPX
04-16-2011, 05:10 PM
I know that JF has extreme advanced knowledge in fluid dynamics. He has worked with companies like OJ to improve their props.
What JF posted is very well put together and tells the story of "ONLY" the strut. He in no way implied that it was a complete system, i.e. hull drag and flow, etc.

I am sure that MC gave in the cold shoulder because they do not want to be proven wrong.

Thank you JF and God Bless!

TX.X-30 fan
04-16-2011, 05:17 PM
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.




Sounds exactly how out fearless leaders in Washington speak to us.


And all the CR supporters too................. Haaaaaaaaaaaaaa

DooSPX
04-16-2011, 05:21 PM
Sounds exactly how out fearless leaders in Washington speak to us.


And all the CR supporters too................. Haaaaaaaaaaaaaa

Exactly!

"Slight thread jack"
You know Stu, we have been agreeing on quite a few topics as of late... what the heck is wrong with that picture? :rolleyes::D

MIskier
04-16-2011, 05:46 PM
I know that JF has extreme advanced knowledge in fluid dynamics. He has worked with companies like OJ to improve their props.
What JF posted is very well put together and tells the story of "ONLY" the strut. He in no way implied that it was a complete system, i.e. hull drag and flow, etc.

I am sure that MC gave in the cold shoulder because they do not want to be proven wrong.

Thank you JF and God Bless!

I never said that he was implying he had studied the whole system, what I said was to have a clear picture of what really occurs one needs to know if there has been a reduction in cavitation, and how the flow along the bottom of the boat is affecting the flow through the prop, that is where my reference to the system came in.

He also tells no where near the "story" of the the prop, he told you there was an increase in drag, which you can tell simply by looking at the strut that there is an increase in wetted area = more drag.

This leads to my concern of people drawing conclusions on partial information.

Maristar210
04-16-2011, 05:47 PM
Was MISkier in the conference room in Vanore when they decided Cash Rewards was a good idea as well?

No one likes an arrogant person MI. No one really cares if you were an intern getting coffee for Phil either...

Hoosier Bob
04-16-2011, 05:52 PM
Exactly! This is only regarding the strut! From what I heard most of the mileage increases were from the optional "Sail" kit! If you already have a Skylon you can save about $200!:D

PS. PUT THE SAIL DOWN AT SPEEDS OVER 20 MPH!I know that JF has extreme advanced knowledge in fluid dynamics. He has worked with companies like OJ to improve their props.
What JF posted is very well put together and tells the story of "ONLY" the strut. He in no way implied that it was a complete system, i.e. hull drag and flow, etc.

I am sure that MC gave in the cold shoulder because they do not want to be proven wrong.

Thank you JF and God Bless!

MIskier
04-16-2011, 05:57 PM
If you look at the turbulent kinetic energy, and turbulent integral columns they show that there is a reduction in the amount of turbulent flow, which is exactly what the strut is supposed to do.

I missed that my first time through, my apologies.

scott023
04-16-2011, 08:31 PM
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.

Here's the know it all geek that got his lunch stolen all through school because he thought he was better than everyone else. Your attitude here is obviously disliked by the masses... doesn't that tell you something?

MIskier
04-16-2011, 09:21 PM
Here's the know it all geek that got his lunch stolen all through school because he thought he was better than everyone else. Your attitude here is obviously disliked by the masses... doesn't that tell you something?

Fortunately I was a geek that enjoyed the weight room, so I didnt really have to worry about stolen lunches8p

CantRepeat
04-16-2011, 09:33 PM
I never said that he was implying he had studied the whole system, what I said was to have a clear picture of what really occurs one needs to know if there has been a reduction in cavitation, and how the flow along the bottom of the boat is affecting the flow through the prop, that is where my reference to the system came in.

He also tells no where near the "story" of the the prop, he told you there was an increase in drag, which you can tell simply by looking at the strut that there is an increase in wetted area = more drag.

