Quantcast

Propellers from asia...

Help Support intlwaters.com:

Carl Van Houten

Well-Known Member
Supporting Member
Vendor
Joined
Mar 6, 2011
Messages
1,151
Not that they don't work on something but I have never seen anyone using them.
 

PiroSteel

Well-Known Member
Joined
Jan 14, 2016
Messages
78
There are the power of the placebo effect or effective with low rpm of rubber engine

nice work and play
 

RobertDoak

Well-Known Member
Supporting Member
Joined
Sep 14, 2018
Messages
587
I do look at many videos from other countries and in the Malaysia and Vietnam area these seem common...also there hand cut but thats obvious. I would like to know about there efficiency...these to me look more like a screw pulling water than the typical prop that I'm used to seeing here in the States
 

Kevin Burns

Well-Known Member
Supporting Member
Joined
Jun 15, 2014
Messages
88
I do look at many videos from other countries and in the Malaysia and Vietnam area these seem common...also there hand cut but thats obvious. I would like to know about there efficiency...these to me look more like a screw pulling water than the typical prop that I'm used to seeing here in the States
props do pull water, they are called screws, screws don't really screw in, they pull wood towards the screws head, we just feel it as the screw is pushing inward but it's really just the opposite.
The water that is expelled (Pulling water) is what pulls water around our props. It's actually the front of the prop that pulls our boats forward, the more water one can expel the more faster the water moves in front across our prop the greater the suction. So our props pull water not really into our prop but across and around our blades.
The faster water moving on the front side of the blade is what propels our boats forward, "The faster water sucks our prop threw the water ("Lift" much like a wing on a airplane) The slower water on the cup/back side of our props is why the water moves faster on the front (Again much like airplane wing) This is why we polish the front side of the blades and don't polish the rear/cup side of the prop, the rough back/cup side of the blade is to lower friction and limit cavitation. Cavitation is from the slower water moving across the blades of the back/cup side of the prop creating drag, drag makes friction, friction makes heat, cavitation is caused from heat, boiled water. The boiled water limits the speed in that the water is pulled into the prop do to the heat bubbles "less dense water" (the water simply breaks up and the speed of water lowers). This is why some people de-tongue props, to limit cavitation, they just don't know it and call it slipping. A trick is to put a water pick up in the mid section of the hull and expel fresh cold water in front of the prop to help with the heat that the cup side produces. Much like an airplane wing the bottom of the wing gets hotter than the top do to drag of the air, whereas the top of the wing has very minimal drag and the wing is sucked upward. our props work just the same. thrust the rooster tail is not what pushes our boats forward, the rooster tail is what pulls water to the prop.
 

PiroSteel

Well-Known Member
Joined
Jan 14, 2016
Messages
78
props do pull water, they are called screws, screws don't really screw in, they pull wood towards the screws head, we just feel it as the screw is pushing inward but it's really just the opposite.
The water that is expelled (Pulling water) is what pulls water around our props. It's actually the front of the prop that pulls our boats forward, the more water one can expel the more faster the water moves in front across our prop the greater the suction. So our props pull water not really into our prop but across and around our blades.
The faster water moving on the front side of the blade is what propels our boats forward, "The faster water sucks our prop threw the water ("Lift" much like a wing on a airplane) The slower water on the cup/back side of our props is why the water moves faster on the front (Again much like airplane wing) This is why we polish the front side of the blades and don't polish the rear/cup side of the prop, the rough back/cup side of the blade is to lower friction and limit cavitation. Cavitation is from the slower water moving across the blades of the back/cup side of the prop creating drag, drag makes friction, friction makes heat, cavitation is caused from heat, boiled water. The boiled water limits the speed in that the water is pulled into the prop do to the heat bubbles "less dense water" (the water simply breaks up and the speed of water lowers). This is why some people de-tongue props, to limit cavitation, they just don't know it and call it slipping.A trick is to put a water pick up in the mid section of the hull and expel fresh cold water in front of the prop to help with the heat that the cup side produces. Much like an airplane wing the bottom of the wing gets hotter than the top do to drag of the air, whereas the top of the wing has very minimal drag and the wing is sucked upward. our props work just the same. thrust the rooster tail is not what pushes our boats forward, the rooster tail is what pulls water to the prop.
I'll try to understand this in my gameplay time

Thanks
 

Kevin Burns

Well-Known Member
Supporting Member
Joined
Jun 15, 2014
Messages
88
Thrust from the cup side of prop pulls water towards the front side of the prop. Thrust is actually flowing off the prop at a slower rate than the oncoming water at the front side.

The water that is sucked “Pulled” into the front side of prop is moving faster than the thrust because the water on the cup side is getting cupped “Slowed down”, heated from drag (This is why we don’t polish the cup side) to limit heat causing drag and not creating cavitation (Boiled water), all that on the back side/cupped side lowers the speed of the water. Cavitation is boiled water; boiled water is less dense than cold water. The more cavitation the less the prop pulls water into the prop “Really around the prop”. Have you ever noticed when you place your hand behind a turning prop you don’t feel the thrust in the palm of your hand; this is designed this way to fan out to be able to pull water from the front side and around the prop. The water that is moving faster on the front side of the prop in essence never really touches the prop so a Micro Minuet space is between the front side of the blade and the water; this creates a suction that pulls the prop forward. This is why we polish the front side to get maximum suction to the blades to maximize forward momentum. This suction is called “Lift”. We know lift with airplane wings and an arrow pointing upward; now with a prop the arrow showing lift, points forward. heli blades, same thing but the arrow points up

Airplane props and submarine props are long thin blades, why?

Cavitation is why.

