Radical Prostar Modification

[jipster43]

Check out this thread. Sounds like he's on to something.

http://ballofspray.com/vanillaforum/comments.php?DiscussionID=1783&page=1#Item_8

JP :)

[east tx skier]

That's some serious tinkering.

[DemolitionMan]

I have some pics of that boat from 2003 homecoming. I will see if I can find them.

[Jesus_Freak]

Copied from the thread:

Next, a 3/4 inch hole was drilled through the hull just in front of the prop. The hole was tapped so a 3/4 pipe could be threaded in to keep the opening above the waterline. This opening to air allowed air to get sucked into the prop. Adding some air into the prop is an established racing trick (surface piercing propellers) which added efficiency to the prop - as evidenced by 50 lbs less skier weight on PP Classic to make times with the bubbles. The coolest side effect is the softening of the wake. It is noticeable and quite nice.

Very interesting indeed! I need to soak on this a while...

[TMCNo1]

I have some pics of that boat from 2003 homecoming. I will see if I can find them.

I remember that, the shafts were chain driven off the transmission and made a little racket when it ran.
They pulled a bunch of skiers to set some kind of record IIRC, but don't remember how it turned out.

[Skipper]

Copied from the thread:

Next, a 3/4 inch hole was drilled through the hull just in front of the prop. The hole was tapped so a 3/4 pipe could be threaded in to keep the opening above the waterline. This opening to air allowed air to get sucked into the prop. Adding some air into the prop is an established racing trick (surface piercing propellers) which added efficiency to the prop - as evidenced by 50 lbs less skier weight on PP Classic to make times with the bubbles. The coolest side effect is the softening of the wake. It is noticeable and quite nice.

Very interesting indeed! I need to soak on this a while...

The non-scientific world is anxiously awaiting your analysis. Just like BP, I am ready to drill, damn the side effects!

[uncleboo]

Cutting holes in the mastercraft--good luck with that. I don't think my wake is hard enough to warrant that. I guess he isn't worried about resale value. FS: Mastercraft with Speed Holes:)

[maxpower220]

Well, this guy is mixing apples and oranges.

"This opening to air allowed air to get sucked into the prop. Adding some air into the prop is an established racing trick (surface piercing propellers) which added efficiency to the prop - as evidenced by 50 lbs less skier weight on PP Classic to make times with the bubbles."

An explanation of surface props: http://www.well.com/user/pk/SPAprofboat.html

Mixing and matching theories is never a good thing, especially if you don't really understand what you are doing.
I suggest that you return the drill bit to the tool box and maybe order a new prop.

[rd1900]

This is interesting and could be applied to our boats (from the explanation of surface props):

In fact, for conventional installations a net performance increase can often be realized by enclosing submerged shafts in non- rotating shrouds, despite the increase in diameter.

[Skipper]

I don't understand how drilling a hole in front of the prop to install a straw will improve the performance of the boat? The guy said that it took off 50 rpms from PP and made the wake softer. How does the air get sucked into the hole and why does that cause the propeller to be more efficient? How does that soften the wake?

[03 35th Anniversary]

Check out this thread. Sounds like he's on to something.

http://ballofspray.com/vanillaforum/comments.php?DiscussionID=1783&page=1#Item_8

JP :)

The link is dead... :(

But if this is the boat I think it is, it was paired off against the 2001 or 2002 190 with the 8.1 that didn't have a hook (The Beast) and this boat ate The Beast A$$ everytime!!! Even when The Beast cheated and jumped the gun!

[bbeach]

I slalom'ed behind the Beast at one time and needless to say it was a STRONG pull!

[Jesus_Freak]

Well, this guy is mixing apples and oranges.

"This opening to air allowed air to get sucked into the prop. Adding some air into the prop is an established racing trick (surface piercing propellers) which added efficiency to the prop - as evidenced by 50 lbs less skier weight on PP Classic to make times with the bubbles."

An explanation of surface props: http://www.well.com/user/pk/SPAprofboat.html

Mixing and matching theories is never a good thing, especially if you don't really understand what you are doing.
I suggest that you return the drill bit to the tool box and maybe order a new prop.

Agreed. The benefits of surface props are not directly related to the fact that a low density fluid (air in this case) is mixed in with the water as part of the thrust mechanism.