This leads to my concern of people drawing conclusions on partial information.

Hey bud, no one really gives a hoot about the system.


What we wanted to know is how the new strut could work with our older boats, at this point. You're over the top fan boy know it all bull crap without even posting facts, which JF did post, supports our thought.

The post about how it was wrong that JF post real world facts and he would not get more work from MC proves you have an agenda. An agenda that is more worried about the factory over the users. Which we don't buy into. If all you care about is the factory and your rep, your pretty much useless to the masses. I see you burning bridges here.

CantRepeat
04-16-2011, 09:34 PM
Fortunately I was a geek that enjoyed the weight room, so I didnt really have to worry about stolen lunches8p

I bet your next in line to fight GSP too.

CantRepeat
04-16-2011, 09:43 PM
No one likes an arrogant person MI. No one really cares if you were an intern getting coffee for Phil either...

LOL :D:D:D

I'm liking where this is going.

CantRepeat
04-16-2011, 09:53 PM
I never said that he was implying he had studied the whole system,


What is the "whole system"? It's a strut with a bullet on the end of it. Nothing else has changed on hulls that have not changed. To say that it some how changes the hull of boat is just crazy. Yeah I know you didn't say that but what else is there?

I'm pretty sure nothing else as change to make a system.

MIskier
04-16-2011, 10:00 PM
What is the "whole system"? It's a strut with a bullet on the end of it. Nothing else has changed on hulls that have not changed. To say that it some how changes the hull of boat is just crazy. Yeah I know you didn't say that but what else is there?

I'm pretty sure nothing else as change to make a system.

The complex relationship between the hull bottom, prop shaft, strut, and prop all work together to influence the characteristics of the boats wake, which changing to the new strut does influence how the water flows hence the use of the term system. I was trying to explain it in a way that someone who may not be familiar with fluid dynamics would understand.

Stutsman230
04-16-2011, 10:05 PM
IMHO I believe that the bullet does nothing more than "straighten" the water flow into the leading edge of the prop. The propeller is most efficient when all the propeller blades get equal non twisted water flow.

Maristar210
04-16-2011, 10:08 PM
“Nobody can be so amusingly arrogant as a young man who has just discovered an old idea and thinks it is his own.”

Anyone know who said the above??????


PS MISkier: Phil likes cream in his coffee. Wade Cox's.

CantRepeat
04-16-2011, 10:09 PM
The complex relationship between the hull bottom, prop shaft, strut, and prop all work together to influence the characteristics of the boats wake, which changing to the new strut does influence how the water flows hence the use of the term system. I was trying to explain it in a way that someone who may not be familiar with fluid dynamics would understand.

Really? Did you think we didn't know that? Did you think that most of us were not asking about how it would affect our "current" boats? It was clear to see that most of us were asking about how the strut would work for us. Not how some kid who says he was tossing around numbers in some dark alley with MC could market something.

Are you that obtuse to what is going on here. Are you of such higher education that you didn't see the process? Or are you so worried as to what your rep might be that you wanted to do the one ups'menship.

I'm done here because at this point you and I will only go down hill. You just don't get it.

CantRepeat
04-16-2011, 10:10 PM
“Nobody can be so amusingly arrogant as a young man who has just discovered an old idea and thinks it is his own.”

Anyone know who said the above??????


PS MISkier: Phil likes cream in his coffee. Wade Cox's.

I owe you a beer brother.

cbryan70
04-16-2011, 10:10 PM
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.

Guess what...no one cares that you work/worked for MC.... Going to guess the majority of people that are reading your post thing your an arrogant *** hole. Heave forbid someone do some work on the side for the fun of it and provide information that may not leave MC in the greatest light. They do of course do EVERYTHING perfect...I remember that last venture of screwing customers out of 10's of thousands of dollars.

cbryan70
04-16-2011, 10:11 PM
Was MISkier in the conference room in Vanore when they decided Cash Rewards was a good idea as well?

