Ship hull kinks

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 From:  JPBWEB
4589.1 
Hi guys,

I am working on a ship hull, a T3 Fleet Oiler of the US Navy, using my usual method of basically Network command to generate in one go the entire half ship. This works quite well (see below) but there is an unwanted kink showing in the bow area. There are several ways to handle this, such as using a blend between the two halves, like in the stern, where a kink is wanted by the way. But surely, Network should work well with such simple flowing curves. The curves over there are smooth, fair and all that and there should be continuity from one side of the hull to the other. Such continuity happens correctly with the flat bottom. I really wonder why. Any thoughts ?

I also include the 3dm model for illustration purpose.




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 From:  Michael Gibson
4589.2 In reply to 4589.1 
Hi Jean-Paul - the part that is not so simple with your Network is the sudden 90 degree turn of the section at the end.

You've got several curves approaching that all in similar positions:



Then suddenly the end one is in a much different orientation to the others:



That sudden shift in orientation is going to make that area complicated.

Think of it like Loft (which Network is similar to in several aspects) - just because you have simple flowing curves doesn't necessarily mean that a loft through them is also going to be a simple shape if they have violent sudden changes in orientation between each of the sections...

You might try making the network not quite come all the way to the tip, maybe try to only model up to a 45 degree angle at the end instead of a full 90 degree sudden turn at the end. Then that might be more natural to put in a blend in that area between the 2 halves to complete the shape...

But compression or sudden changes in orientation will tend to apply a lot of constraint pressure on the generated surface in those areas and that tends to make for a type of bunching effect.

- Michael

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 From:  bemfarmer
4589.3 
I call that the sonar bulge.
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 From:  JPBWEB
4589.4 
I reworked the model towards a more extensive but still faily 'natural' or intuitive network of curves, with much better results. The bottom is very flat, and the bulbous bow is smooth as desired.



There is still a very annoying but barely detectable kink near the bow, probably due to the pointy shape of the lowest closed curve. That should be easily fixable.



It is quite amazing what can be achieved with one single network of curves. But the party is not over yet. The stern side is a bit messy still, and will require more attention, and a first check back to the blueprint seems to indicate that the shape of the hull is broadly in line but quite systematically wider. I suppose that a tightening of the tolerance of the network command (that Rhino provide but MoI does not yet) should help with that.

But overall, I find this quite encouraging, I'd say.

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