Unusual Rudder Design, but is it any goodl?

[CaptainAB]

I took the attached photograph of a 40' shallow draft river boat whilst it was on the slip. It has a design of rudder I've not seen before.

Does anybody know anything about it? Does it have any special benefits maybe for low speed work or perhaps in very shallow water?

Curious

Alan

[Gilbert]

I will go out on a limb here and do a little guessing, but I think my guess will have some merit.
The central plate should have been adequate for most boats to get good control and maneuverability, although the horizontal plates that the port and starboard vertical plates are mounted on would have been better if they were on the top and bottom of the central plate.
However, the fact that the propellor is in a tunnel made the single plate less effective than if it were not in a tunnel. Apparently this is a vessel that requires exceptional maneuverability and so the port and starboard vertical plates were added to try to improve maneuverability. It must have made some improvement or they probably would have removed them. Having had no experience with a rudder like this, I can't really give you a good answer as to how effective it is.
You might try talking to the crew.

[Petros]

I would also guess this is an attempt to get more rudder authority without making the rudder profile any larger. It might also have the effect of vectoring the prop wash.

[Fanie]

Yes, almost like an open frame jet drive.

[MikeJohns]

I have to laugh sometimes, when it comes to rudders we see all types of experimentation. Nearly always detrimental wrt drag.

There is nothing to recommend the configuration shown, the drag penalty is very high for a number of reasons.

They would be significantly better off (far less drag and much more lift) using a semi balanced foil shaped articulated rudder.