No one likes an arrogant person MI. No one really cares if you were an intern getting coffee for Phil either...

Damn it beat me to it

cbryan70
04-16-2011, 10:12 PM
Fortunately I was a geek that enjoyed the weight room, so I didnt really have to worry about stolen lunches8p

Just *** kickings? Wait I bet you were the biggest baddest in your school as well

MIskier
04-16-2011, 10:40 PM
Cheap person attacks, this place is turning into skifly

cbryan70
04-16-2011, 10:40 PM
Cheap person attacks, this place is turning into skifly

Good leave then.

Justjoe
04-16-2011, 10:46 PM
Pickle sniffers.

Maristar210
04-16-2011, 10:46 PM
Phil needs some coffee on your way out. No one else give a s hit that you are here. LEAVE

cbryan70
04-16-2011, 11:07 PM
if you want real unbias mc info we can just ask mymc...way more knowledgeable then most at mc

mccobmd
04-16-2011, 11:13 PM
I'm not emotionally involved in the discussiont but CantRepeat did properly use the word "obtuse" in a cogent, relevant post. That, Sir, is impressive. :worthy:

Hoosier Bob
04-16-2011, 11:24 PM
Holy crap obtuse and cogent spelled with one N and no A!!! We are on a roll tonight! Nice Job! Next guy to spell supposedly with a B gets banned!I'm not emotionally involved in the discussiont but CantRepeat did properly use the word "obtuse" in a cogent, relevant post. That, Sir, is impressive. :worthy:

cbryan70
04-16-2011, 11:57 PM
Bob???? is it true? are you sober? BS

JohnE
04-17-2011, 10:04 AM
Wow, I never thought I'd see certain people in such accord on this site. MI has accomplished what nobody else could.

JF, thanks for the thread. Please keep the contributions coming.

CantRepeat
04-17-2011, 10:31 AM
Wow, I never thought I'd see certain people in such accord on this site. MI has accomplished what nobody else could.

JF, thanks for the thread. Please keep the contributions coming.

Yup, thanks for posting, JF. Many of us really do appreciate your work.

Skipper
04-17-2011, 02:04 PM
I am still confused. Does the strut go in front or behind the obtuse? And what is a cogent? Why is that guy that makes coffee such a plick? Man, I'll never figure this out.

Matt L.
04-17-2011, 02:55 PM
This is nothing more than marketing to sell the perception that MC has made some great innovation that the others haven't.

Do we really think a few square inches of extra bronze is going to make a hill of beans difference when you have many thousands of pounds of boat on top of it.

Please!

Matt

TX.X-30 fan
04-17-2011, 03:48 PM
This is nothing more than marketing to sell the perception that MC has made some great innovation that the others haven't.

Do we really think a few square inches of extra bronze is going to make a hill of beans difference when you have many thousands of pounds of boat on top of it.

Please!

Matt





Ding Ding Ding............we have a winner.......:D

CantRepeat
04-17-2011, 03:59 PM
This is nothing more than marketing to sell the perception that MC has made some great innovation that the others haven't.

Do we really think a few square inches of extra bronze is going to make a hill of beans difference when you have many thousands of pounds of boat on top of it.

Please!

Matt

It's not just a few square inches of extra bronze... it's a "system". :D

Table Rocker
04-17-2011, 07:56 PM
I am far from an engineer and I should not weigh in on such and emotionally charged subject, but just because something increases drag does not mean it has a negative impact on performance. Winglets on the wings of a jet would be an example of added material that increases drag and performance. They are the small vertical wings that are now common on the wingtips of jets. By forcing more air to travel over the wing instead of off the tip, more lift is generated making up for the increased drag. On a jet's wings you will also find plenty of structures that could be cleaned off for less drag, but they are there to direct airflow.

