Delftship and Godzilla/Michlet

[Hector MacNeil]

Let me first of all say that Delftship is a brilliant piece of software, I only have the free edition, can’t imagine what the full version can do. Unfortunately I’m just a “poor pensioner”…..ok you can put your hankies away now ;o]]

Seriously, can any kind hearted soul explain to me how to adapt my in.mlt file as input to Godzilla?

I’ve run Michlet for a number of different input conditions but if I try to run Godzilla it just flashes on the screen momentarily, then nothing. Obviously there’s something not quite right with my “in” file.

I realise this is a Delftship forum and not a Michlet one, but maybe somebody has the knowledge I lack.

p.s. ooopps! can’t upload in.mlt file

[Leo Lazauskas]

Godzilla requires quite a few extra lines that are not generated by Delftship.
You must read the Michlet and Godzilla manuals and work through the examples.

[Hector MacNeil]

Thanks Leo.

I’m working through the examples and reading the manual and it’s becoming self explanatory.

What I would like to know is, once I’ve optimised my hull design in Godzilla, can I then use this output data as input back into Delftship?

[Leo Lazauskas]

Thanks Leo.

I’m working through the examples and reading the manual and it’s becoming self explanatory.

What I would like to know is, once I’ve optimised my hull design in Godzilla, can I then use this output data as input back into Delftship?

Not directly.
However, if you calculate the drag after running Godzilla or Michlet, the program produces files names fsoff1.txt,… fsoff5.txt which contain offsets that can be read by Delftship.
You will then have to input various values required by Delftship.

Good luck!
Leo.

[Guillermo Estalrich]

Hi Clansman, How did it go with MIchlet?? I’ve the same problem (flashing black screen and autoquit of Michlet without processing data) running Michlet with a DelftShip exportes file, did U find any bug in the michlet export file?
Regards

[Leo Lazauskas]

Error messages are written to the out.mlt file.

There were some changes made in Michlet which means that a couple of lines have to be changed in the file created by Delftship. These were described in the manual.

[Hector MacNeil]

Hi Leo & Guille1963,
My problem isn’t with Michlet, it works perfectly with the output from Delftship, with no changes to the export file. Does this mean that since I haven’t made any changes to the export file the Pressure, Resistance and Wave Analysis output I get, is rubbish!

My problem has been with Godzilla. I’ve worked through the examples and the manual and I still get the momentary flashing screen, although it stays longer than before. My out.mlt shows “error: Nothing to optimise. Check limits on parameters”. And the godzout.mlt shows “0.0,0.000000”.

Does this mean that the design I have is already optimised to the limit or does it mean that my input data needs a lot of scrutiny?

[Leo Lazauskas]

Hi Leo & Guille1963,
My problem isn’t with Michlet, it works perfectly with the output from Delftship, with no changes to the export file. Does this mean that since I haven’t made any changes to the export file the Pressure, Resistance and Wave Analysis output I get, is rubbish!

My problem has been with Godzilla. I’ve worked through the examples and the manual and I still get the momentary flashing screen, although it stays longer than before. My out.mlt shows “error: Nothing to optimise. Check limits on parameters”. And the godzout.mlt shows “0.0,0.000000”.

Does this mean that the design I have is already optimised to the limit or does it mean that my input data needs a lot of scrutiny?

It means that there are no variables to optimise.
This can happen when all the allowable minimum and maximum values are identical for each variable.
For example, if the minimum allowable length is the same as the maximum allowable length, then length will not be varied during the optisation process.
Try allowing a range of values for the hull length AND the length overall.

[Hector MacNeil]

Hi Leo,

WOW!!

I did as you suggested and widened the length variables from the design 6.4 to a min 5.0 and max 10.0. I also changed a single speed to 5 design speeds. And the program sprung into action.

I stopped it after 2 million evaluations. Will it eventually stop by itself?

The changes made during the evaluation were to: length, beam, wetted surface area, LCB and LCF. These were all reduced. It gave me a best fitness of 10.5498, is this good?
So is this the optimised hull design?

I ran the Pressure, Resistance and Wave options after the evaluation and I will endeavour to compare the before and after traces – still to do!

At this moment in time I’m one happy bunny………!

Many thanks.

[Leo Lazauskas]

Hi Leo,

WOW!!

