Michlet-Info

[DEboater]

Hello all,

I need links to info on Michlet. I've read the standard manual about 3 times and still very fuzzy on how to use the input files. Are there other resources/guides on the input/output files in michlet, i.e. how to input/run a .mlt file into the Michlet program?
Any and all info on Michlet would be appreciated.

Thank you.

Nick

[Leo Lazauskas]

I warn people it's not an easy program for beginners. See, I wasn't joking!

1. To run one of the examples, copy an input file from the examples sub-directory to the directory where the .exe file resides.
2. Rename that input file to in.mlt
3. Run the batch file michlet.bat

Leo.

[DEboater]

Well thats simple enough.
I've been told Michlet is a bit laborous, but i need a decent prediction tool for a 35m catamaran L/B~10 (not planing) to compare to my other methods of resistance prediction.
So besides that users manual is there any other good information on Michlet out there?

Thank you.

[Leo Lazauskas]

Originally Posted by DEboater

Well thats simple enough.
I've been told Michlet is a bit laborous, but i need a decent prediction tool for a 35m catamaran L/B~10 (not planing) to compare to my other methods of resistance prediction.
So besides that users manual is there any other good information on Michlet out there?

Thank you.

1. There's not much around that I know of. There are now some new manuals in pdf format on the Michlet web page, but they are essentially the same as for version 8.07.

2. Maxsurf's Hullspeed is another program you should consider.

3. One of my other codes "Flotilla" is not yet freely available. I'll release it when I finish writing the manuals (if I don't die of boredom during the process). It includes estimates of the sinkage and trim of catamarans and the effect on resistance. Do you include dynamic effects in your other methods?

All the best,
Leo.

[DEboater]

We will probably be using Maxsurf's Hullspeed as long as it is available to us and also NAVCAD (carefully and with constant suspicion). I'm hoping to figure out Michlet well enough to use it in about 2 weeks when our hullform will be completed. This is all for our senior design project.
Thank you for your help and I am sure more questions will come.

Regards,
Nick Weinhold

[Leo Lazauskas]

Originally Posted by DEboater

We will probably be using Maxsurf's Hullspeed as long as it is available to us and also NAVCAD (carefully and with constant suspicion). I'm hoping to figure out Michlet well enough to use it in about 2 weeks when our hullform will be completed. This is all for our senior design project.
Thank you for your help and I am sure more questions will come.

Regards,
Nick Weinhold

After you get the hull offsets and other data into Michlet, and if your design is not super-secret, I'd be happy to run it through Flotilla to see how much dynamic sinkage and trim affects resistance estimates.

Now, get back to work student!
Leo.

[DEboater]

Thank you for the offer to run our model through Flotilla, much appreciated.
Hopefully we'll have the hull done in a week.

Working diligently is difficult living in uptown New Orleans on a Saturday night, but i'm making an attempt...for now at least!

[Guest625101138]

Nick
Just to take it a step further have you actually considered using GODZILLA to provide hull shapes for you.

I always start out with michlet/GODZILLA these days as it is good to have some idea of what the lowest drag hull looks like for the speed you are aiming for.

If it is a sailing cat then a bit more complex as it is iterative and depends on the point of sailing.

I can do it in a few minutes for a boat in level trim if you are interested. Need your design displacement, max/min LWL, max/min BWL and the target speed.

Rick W

[DEboater]

Thanks for the offer Rick but we have a maxsurf model started already. I have access to maxsurf, rhino and cad and those are the ones often used in industry so that's why we're sticking to them. Also, this is not a sailing or pleasure catamaran. It is a 35m high speed naval patrol boat (anti piracy missions, region of operation is the gulf of aden/horn of africa/indian ocean.) The hullform will be similar to that of a high speed ferry, with some type of propellers/diesel propulsion system.

[Guest625101138]

Nick
I am not sure if you appreciate the ability of GODZILLA. It is the optimising function that sits in Michlet. It is able to arrive at the lowest drag hull form based on the total drag determined by Michlet.