Kort nozzles on ships would also add drag, but at certain speeds they are of great benefit by focusing the thrust of the wheels. Spoilers on race cars are another example where engineers are constantly tampering with the drag vs. downforce trade off. Hooking a hull would be yet another example of adding drag. When the Aussies showed up at the America's Cup with a winged keel, did it have more drag than a non-winged keel? I would suspect that it did, but the boat won the cup.

I don't know if the strut is an improvement or not, but knowing that it has increased drag over the old strut doesn't tell me very much. I think that is what MI's point was. But then again, if you are looking for somebody that knows a little fluid dynamics, I know as little as anybody.

DooSPX
04-17-2011, 08:00 PM
I am far from an engineer and I should not weigh in on such and emotionally charged subject, but just because something increases drag does not mean it has a negative impact on performance. Winglets on the wings of a jet would be an example of added material that increases drag and performance. They are the small vertical wings that are now common on the wingtips of jets. By forcing more air to travel over the wing instead of off the tip, more lift is generated making up for the increased drag. On a jet's wings you will also find plenty of structures that could be cleaned off for less drag, but they are there to direct airflow.

Kort nozzles on ships would also add drag, but at certain speeds they are of great benefit by focusing the thrust of the wheels. Spoilers on race cars are another example where engineers are constantly tampering with the drag vs. downforce trade off. Hooking a hull would be yet another example of adding drag. When the Aussies showed up at the America's Cup with a winged keel, did it have more drag than a non-winged keel? I would suspect that it did, but the boat won the cup.

I don't know if the strut is an improvement or not, but knowing that it has increased drag over the old strut doesn't tell me very much. I think that is what MI's point was. But then again, if you are looking for somebody that knows a little fluid dynamics, I know as little as anybody.

Thank you for the post! It had a lot of informative detail. :D:D

CantRepeat
04-17-2011, 08:17 PM
By forcing more air to travel over the wing instead of off the tip, more lift is generated making up for the increased drag.



I thought what they did was keep air from swirling over the tip of the wing and back down on the top surface.

To change the subject, and I mean too, there is a big misconception about how a wing generates lift. Lift is generated from the top of the wing, not the bottom as a lot of people believe.

And we all know those Aussies are cheaters!!

1redTA
04-17-2011, 08:44 PM
The wing uses Bernoulli's principle right.

As far as the strut's performance :
old strut VS bullet nosed strut
Ford VS Chevy
Nautique VS Mastercraft
Pelosi VS Palin

looks like it will come down to personal preference

CantRepeat
04-17-2011, 09:24 PM
The wing uses Bernoulli's principle right.

Pelosi VS Palin



Really? :D

Hoosier Bob
04-17-2011, 10:08 PM
Word travels fast. 3 1/2 weeks. Longest time since third grade!:DBob???? is it true? are you sober? BS

CantRepeat
04-17-2011, 10:21 PM
Word travels fast. 3 1/2 weeks. Longest time since third grade!:D

Quiter!! :D

Hoosier Bob
04-17-2011, 10:26 PM
Ha! I know, don't remind me.:mad:Quiter!! :D

mccobmd
04-17-2011, 10:37 PM
This is nothing more than marketing to sell the perception that MC has made some great innovation that the others haven't.

Do we really think a few square inches of extra bronze is going to make a hill of beans difference when you have many thousands of pounds of boat on top of it.

Please!

Matt

I don't know about the performance but I do know if you can make something look cool enough people will buy it whether it works or not.

Matt L.
04-17-2011, 11:10 PM
It's not just a few square inches of extra bronze... it's a "system". :D

Thanks for correcting me. Now that I know it is a "System" I've seen the light! I'm getting my CNC guy on the line. I'm sure he can have one for my 24' 10" 240SC by week's end.

I'll be topping 55 mph by Easter!!!

That or I could visit a local adult novelty store and super glue a "System" to my existing strut for the same effect a whole lot cheaper. Anyone who pays MC for this is doing nothing more than getting a "System" up their backside. On the trailer it might be positioned just right, lube up!

