Round chine hulls in Rhino

[shu]

Does anyone have experience fairing round chined hulls in Rhino?
By round chined, I mean a hull with fully developable topsides and bottom (flat in section), but a radiused chine. It seems easy to do hard chines or a fully rounded hull, but the immediate transition from zero curvature to a specific radius is giving me the fits.

[ludesign]

Originally Posted by shu

Does anyone have experience fairing round chined hulls in Rhino?
By round chined, I mean a hull with fully developable topsides and bottom (flat in section), but a radiused chine. It seems easy to do hard chines or a fully rounded hull, but the immediate transition from zero curvature to a specific radius is giving me the fits.

It probably does not help but this took ten minutes to model in TouchCAD. The intemediate part can be a radius or a smooth transformation. TouchCAD comes with a very powerful built in unfolding engine.

[cestes]

To do this in Rhino, create your hard chine from stem to stern as normal.

Next, use the pipe command with the same strar and finish radius to create the constant portion of your bilge radius, assuming you want a constant radius somewhere along the chine.

Next, use the pipe command with the same radius as the constant section at the aft end and a different radius (presumably, very small, approaching zero) at the forward end.

Now, join these two pipes together and trim the side and bottom to the joined pipes.

Finally, use the BlendSrf command to create the smooth transition.

If you don't like the transition, particularly at the bow, remove the blend, untrim the bottom and side, adjust the angle between the two and repeat the above.

Hope this helps.

[Wolverine]

Be careful. Straight topside and/or bottom section shapes are probably not developable. Some straight sections may be found in a developable surface but, more commonly, sections cut through a developable hull are convex (bulging outward) between sheer and chine and between chine and keel.

[cestes]

Wolverine: Nice thing about the method described is that you start with a pair of developable surfaces (presumably). The blend does nothing to change this. After you do the trim, what's left is still developable, just a little smaller. The blend then creates a surface between the two, which is tangent to each at the respective ends.