Michlet Offsets from Rhino or GHS?

[gdmw]

Does anyone have a fairly simple procedure for generating Michlet offsets from either Rhino or GHS geometry files? Perhaps a macro or script that applies an "egg slicer" approach to cutting evenly spaced stations and waterlines, then exports the lateral offsets to a text file?

BTW, Michlet does not recognize a Dvorak keyboard layout that some of us use to minimize RSI or speed up typing.

Geoff

[Guest625101138]

Freeship and Michlet import/export happily. There is one little screw up with the number of waterlines but this can be set at the time of importing.

So if you can get your hull into Freeship it will do the transfer. It will import common offset text files. DelftShip pro will import iges and export to Michlet.

I fiddled with an Excel file to generate stations from Michlet but it is much easier just to use Freeship.

If you have an IGS file of the hull I can produce the .mlt file for you. Just let me know the speed range you want.

Rick W.

[gdmw]

I work in an organization that sees freeware as a security threat, no matter that it's been blessed by any particular authority. Our marine work is a small part of the big picture, so there's reluctance by management that doesn't really understand the marine industry to get more and more specialized software. Also, our hulls are proprietary (even with three boats of similar design in the water), so I can't just send the files to anyone I haven't met, especially overseas. Are there any solutions that don't involve getting new software?

[yipster]

not absolutely sure but think Leo Lazauskas also has a non-freeware version

[Guest625101138]

Originally Posted by gdmw

I work in an organization that sees freeware as a security threat, no matter that it's been blessed by any particular authority. Our marine work is a small part of the big picture, so there's reluctance by management that doesn't really understand the marine industry to get more and more specialized software. Also, our hulls are proprietary (even with three boats of similar design in the water), so I can't just send the files to anyone I haven't met, especially overseas. Are there any solutions that don't involve getting new software?

You should NOT be using Michlet - It is freeware.

You can buy Delftship pro. Of course it is not as "cost effective" as FreeShip but overcomes your company's policy - how can you beat zero cost with exceptional functionality. It has slightly different functionality to FreeShip but imports from and exports to Michlet in the same way as FreeShip.

The real value with Michlet is the Godzilla component and I am certain this will produce a better hull shape than any other trial and error approach you may be using now! It conducts about 1000 trials a second, building on the best result, so you can get years of development done in a few seconds.

Give me you design constraints and I will get Godzilla to produce you the best underwater form.

Rick W.

[gdmw]

It's not impossible to get freeware or specialized software, just arduous.

I was able to install FreeShip without having administrative rights on my computer. I-DEAS let me export my hull as VRML, but apparently not the version 1.0 that FreeShip needs. So I tried exporting from Rhino, which did let me choose version 1.0. My first try gave an out-of-memory error, but minimum mesh size worked. Even so, the Michlet Export icon is greyed out. I'm not surprised, as each of my symmetric hulls has asymmetric control fins attached. Also, they do not constitute any of the three FreeShip options for monohull, catamaran, or monohull as catamaran. A lateral thruster duct doesn't help, either. I'll try going back to chop off the fins, then repeat the process on the forward and aft hulls separately. Or am I wasting my time?

The Godzilla component of Michlet doesn't seem to let me constrain the longitudinal metacentric height, just the transverse one. The waterplane area lets me approximate the heave natural period, and the GMt lets me approximate the roll natural period, but I need the GML to see whether the pitch natural period is a problem with respect to the others and to the sea spectrum. Zero speed seakeeping is one driver, and resistance at cruise speed is secondary to that.

Geoff

[Leo Lazauskas]

Originally Posted by gdmw

It's not impossible to get freeware or specialized software, just arduous.

I was able to install FreeShip without having administrative rights on my computer. I-DEAS let me export my hull as VRML, but apparently not the version 1.0 that FreeShip needs. So I tried exporting from Rhino, which did let me choose version 1.0. My first try gave an out-of-memory error, but minimum mesh size worked. Even so, the Michlet Export icon is greyed out. I'm not surprised, as each of my symmetric hulls has asymmetric control fins attached. Also, they do not constitute any of the three FreeShip options for monohull, catamaran, or monohull as catamaran. A lateral thruster duct doesn't help, either. I'll try going back to chop off the fins, then repeat the process on the forward and aft hulls separately. Or am I wasting my time?

The Godzilla component of Michlet doesn't seem to let me constrain the longitudinal metacentric height, just the transverse one. The waterplane area lets me approximate the heave natural period, and the GMt lets me approximate the roll natural period, but I need the GML to see whether the pitch natural period is a problem with respect to the others and to the sea spectrum. Zero speed seakeeping is one driver, and resistance at cruise speed is secondary to that.

Geoff

Strange that you are having trouble with installing Michlet. I sold a version to the Combatant Craft department of nswccd.navy.mil a few years ago. Maybe there's a block on using other versions. If you're in that part of Virginia, ask some other NAs.

I have deliberately left out many features in Michlet so I can pick up a bit of contract work here and there. Another reason is that I hate writing manuals. I don't need manuals to run my own codes .