This has to be one of the best marketing driven design items ever seen :banana: this was the closest smilie I could get to a "System" without getting banned.

Later,

Matt

06' X-2 R8R H8R
04-17-2011, 11:13 PM
Its a "BRONZE SYSTEM".....Now lets all just geet along.

Doug G
04-17-2011, 11:55 PM
JF, Thanks for the post. I enjoy reading about things I know nothing about and systematically learning.

AussieMC
04-17-2011, 11:58 PM
And we all know those Aussies are cheaters!!
Now that's a little harsh, we didn't cheat, unless cheating incorporates superior design & engineering.
A quick question about the strut, can JF do an analysis on wether it works upside down?:)

Doug G
04-18-2011, 12:17 AM
Only if the water is spinning backwards. But then all positive values are negative and bad is good

thatsmrmastercraft
04-18-2011, 01:27 AM
I am far from an engineer and I should not weigh in on such and emotionally charged subject, but just because something increases drag does not mean it has a negative impact on performance. Winglets on the wings of a jet would be an example of added material that increases drag and performance. They are the small vertical wings that are now common on the wingtips of jets. By forcing more air to travel over the wing instead of off the tip, more lift is generated making up for the increased drag. On a jet's wings you will also find plenty of structures that could be cleaned off for less drag, but they are there to direct airflow.

Kort nozzles on ships would also add drag, but at certain speeds they are of great benefit by focusing the thrust of the wheels. Spoilers on race cars are another example where engineers are constantly tampering with the drag vs. downforce trade off. Hooking a hull would be yet another example of adding drag. When the Aussies showed up at the America's Cup with a winged keel, did it have more drag than a non-winged keel? I would suspect that it did, but the boat won the cup.

I don't know if the strut is an improvement or not, but knowing that it has increased drag over the old strut doesn't tell me very much. I think that is what MI's point was. But then again, if you are looking for somebody that knows a little fluid dynamics, I know as little as anybody.

See how much easier an explanation (whether you agree or not) is to read when it is posted by a grown up.

CantRepeat
04-18-2011, 07:05 AM
Thanks for correcting me. Now that I know it is a "System" I've seen the light! I'm getting my CNC guy on the line. I'm sure he can have one for my 24' 10" 240SC by week's end.

I'll be topping 55 mph by Easter!!!

That or I could visit a local adult novelty store and super glue a "System" to my existing strut for the same effect a whole lot cheaper. Anyone who pays MC for this is doing nothing more than getting a "System" up their backside. On the trailer it might be positioned just right, lube up!

This has to be one of the best marketing driven design items ever seen :banana: this was the closest smilie I could get to a "System" without getting banned.

Later,

Matt

Great post Matt! :dance:

CantRepeat
04-18-2011, 07:07 AM
Now that's a little harsh, we didn't cheat, unless cheating incorporates superior design & engineering.
A quick question about the strut, can JF do an analysis on wether it works upside down?:)

Just yanking on the chain a little. :D 8p

Jesus_Freak
04-18-2011, 07:13 AM
Gentlemen, please accept my apology for creating such an emotionally charged environment. I have no pony in the race, axe to grind, etc.

I seek truth, and I have more than 15 years of proven, post-grad, professional experience doing so. I considered the overall system. My goal was to see if the flow was "cleaner" with the use of the cone. My measures included those issues we expected to see, such as drag, AND those issues that indicate an improved prop performance, such as axial velocity, turbulent scale, and entropy generation (total pressure conversion).

I am trying my absolute best not to inject my opinion here. If you PM me, however, I am free to tell you what I think about the data. That is no different than any person on here doing his/her own testing and then sharing his/her informed opinion.

eficalibrator
04-18-2011, 07:42 AM
You have to look at the CFD in context. It was just a static flow snapshot of a dynamic event. Without the rotating prop in there (at least), you're only seeing part of the picture here. As JF pointed out, they may very well be trading static Cd for a reduction in turbulence that may in turn reduce the prop's losses when spinning. We don't really care what the drag is when the prop isn't turning and this abbreviated analysis only shows that case, not the one we're really interested in. I certainly wouldn't write this design off based only on this data.

