Opinions for Underwater Exhaust Deflectors

As the underwater exhaust deflectors in WET EXHAUST SYSTEMS are a very common practice nowadays, indeed only few are sure wether they work or not, I would really appreciate If somebody could submit any experience regarding these systems

the exhaust deflectors are laminated in wet systems and consist of a longitudinal device like "spray rail" , their length is six times the diameter of the under water exchaust. their purpose is to deflect the exhaust gases away from propellers.

in the following photo you can see the STBD deflector of our Yacht which is currently in the Italian Shipyard

Don't you see that these devices have nothing to do with the wedge and the turbulence which is created by them?

-Exhaust thrust slot.

Just to put the things in order the device's you are referring as ventury, correct term is Exhaust Thrust Slot and invented by Cpt. George Vonwidmann (the wet exhaust system)

It is trent now in almost all Italian Shipyards to install them in wet exhaust systems. The exhausts gases as vacuumed to the sea (when yacht is underway) form a gas layer (covering the underwater keel of the Yacht above seawater – as the specific gravity of the gases is less that seawater special gravity) which is then sucked by the propellers. This phenomenon creates turbulence to the propellers area and thus cavitation and vibration. In order to eliminate this phenomenon designers are incorporating underwater exhaust deflectors. These deflectors, in the form of laminated curved spray-rails, begin from the under water wedge (the side of wedge which in near the keel) and run curved to the bow. The length of the exhaust deflectors is 6 X Diameter of the Slot, the Height is equals to the height of the wedge and turns to zero at the end point. The end point is located in the same line with the centre of the slot.

As a consequence the exhaust gases are driven away from the propellers to the sides of the Yacht. These structures do no affect the drag or resistance of the Hull.

K1W1 devices like these are absolutely necessesary also in case that somebody wants to install interceptors.

In our Yacht even though we hadn't considered the deflectors value in conjuction with the Interceptors, indeed when the engineers of the interceptors company saw that the Yacht was featuring these devices they were very happy.

Below is a rough made drawing showing the correct dimensions and layout in respect with the slot

of course the dimensions there refer to our Yacht.

Below a photo taken during their lamination. You can see their layout in respect to the shaft tube and shaft bracket