Work Flow from other CAD to DELFTship

Hi All,

I am trying to figure out a workflow for hull modeling. My primary MCAD is Shark Fx by Punchcad. It has a full set of tools to go from a 3D solid model to construction documents but lacks a couple of needed tools, particularly the ability to flatten developable surfaces for CNC cut patterns and hydrostatics. I had thought to develop the hull model in DELFTship, then bring it into Shark to create the 3D solid, sections, etc. But, try as I might I am having a difficult time learning how to use DELFTShip. As a result, I would like to develop the hull shape in Shark and import it to DELFTship for flat patterns and hydrostatics. The problem is that I have not found a format that will work for data exchange. I have a pretty good collection of export formats available to me. VRML imports but the defining lines of the surfaces of a hard chine hull come in as control curves for a round hull. I have attached the hull model in Rhino format (one of my export options).

Mark-

 

Since you can export to Rhino, you could develop your hull with Rhino. It works really well. If you google "Rhino hull design tutorials" you will find some useful information.

import and Export with Delftship is always difficult. VRML or IGS seem to work the best but not always satisfacotrily.

 

You could still do your hull design in MCAD and then export to Rhino for the hydrostatics and plate expansion. Still exporting/importing is always a pain and generally sucks. If possible you should try to do as much as you can with one piece of software.

Anyhow, I was able to unroll your model in Rhino easily. The default Rhino hydrostatics only include centres, volume, wetted surface area, length on WL, and waterplane area. Not stuff like the yachty prismatic coefficient and it won't let you add weights to get metacentres. Still I find it is all I usually need for preliminary work. In order to get meaningful numbers out of it you need a completed hull joined into one polysurface.

 

I would learn the Hydro software and use it to develope your hull. My experience in the reverse is severely unfair hulls. You get all of your hydros directly and if you have to change something, you see the effects immediately.

 

Why not design the surface it the software you have which works best for that purpose, and then export the design to the "hydro" software for analysis. Based on analysis results modify the design in the design software, analyse it again, modify again, etc. I don't see how this results in unfair hulls.

 

Unfortunately, the problem exporting the hull into a hydrostatic program. I suggested using the hydrostatic software for hull development because it has the tools for the task. Freeship/Delphship has a limited number of ways to import surfaces. I'm not sure that Shark of Rhino has that export capability.

I don't mean to say that you can't build a fair hull in a CAD system. I think that it is more work. I just feel that there are more tools for hull development in a hydrostatic package.

 

Shark of Rhino ????

When you say "hydrostatic software" are you refering to FreeShip/DelftShip and derivatives? I can export VRML files of a hull surface from Rhino, import the file into FreeShip Plus, and run the hydrostatics analysis on the surface.

Rhino exports about 50 different formats and imports almost as many, and that's not counting all the variations of individual formats.

That probably depends on the CAD system. There are vast differences between software intended primarially for mechanical and architectural design, particularly software which started as computer drafting software, and software such as Rhino and Alias which were developed for designing arbitrary surfaces. It also depends on what the individual has experience with. I've experimented with FreeShip Plus but find it much simplier to get the shape I want with Rhino.

 

Shark or Rhino.


David,

Thanks for your insight. It's been a long time since I ha ve demo'ed Rhino and I think there have been tremendous steps forward with it in the intervening years. It's time to look at it again.

Hydrostatic software: Freeship, Maxsurf, Prosurf, Fastship, etc...

 

Hi All,
Thanks for your replies! I had looked at Rhino with a plug in but I was hoping not to need to purchase two pro-level cad packages. Shark is a very good professional MCAD package and I already own it, but lacks the capabilities in my first post. I have been experimenting with FreeShip and DelftShip (FS/DS) and found that import chines works but the import file must be manually created. I have also managed to get a bit of a handle on developing the hull in FS/DS but I really don't like the way hulls are developed. I prefer to create the shape I want directly rather then starting with a prototype hull and pushing/pulling it into shape. With a limited number of control points it may still be pretty fast to do it that way though. I have not tried importing a VRML file*created in*Rhino, just Shark with the described problem.

 

I'd keep plugging away at it. It feels a bit daunting and first and definitely cumbersome to create your hull by moving a bunch of control points in an infinite number of places. I think it's the best option for the price. I'm in the same ballpark when it comes to CAD software. It's hard to justify commercial quality for entertainment purposes. It becomes less daunting and cunbersome with time and experience. If you're already modeling in Shark, it will be a simple task to import the DXF model from Freeship and utilize it's control mesh to create it's solid model. I'm on a quest for direct utilization of Freeship output.

I'm posting a screenshot of my current project hull with it's control mesh displayed. Hope it might provide a little inspiration. Once, you get your hull close to where you want it, you will want to start working with the hull fairing tools. Control Curves and Guassian Curvature display are the two key tools in this regard.

 

FreeShip

Thanks LP, I am working on it. In fact I have a question for anyone looking at this thread.

I have a hull close to what I want but I can't unroll the sheets. I understand that I need to have each plate on a separate layer, but can't seem to change the objects layer. I developed the hull from the round hull prototype so it is all on one layer. How do I change each separate surface to it own layer?

Also, I want to put a traditional long keel on the hull, similar to the one you have LP, but to the transom with a transom hung rudder. The appendage tools don't have that available. I have attached my model.

 

A quick response to your question. Create a layer under the layers menu icon. Make sure you are in wireframe mode. Turn on Mesh display. (Third button right of your display resolution drop down menu.) Select all of the mesh panels you want on a different layer. Select the layers drop down menu and select the new layer. Make sure you deselect all of the mesh panels or you might find they are on a different layer.

You're using a later version of Freeship so I can't view your model. There are multiple ways to add an appendage. If you are looking for a foil shape, you can use the keel and rudder wizard under TOOLS and modify it to suit your needs. Another way is to EXTRUDE an edge from the centerline of your transom. Just extrude it a short distance and extrude it again. Delete (trashcan) the first extrusion and that leaves you a square NURB to start building your rudder shape out of through further extrusion, and edge work.