Skipper
04-18-2011, 09:07 AM
Gentlemen, please accept my apology for creating such an emotionally charged environment. I have no pony in the race, axe to grind, etc.

Funny how this thread went south of cheese so quickly....it all started so innocently. Just somebody trying to share a little information with others. Thanks for the efforts JF.

ahhudgins
04-18-2011, 09:58 AM
At first I was just joking, but now I would actually like to see a before and after video of the wake. I know that I had an obvious performance change in my boat when I went from a 3 blade prop to a 4 blade, but it wasn't just a "feeling". The OP stated that he "felt" as if the boat had less drag going down the lake and the wake "seemed" flatter. If the strut was supposed to change the wake, I want to SEE it. My slalom is not a level that I could tell the difference between a hard and soft wake. If I were a die hard slalom skier I wouldn't care about the math, I would want to see a change in my skiing level due to a wake change.

Table Rocker
04-18-2011, 02:47 PM
I thought what they did was keep air from swirling over the tip of the wing and back down on the top surface.That is my understanding as well. By directing the air over the wing instead of off the tip, the wingtip vortices are reduced and moved.

Sodar
04-18-2011, 02:54 PM
I don't agree in MISkier's know-it-all attitude, but he is correct. The strut itself obviously has more surface area and creates more drag than the standard strut, but as a complete system with the shaft, prop and other running gear, it probably does something to improved the efficiency. How much of a benefit is created is something Jesus Freak and his uber-sophisticated talk and equipment can calculate. After his analysis, he can get on here and try to decipher it to us peons, but to me it is all Greek.

The new strut uses the same hydrodynamic principle as a bulbous bow?

http://en.wikipedia.org/wiki/Bulbous_bow

MIskier
04-18-2011, 03:10 PM
I don't agree in MISkier's know-it-all attitude, but he is correct. The strut itself obviously has more surface area and creates more drag than the standard strut, but as a complete system with the shaft, prop and other running gear, it probably does something to improved the efficiency. How much of a benefit is created is something Jesus Freak and his uber-sophisticated talk and equipment can calculate. After his analysis, he can get on here and try to decipher it to us peons, but to me it is all Greek.

The new strut uses the same hydrodynamic principle as a bulbous bow?

http://en.wikipedia.org/wiki/Bulbous_bow

Same shape, different function, the best way to think of a bulbous bow is like noise canceling headphones that use an opposite sound wave to cancel out the surrounding noise. The buld acts to generate the "negative noise" in this case an inverse of the bow wave, thus the 2 cancel one another out reducing the resistance the ship has to overcome because the ship is no longer pushing a bow wave.

The strut is more like the vortex generators on an airplane they both help the fluid to flow in a more desierable way.

Kingsley X-1
04-18-2011, 04:40 PM
they though Reggie Fountain was a crazy person when he started adding ventilating steps his deep-V race boats back in the early to middle 90's. i am not sure if he was the first in the performance boat industry to do this because the technology has been around forever on float planes...but now almost every performance boat has them.

MIskier
04-18-2011, 04:56 PM
He was the first to bring the designs to the production powerboat market, but Micheal Peters pioneered the design in offshore racing powerboats starting in the early '80s. The first stepped hull design was in the '30s and that was inspired by float planes, which actually helped to pioneer the science behind planing watercraft with the savitsky papers.

If you are at all interested in these designs there was a great article entitled Peters on Powerboats in Professional Boat builder magazine a few months ago.