If you are interested in the form of the hull for the lowest drag for calm water then it is very useful. It can work with a wide variety of constraints as well.

The GODZILLA output is a simple table of offsets that can usually be imported to 3D rendering packages.

Rick W

[DEboater]

You are correct, I have no idea about the software. I do know that time is of the essence and have a good grasp on 3 programs already I'm not sure if I have the time to learn another one, but i'm open to the idea.
How user friendly is it?
Is it a program where you create the hull from scratch or import a set of offsets first and it just optimizes the hull lines?
What type of vessels have you used it on/is it good for?
Our vessel may not necessarily need to be optimized also, the mission requirements will likely prevent us from creating a truly optimal hull (just guessing at that right now, 90% sure) also there is the time factor too.

Thanks for the suggestion!

Nick

[Guest625101138]

Nick
The starting hull does not matter at all as long it is within the set constraints. GOZILLA will produce the same end result for any set constraints. It is based on Michlet so is accurate as Michlet is.

I find Michlet to be very good with the slender hulls and speed range I play with. Michlet also considers wave interaction of hulls so is very good for multihulls. I have more confidence in Michlet results for these boats than any tow testing.

The boats I design/make are not much bigger than models but go very well and within 1 to 2% of the Michlet prediction. An example shown here:
http://www.adventuresofgreg.com/HPB/...5_archive.html
The largest boat I have started with GODZILLA and that has been built and tested displaces 420kg.

I find the insight you get from looking at hulls with lowest drag for set constraints to be very useful.

If you advise the target speed, displacement, max/min LWL and max/min BWL for the hulls and the overall ship I can prepare an input file for you. I will also do a run. It is literally 5 minutes effort.

Rick W

[DEboater]

Here are some of the parameters:
Target max speed: 35 kn
Displacement (total): 150 t - 146 m^3
LWL: 31 m 29-32 m
BWL: 3 m 2.5-3.2
Boverall: 10 m can vary..
T: 1.5-2 m
Cb~0.4-0.5
These figures are extremely preliminary and are soley drived from a Parametric study and practical experience, matter of fact they do not even "add up" yet. So i'd be hesitant on doing anything just yet, but we should have more solid numbers by the end of the week. Its up to you if you want to put any time into it.

Thank you,

Nick

[Guest625101138]

Nick
The in.mlt file attached should be put in a folder with alleg40.dll, godzilla.bat and mlt807w.exe. (Any text editor can read ,mlt files)

The optimisation can be started by double clicking on the godzilla.bat file then pressing <shift> <G>. Pressing any key will stop it.

To see the resistance curve, stop the optimisation by pressing any key then press <shift> <R> followed by <t>.

To finish press <Esc> until you get the question then answer <y>.

There will be 30 or 40 additional or updated files with the hull data in the folder. The ship_output_by_speed.mlt has most of what you want. I got 2146Kw at 18m/s.

The froude number is quite high so without constraining coefficients you get a hull with very high block coefficient. These are beyond what I have actually tested. With froude above about 0.8 I compare the drag with a planing hull calculator to see if the displacement hull is best. I also prefer hulls that will have some lift rather than just round section even if predominantly displacement.

Leo has developed a more comprehensive program that can look at sinkage, lift and trim on a hull but it does not have any optimising component yet.

Anyhow just watching how the hull morphs is interesting. You will see if you reduce the design speed the hull will get a more conventional look.

I have seen some modern cats with very high block coefficients but nothing quite like I have here.

I have found playing with GODZILLA very useful in understanding the interplay of parameters and constrains. It is far more insightful than parametric analysis. It is also extremely fast. You should do about 10,000 iterations in a few minutes.

Rick W

[Leo Lazauskas]

Originally Posted by Rick Willoughby

I have seen some modern cats with very high block coefficients but nothing quite like I have here.

Ntheta should be much larger for cats operating at high Froude numbers.

"Optimising" for a single speed is not always the best strategy.

Good luck,
Leo.