Airplanes use long narrow (De-Tongued) blades to limit cavitation to get a higher volume of air moving around the front side of the blades, cavitation is not only in water but air as well. To prove this: have you ever heard the sound of a prop plane diving? Yeah that high pitch sound is the air actually hitting the prop, in a dive the plane is simply going beyond what the trust of the prop can suck/pull around the blade and the lift effect is lost so the tiny space between the air and front of prop is gone so the higher pitch sound is the air hitting the prop is all.

The submarine uses long de-tounged blades simply to stop cavitaion “Boiled water” (Bubbles from the boiled water) that can give away the position of the sub.

De-tonguing a taller diameter prop that would normally be needed is to remove surface area to limit or lesson cavitation (Less of a cup, less friction, less heat, less cavitation) a higher rate of water from more dense water that equals more thrust that equals a better pulling power to pull water into/around the prop, so the more water we can get to passes in front and around the prop, the more forward suction “lift”, the faster the boat. The narrow blade yield less area wideness wise, so less heat is generated as the blade is not as wide. The prop is not slipping, it's not creating as much cavitation so the flow of water into/around the front side is greater, so the engine has to work less (Efficiency) and thus higher rpm.

This is why when we put our boat in the water it takes a split sec to spool up and go. The thrust is working to suck/pull water into the prop and the sec it takes is the suction on the front side growing. When we first put our boat in the water the front goes up, that is the cup scooping water, this pulls the transom down, not forward, if you really look there is no rooster tail yet, once the boat levels out the flowing water is now creating forward lift that overpowers the cup effect and the transom rises, the cup is not propelling the boat. The front of the prop is because it took a split sec to build/generate the lift (Get the water flowing around the prop). When the boat is in a wheelie the boat isn’t really moving, the cups pull the prop down and the bow lifts up, but your not really moving forward what you’re seeing is a jump between the cup gulp and the suction/lift. The movement you’re seeing is the time it takes to get maximum forward lift, your watching the water build turbulence, this is why boats start out slow and gain speed(2 feet or so). The rear of the prop is not what pushes the boat forward, it does however pull the transom downward, the front side forward lift is what pulls our boats, any boat, airplane forward. This is also why you toss forward a outrigger or hydro to start the flow of water into the prop.
Same as a jet engine, it is not the heat out the back that pushes the jet forward, that heat sucks air into the turbine blades, again forward lift.

Boats barrel roll when forward lift is lost and the cup side of the prop digs in, the transom goes down, the bow lifts and the cup “For lack of better words” gets stuck (takes a scoop of water) because the cup scooped water greater than the engines output so the hull spins. the engine can't turn the prop so the hull spins. Again because the back of the prop does not propel the boat.

As far as the water trick to cool the water via a water pickup and dumping it on the prop. This is not a new trick, example: A torpedo uses a small diameter high pitch prop (Very high cavitation) do to small size of vessel. This dumping fresh water on the hot prop is to limit cavitation "Increase the flow of water" into/around the front side, not to hide the torpedo but to make the prop more efficient do to limited fuel supply, and speed. :Greater range from less cavitaion...efficiency. The boiling water from cavatation is less efficient at pulling water into/around the front side of the prop.

A cavitation plate, it simply takes the boiled (The slap of hot water on the plate cools it a bit" and mixes it with colder water spraying up from under the hull, and dumps it back onto the prop, to lower the heat of the water coming of the prop. To limit cavitation to enhance thrust to enhance turbulence to get the fastest water possible to flow in front and around the prop. Thrust (Rear side) is what pulls water into and around our props; thrust does not propel the boat, forward lift from the front side of the prop does.

Asian props simply focus the thrust in a more tight circle to increase turbulence "Water flow"= pulling power at a smaller diameter. The props are longer to account for the small diameters. Keeping the lift area. Plus a small diameter prop will allow the boat to turn tighter at higher speeds. Watch a race and notice the speeds they 90* those boats. Those props are for right/left turn courses. "Offshore" style.
 

RobertDoak

Well-Known Member
Supporting Member
Joined
Sep 14, 2018
Messages
587
Kevin
Thank you for the lesson ...i really had no idea that there was so much going on when the prop hits the water....
 

Thomas Hulbert

Well-Known Member
Joined
Jul 2, 2005
Messages
478
Those props might be for a flat bottom style boat they run in thialand etc .

Long tail as seen in a bond movie ( man with the golden gun ).

Also some vid of them on utube yet not much prop pics. They drag them in the vids I have seen
 

RobertDoak

Well-Known Member
Supporting Member
Joined
Sep 14, 2018
Messages
587
Robert...
Being I'm a red blooded American and believe in buying American when ever possible....i will let someone else take the plunge...
 

Christian Lucas

Well-Known Member
Joined
Aug 23, 2012
Messages
308
Hi,
yes this type of propellers have interesed me a long time and as it was not easy possible to get them i have starte to build them by myself. So the result looks not so bad and the first try workes well.
Robert , all Robert here , so no need to buy outside US , do it yourself is the best way . You can style the propeller like you want and you learn a lot how to do. I start with a berrilium copper plate cutting the outline with a plate cutter. To get the blade with an angle of attace i cut a slot in the middle of the plate and made a hub with a cone on one sind of it. Now i can slide the Plate ofer the cone that give the propellerblade a angle of attace. Then i soft solder it and when cool down i can trim the shape by a hammer and different dia round steel parts. That will give the typical blade shape where the leading edge is roundet parallel to the propshaft axis or with a low angle . This style of propellerblade will force the water from out to the inner part and as there is no room it will accelerated to the trailing edge with high speed out. There are some realy nice videos on youtube,
and with singel prop,

They are realy cool,with the open design , no tape to make the boat waterprofe. lots to learn from the other world.

Happy Amps Christian
 

Attachments

Latest posts

Top