CantRepeat
04-18-2011, 05:02 PM
I don't agree in MISkier's know-it-all attitude, but he is correct. The strut itself obviously has more surface area and creates more drag than the standard strut, but as a complete system with the shaft, prop and other running gear, it probably does something to improved the efficiency. How much of a benefit is created is something Jesus Freak and his uber-sophisticated talk and equipment can calculate. After his analysis, he can get on here and try to decipher it to us peons, but to me it is all Greek.

The new strut uses the same hydrodynamic principle as a bulbous bow?

http://en.wikipedia.org/wiki/Bulbous_bow


Well, without more information we don't know that he is correct. People can say all day long it will help mileage in some fancy web video. Or people can say the wake felt softer. But before I lay down $300 bucks I'm gonna need more then some pushy college intern name dropper that talks badly of JF saying it's golden.

But really. If the numbers were published that proved it would give a 3% increase in full efficiency at 25+ mph I'd buy one in a second. I'm sure there's a lot of 02 to 10 owners who would buy them if it was shown to work.

Jesus_Freak
04-21-2011, 06:39 AM
Thanks to all for the PMs and posts. I cannot now due to an extremely compressed schedule, but I will reply to those as soon as I can, as well as respond to the various issues brought forth on this thread since I last visited the site.

Jesus_Freak
04-30-2011, 08:41 AM
Hi all. Thank you for the posts and PMs. I have finally made the time to get on here and respond to a few points:

IMHO I believe that the bullet does nothing more than "straighten" the water flow into the leading edge of the prop. The propeller is most efficient when all the propeller blades get equal non twisted water flow.

The results show that it does not straighten.

I am far from an engineer and I should not weigh in on such and emotionally charged subject, but just because something increases drag does not mean it has a negative impact on performance. Winglets on the wings of a jet would be an example of added material that increases drag and performance. They are the small vertical wings that are now common on the wingtips of jets. By forcing more air to travel over the wing instead of off the tip, more lift is generated making up for the increased drag. On a jet's wings you will also find plenty of structures that could be cleaned off for less drag, but they are there to direct airflow.....

Excellent point, which is why I have tabulated other effects and results.

You have to look at the CFD in context. It was just a static flow snapshot of a dynamic event. Without the rotating prop in there (at least), you're only seeing part of the picture here. As JF pointed out, they may very well be trading static Cd for a reduction in turbulence that may in turn reduce the prop's losses when spinning. We don't really care what the drag is when the prop isn't turning and this abbreviated analysis only shows that case, not the one we're really interested in. I certainly wouldn't write this design off based only on this data.

This is one of my favorite posts of all time. Given that I am the only human in this solar system who knows anything about how I studied this, I find it confusing (mostly amusing) that you have decided to "write off" my "abbreviated analysis". Tell us more about what I did or did not do. :D ;)

The data show that there is no useful physics trade going on here.

I don't agree in MISkier's know-it-all attitude, but he is correct. The strut itself obviously has more surface area and creates more drag than the standard strut, but as a complete system with the shaft, prop and other running gear, it probably does something to improved the efficiency. How much of a benefit is created is something Jesus Freak and his uber-sophisticated talk and equipment can calculate. After his analysis, he can get on here and try to decipher it to us peons, but to me it is all Greek.

Hi Cam. That is my point that I looked at more than drag. The reason I kept it in Greek form was to minimize the amount of opinion I injected into the conversation. I wasn't trying to superfluous. Short version: The data show that there is not a valuable trade-off.

Miss Rita
04-30-2011, 10:01 AM
The flow analysis is very interesting; I only wish I had the brains to figure it out. The bottom line is that all the intuitive conclusions are just that: intuition. Without some kind of objective before-and-after analysis of on the water performance no conclusions can be made.

