lateral plane area and twin rudder

[Filip Patcev]

Hi,

I have design of small sailboat with twin rudders but hydrostatic report doesn’t include rudders in lateral plane area. When I have single rudder in the center than it works. But I need twin rudders. Any suggestions?

Thanks.

[Marven]

1. Place the rudder on the center and double the calculate area
2. Ignore the rudder, and manually add the area. I beleice the planform area is also displayed in the keel/rudder wizard

[otaku]

Interestingly, last night i found that on my twin-rudder model, reducing the gap of some 3 feet between the hull and the rudder decreased the resistance. I am not using a single rudder with doubled surface, since i’m designing a twin-rudder ship and want to have the rudders exported as .dxf and other formats.

So, is there something beneficial going on that we aren’t appreciating?

[Filip Patcev]

Marven, thanks for your answer but one more question: in which way is calculated center of effort of lateral plane – is it geometric center or some other method (hydrodynamic, etc.)?

[Marven]

Hi Filip,

DELFTship uses calculates the geometric center of the longitudinal section on the centerplane. Only the hydrostatic layers are used for this section, so most likely that would be the hull, keel and rudder.

[Author]

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