How To Hull Thrust/Drag/Friction Calculation from AutoCAD Model?

[Shafri]

I've designing my boat in AutoCAD since Free!Ship cannot do sharp changes in boat shape/profile on my boat superstructure, it does it with spline/nurb or something like that which is limiting for me. So my noob question will be, since AutoCAD is generic 3D modeling without any specific marine analysis module/plugin...

How do i make computerized analysis on my boat hull designed in AutoCAD?

the possibility would be:
1) available AutoCAD plugin?
2) exporting from AutoCAD file and importing to another analysis program?
3) exporting and do our own analysis (manual)?

Any idea?

Here is (picture) how i model my boat in AutoCAD...
i'm using edgesurf to make the meshes, quite rough tough, i'm yet to be able to generate smoother splined meshes

[pavel915]

OK, so far i know freeship will not be good for the superstructure modeling , but you can make the hull in freeship and then export the 3d mesh to autocad.
If you need information regarding drag then the thing you need at first is to know which method you should use for your boat. If you want to use empirical methods like holtrop then you have to see whether if your boat is compatible with that or not.
Freeship can give you the different hydrostatic parameters which you will need to calculate drag according to any empirical formula , otherwise freeship can export the model to michlet. If the boat is a finer one then michlet may be compatible for your boat(you have to know about the range of boats for which michlet will be compatible)

So I will still recommend you to use freeship, or if you want to spend some money then you should buy rhino.

But i still believe, if drag calculation is your main concern, theoretical knowledge is more important than using a software.

[Shafri]

looking back closely my design, for each boat side, there is one sharp line that run from the front (a little bit below the bow? but above the water line) to the back connecting to transom, which i believe will be below the water line. so my hull will include this intersecting sharp line as well, which is still difficult for me to create in free!ship. thanx pavel for additional info like holtrop, michlet etc. i'll be looking into that. for theoritical knowledge, i have zero ,so maybe i should dig deeper on that, any link to usefull info? thanx.

[Tackwise]

Have you tried the 'knuckle line' feature in Freeship? From your acad drawing it seems to me that the hull is easily enough to reproduce in Freeship. Probably a whole lot easier than doing the same job in Acad.

I am guessing you have extensive experience with acad (compared to Freeship), which makes the acad seem easier than freeship. My advice would be to jump into freeship a little deeper, as it will pay back in ease of creating hulls shapes compared to doing the same in acad.

As for the drag calculations Pavels comments are very true:

But i still believe, if drag calculation is your main concern, theoretical knowledge is more important than using a software.

[Shafri]

ok mr tackwise, you solved it magnificently, i didnt know the term is knuckle/crease. one big problem solved. now the second problem emerged...

i tried to export back to acad since it is the only thing i know most(taught in college), for what? so i can print each boat profile (in large scale), in order to building it later. its the cut'ed' boat section at several places (parallel to beam). can be seen as red lines in my 1st picture. any tips of doing it in freeship? or exporting to acad? i've tried dxf export, but all i got is a blank space in acad.

[Shafri]

and again.. maybe i should do it deeper myself i know, freeship should be the way designing boat, but my knowledge makes it too alien for me at the freeship environment. + the manual pdf more explaining on the term/jargoning rather than a function on each menu by menu. o well, maybe i should print it and read it during afternoon coffe time.

[Tackwise]

To learn the potential of Freeship you will need to play around with it.
You can also try the following tutorial:
http://www.hapby.v-nam.net/FREEship/...Tutorial1.html

Your profiles (and others) are created with the 'intersections' button (located far right on the ribbon). Try it out to see the effects. (note: they can be made invisible, so if you see no effects, check whether they are visible, again a button on your ribbon)

good luck
Tackwise

[Shafri]

ok thanx mr tackwise. and also to pavel for his outstanding published thesis and ppt. that reveals how actually a naval architect works.