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A ship's hull ....

Posted by Replace 
A ship's hull ....
October 13, 2016 08:15AM
For a friend of mine, who recently has been promoted to command a naval patrol vessel, I would like to build her (!) ship as a miniature in a bottle.

There is enough photo material of that ship available and I am confident that I can design all upper structures with my moderate skills in OpenScad,
but I am afraid that the hull will be a problem.

Has anyone ever designed a ship's hull ?
What would the 'plan of attack' be ?

It is not a simple addition of cubes and spheres.

Maybe try to manually design a number of cross sections and hull them together ?
It will probably not be fluent.....

Any help is appreciated
Thomas


www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
Re: A ship's hull ....
October 13, 2016 10:38AM
Why don't you post a photo where we can see that particular ship's hull. Not all ship hulls are the same, so having an image would help us to understand what you are trying to do.
Re: A ship's hull ....
October 14, 2016 03:21AM
This is the vessel.....



Edited 2 time(s). Last edit at 10/14/2016 03:22AM by Replace.

www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
Re: A ship's hull ....
October 14, 2016 04:59AM
I'd probably start by designing the shape of the (thin) frames at regular intervals along the length of the ship (just as you would do when physically constructing the vessel), and then use the "hull" function to connect them. You only need to construct one side, then mirror the half-hull to create the whole. If you can work out a general set of shapes for each frame, you may be able to use a loop that increments or decrements the parameters of the shapes in a regular sequence as it progresses along the length of the ship. Maybe in 3 sections - prow, forward section and aft section. This would enable you to easily construct more frames with closer spacings so the result is smoother. My suggestion for the frame shapes would be to approximate by having 2 or 3 chines. Assuming the length of the ship is oriented in the Y direction, the keel will be fixed in X, giving you the zero reference for the X position (bottom of lowest chine), and the top of the top chine is the deck line which gives you the zero reference for Z. Y is the station position of the frame, given by the loop counter. Your variables for each frame are then the radii of the curves between the chines (could be negative if there is a reverse curve or "hollow"), and the X & Z positions of each chine - possibly easiest to pick up those variables by interpolation from a table. You then make a module that constructs each frame shape from those few variables - start at deck & first X, curve of (radius1) to 1st chine X,Z position, curve of (radius2) to second X,Z chine position etc.

Dave
Re: A ship's hull ....
October 14, 2016 08:33AM
Watch out, the shape of this type of ship hull is not entirely convex, so if you use OpenScad's convex hull() function, you will be loosing the convex "cavities" in the front part of the hull.
Re: A ship's hull ....
October 14, 2016 08:50AM
Ok, thanks.
just as I thought. (I did not know the word 'frame' so I wrote cross-section.
I will try to get hold of the frame design and start from there. thanks for the confirmation of the approach.

I did not understand the chine part... sorry

Is it true that the hull, if applied to f.i x100 frames, will follow the outlines of all of them ?

And if it is not smooth, just put more frames in between ?
Sounds easy, if I have the first frame :-)


www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
Re: A ship's hull ....
October 14, 2016 02:12PM
Maybe you're overthinking this...

Probably no-one (including your friend), except for a handful of naval architects, knows what the shape of the hull below the waterline actually is. So some generalised approximation is going to be perfectly acceptable. Look for a hull of a similar sized and performing ship, and it will be near enough.

Or maybe just ignore the whole issue and present your friend with a waterline-up model?
Re: A ship's hull ....
October 14, 2016 03:54PM
Yes,
I will either make the underwater section up, or I will put water around it :-)


www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
Re: A ship's hull ....
October 15, 2016 04:31PM
On Thingiverse there's an OpenSCAD boat generated using Bezier curves ... I'd start from that and adapt.

In fact, a search of Thingiverse for Bezier curves and OpenSCAD gives lots of results...
Re: A ship's hull ....
October 15, 2016 06:30PM
Is it a secret that this is a
Holland class offshore patrol vessel of the Royal Netherlands Navy
[products.damen.com]





Turbosquid has model

[www.turbosquid.com]

confused smiley
Re: A ship's hull ....
October 16, 2016 05:05AM
It is less a secret than might be exected.
You can google images from the hull sections being transported out of the factory , to be asembled elsewere.

Thanks for the link.


www.3daybreaker.blogspot.com

Orca V4.4 rebuild to Ramps with Mk8 and E3D, as well as a Rostock Delta Mini and an OLO in backorder :-)
Re: A ship's hull ....
October 17, 2016 07:53AM
Quote
Replace
Ok, thanks.
just as I thought. (I did not know the word 'frame' so I wrote cross-section.
I will try to get hold of the frame design and start from there. thanks for the confirmation of the approach.

I did not understand the chine part... sorry

Is it true that the hull, if applied to f.i x100 frames, will follow the outlines of all of them ?

And if it is not smooth, just put more frames in between ?
Sounds easy, if I have the first frame :-)

I was using terms that were used in the wooden yacht I built many years ago. The "frame" is the cross section at each station, these are built first and mounted on a "strongback" (looks like a horizontal ladder), and then "stringers" (long thin wooden batons) are run along the frames, and then planking or plywood hull is fixed over that framework.

"Chines" are lines running along the hull from bow to stern where the angle of the hull makes a marked change. You can have "hard chines" where the change is abrupt and angular, or "soft chines" where the change is rounded so that it blends in. A square, flat-bottom hull would have one hard chine on each side with an angle of 90 degrees (and no keel). In construction the metal plates or sheets of plywood would be cut so that their edges run along a chine.

No, you will not be able to use the "hull" function on all frames together, it will be used in the loop between each pair of frames. If the frames are close together it will not fill in the convex parts. Your table can describe frames quite far apart, and your loop can interpolate between entries to give you more frames and a smoother hull.

Dave
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