Boat Hydrostatics visualized

Anything to do with hull shapes in general (i.e. not specific designs)
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Heimfried
Quiet member
Posts: 12
Joined: Sat Nov 23, 2019 4:49 pm

Boat Hydrostatics visualized

Post by Heimfried »

Hi everyone,

a few years ago I coded a website which showed a kind of calculating sheet regarding boat hydrostatics. It displayed also graphic elements as longitudinal and transversal cross sections of a hull, the shape of the waterline and the righting arm curve.

Now I elaborated a webpage with 3D graphics wich are easier to understand - in any case I hope so. If you are interested:
http://www.bootsphysik.de/index_x3.php

The button "English" is top right.
The page is at an intermediate state, and will contain bugs, the link is therefore a temporary one. Questions and remarks are welcome!

Gruß, Günter

Heimfried
Quiet member
Posts: 12
Joined: Sat Nov 23, 2019 4:49 pm

Re: Boat Hydrostatics visualized

Post by Heimfried »

The webpage is a bit further developed. SVG graphics instead of pixel, 3 views from different angles shown simultaneously.

http://www.bootsphysik.de/boot21.php

(Button "English" top right.)

Gruß, Günter

John Perry
AYRS Chairman
Posts: 81
Joined: Tue Nov 08, 2016 6:39 pm

Re: Boat Hydrostatics visualized

Post by John Perry »

Hi Helmfried - Well done - lots of work in that I am sure. I know its lots of work because in the early years of this centuary I tried to do something a bit similar.
I wrote software to:
  • Design a hull shape, the location of the waterline changing automatically as the shape is edited
  • Add weights to the hull
  • Carry out hydrostatic calculations
  • Display lines drawings and export tables of offsets
  • Click and drag with the mouse to move individual heavy items around in the hull and see the waterline change in real time
  • View the hull in shaded perspective from any angle with control over lighting etc.
The software was writtain in C++ with Microsoft Foundation Classes as the link to the Windows Application Framework. The 3D views were done with OpenGL. I went as far as making it all installable and uninstallable from a single .exe file. I still have a copy of that .exe file and seeing your post I installed it on my current Windows 10 system, not really expecting it to work. Well, most of it did work, unfortunately the comprehensive help system that I made for the program is simply not supported by recent versions of Windows - that apart from anything else would rather limit the wider use of this software. Another problem is that the toolbar that controls zooming, panning, rotating is simply not displaying, I dont know why not, however I found that some control over these view functions was possible with just the mouse buttons and mouse wheel. In this software the hull shape is defined by a number of longitudinal splines which are controlled by dragging control points on the splines with the mouse or setting the position of these by entering coordinates. Splines could be added or removed from the model and control points could be added or removed from each spline. Round bilge and hard chine hulls were both possible.

So, I was writting a 3D Cad package, but one that was limited to the kind of shapes that you see in boat hulls. Although it did the hydrostatic calculations automatically as the hull shape was edited, It had no way to design things like rudders, galley layouts, masts etc. On the other hand a general purpose CAD package would not automatically do hydrostatic calculations but it would design every part of a boat, right down to the last nut bolt and washer. By then I had gained some familiarity with Solidworks and realised that if I designed a hull with Solidworks it was actually not that hard to get an idea of its hydrostatic properties by making an intial guess at the waterline plane, slicing a solid model at that plane, noting the location of the centre of bouyancy and centre of gravity then iteratively adjusting the location of the waterline plane to find a good balance. If only interested in the non heeled hydrostatics (which is probably all you need for multihulls) this might perhaps take half an hour. It takes more than that to produce a complete righting moment curve for a monohull, but still doable if needs must. So it seemed that overal it was better to use software like Solidworks and accept that the hydrostatics will take a bit of fiddling around, or I think I could have brought a plug-in that actually added hydrostatic calculations to Solidworks. Or maybe I could alternate between Solidworks and my own software, copying the hull from SolidWorks to my software purely for Hydrostatic analysis. Perhaps write my own plug in to do the copying since I think Solidworks has some kind of interface for developing add on software.

So, my conclusion to all this - 3D software like Solidworks, Siemens NX, Catia, Autodesk Inventor is now so slick and effective that it does not seem worth trying to make software that only designs boat hulls, unless perhaps this software interacts with a general purpose CAD package(s). I wondered if you might be thinking along the same lines.

Of the CAD software I have listed above, my experience is mainly with Solidworks, but also a bit of Inventor at one time, both seemed very good. I believe that there are also a number of free general purpose CAD programs these days, but I havent tried any of them, maybe someone here has done?

I attach a few screen shots from my software - this should give you an idea of how it works. If it is of interest I could make a Windows install/uninstall file available.

Tackling a project like you and I have done does at least give one an appreciation of how much work must have gone into producing something like Solidworks! Presumably work done by hundreds, maybe thousands, of professional programmers, hard for a single amateur to match that!


BDraw_screenshot_Lines drawing.png
Lines drawing - various display options available, also output of table of offsets as .dxf or .csv files
(180.31 KiB) Not downloaded yet
BDraw_screenshot_Lines drawing.png
Lines drawing - various display options available, also output of table of offsets as .dxf or .csv files
(180.31 KiB) Not downloaded yet
BDraw_screenshot_hydrostatic data window_01.png
Output of displacement calculations - clearly a glitch in the labelling of one of the graphs. All output printable
(156.97 KiB) Not downloaded yet
BDraw_screenshot_hydrostatic data window_01.png
Output of displacement calculations - clearly a glitch in the labelling of one of the graphs. All output printable
(156.97 KiB) Not downloaded yet
BDraw_screenshot_Editing window_02.png
Hull shape editing window above, two 3D views below, also a table for adding weights to the hull. Waterline adjusted in all views as hull is edited or weights changed
(115.25 KiB) Not downloaded yet
BDraw_screenshot_Editing window_02.png
Hull shape editing window above, two 3D views below, also a table for adding weights to the hull. Waterline adjusted in all views as hull is edited or weights changed
(115.25 KiB) Not downloaded yet

Heimfried
Quiet member
Posts: 12
Joined: Sat Nov 23, 2019 4:49 pm

Re: Boat Hydrostatics visualized

Post by Heimfried »

I aggree that it would be a waste of time for a single amateur to try to compete against professional software. There is only room for developing software tools in niches which are not covered. I would by far not be able to develop a (specialized) CAD Software, I'm not even able to work with it (e.g. "Freeship").
After I was interested in calculating boat hydrostatics, I developed an Excel-VBA folder which could find the CofB of a given hull in every (reasonable) draft, heel and trim and find automatically by iteration the equilibrium.
I found that some boaters were interested in this kind of things, but were frightened by "only looking at numbers, numbers, ..". So I went online to visualize the results graphically. Developing such a "little tool" demands hundreds and hundreds of hours. Most of them not used for the mathematical core but for the user interface to make it working and understandable.

I would like to play with your software, and I think I'll find some time in the winter. But my system is Windows 7 now and I suspect, I'll be forced to upgrade in the next time.

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