knozzels

[captword]

I know that they use knozzles on Tugs , trawlers and some small ships to increase effeicencey. they are displacement vessels. Is it possible if designed right to use them on planing vessels? I know that in tunnel boats that if you put a slight wedge in the end of the tunnel that you increase the speed and attitude ofe a boat. I know that a nozzel will create drag. Can the nozzle be done in a way that the gain will out weigh the loss from its drag?
Howard

[DaveB]

I think that nozzles are designed to maximize thrust at the cost of top end speed... I don't think that they could be used to improve speed on propeller driven craft. Having said that they are certainly used on waterjets. Without the nozzle, the flow isn't accelerated nearly as much and the vessels that they're attached to wouldn't be propelled nearly as fast.

Dave