Rudder design


I tried to replicate this tip of the rudder but find it very difficult.


Again this is a material from by reinhard siegel.

Four sided surface (tip of rudder) but somehow when i do it in rhino the surface has a very awkward twisting at both extremes (not professional). Any idea how to approximate reinhard’s rudder tip?

@davidcockey hello! Any idea? You’ve claimed to have some experience with MultiSurf from aeroHydro

Hint - does that rudder tip look like a boat hull to you?

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Most of the rudder I design use the following method quite successfully:

  1. draw a leading edge curve with tip radius.
  2. draw a trailing edge curve.
  3. import my favorite NACA thickness section and scale appropriately for a tip and root chord.
  4. sweep two using the the leading and trailing edge curves as the guides and root and tip chords as those to be swept along the leading and trailing edges.

I’ve included a couple of simple screen shots for your perusal; it’s something I did in 5 minutes for the purposes of this response.

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Hello @Robb! Good approach! Is it possible to round the creased edges at the bottom? Those creased edges produce unnecessary turbulence…

Also, would you mind uploading the file?


Consider the practicalities of the design before considering unnecessary turbulence.

Is this a high end race boat or a day cruiser?
Is it dry sailed or moored?
Can the creased edges be sanded round as a post process?
How will it be built, female moulds or glass over a foam blank?

Also consider whether the trailing edge should be sharp or blunt? Sharp TEs usually chip easily.

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If you round the trailing edge tip from the tip cord to the trailing edge as you suggest you are inviting early separation of water flow at that critical area. Take a look at this simple rudder I did some years ago for a thirty foot racing boat. This was an outboard rudder with a shape somewhat inspired by the work of the well known aerodynamicist, Burt Rutan. His typical wing and rudder trailing edges are even more pronounced than the rudder I’ve included in the attachment. I have used this shape in various aspect ratios quite successfully and achieved great results.

Give this type a try and I think you will find some good results. Regard, Rob

Annapolios Thirty outboard rudder only.3dm (214 KB)

Hi thank you very much! Very useful!