In fact, for conventional installations a net performance increase can often be realized by enclosing submerged shafts in non-rotating shrouds, despite the increase in diameter.

Agreed, but shrouds, depending on the design, have caused problems in gas turbine applications.

I don't understand how drilling a hole in front of the prop to install a straw will improve the performance of the boat? The guy said that it took off 50 rpms from PP and made the wake softer. How does the air get sucked into the hole and why does that cause the propeller to be more efficient? How does that soften the wake?

This is why I said I needed to soak on it. I can see some potential benefit from air bubbles providing "lubrication" in a sense to the viscous layers of water immediately next to the blade, which might help reduce turbulence generation losses. At the same time, it might increase slip. Lets think of the extrema: Inject mucho air and the prop free-spins in the air. Inject no air and you get a stock configuration. I am not convinced that "some" is beneficial.

[Jorski]

In higher performance applications, inducing air allows the prop to slip a little upon acceleration which helps get a prop to spin up to speed faster. This generally allows you spin a larger more efficent prop.

Prop characteristics such as increased rake and cup allow the prop operate quite well in an aerated environment.

On outboards and I/0s, many high speed props (chopper, cleaver and other surface piercing props) either have holes in the hub to allow exhaust gases to bubble over the prop, or use a much narrower hub so that the exhaust gases are pushed out directly ober the hub and onto the blades.

Notice the whole at the leading edge of the blade:
http://www.cd-marine.de/Prop/LaserII_.jpg

A direct drive doesn't route the exhaust in that way, so what that guy is doing has some merrit, and he isn't exactly inventing anything here. Other ways that high speed boats introduce air is through hull vents and steps.

He may also be affecting the way that the water let's go of the hull at the transom, that may explain the change in the wake shape as much as the affect on the prop.

[Jesus_Freak]

In higher performance applications, inducing air allows the prop to slip a little upon acceleration which helps get a prop to spin up to speed faster. This generally allows you spin a larger more efficent prop....He may also be affecting the way that the water let's go of the hull at the transom, that may explain the change in the wake shape as much as the affect on the prop.

Ahhhhh. OK, so the benefit is the slip I talked about which allows for faster spin-up. Makes sense. I was running on thought experiments and had not surfed the web for it. Thanks.

The small hole through which the air line passes will not affect how the water "lets go" of the hull, so the effect is either ficticious or has another cause.

[jipster43]

The fella' conducting these experiments is definitely a mad scientist, but he is also a very competitive skier living on his own lake logging more water time than 99% of all skiers much less boat owners. Throngs of competitive skiers have attested to his mixing of apples and oranges and they all seem to agree the slalom wake is much improved while leaving the preferred trick wake unchanged. I certainly don't have the background to comment on the validity of his theory, but the outcome seems to have been universally applauded. According to Eric this modification may very well end up on Prostars in the near future.

I'm blown away most by his ability to believe enough in his idea to pick up a drill and uncork his own hull. That's pretty durn brassy!


JP :)

[thatsmrmastercraft]

Must have large (brass of course) cajones.

[TX.X-30 fan]

Ahhhhh. OK, so the benefit is the slip I talked about which allows for faster spin-up. Makes sense. I was running on thought experiments and had not surfed the web for it. Thanks.

The small hole through which the air line passes will not affect how the water "lets go" of the hull, so the effect is either ficticious or has another cause.




How do you get slip at first throttle, I assume the air is drawn in at greater volumes as the prop spools and speed increases??

[kkkeating]

Something does not match; the photos show the hole between the prop and rudder, so there's no way air is getting to the prop. There's no scupper under the boat, so I doubt much air is being drawn below, as I don't see a strong vaccum point. Plus, as air rises, I can't really see it leaving the bottom boat surface by more than a inch.

[Skipper]

I was told there would be no math?

[TX.X-30 fan]

I was told there would be no math?






Haaaaaaaaaaaaaaaaaaaa!!

[Jesus_Freak]

How do you get slip at first throttle, I assume the air is drawn in at greater volumes as the prop spools and speed increases??

I am defining "slip" here in the context of general particle physics: relative motion between the prop and surrounding water. There will normally be relative motion, i.e. the prop will always move somewhat faster than the surrounding water during periods of boat acceleration as well as during times of constant boat speed. The slip is greatest in the start-from-rest situation.

