nacelle pods & catamarans

[Oceansurfer]

I have recently finished construction of a 'Wharram type' cat. It's powered by an outboard mounted in a central nacelle pod, about 2/3's of the way back from the bows. Even though the outboard cavitation plate is 20 cm below the static waterline, the propeller still sucks air and cavitates when running at speed.

I'm considering a prop guard/kort nozzle kind of attachment around the prop to contain the thrust, but questioning whether it'll do any good.


Any insight would be greatly appreciated

[boatsmith]

piccies please

[atoll]

you need to use along shaft sail drive type outboard,a normally pitched outboard with a short shaft is not going to cut the mustard

like this

http://www.yamahaoutboards.com/outbo...hrust/overview

[Oceansurfer]

Yeah atoll, thanks for that... We're using an extra long shaft and have already tried a large 14" x 11" Yamaha Dual Thrust prop (which didn't do jack)

I think Valhalla and StuM hit it on the head with the changing position of the colliding bow wakes and troughs as speed increases

We're going to try a couple of things and post the results