Who Uses Godzilla?

I am interested in knowing who has used Godzilla to develop a hull form and then built and tested the resulting hull.

I have built and tested three hulls generated by Godzilla and have been more than pleased with the result.

Rick W.

 

I would like to use it, is it a separate application to Delftship (free)?

 

Brian
It is a selectable component of Michlet. This is unrelated to FreeShip other than Freeship can import Michlet offset files and export Michlet .mlt files. So they are useful together.

If you have downloaded Michlet from cyberiad:
http://www.cyberiad.net/index.htm
then you will already have Godzilla.


Rick W.

 

Thanks Rick W., I was asked to leave contact info which I did. Very interesting stuff. That - if I get it, will keep me busy mentally with less dilettantism on the net

Were you aware that Freeship is now incorporated into Delftship? with that now being Delftship (free) edition. I now have version 3.2 running using "wine" to interface my linux mint to XP compatibility.

Thanks and regards

 

You know ... I tried DelftShip and found the interface to be inferior to FreeShip, at least for the kind of work I do. What's more, FreeShip is fully functional whereas DelftShip has things disabled that still work in FreeShip.

First I tried FreeShip then I thought I was making a good move to DelftShip ... until I tried it. It didn't take me long to go back to FreeShip.

Just one man's opinion ...

 

I have used gozilla to optimize LCB, LCF, WS and Cp of racing row boats.

http://www.suursoudut.net/eng/default.asp

 

i'm drawing two hulls, one normal with a keel, the other with a big dent in the bottom where the keel comes in
acording to area rule the latter should have less drag, Rick, can you elaborate a little on the best way to compare those

 

Ken
You are right. I actually purchased Delftship pro. I have had so much fun using FreeShip that I thought I should make a contribution. For most of things I do it is way faster than something like AutoCad. Pro has the ability to import iges 3D files which adds a bit if value for me as well. On the other hand you have to pay almost twice initial cost to get the Cross-Curve functionality that FreShip has. So it is a mixed bag.

Rick W.

 

I would draw both hulls with their different keels mounted. Then produce Michlet files, having adequate stations to differentiate the keel shapes, so I could compare drag of the two forms.

However before I got to that point I would use Godzilla to optimise the hull shape first. Unfortunately there is no means of getting Godzilla to produce a keel. So the keel is a separate exercise.

I use JavaFoil to compare the performance of lifting foils. The Sears-Haak shape you refer to will get you the lowest drag for the section area but it will stall early. So it may not suit your purposes. If it is just a means of getting weight low then it might make sense.

So having got the best hull and the best keel independent of each other you would go back to Michlet just to see if the drag result gives what you expect when in combination.

I hope I have interpreted your question correctly.

I have not actually validated Michlet against a keel but I have compared its result with a submerged hull I built and it was close to the mark. Made me realise I would need to submerge it deeper if I wanted to get the wave drag reduction I was after.

Rick W.

 

Hi Rick, as said in the "Michell v CFD and EFD: Round 2007" thread i drew 8 stations and keel as part of the hull.
your ahead of me here as i did not use godzilla yet but check it out and see how it handles keel and indents over a few stations
actually only want to see what difference a hull and keel with area rule makes, lift and stall i'll leave open but will check displacement


wakes me up now to old wonders like eighter having the foil sharp into a hull or blended in as well
planning on getting that manual out of the draw again this weekend, thanks

 

Would love to use Godzilla

Hi everybody, and Happy New Year to all

Thank you Rick for this thread. I do not use Godzilla yet, just made one or two little experiences with Michlet.

A long time ago I download WinEdt for offset purpose but never achieve anything, instead with NotePad I achieve a basic Michlet drag curve.

In fact I am neither engineer nor computer wise. That is why I would be pleased to gather some advices to run Godzilla for the following project.

My goal is to run existing A-Cat hull shapes in Godzilla at different speeds.

The actual hull offsets are on a paper, as a result I will have to mesure many points by hands and put them in XYZ txt format, but the resulting hull will be far from smooth lines, so as a pre-requisite I guess I will have to smooth my handmade job, before running any software?

But to do that, I don't know which FreeShip/DelftShip version is required, the same for WinEdt ? or any other software ?

If in addition, somebody could provides me with a basic step by step process , from XYZ offsets to the optimized hull shape's outcome from Godzilla, via FreeShip, WindEdt, or anything else, it would be great?


Thanks in advance.

EK

 

EK
Godzilla develops the optimum hull for given constraints. So the main issue is to determine your design constraints. You do not need a starter hull as it will create a very generic hull from basic input. Usually it does not matter what you start with as it will end up with much the same hull every time for any given set of constraints - there is likely to be only ONE optimum for any set of constraints.

A sailing cat is an interesting exercise because you have so many possible conditions of operation. I looked at a design case today. I set the design speed at 20kts, the hull length less than 12m and the displacement 4 tonne. The design case was the entire weight carried on one hull sailing to windward. So the second hull did not even need to be included in the hydrodynamic analysis. Just windage in overall performance.

So if you describe what you want to achieve I can discuss the constraints that need to be included to see if Godzilla can produce a better shape. The results are sometimes surprising but usually make sense when you think about them.

Rick W.

 

Thanks Rick

Thank you for your support, I saw your 12 m Cat. I have a lot of confidence in Mitchlet & Godzilla, because a long time ago, I download from cyberiad a pdf file about a hull optimization for a 300kg and 6m lenght boat at different speed (may be a solar vessel ?) and the 15knts optimum solution perfectly "predicts" or fits a former experience conducted by the designer of the Hobie-Cat tiger.

I guess that the relative magnitude of aero & hydro drag according to true wind & boat speeds, is a source of performance optimization for a A-Cat, it is a bit intuitive, but I believe it worth to be investigated.

For a A Cat, of course I'll consider only one hull.

I 'll try Godzilla from scratch as you suggest, but I have still 2 questions
1-From Godzilla's optimum solution to offsets ?
2-Also I have the Flyer's hull shape on a paper, any suggestion on how to put it on Michlet after consistent smoothing, in order to have a benchmark?

 

Agreed, I did the same here.

I've read a number of Leo's research papers and am trying to get my hands on a few more. The comparative testing that he and others have done has convinced me that:
- The accuracy of Michlet resistance predictions is comparable to that of CFD or tank test results, when the vessel being considered is well within the limitations of the theory (length/beam ratio not excessively low, fair hull lines, hull shape does not encourage flow separation ahead of the transom, etc.).
- Optimum hulls generated by Godzilla are quite close to global optimums for the given constraints, provided you set constraints reasonably and repeat the optimization a few times with different seeds to ensure you are getting consistent results.

Erwan,
1- Once Godzilla is approaching an optimum solution and has levelled off, abort the iteration and compute the hull resistance the usual way (shift R then shift C). When you close Michlet properly, there will be a file off1.mlt and a file fsoff1.txt which contain the offsets table of the optimized hull in Michlet and Freeship co-ordinates, respectively.
2- Using Freeship/Delftship to produce and fair the model from the printed lines, then exporting to Michlet format, is the easiest method I can think of.

 

Thanks Marshmat

Thank you very much, I know how to start now.
I guess you had opportunity to do the same exercice for bigger cat;........ as your place is C-Cat crownded !

My best wishes for the new year

Regards

EK