Posted by tmann45 on 07/25/14 - 7:29 AM
#9
lost sailor wrote:
ventilation is when your propeller drags air from above the water into the blade.
You know your propeller is ventilating when your forward speed drops as the engine revs up suddenly
Perhaps I'm misinformed but I thought that's what cavitation was? Like when taking a sharp turn at too high of a speed and the boat slows as the engine revs higher...
Cavitation is misused very often when it is actually ventilation as described very well above. And the flat plat above your propeller is better described as an anti-ventilation plate.
Cavitation is as per:
Merriam-Webster - the formation of partial vacuums in a liquid by a swiftly moving solid body (as a propeller) or by high-intensity sound waves; also : the pitting and wearing away of solid surfaces (as of metal or concrete) as a result of the collapse of these vacuums in surrounding liquid
Wiki - the formation of vapour cavities in a liquid – i.e. small liquid-free zones ("bubbles" or "voids") – that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to higher pressure, the voids implode and can generate an intense shockwave
There is no sucking of air from above the water level in cavitation.