- Sep 14, 2018
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.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
I'll try to understand this in my gameplay timeprops 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.