Hull Bow rounding Blend


Any clue on how to round the bow of a sailboat? There are many threads posted by reinhard siegel on ship surfacing

I dont like trimming and working within tolerance. image

The “problem” is that the blend is 3 sided. What Are its disadvantages?

hard to suggest alternatives without the file

The bow needs to be built as a separate surface of arc curvature or bezier curvature etc. The majority of it can be 4 sided as it descends below the water line. Where it comes to a point, build small three sided patch(s)
But thats the easy part. The bow section will have to smoothly transition into the side surface which requires a tangential match along the vertical length of the seam. Thats where you might want to consider grasshopper. This problem is much deeper water than it first seems. Most solutions are sub optimal.

Hello! I cannot share my model because my pc does not recognize my wifi so im writing with my Mobile. But can you attempt to build a boat or similar to show the grasshopper part?

Something like this

something like this maybe?


Anyways, is there any other alternative? Just curious. The simpler the solution, the better.

Thanks for the reference. I found the discussion by Reinhard Siegel on rounding stems and transitions in AeroHydro. I investigated AeroHydro a decade ago and had a copy for a while before settling on Rhino. My impression at the time was any geometry created in AeroHydro could also be created in Rhino though translating from AeroHydro terminilogy to Rhino terminology can be a bit challenging. Based on their claim AeroHydro may be much more history type “parametric” than Rhino.

Working with tolerance is inherent in NURBS surface modeling though the user may not be aware of it. There are a few exceptions such as working exclusively with untrimmed single span surfaces and being very careful with control point locations and differences in degree between adjoining surfaces.

It is difficult to avoild trimming in surface modeling, and frequently methods used to avoid trims result in considerably more complexity and/or singularities than going ahead and using a trimmed surface.

One method for creating rounded stems is to use fillet surfaces. Experiment with FilletSrf and VaribleFilletSrf. FilletSrf in V7 offers G2 blend surfaces in addition to circular fillets.

Another approach is to build the base surfaces with the edges not touching or trim the base surfaces, and then build blend surfaces using BlendSrf or VariableBlendSrf.

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This is surfacing - you got: GOOD - FAST - SIMPLE Pick any two…
In this case you want simple and fast, so it wont be good.
If you want good and simple, it wont be fast.

These are just the realities of entering a technical discipline where the creators of the tools are genei that detest writing manuals for newbies, and far beyond caring if the path to results has breadcrumbs along the way to keep you going.

When you give simple things to a computer, you allow it to perform more efficient than complex. Every system likes simpler solutions, in mathematics and even in engineering. And like david says, the simpler also results harder to achieve. In maths for instance, there are problems that unfortunately can only be solved with complex calculations like calculus, were uncertainty and errors are guaranteed. try solve them with simple algebra, so difficult that some of them almost impossible.

In engineering, ww2 german handguns like Luger or even japanese Nambu had such complex mechanism that were unworthy for battle since the mechanism usually failed because it was very fragile. Not ideal. American handguns were opposite, simple mechanism and did perform better. In case of revolvers, the mechanism is so elementary that the system itself allows to be more “perfect” than other systems. Thats my philosophy. I do not need you to think the way i do.

The simpler, the harder to achieve but the better it results.

This tutorial might help:

To get a similar shape to the one in that photo I’d approach it like this - the side is a primary surface, everything else is just a blend off of that, and one trimmed corner.

BowTrimmedCornerNoBiggie.3dm (105.3 KB)

Hello gentlemen,

Is it possible to make something like this? Something editable and simple.


Hello sky! Im currently without wifi so im not able to open file. Later perhaps but thanks!