Claudio Valerio Parboni
Junior Member
- Joined
- Jul 17, 2018
- Messages
- 17
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- Location
- Roma
Dear All,
I am currently facing the task of sizing a twin rudder system for a sailing yacht.
My current method has been to heel the boat at an expected heel angle (IE 20°) and establish an ideal value for lead, then size rudder area (projected on the heeled plane) based on said lead.
I am using the Nomoto method: (Extend the keel to the DWL to account for hull contribution, use a rudder reduction factor of 0.4 and take the individual CLRs about the foil's quarter chord line). This is mentioned both in Principles of Yacht Design and Fabio Fossati's Aero-Hydrodynamics book.
I am not entirely sure on this method since in these books it only mentions single rudder systems, I also immagine that a rudder which is offset to leward will produce a "bear-away" moment, thanks to its own drag and I am not sure how much it contributes to lead calculation (probably very little).
I have searched a bit on the past few days but I could not find much on papers nor on this forum.
wanted to hear your thoughts.
Hopefully I am just overthinking over a simple issue.
Cheers,
Claudio
I am currently facing the task of sizing a twin rudder system for a sailing yacht.
My current method has been to heel the boat at an expected heel angle (IE 20°) and establish an ideal value for lead, then size rudder area (projected on the heeled plane) based on said lead.
I am using the Nomoto method: (Extend the keel to the DWL to account for hull contribution, use a rudder reduction factor of 0.4 and take the individual CLRs about the foil's quarter chord line). This is mentioned both in Principles of Yacht Design and Fabio Fossati's Aero-Hydrodynamics book.
I am not entirely sure on this method since in these books it only mentions single rudder systems, I also immagine that a rudder which is offset to leward will produce a "bear-away" moment, thanks to its own drag and I am not sure how much it contributes to lead calculation (probably very little).
I have searched a bit on the past few days but I could not find much on papers nor on this forum.
wanted to hear your thoughts.
Hopefully I am just overthinking over a simple issue.
Cheers,
Claudio