I did as you suggested and widened the length variables from the design 6.4 to a min 5.0 and max 10.0. I also changed a single speed to 5 design speeds. And the program sprung into action.

I stopped it after 2 million evaluations. Will it eventually stop by itself?

The changes made during the evaluation were to: length, beam, wetted surface area, LCB and LCF. These were all reduced. It gave me a best fitness of 10.5498, is this good?
So is this the optimised hull design?

I ran the Pressure, Resistance and Wave options after the evaluation and I will endeavour to compare the before and after traces – still to do!

At this moment in time I’m one happy bunny………!

Many thanks.

It should stop after 9 million evaluations, I think. That is the limit in version 9.30 which I haven’t released yet.

I can’t comment on whether the fitness is good or bad. It depends on the objective function, the number of design speeds, and the vessel.

It’s now time for a little humility 🙂
I don’t mean this to sound harsh, but you have very little idea of what you are doing at his stage.
You should go through the examples and read the manual a few times.

On the bright side, you have made a great start by using one variable and seeing how that changed.

Remember that in this sort of optimisation, you should re-run Godzilla a few times, using a different random seed each time. If the program gives you the similar lengths each time, then you can have some confidence about the result.

If you find the optimal length is sometimes short, other times long, then that is interesting in its own right. The shorter hull will have less skin friction, but probably higher wave resistance. The longer hull will have higher skin-friction and lower wave resistance. Now it is up to you to decide which hull is suitable for your particular application.

If the length of your vessel hit one of the constraints (e.g. 5.0 or 10.0) increase the maximum or decrease the minimum. What you want is for the “optimal” length to be between the two constraints, and not equal to one of them, if you can help it. Sometimes a vessel wants to be as short, or long, as it can get. Then, other constraints should examined carefully.

Have fun!
Leo.

[Hector MacNeil]

Hi Leo,

You’re actually spot-on, I have little idea as to what I’m doing at this stage. But with the help you’ve given and the explanations in layman terms I’m beginning to see a light at the end of the tunnel. For which I thank you very much.

I bought a 17ft Wilson Flyer boat 4yrs ago and since the sea state can change quickly here, we’re open to the Minch and the Atlantic, I decided I would like to redesign her and give her greater stability.

I thought that probably a good starting point would be to increase the length and beam and that’s when I found Delftship. Then I found Michlet and Godzilla. My hope was that these three excellent pieces of software would eventually provide an optimum design. And with the help you and Marven have given I feel I’m getting somewhere near to that goal. The rest, I hope, is just fine tuning and at least I’ve now got the three pieces of software speaking to me, which I feel is a great achievement.

Ok I know what you’re thinking, why after all this time doesn’t he just remain a landlubber, it would save a lot of hassle! But it’s the excitement and the challenge of doing something new. The creativity!

Many thanks.

[Leo Lazauskas]

It’s a very good start, but “design” is so much more than minimising calm-water resistance.
For your particular circumstance, sea-keeping seems like a much stronger driver of the
final design.

All the best with your venture!
Leo.

[Jesus Cruz]

Where can i get a demo of godzilla?, sounds interesting…

[Leo Lazauskas]

Where can i get a demo of godzilla?, sounds interesting…

Michlet and Godzilla are not separate programs.
The Michlet home page is:
http://www.cyberiad.net/michlet.htm

[Jesus Cruz]

Any place I can get a manual??, ususally i learn to use a software by just click on the icons and see what happenes, but here no icon at all, so I´m asuming that works by writen commands, so I´m kind of lost

[Leo Lazauskas]

Any place I can get a manual??, ususally i learn to use a software by just click on the icons and see what happenes, but here no icon at all, so I´m asuming that works by writen commands, so I´m kind of lost

That method definitely will not work, so the program is probably not for you.
Michlet is a complicated program that requires some experience with naval architectural terms and hydrodynamics concepts.

The manuals can be found in in the docs sub-directory after you unzip the program. You should also go through each example.

Remember, too, that Michlet is NOT a boat design program. It is a “hydrodynamics workbench”.

[Othmar Karschulin]

Hi all,
I played with a boxform hull and different rockers to examine the best one. After Export to Michlet it Shows there a completely other cross section. Someone knows what’s happened?
See the screenshots here:
http://www.multihull.de/temp/hull8_delftship.jpg
http://www.multihull.de/temp/hull8_michlet930.jpg

[Author]

Posts