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Need help with Rudder Designs
- Thread starter pamarine
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I know it's old as dirt, but I went down a rabbit hole and wound up here, then found the SNAME article AdHoc was referring to so I wanted to link to it in case anyone else is looking for it.
http://www.sname.org/HigherLogic/Sy...tFileKey=08951178-613f-4e47-a762-5b272c4c92a1
http://www.sname.org/HigherLogic/Sy...tFileKey=08951178-613f-4e47-a762-5b272c4c92a1
ToMeK
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Hello everyone,
Dealing with rudder design at the moment, I am trying to find reference @Ad Hoc mentioned in one of previous comments. It is:
The performance of High-Speed Rudders in a Cavitating Environment by Gregory & Dobay; 1973
I searched everywhere, including SNAME small craft papers I bought from SNAME but I could not find it since it is earlier year.
May I kindly ask someone who has a copy to share it with me if possible.
Many thanks,
Tom
Dealing with rudder design at the moment, I am trying to find reference @Ad Hoc mentioned in one of previous comments. It is:
The performance of High-Speed Rudders in a Cavitating Environment by Gregory & Dobay; 1973
I searched everywhere, including SNAME small craft papers I bought from SNAME but I could not find it since it is earlier year.
May I kindly ask someone who has a copy to share it with me if possible.
Many thanks,
Tom
jehardiman
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It was a paper presented at the 1973 SNAME Spring Meeting at Lake Buena Vista, Florida. You may need to go directly to SNAME (most likely as a member) for a reprint of the meeting papers to get a copy.
I remember SNAME being inexpensive, but that was a student membership many years ago. I didn"t actually need it, I'd just borrow someone else's PNA (Principles of Naval Architecture) on the very few occasions I needed it. And very little of my engineering experience, such as it is, has had anything to do with NA or ME.
It may be helpful to look at Hoerner's Fluid Dynamic Lift and Fluid Dynamic Drag. Mostly oriented toward aircraft, but a rudder is quite similar to an airplane's tail surface. There is a section on low aspect ratio wings which may be relevant for most keels and rudders. Some things that are different in the water: free surface effects, such as wakes or ventilation. This would be quite relevant for a transom mounted rudder, such as on some Cape Cod Catboats and many dinghies. It isn't very relevant for a rudder on the bottom of a hull, significantly below the surface. Cavitation doesn't happen to air. It also doesn't happen to slow boats. I think there may be something else I'm forgetting right now. In the water, one generally doesn't have to worry about Mach effects aka compressibility or large changes in density, which can be very different as an airplane changes altitude. In any case, if you don't want to find or buy the Hoerner books, they can be found here: Fluid-Dynamic Drag : Sighard F. Hoerner : Free Download, Borrow, and Streaming : Internet Archive https://archive.org/details/FluidDynamicDragHoerner1965/page/n19/mode/2up
There is also
ntrs.nasa.gov
Many of the references Hoerner quotes can be found here. Also chase down "The Magic NACA Archive", which can be found in several places, one of them taken over by something with a name like Cranfield. Cranfield has a bunch of other good stuff. Additionally there is a US military site with a bunch of useful stuff. DTIC or something like that. Maybe it has navy papers in it.
That's probably more than you need. There is a simple equation for induced drag which I think has only one fudge factor. One trap to remember is that, usually, actual induced drag is determined in part by span, rather than aspect ratio.
It may be helpful to look at Hoerner's Fluid Dynamic Lift and Fluid Dynamic Drag. Mostly oriented toward aircraft, but a rudder is quite similar to an airplane's tail surface. There is a section on low aspect ratio wings which may be relevant for most keels and rudders. Some things that are different in the water: free surface effects, such as wakes or ventilation. This would be quite relevant for a transom mounted rudder, such as on some Cape Cod Catboats and many dinghies. It isn't very relevant for a rudder on the bottom of a hull, significantly below the surface. Cavitation doesn't happen to air. It also doesn't happen to slow boats. I think there may be something else I'm forgetting right now. In the water, one generally doesn't have to worry about Mach effects aka compressibility or large changes in density, which can be very different as an airplane changes altitude. In any case, if you don't want to find or buy the Hoerner books, they can be found here: Fluid-Dynamic Drag : Sighard F. Hoerner : Free Download, Borrow, and Streaming : Internet Archive https://archive.org/details/FluidDynamicDragHoerner1965/page/n19/mode/2up
There is also
NASA Technical Reports Server (NTRS)
That's probably more than you need. There is a simple equation for induced drag which I think has only one fudge factor. One trap to remember is that, usually, actual induced drag is determined in part by span, rather than aspect ratio.
True, but I think there are many papers in there which you don't have to be a post-graduate student to get some understanding out of.
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