Creating frames using Rhino or other software

[Andrew Mason]

Originally Posted by marshmat

In Rhino, with the hull modelled as a NURBS surface or polysurface:
- On a new layer, create a plane in the front view, so that it extends past the boat on all sides
- Array this plane along the length of the boat with the desired station spacing
- OffsetSrf the hull- point the arrows inward and set the distance equal to the frame thickness. (If you're being picky, do another offsetsrf for the inside of the hull skin as well.)

Marshmat

You need to be aware that using an offset surface to get your constant frame web depth will give incorrect results when the hull skin is not parallel to the centreline of the boat. It will give the correct result for the skin thickness, and you will find the skin thickness deduction will vary around the frame based on the 1/cosine of the angle between the surface normal to the hull and the plane of the frame.

However, with web frames the result will be that the web depth will vary around the frame rather than being constant, and will be different at different frames, typically being greater in frames near the ends of the boat where the hull pinches in and less in the more parallel middle part of the boat.

[Raggi_Thor]

Normall you use offset surface to find the inside of the hull skin, the outside of the frames and the offset curve to make the inside of the frames.