PolyCAD tutorial: Hydrostatics for Delftship, Freeship, Rhino files

[quequen]

Beyond the amazing capabilities as a 3D modeler, PolyCAD (free) has also beautiful Hydrostatic Analysis features. You can perform dynamic and interactive analysis of your hulls and underwater body, trim, heel, move your CG etc. and see what happens in 3D and in real time. I made a tutorial on the topic.

Note: by now, PolyCAD 9 has a small bug that prevents calculation of GZ curve beyond 90 deg., Marcus knows this issue, so it will be fixed soon.

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http://www.youtube.com/watch?v=MzFI-dlmllE
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Have fun!

 

[kvsgkvng]

I downloaded PolyCAD from the original site and it asks me an authorization code. I guess it is not free...

 

[quequen]

kvsg: by now PolyCAD is free but you must to register. Ask for that authorization code by e-mail, check the site for registering instructions

 

[quequen]

The next release (wich will be available soon) fixed the bug. Now you can go to 180deg.
In addition, it also has new features:
- as you drag the mouse over the stability curve, a point moves on the curve showing where you are.
- as you move along the curve, all the immersed body hydrostatics are calculated in real time for each heel angle, including Cp, Cb, LWL, LCB, VCB, TCB etc.
- you can show the maximum depth of the immersed body, in real time, for each heel angle.

Some hints Marcus e-mailed me:

To perform a set of Draughts for the Sectional Area curves, or a set of heel angles for the GZ curve, you can write this format between parentesis:
(0 180 5) means from 0 to 180 in steps of 5
(0.19 0.22 0.01) means from 0.19 to 0.22 in steps of 0.01

There is no need of mirroring the volume (if it is totally symetrical) to perform hydro calculations.

 

[quequen]

PolyCAD 9: Multihull hydrostatics

Marcus has been working hard: PolyCAD 9 is now available for download, with all the previously mentioned features and corrections, plus:
- Heeling angle now shows on the table, beside Trim angle.
- added many hydro values characterizing the underwater body:
Immersed Draught
Immersed Cb
Immersed Cm (Ax)
Breadth at Waterline (Bwl)
- As mentioned, Immersed Draught shows also on the graphic screen
- new "Search" function in the help file (very useful)

Here a new PolyCAD 9 tutorial, performing heeled hydrostatic calculations for a Multihull (catamaran):
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http://www.youtube.com/watch?v=ClPGe874ghs
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PolyCAD site:
http://www.polycad.co.uk/

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[Andy]

PolyCad is an excellent piece of software. All it really needs is a lot more tutorials...keep them coming! A video walk-through of creating a hull and doing basic calculations would be ideal, I think once people are that far in they will figure the rest out themselves to an extent.

 

[quequen]

PolyCAD 10

PolyCAD 10 new release

PolyCAD has a new release, with a totally renewed interface.
It also has new improvements in the Hydrostatics module that allows many different approachs. Attached an example of a .xls file done directly from PolyCAD hydro info.

Andy, I agree. Just more tutorials is what PolyCAD needs to be more popular.

http://www.polycad.co.uk/

 

[Leo Lazauskas]

Can PolyCAD output a table of offsets at equally-spaced sections and
waterlines up to some specified draft?
That would be a very useful feature because it means they can be used
as input to free resistance prediction software like Michlet, Ulimich
and a soon to be released Excel version of similar programs.

Incidentally, on your page of Links at http://www.polycad.co.uk/links.htm
the following seemed dead when I tried them:

IGES Preservation Society - Description of some of IGES5.x
http://www.iges5x.org/

Prof. David F. Rogers
http://web.usna.navy.mil/~dfr/rogers.html

All the best,
Leo.

 

[quequen]

Leo, I've emailed your post to Marcus Bole.
Marcus already wrote a file interface for Michlet, so maybe we'll see it working soon.
Now he is thinking on some way to implement Performance prediction, resistance etc. "on the fly", something similar to the Hydrostatic module, so you can modify your geometry and see what happens to your performance immediately. Something like a direct input-output link to Michlet, Holtrop or Delft Series. Perhaps you could give him some idea?

Interesting your excell version of Michlet, please start a thread on it!

 

[Leo Lazauskas]

Leo, I've emailed your post to Marcus Bole.
Marcus already wrote a file interface for Michlet, so maybe we'll see it working soon.
Now he is thinking on some way to implement Performance prediction, resistance etc. "on the fly", something similar to the Hydrostatic module, so you can modify your geometry and see what happens to your performance immediately. Something like a direct input-output link to Michlet, Holtrop or Delft Series. Perhaps you could give him some idea?

Interesting your excell version of Michlet, please start a thread on it!

Thanks, Quequen.
I doubt that Marcus will be able to easily hook up Michlet to PolyCAD to
calculate resistance "on the fly" because of the way I wrote Michlet.

The Excel program I mentioned is not Michlet: it is much simpler in some
ways and more complicated in others. Marcus will not be able to use that
for on the fly calculations either, because it requires the user to click
a button to calculate the resistance.

 

[Concordia Uni]

Is there a way in Polycad to model ballast and then have that affect the GZ curve.
I downloaded the VOR70 model from the website and I want to add a weighted keel to the analysis.
I doubt that the software will incorporate the canting feature for the keel but It would be a good start for a fixed keel.

 

[quequen]

Concordia, here is what I do to solve this kind of problems:
1- Model your boat in Freeship or Delftship, including kanting keel and bulb. Organize it in layers and give them the right weight properties. Compute the hydrostatics report.
2- Export just the hull and deck to PolyCAD and input the hydrostatic data from your report. That's all.

And yes, you can model canting keels at any angle and compute the entire stability curve for that condition.