Hull analysis plugin for Rhino

[Karsten]

After I received lots of encouraging comments for my free Rhino hull balance script I decided to develop a bit of a toolbox for the yacht designer.

So far I have a plugin under development which calculates the following values:

• Displaced volume
• Waterline length and width
• LCB
• VCB
• Cp
• Cross section area curve

I will also add hull length and width. Link to a demo video is below. I would very much appreciate any comments and requests for additional features.

https://www.youtube.com/watch?v=ypvCEGhU81Q&feature=youtu.be

 

[TANSL]

The first thing I want is to congratulate you for what you are doing, as I did in the other thread that you have open.
You must continue calculating things because, unfortunately, if you calculate only 5 of the 8 parameters necessary, people will not use your plugin.
As for your other thread where you calculate the balance of the boat: I suppose to do it, previously, had calculated all the values shown in the current thread.

 

[SukiSolo]

Good work Karsten. Personally I find the Curve of Areas a particularly useful piece of information, to help aid things, so this would be most helpful to me. I do extract the information but it seems a bit 'longhand' currently.

Thanks for posting and good luck with the project, much appreciated.

 

[Alik]

Section area curve was available from RhinoMarine plug-in; I am quite sure Orca does it. So good exercise, but what's the point?

 

[Karsten]

I calculated a few more values. An example is shown below. The data is just an example and I'm aware that it is a pretty extreme boat. The units depend on the model units. The plugin is also able to analyse asymmetric hulls.

My idea is to create a toolbox which makes yacht design in Rhino faster and simpler. I'm aware of Orca3D but I don't personally have it. I think RhinoMarine has been discontinued. At the moment this is just for my personal enjoyment but if others are interested I might share the plugin in some way.

Once this plugin is working I would like to combine it with my hull balance script so that the results shown below can be calculated in a range of heel angles (for example 0 - 45 degrees in 3 degree steps). I'm planning to export the results as a CSV file so that the results can be plotted in Excel.

Hull length = 12000 mm
Hull width = 3005.080078125 mm
Canoe body draft = 375 mm
Waterline length = 11071.8098414454 mm
Waterline width = 2430.96501953221 mm

Displaced volume = 4301652481.25428 mm3
Cp = 0.533277598453803
Cb = 0.426193406426212
Displacement / LWL^3 = 0.00316941761649015
LCB = 6183.22508207987 mm
LCB / LWL = 0.557418765560104
VCB = -145.47989816832 mm
Wetted surface area = 19463760.5445615 mm2

Max section area = 728556.71153826 mm2
Max section area coefficient = 0.799196155364348

Waterpane area = 17244089.6895899 mm2
Centre of flotation = 6593.02334405709 mm
CF / LWL = 0.595478376026408
Waterpane coeficcient = 0.640682623499249

 

[TANSL]

Has merit what you're doing. Courage and move on.
One way to check that some calculations are serious to evaluate the accuracy in the calculation of the wet surface. It is one of the toughest values calculated correctly.
Should also calculate the moments of inertia of the float. I think, with that, you could say that your app is worth to design boats.

 

[DCockey]

RhinoMarine was discontinued in 2009. Orca3D is the successor to RhinoMarine.

 

[Dr34m3r]

keep going ! what is the point ? Point is , he love to do it

 

[Karsten]

I'm happy to present the latest version of my toolbox. I added a new tool which allows to calculate the righting moment curve and pretty much any other parameter in a range of heel angles. Video is here:

https://www.youtube.com/watch?v=z4pIhILMaIo

To see the new tool in action you can forward to about 3 minutes.

 

[TANSL]

I have not the slightest intention of being negative but rather, trying to help. Some thoughts:

• Have you taken into account when calculating the righting moment that displacement should be the same in each of the heeling?
• The righting moment curve thoughts about having a value less than zero when the heel is zero. This is only possible if the initial position of the ship has a certain list.
• The boat, while heeling, will also acquire variables trims.

Perhaps I was not able to correctly interpret the video.

 

[Karsten]

Hi Tansl
Thanks for your questions. You are not negative at all.

The displacement is the same for all hulls created. The hull surface is automatically moved in the z- direction until the displacement matches the input value. This iteration is stopped when the error is less than 1%.

In the video I used the 'Line' plot function in Excel. The righting moment at zero heel is plotted at x = 1. Therefore it looks like the curve is not going through x = 0 and y = 0. If you use the 'Scatter' plot in Excel the curve is plotted correctly. Nevertheless the righting moment at zero heel often shows an extremely small value due to rounding.

The plug-in calculates the righting moment in length^4 (volume times lever arm). If you use Millimeters as the length unit the values get very big. To calculate a righting moment in kg * m you would have to multiply the plug-in results by the water density.

The hull surfaces are automatically rotated around the lateral y- axis until the longitudinal position of the centre of buoyancy matches the x position of the centre of gravity. Again this is done via iterations and the typical error is approximately 1.5 mm for a 14 m long hull.

Hope this answers your questions.

 

[TANSL]

That answers my questions, of course it does, and from what I understood, I'm surprised how correctly calculate your procedure. Congratulations. I think this is fast becoming a very very good solution for naval architecture.
Sorry if my questions have been seem trivial, but I believed important to check these things to calibrate your application.
BTW, would it be possible to have a beta, or test release to tinker with it?.

 

[Karsten]

The plug-in is completed for now. It is available as a free download here:

http://www.food4rhino.com/project/na-toolbox?ufh

The zip file contains the plug-in file (for Rhino 5 only), icons to make custom buttons and installation instructions. Enjoy and let me know if you find any issues.

 

[Karsten]

A new free version of the plug-in is available for download via the Food for Rhino link in the post above. The new version makes it possible to analyse multihulls and classic V planing hulls. Previously the results for hulls with immersed transoms were not very accurate due to the step in the section area curve. The new version allows to specify a section close to the transom to fix this issue.

I have also released a pro version which has all the features of the free version. Additionally it is possible to calculate all hydrostatic properties in a range of heel angles. This is ideal for calculating the righting moment curve and finding the heel angle at minimum wetted surface area.

Additionally it is possible to assign mass data to Rhino materials. The data is stored in the material notes box. Existing notes are moved to the end. Each material can have a density, area mass and point mass.

To calculate the combined mass and centre of gravity of multiple objects the plug-in automatically detects if the object is a solid, surface or point. Volumes will be multiplied by the density, areas by the area mass and point objects will have point masses applied. The NA toolbox is therefore ideal for tracking masses as well as hydrostatic analysis. A video is here:

https://www.youtube.com/watch?v=xThneyncheo

The pro version can be purchased here:

http://www.kj-engineering.com.au/shop/hull-analysis-1-detail

 

[DCockey]

Does the toolbox use the traditional integration of sections for calculating hydrostatics, or does it use the volumetric integration functions available in Rhino?