An Indy race car has tremendous drag, but I think you have to agree that it has tremendous performance.

eficalibrator
04-30-2011, 10:35 PM
This is one of my favorite posts of all time. Given that I am the only human in this solar system who knows anything about how I studied this, I find it confusing (mostly amusing) that you have decided to "write off" my "abbreviated analysis". Tell us more about what I did or did not do. :D ;)
Please don't get offended. I'm merely pointing out that the data presentation is abbreviated, not necessarily your complete analysis. As a fellow engineer, I recognize that you posted "the punchline" or executive summary and not the complete report of your findings. I was just pointing out that it would certainly be very easy to dig deeper into the data to find more of the story if it were one's line of business. I respect your desire to maintain your clients' confidentiality, so I'm not blaming you for only posting what you did.

Jesus_Freak
05-06-2011, 05:28 AM
The flow analysis is very interesting; I only wish I had the brains to figure it out. The bottom line is that all the intuitive conclusions are just that: intuition. Without some kind of objective before-and-after analysis of on the water performance no conclusions can be made.

An Indy race car has tremendous drag, but I think you have to agree that it has tremendous performance.

I did a before-and-after analysis of the performance. The table provides data before and after. That is how I generated the % change numbers on the measures. The only part you will get from being "on the water" that I didnt study is wake performance. I have clearly noted that; I have no idea how the wake looks or is affected.

One beauty of a computational study (other than the obvious cost/time/energy benefits) is the ability to isolate the variables of interest. Looking for, and measuring, subtle differences on the water can be an enormous challenge. The spread-to-capability ratio of the data is simply too high. It is sometimes mathematically irresponsible to make conclusions based on it. I am all about "real world" testing if the data can be collected such that the variables of interest are not masked by experimental uncertainty.

It was most certainly objective. In fact, I was hoping the data would show the opposite story. I happen to be a MasterCraft fan. I certainly respect the leadership and engineering staff I have met and worked with. My goal was to provide an objective data set.

Jesus_Freak
05-06-2011, 05:31 AM
Please don't get offended. I'm merely pointing out that the data presentation is abbreviated, not necessarily your complete analysis...

Thank you for your clarification, but I was not offended. :)

CantRepeat
07-07-2011, 03:47 PM
I was told today that it was Ilmor that designed the new strut and that OJ was producing them. Is this accurate? I ask only because I was under the assumption that OJ designed it.

DooSPX
07-07-2011, 06:15 PM
I was told today that it was Ilmor that designed the new strut and that OJ was producing them. Is this accurate? I ask only because I was under the assumption that OJ designed it.

I think you are correct my friend. I spoke briefly with Eric, and given the contract with OJ and MC he could not say "yes" or "no" to many facts but lead to that fact. Also lead to other opinions about it as well, but I cannot/will not disclose.

EJ OJPROP
07-08-2011, 07:02 AM
The strut was designed by Master Craft staff and we, OJ, make it.

CantRepeat
07-08-2011, 07:51 AM
The strut was designed by Master Craft staff and we, OJ, make it.

I assume that staff does not include Ilmor engineers? :D

EJ OJPROP
07-08-2011, 08:21 AM
Correct Sir

terrafirma
08-10-2011, 09:49 PM
Having built a racing yacht before and witnessed small changes to rudders, keel fins and bulbs I can say the smallest things can sometimes make a huge difference. Back in 1995 we built a 41 foot racing yacht to compete in the Sydney to Hobart yacht race. We ended up winning in the first year, but thats another story. Early on we were suffering from harmonics coming from the keel fin which was extremely narrow and the trailing edge was the culprit. We ended up making the trailing edge a 45 degree angle and the problem was solved. We also added small curves to where the keel fin joined the hull and where the bulb joined the keel fin, these small changes "Cleaned" the flow, less disturbed water and increases in speed. In the case of the Mastercraft strut the concept is to clean the flow before it reaches the propeller, thus potentially allowing the prop to work better. I have no doubt this is more a marketing addition than a necessity, does it work, I'd say yes, would the difference be noticeable? I doubt it, would love to see actual performance figures, if none have been published it's not hard to see why. I have ordered a new X14 and will take my strut thankyou very much, after a few Jack Daniels the MC Strut will become legendary..! LOL