Something does not match; the photos show the hole between the prop and rudder, so there's no way air is getting to the prop. There's no scupper under the boat, so I doubt much air is being drawn below, as I don't see a strong vaccum point. Plus, as air rises, I can't really see it leaving the bottom boat surface by more than a inch.

To me, the hole looks to be above the prop. I have not studied it carefully, but it looks as though the injected air can indeed get pulled into the blade suction surface swept volume.

[captain planet]

I don't understand how drilling a hole in front of the prop to install a straw will improve the performance of the boat? The guy said that it took off 50 rpms from PP and made the wake softer. How does the air get sucked into the hole and why does that cause the propeller to be more efficient? How does that soften the wake?

It's a law of physics; a fluid passing over the end of a conduit creates a vacuum. The water passing over the end of the hole in the bottom of the boat creates a vacuum and pulls air through the hole.

[kawagaskier]

A hole placed perpendicular to the flow of the water would yeild no net pressure increase or loss in the hose attached to the hole, however because of the hole placement just ahead of the passing prop blades and the prop facing downward with respect to fluid flow would cause a vacuum pulling air in.

I wonder what happens when he reverses hard, does it blow water up the tube into the boat? I guess it depends on how long the hose is...

[captain planet]

A hole placed perpendicular to the flow of the water would yeild no net pressure increase or loss in the hose attached to the hole, however because of the hole placement just ahead of the passing prop blades and the prop facing downward with respect to fluid flow would cause a vacuum pulling air in.

I wonder what happens when he reverses hard, does it blow water up the tube into the boat? I guess it depends on how long the hose is...

It would depend on how fast the water is passing the hole. The faster it passes the hole, the greater the vacuum created. If it is real hard reverse, it will pull air as it does when it is going forward.

[kkkeating]

With the boat traveling at 30 MPH and with the hole behind the prop, there's no way air is getting to the prop nor do I see how the prop can cause enough of a vacuum to make a difference.60096

[dmminfla]

With the boat traveling at 30 MPH and with the hole behind the prop, there's no way air is getting to the prop nor do I see how the prop can cause enough of a vacuum to make a difference.60096

Thats not the hole see the drill bit in front of the prop.

[kkkeating]

Now it makes a little more sense

[TayMC190]

I am defining "slip" here in the context of general particle physics: relative motion between the prop and surrounding water. There will normally be relative motion, i.e. the prop will always move somewhat faster than the surrounding water during periods of boat acceleration as well as during times of constant boat speed. The slip is greatest in the start-from-rest situation.



To me, the hole looks to be above the prop. I have not studied it carefully, but it looks as though the injected air can indeed get pulled into the blade suction surface swept volume.

The slip kind of works like a 2 stroke theory... a 2 stroke dirt bike has its power from being able to rev faster to hold what is known as a power band. In this since by injecting a selected amount of air to the prop, it will allow as stated a larger more aggressive prop. This in turn will allow in theory more performance/ efficiency... It helps reduce the amount of friction to a level that won't affect the pull or torque.

I feel the guy has a valid theory and design... I'd be interested to see further testing... Could be on to something big for MC

[TX.X-30 fan]

I am defining "slip" here in the context of general particle physics: relative motion between the prop and surrounding water. There will normally be relative motion, i.e. the prop will always move somewhat faster than the surrounding water during periods of boat acceleration as well as during times of constant boat speed. The slip is greatest in the start-from-rest situation.



.



This even makes sense to me............ thanks JF.

[JohnnyB]

OK, who's going to drill a hole in their boat and post the test data for us?? :D

[kkkeating]

Can't we just take out the drain plug in the bottom of the boat, it'll save a lot of drilling! :rolleyes:

[ncskimore]

I am not sure if there is a relation to these modifications but Mastercraft made the following July 15th posting on Facebook regarding testing of a new technology called "Pureflow" at Lake Prior, TN. The video doesn't mention anything about the tests but feel free to check it out.

http://vimeo.com/12515119

"MasterCraft Boat Company: As requested, here is a ski video of Marcus Brown, Karen Truelove and Dorien Llewellyn shot by Jaret Llewellyn. Enjoy!! By the way, this was MasterCraft testing a new technology developed in house by one of our own engineers called PureFlow... more on that later.

