Cavitation plates

[Sea Dog]

Cavitation can be had on several surfaces, like the rudder, or the hull above the propeller, and on the propeller itself (as said) so a plate at the bottom of the weed hatch tunnel can be called cavitation plate if you get any cavitation on it? Right

 

Not really right, no, but it probably doesn't matter too much.

 

Think of cavitarion as the ripping of holes in the water - the resulting "bubbles" collapsing is what makes the associated noise. It can also cause damage to the prop, which some will have seen in high revving applications such as outboards. In applications where it matters, eg warships, one technique to overcome it is to inject air through tiny holes on the propeller which fills these cavitation "bubbles" and stops them collapsing. So you're actually using ventilating to combat cavitation! You can also get cavitation, as you point out, from a rudder or stabiliser fins if the vessel goes fast enough, sometimes known as rasp. Cavitation needs relatively high speeds to cause it, beyond what I think is achievable with any surface on a narrowboat.

 

So whilst anti-ventilation could be a better description of what it does, if the plate concerned is best known as a cavitation plate in narrowboat applications, any distinction is a bit academic and I don't think it matters that much as long as anyone concerned understands what you mean.

 

For what it's worrth, my experience bears out what Dot Piper said to Neil2 above and, on my Piper at least, I don't think I need one.