Now that I'm unemployed again, I doubt that I'll be releasing much for free until I get my head above water financially.

Good luck!
Leo.

[Guest625101138]

I understand your problem with computers. I now have my own as I got fed up with the IT people taking ever increasing control. My employer has 80,000 employees and most have no deeper computer knowledge than word processing. Not much beyond basic use of MS Word. So I understand the IT problem but I do not want to be constrained by other's lack of understanding.

However I do not understand why the Michlet export is greyed out. Just open the default hull and see if it is still greyed. You may have a version where the functionality is not turned on. I tried a few things with FreeShip and the only way I could get Michlet to grey out was to delete all the points.

I do not think I have ever exported a catamaran from Freeship other than as single hull. The export does not work properly with two hulls. I use a single hull and select to export as catamaran when the export window pops up. If there is a way to do I have not yet got it right. In any event I usually start with Godzilla. I don't think Godzilla produces an asymmetric hull either.

Finally I think you are snookered from doing it simply by the fact that FreeShip only allows symmetrical hulls if you want hydrostatics. Without hydrastics there is nothing to export to Michlet although the menu is still active. I have not played around with asymmetric hulls so not functionality I have had to explore.

Rick W.

[Martijn_vE]

Originally Posted by Rick Willoughby

However I do not understand why the Michlet export is greyed out.

The option in the menu is only disabled when:

1. There's no hull geometry (obviously....)
2. You haven't set your main particulars

[Guest625101138]

Originally Posted by Leo Lazauskas

....

Now that I'm unemployed again, I doubt that I'll be releasing much for free until I get my head above water financially.

....
Leo.

Leo
How could someone of your talent be unemployed??? Australia is an abysmal place for supporting real talent.

I wish I could afford to employ you full time. Maybe you you need to advertise - math gun for hire.

Have you got some Michlet functionality that an average joe would be prepared to pay for.

Good luck with whatever pursuit you eventually end up in.

Rick W.

[yipster]

VRML still puzzles me, tried both versions and version convertor.
a poor exchance file format but never understood why VRML import
in freeship only occasionaly gave the right mess

[gdmw]

The port forward bare hull (which is symmetric inboard and outboard) imported from I-DEAS through Rhino (via IGES) to FreeShip (via VRML), but the mesh wasn't quite symmetric, and the Michlet export was still grayed out. Then I found the "Project Settings" that Martijn mentioned. Populating those fields let me access the Michlet export icon.

When I tried it (with either the "Monohull, send as catamaran" and "Catamaran" options), the resulting in.mlt file had all zeroes for offsets, and the displacement was zero. So I went back to Rhino and split the hull on its own centerline, deleted the inboard, cutting, and waterplane surfaces, and exported to VRML (this time with medium mesh density). The subsequent Michlet export file from FreeShip still shows all zeroes in the offsets.

I'm allowed to enter a Length, but not a Volume in the "Hull geometry" tab of the "Michlet file generator" window that I get when I click the Michlet icon in FreeShip. It also shows a grey window below the data input area. Am I supposed to see some graphics there? The scroll bars are very slow, as if I'm looking at a very small part of a very big field. Moving them does not reveal anything.

Geoff

[Guest625101138]

It sounds like the boat leaks. You do not need to enter a hull volume as Freeship will work it out. Do a leak check. Or look for green points below the waterline. Do all the edge points on the keel line have zero "y" coordinate.

Rick W.

[Steve Baer]

Cutting sections through geometry and exporting those sections to a file is pretty simple with RhinoScript. I don't know the Michlet file format so there may be a lot of data that is more difficult to place in the file. You can get a lot of RhinoScript help at the Rhino plug-ins newsgroup.
news://news.rhino3d.com/rhino.plug-ins

Thanks,
-Steve

[Guest625101138]

I have attached a Michlet input file with a txt extension so it is easily opened.

The hull is the starter hull from FreeShip with 11 stations anf 5 waterlines set at <Export> to make the Michlet offset matrix very small. The hull matrix directly from the file is:
<
# ============================ FIRST HULL ==============================
# Offsets
0.000,0.000,0.000,0.000,0.000
0.000,0.000,0.000,0.000,0.000
0.000,0.000,0.000,0.000,0.000
0.000,0.000,0.000,0.000,0.162
0.000,0.000,0.381,0.573,0.692
0.000,0.482,0.667,0.784,0.871
0.000,0.408,0.638,0.773,0.872
0.000,0.000,0.000,0.436,0.649
0.000,0.000,0.000,0.000,0.000
0.000,0.000,0.000,0.000,0.000
0.000,0.000,0.000,0.000,0.000
# Displacement Volume (cubic metres)
5.7960
# Length (metres)
12.0000
# Draft (metres)
0.5000
>
So the values shown are the beamwise coordinate. The stations (longitudinal coorinate) are equally spaced (12/10m) and the waterlines are also equally spaced (0.5/4m). So if you have an offset table it is not particulary hard to make a transformation in Excel that will produce the Michlet offsets.

Leo has simpler means of generating a hull using his functions but this offset matrix has to be the most efficient means of specifying a generalised surface.

Rick W