Additive loft - draw vessel's hull

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nen1981
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Additive loft - draw vessel's hull

Post by nen1981 »

Good day,

I would like to draw a hull of a ship. Prepared transverse frames / sketches. Unfortunately I am unable to make it solid. Tried to proceed via loft functions, surface sections and etc but failed...

I am unable to connect it with loft because of different quantity of segments. Unable to cover with surfaces because some of them are twisted. Would be much obliged for any assistance

thanks in advance

freecad version 0.20.
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изображение_2022-10-04_141329022.png
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onekk
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Re: Additive loft - draw vessel's hull

Post by onekk »

You could decide a number of segments and make all the profiles with this number.(except for the point at the end).

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Carlo D.
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nen1981
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Re: Additive loft - draw vessel's hull

Post by nen1981 »

Thank you, will try to correct the sketches.

By the way, what is the reason of such kind of artefacts on the loft? It appears only in case I connect more than 4-5 sketches in loft....
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изображение_2022-10-04_181006398.png
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onekk
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Re: Additive loft - draw vessel's hull

Post by onekk »

Simply the fact that segments are not spreaded with some regularity across the sections.

See maybe:

https://wiki.freecadweb.org/Part_Loft_Technical_Details

and:

https://wiki.freecadweb.org/Part_Loft#L ... plications

For some technical advices about Lofting.

Even if it is amrked a Part Loft, technical details are valid even for PartDesign WB, see second link, it cite explicitly:
PartDesign Sketches

The profile may be created with a sketch. However only a valid sketch will be shown in the list to be available for selection.
The sketch must contain only one open or closed wire or line (can be multiple lines, if those lines are all connected as they are then a single wire)
Loft is one of the ways to go sometimes a simple "ruled surface" with "carefully build" sections will make better results.

Take in account that many times what you design has to be made, and as example an hull probably could be made with "piece of steels" so some "welding lines" or some other "common line" could make a good idea even when modelling in 3d, to place maybe "segments points" in a "cross section" of an hull.

Regards

Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
- Learning how to model with scripting.
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papyblaise
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Re: Additive loft - draw vessel's hull

Post by papyblaise »

some general advice:
-the sections must be drawn in the order of their use (not obligatory, but recommended)
- the sections must be drawn on parallel planes and oriented in the same direction
-the sections must be drawn in the same direction, in the same direction, and have the same number of segments (this point is very important)
-in the numbering of the sections follow each other to avoid selecting them with the dowsing rod
in my attached file, I manage to make some length, but it is necessary to redo the junction sections
when a novice embarks on such a project, do it slice by slice between 2 or 3 sections maximum

Edit :after some additional investigations, I see that the central sections which do not have a very smooth loft are made of B-spline in zig-zag while a simple portion of elipse would suffice,
and especially constrain
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chrisb
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Re: Additive loft - draw vessel's hull

Post by chrisb »

nen1981 wrote: Tue Oct 04, 2022 3:10 pm By the way, what is the reason of such kind of artefacts on the loft?
Think of it like a wave running onto the beach. The more sections you have, the more likely you will hit such a "smoothness catastrophy".
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nen1981
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Re: Additive loft - draw vessel's hull

Post by nen1981 »

Thanks to all who replied. Your assistance was very useful. It seems I understood main idea. In any case I will once again correct the sketches for smooth outside shell. But the process is clear for now.
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изображение_2022-10-05_163002644.png
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hammax
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Re: Additive loft - draw vessel's hull

Post by hammax »

... using Gordon surface, less frames and equal sketch structures for generating a hull shape.


Hull_2.PNG
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hull_2.FCStd
FC.20.1
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Last edited by hammax on Thu Oct 06, 2022 5:46 am, edited 2 times in total.
freedman
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Re: Additive loft - draw vessel's hull

Post by freedman »

I'm not putting a challenge on this but it would be interesting for someone to do a bulbous bow.
https://en.wikipedia.org/wiki/Bulbous_b ... rydock.jpg
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papyblaise
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Re: Additive loft - draw vessel's hull

Post by papyblaise »

even that, it has already been done ... VincentB was still called Glouglou :lol:
a few days ago, we drew the nose of a submarine, it was enough to draw a container ship that hit one... :lol: :lol: :lol:
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