Savitsky Power Requirement Prediction Plugin for Rhino3D

This is a plugin I have developed to use within the Rhino3D CAD modeler and enables the designer to quickly evaluate power requirements for planning hull boats using the Savitsky method.

The attached file is the installer. After installing the plugin you can run it by typing "quickSavitsky" at the command line of Rhino. You will be asked to type in the displacement, LCG, VCG, etc of the boat and then to click on the planning surface of your model. You can select the speeds to evaluate. Results are reported in the Rhino command line, so you can review them, and copy them as usual.

Savitsky method restrictions are not checked, so you are responsible to check the meaningfulness of the results!

Keep in mind that this is a beta version and may contain bugs, mistakes, etc so your feedback is needed in order to improve it!

I have Rhino version 5.0 so I do not know if it works on older versions.

 

Congratulations for your effort! It is a very interesting project.

May I ask how the plugin works? With the short or long Savitsky's method? Where does the software measure the deadrise of the hull? At the transom? An average value?

Many thanks.

 

Thank you ZeusGaryulo.

The plugin is developed around the Savitsky's general case, and you will have to enter thrust line angle and thrust line distance from CG besides displacement. Deadrise angle and wetted beam is derived automatically from geomertry. Although not exactly correct, the deadrise derived is at transom. I am working on a simple GUI, to be able to override the derived values as sometimes cannot be extracted from the model.

The plugin derives the deadrise angle, wetted beam, and then computes for each speed to be evaluated the Speed coefficient, and lift coefficients. From the relevant non-deadrise lift coefficient it computes the Lambda and Delta-Lambda values. Then, for two predefined trim angles it computes pressure drag, friction coefficient and friction resistance. Then it calculates the relevant arm levers and computes moments for both angles. Finally using interpolation it derives equilibrium trim angle for zero net moments, actual bare hull resistance and effective power.

I am working on a GUI to manage values easily, and present output as well as an option for exporting the results into a spreadsheet. I am also trying to combine this with a weight-plan plugin which assigns surfaces and points of the model to specific materials and weights. The idea is to build composite materials, add solid materials or specific equipment weights to a library, then assign them on your surfaces, derive your total mass, CG and cost of materials and move to speed prediction for a performance estimation.

 

All this can be enormously helpful. I encourage your work.

 

Hi vkstratis ,
I do not fathom why you have made this plug-in! I do not see any sense in this that you have made!
In plug-in Orca3D for Rhino already there is function Speed/Power-Planing Analysis on method by Savitsky. This function for a long time works ideally. I tested it many times.
____________________
NA Razmik Baharyan

 

I use Orca3D myself. I also use Maxsurf Resistance and NavCAD. I also use a spreadsheet and I am pretty sure there are numerous other software, and spreadsheets out there for someone to use. I don't see any sense in your comment. I never claimed anything more or less. I just developed this for my own joy and use and decided to share it with anyone who might feel it is useful. Nevertheless thank you for your comment.

 

vkstartis not have in mind the comments of people who have not even trained to assess the quality of some calculations. Some think that, know how to use a program, is the same as being naval architect.
Today it is difficult to invent anything, everything has already been invented, but it is very interesting that there are people engaged in trying to improve what already exists. So, go ahead with your project. First, you enjoy yourself trying to do something, the same probably, but in a different way. If, in addition, it is useful for others, the only thing we can say is: "vkstartis, thanks for trying."
And you do not have to thank anyone for a totally unfortunate comments, imo.

 

Hi vkstratis,
Combination of trades Marine designer and skills of the programmer extremely seldom meets and for this purpose the respect and encouragement is deserve.
But to convince and other people in this that the program created by you is good and it is possible to trust and use it, proofs by means of testing are necessary, differently Classification organizations introduced calculations do not recognize.
On my opinion the best method to prove quality of the program this is comparison of the outcomes received with it with outcomes received for too model in hydrodynamic development water pool.
______________________
NA Razmik Baharyan

 

You would do well to tell this to Mr. Savitsky because vkstratis has not invented a new method that need to be verified. It is assumed that the method of Savitsky works properly, or is it necessary to check it?. What does MaxSurf manual says in this regard?

 

Thank you TANSL for your comment which is exact. There is no invention here just another implementation of a method that works for many people out there.

TANSL, I have made some improvements and added the weight/cost capability that allows the user not only add equipment and items (something like Maxsurf's loadcases) but also to "build" composite materials out of already defined resins/reinforcements. Total mass and COG can be reported or feed the resistance/power module to estimate hull performance. I will be glad to send you the latest version if you are interested for a review.

 

vkstartis, thank you for your offer. I am a user of Rhino, not very expert, but I have not Orca3D. I do not think, therefore I can be very useful. If despite that you think I can help, send me a copy of your work.
Although I perform calculations with other programs, including some developed by myself, the quality/price ratio in Rhino makes it ideal for developers to add plug-ins that allow it to perform all the naval architecture calculations, for all types of ships and floating structures possible.

 

Hi vkstratis,
My opinion is this: The RhinoMarine old version is very good add-on, only need to have the capacity of tanks implementation with its free surface effect for give an acceptable report so if you are writing a code that allow including this parameter will be important improvement. May be is not you task as hull speed performance but if you decide this implementation will be a valuable tools for vessels safety.

 

I agree with GIOVD. All this plus the inclusion, in some way, of the stability criteria make of Rhino a great tool for any boat designer. (With the huge advantage of not having to import-export files between different applications).
There remain only two last tasks:
- Ability to create and print project drawings.
- Give the results in a format that allows to automatically include them in the final report of the project.

 

Dear all,

My intention was not to replace or offer an alternative to any existing software. Orca3D works really good and the leatest WIP versions offer stability createria check, although accounts no free-surface effects.

The attached plugin has recently evolved to an easy to use addition to Rhino to quick estimate mass and COG using the 3D model and a material/equipment library defined by the user. It is possible to define composite laminates within the plugin and use them in the material library. Laminate properties are estimated automatically. Then the weight plan output can be used to estimate planninig speed using the extended Savitsky's method. Again all parameters are extracted from geometry. Hydrostatics is another chapter by definition and requires lots of additional work.

If anyone is interested for the purposes of review I can send you the software to check it.

Thank you all for your comments.

 

Dear GIOVD,
There was a time when at the calculation of the Weight, LCG and VCG for concrete Load Case, effect of free surfaces of the fluid in tanks was not taken into account as the additional correction at definition VCG.
This effect was taken into account only as a correction to GMt at calculation of an intact stability.
But since then when I have met and I shall already actively use program Maxsurf Stability, I see that in it take into account FS correction to Vertical Arm for effect of free surfaces to receive the ultimate VCG fluid.
But you should not trouble for this correction when the question is calculation of speed and necessary power by Daniel Savitsky.
The matter is that such calculation is usually made for the total displacement of the motorboat, i.e. in condition in which is in the beginning of trip.
And as we know in the beginning of trip all tanks the filled up to top part and there are not free surfaces.
There is only the fact, that the fluid in tanks augments displacements and changes CG of the vessel as component of deadweight capacity and it is certainly important for calculation by Savitsky.
One more explanation: RhinoMarine for a long time is obsolete and have exchanged with Orca3D plugin.
_____________________
NA Razmik Baharyan