Re: New to modeling how to…

DELFTship forum Hull modeling New to modeling how to… Re: New to modeling how to…

#35189
otaku
Participant

Hi,

Digest this in small, manageable parts unless you need a cure for insomnia.

Okay…

Turn on mesh.

If desired, turn on Stations, Waterlines, Diagonals, and Buttocks.

Before you export, turn on the mesh and interactively use the various shading/gausing/stress view modes to look for inconsistencies in your fairing.

If you have DS Pro:

Turn on the “Show Control Curves” feature

Turn on the “Show Curvature Plot of Intersection Lines” feature

For managing the control curves, select a few at a time and hit F7, keeping a KEEN eye on each viewport. Train your eye to notice movement of larger items on a vp while you may still focus on another vp.

If your hand is unsteady, be sure to save periodically so that you needn’t undo-undo-undo endlessly.

Be sure to check out the Undo History and how it can help you via its graphical history view.

Export the model as a DXF 3D Mesh file.

Export the model as a DXF 3D Polyline file.

Into AutoCAD, import your … wait, in ACAD, you just OPEN the model. You’ll see the very gridded mesh of your hull surface. Depending on your display and shade mode settings in ACAD, you might become disoriented. Depending on your scroll/zoom/UCS settings, you may have lots of flicker — all depending on how many stations, waterlines, buttocks, and diagonals you have in your model.

Creating shell and deck plating in ACAD to obtain solids.

INTERRUPTION:

How *I* do it

I break down the hull into creased areas (not ideal or necessary for a small craft) because I’m designing 560′ ship. There i is no way I want one, large mesh to be my model. This may in theory be something to rave about. Some shops and ship builders like it because it’s simple and greater control can be had over a model with as few control points to herd as possible. I break it down for two major reasons:

— model management, so that memory consumption can be dramatically reduced (I don’t always want to zoom through 177mx19mx30m of steel and structure and ladders, even though the model pans and zooms fairly fast. The eye clutter can be annoying)

— compartment mass and CGs calculations (I want to know mass and centers info on a compartment basis, not just a whole hull basis, and I can get either by selecting items of interest and looking for moments and other info in a very neat and tidy panel or I can export it to a neat CSV file with next to no pre-formatting and faffing about, compared to ACAD, which at least in 2008 has moments and other data of different types on one or more or the same line, frustrating efforts at fast manipulation of exported mass props… at work, that irriated the bejeezes out of me, and is another reason I use Punch! ViaCAD)

But, I don’t have high-end, steep-learning-curve software. I have to force Delftship to give me what I need rather than use it how it is designed.

Ages ago (back in 08), i could not figure out why my color-coded sideshell pieces were not snapping to the stations and creased lines between control points as I hoped they would. My whole, entire rationale behind how I do it is to use the same by-hand faired model as the basis of my chopped-up model.

So now, I use creases at my watertight bulkhead zones. This forces me to keep most of my control points as vertical and horizontal as possible so that any sub-creasing is predictable. Nicely, it even allows me to have some “removable plate” in the event I want to have actual see-through areas rather than do it in CAD.

Traditionally, and for fairing reasons, control points may be placed as buttocks controllers. They might never be horizontal. I used to try to use them as guides for decks, but I realized I could export the waterlines for that. Then, I realized I could add another wl serving as plate thickness. I could later extrude it from centerline outboard to the surface of my sideshell.

I then tell my CAD app of preference (Punch! ViaCAD Pro v7) to convert the mesh into a surface. I then THICKEN the surface. Unlike ACAD, which refuses to allow the user to input a mix of Imperial and Metric units in a drawing file without changing the file settings, ViaCAD allows me to specify any coordinatate in either measurement unit. I can enter the length in fractions or decimal points of a parsec and draft in meters and the beam in feet. It’s my problem if fractions and decimals pose a cutting problem, but it is very generous and useful a feature to not be constrained to pick one over the other.

ViaCAD does not allow thickening of a mesh, nor drawing to or referencing from the mesh in a number of cases. But, after converting it to a surface, I can do many things unless I have too much complex or compound curvature. This is where it can be handy to use creases, and not just for hard chines and hull edges.

Set a crease some minimal distance ABOVE the waterline so that during expected heeling or rolling or pitching, the wetted surface of your model is as faired as you can make it by hand. Above the crease, you can design however you want/need to.

Another good reason for creasing is that as long as your fairing is up to build standards, you can thicken various parts of the hull to differing amounts for balancing, strengthening, and weight/mass distribution. Why have one whole model (whether 10′, 30′ or 500′ or 1800′) all thickened to one value? Real craft and ships are not that way. So, i set my layer thicknesses accordingly. Same for the decks. same for the bulkheads. So, I force DS to be my pre-designer tool and my layer prep. Each compartment has a color and it is different from its neighbor so that I can visually keep track of where I am. Anyway, by breaking down the model into parts, in the case of large vessels, memory consumption and CPU work can be dramatically reduced because smaller parts are drawn, calculated upon, thickened, and so on. I’ve had 60MB models evolve from a 243 kb DS file.

Your choice of CAD tool is not for me to change. But, if you want to know another reason I use VCP for modeling my ships: the colors of the hull sideshell and deck plating are more enjoyable and easier to set and work with. Thickening a surface into a solid is so simple it’s almost childsplay as long as the surface is not overly compound and so long as any extrusions are based on carefully faired lines having no kinks or reversals on close inspection. I don’t believe you get a real solid in ACAD 08, not even in 12 or 13. IIRC, you get lines representing a solid, and you get shading, showing you. You can get some CGs and mass props, but setting materials and such is something that tormented me in ACAD 08. Even TurboCAD 14 or soe (from 2007/2008) tormented me, and nothing tech support suggested was ever satisfactory or really useful. When I tried ViaCAD 2D/3D, I was hooked, and so hooked I upgraded later to Professional.

If you have money or access to use a legit copy, you may indeed be well off using Rhino with Parametrics, or MaxSurf, or several others. Visit popular boat design site for more help that is able to help with design/engineering/theory/etc questions.

Hopefully, I didn’t make you fall to sleep, hehehehe.

RESUMPTION

I am not fully verse in AutoCAD.