MasterCraft X-14V Pro-Certified!
vimeo.com
Marcus Brown, Karen Truelove, Freddy Krueger, Dorien Llewellyn and Jaret Llewellyn come together to test some new products that MasterCraft is working on. After the work is done the boys pull out the ultimate crossover boat for a little fun. X-14V is the only v-drive that is approved to pull WORLD ."

[Jesus_Freak]

It's a law of physics; a fluid passing over the end of a conduit creates a vacuum. The water passing over the end of the hole in the bottom of the boat creates a vacuum and pulls air through the hole.

Yes, but technically, it is not a law of physics (nor is it related to Bernoulli). It is caused by the momentum of the water boundary layer passing over the hole. The boundary layer separates form the hull at the hole, creating a void under it that can only be filled by the air.

A hole placed perpendicular to the flow of the water would yeild no net pressure increase or loss in the hose attached to the hole...

Sorry dude, could not be farther from the truth. ;)

It would depend on how fast the water is passing the hole. The faster it passes the hole, the greater the vacuum created. If it is real hard reverse, it will pull air as it does when it is going forward.

Yes, regardless of the direction (assuming the hole is perpendicular to the hull bottom), there is a speed threshold above which air is pulled into the water. Below this threshold, water will actually enter the hull.

[Jesus_Freak]

I am not sure if there is a relation to these modifications but Mastercraft made the following July 15th posting on Facebook regarding testing of a new technology called "Pureflow" at Lake Prior, TN. The video doesn't mention anything about the tests but feel free to check it out.

http://vimeo.com/12515119

"MasterCraft Boat Company: As requested, here is a ski video of Marcus Brown, Karen Truelove and Dorien Llewellyn shot by Jaret Llewellyn. Enjoy!! By the way, this was MasterCraft testing a new technology developed in house by one of our own engineers called PureFlow... more on that later.

MasterCraft X-14V Pro-Certified!
vimeo.com
Marcus Brown, Karen Truelove, Freddy Krueger, Dorien Llewellyn and Jaret Llewellyn come together to test some new products that MasterCraft is working on. After the work is done the boys pull out the ultimate crossover boat for a little fun. X-14V is the only v-drive that is approved to pull WORLD ."

Didnt see anything real useful here, but man do I love skiing that lake. I have set PBs there almost every time. I wish the water were a little deeper at the island, however.

OK...back on topic...

[TayMC190]

A hole placed perpendicular to the flow of the water would yeild no net pressure increase or loss in the hose attached to the hole, however because of the hole placement just ahead of the passing prop blades and the prop facing downward with respect to fluid flow would cause a vacuum pulling air in.

I wonder what happens when he reverses hard, does it blow water up the tube into the boat? I guess it depends on how long the hose is...

Actually it would, air has density of air to water is way less. Taking the path of least resistance would pull air from the tube, It may not be an astronomical amount but be enough to create the desired effect. I'm not saying this system works but It holds enough value to be tested. I believe there is a chance of improvement from this system.

[Sodar]

They have been aerating props on offshore boats for longer than I have been alive. I can't find a good pic, but here is an 18" x 2" tube on a #6 drive....

http://pictures.dealer.com//lakecumberlandmarine/ee4093a14046387201292ba7c2486129.jpg

[H20skeefreek]

I have tried 10+ times and I've never gotten that video to work.

Didnt see anything real useful here, but man do I love skiing that lake. I have set PBs there almost every time. I wish the water were a little deeper at the island, however.

OK...back on topic...

[etduc]

I have tried 10+ times and I've never gotten that video to work.

Worked for me. You may need a plug in, or check you security levels.

[H20skeefreek]

the first 9 seconds work, after that it just stops.

[etduc]

the first 9 seconds work, after that it just stops.

Hmmm. (Beyond my pay grade. ) That 14v has an amazing slamon wake, for a v-drive.

[joecarew3]

the first 9 seconds work, after that it just stops.

Worked for me too. Awesome video, I could watch it a thousand times! Prolly the coolest Mastercraft Video Ever!:rolleyes:




Your not missing much!