Flattening hull panels with CAD etc...

I've been doing a fair bit of reading about the various software packages which can (or cannot) flatten common side/bottom panels of boats and have a question I cannot answer about using CAD to do so. (Im not highly expereinced with 3d CAD)

Say one took the keel and chine lines in a 3D drawing and divided them into 10 segments along their length. By joining these points in a zig zag pattern one would be left with a series of triangles. Regardless of whether these points origionated on spline or constant radius arcs CAD software could certainly define the straightline distance between any 3 of these points in each triangle

Accepting that any two adjacent triangles could be laid out edge to edge using the common line one could lay these triangles out and acheive a "flat panel" version of the boat side or bottom. This could certainly be done manually in 2D autocad if the straight line distances could be evaluated using a 3d program. Of course the ultimate goal would be to somehow automate this proceedure and vastly increase the number of triangles untill the differences between the actual curves and the straight line segments was negligable.

Im guessing, for the size of boat Im mostly concerned anyway with (16-30 feet), the bow or chine lines would only need to be segmented perhaps every 1/2" to 1" to get a fairly accurate plate shape. Obviously once an automated procedure was developed this number of points could be easily increased for more accuracy.

Is there software that already does this or can AutoCAD, solidworks etc or similar programs be somehow instructed to perform a function like this automatically?

Hopefully I explained that well enough.

I may also mention that my goal is to be able to, within a resonable level of accuracy, draw panels for CNC cutting that I am already aware "can" be made. Im not concerened with using this method to try to push the envelope so to speak on whats developable and whats not. Nothing Im drawing is going to have such radical curves that it can't be made.

Cheers

 

Yes. The hull rendering packages such as Delftship do it. I am not certain if AutoCad will do it but there will be an add on for it.

Google "plate development". Even search this site for "development". It is a question asked every second week.

Rick W

 

Freeship and delftship will attempt to develop it if you tell the program to develop it...regardless if really can be delveloped. To see if this is possible they provide a right click menu with a mode submenu...one of which is developability check. This tells you if the layers are capable of being developed. All green except at the joints between panels is good...red isn't. Below is an example of developable panels. If there were large areas of red anywhere...then that particular panel or shape would probably not be developable and would need to be done a different way. An exception to this is if you used a single point to add a slight curve to the edge of a panel...say at the bow. That point would come up red as in the second hull. From experience I know I can stitch the resulting panels together loosely while they are faced together and unfold them and the plywood will conform provided it is thin enough or the panels are big enough. Not all curves will conform especially if they are highly rounded. The final picture is of a round bilged hull and has only minute amounts of developable area...mainly around the keel where the bottom is flat or has no compound curve.

 

Actualy, that method is not always possible. While it is possible to "tile" a 3-D shape with small tesselations (think balsa core scrims), in order to make a "panel" out of those tiles the rate of curvature must be very, very close to constant along each of the panels internal ruling lines (i.e. the internal join edges), something your method does not guarantee. As Rick said, look up "plate development" especially "conical development" or "conical plate development.

 

As i said my goal here isnt to try to force something I dont know can be made. I have enough expereince with the practical side of things to make sure thats handled in the design phase. These wll be gentle curves suitable for sheet aluminum fabrication.

Im more curious as to developing a method to go directly to CNC cutting machines without having to run a design thru 2-3 different software packages. If the system i suggested could be automated I know it would certainly serve my needs fine, I just dont know how to get a cad package to do the calcs automatically. Manually would work but be obviously tedious. Most manu facturers i am aware of now make a "best guess" and trim the panels once on the jig but to me this seems somewhat "barbaric" in the age of computers etc

Im favouring Solidworks right now for many reasons but this seems to be its one main weak link. It will do everything else i want it to, very well actually.

 

If you like SolidWorks then maybe SurfaceWorks will help you create the 2D cut files:
http://www.aerohydro.com/products/industrial/sfw.htm
There is not a large step taking a 2D cut file to a router cutter. I have personally only done manual lofting from printouts of cut files but there are others here that have set up their own CNC cutting tables - try emailing BG_Geno.

If you do not have the table then you need to talk to the plate shop to see how they accept the data. I have sent 3D igs files to machine shops for 3D part milling. They do the conversion for their particular machine input and make allowance for tool passes and surface finishing. Sometimes they will ask for a slight change in shape to suit the machine tool.

Rick W

 

John

Hi Rapager

Any proper 3D package will do what you are looking for. Solid Works or Autodesk Inventor. If you can find anyone in any form of sheet metal engineering business - they could do the flat patterns for you.

Kind Regards

John

 

Solidworks, Inventor etc will flatten foldable sheet metal parts. They wont flatten surfaces with compound curvature.

Have a look at Rhino,

Maxsurf and workshop do it best in my opinion. You can find them at www.formsys.com. You can buy a 3 surface version of maxsurf and a plate development only version of workshop. That's what I use in conjunction with Inventor.

 

Again the foldable things aren't what concerns me. I wish to find a simple solution to get the lower bow plates and the hull sides into a 2d drawing I can then process using CNC equipment. I just am not expereinced enough with the advanced features of the various packages to know which will do this easily. Again if I were to make an excel worksheet with three columns with each length of the sides of each triangle calculated using 3d cad I can just sit and draw all the triangles in 2d cad and end up with a flat panel which would roughly estimate the outside shape of the panel. The more triangles I used the closer it would get to the actualy panel shape, Im sure there is a calculus fomula to demonstrate eventually you would be almost perfect however if I cannot automate the process Im obviously not going to use say 1000 thin triangles haha

I dont believe the balsacore/tile example as you stated would be an issue as when the panel is drawn it would be flat in 2d. I dont think the material thickness to curvature ratio would make any difference when drawing panels 16-30 feet long when they are only 1/8" or so thick.

Again my question is not so much about the process, I know it would work, its more how to automate that process..


Thanks

p.s. Ive looked at Rhino but when put beside Solidworks I dont think its even close, unless you consider price. Im heavily leaning towards Solidworks but would assume not have to do my design work using two seperate peices of software, especially since solidworks handles the rest of the issues extremely well. I really like the design theory behind how solidworks is based and believe for many of the other aspects of my build will be very favourable.

 

Perhaps you should have a look at TouchCAD. It has a rather different approach where each 3D panel has it's own parametric unfolding setting, and where the unfolded parts are dynamically linked to the 3D model. The advantage is that you can at any time modify the 3D shape and instantly see what happens in the unfold, which acts as a view. The resolution you mention is parametric and can be changed numerically at any time. This also applies to stripping a panel into sub-strips, and analyzing how much double-curvature you have. You can even nudge 3D control points in the Unfold view and instantly see the result, which means that you can dynamically optimize the unfoldability of a 3D panel. You can also nest any number of unfolded parts in the Unfold view without loosing the dynamic link to the 3D model, which means that you integrate the use f the material into the design process, and essentially deliver ready to cut layouts that can be sent directly to the cutter driver program. The TouchCAD package of course also include marine design necessities such as dynamic cross sectioning required for hull fairing and so on. It is also a capable 3D modeler, where you typically design pretty much all major panels in the boat, and dynamically and automatically keep track of the weights and center of gravity of the boat throughout the design process.

You you like to see the process demonstrated, I suggest a visit to this location:

http://www.touchcad.com/tc3trainMarin.html

www.touchcad.com

 

JohnGilpin

Hi Rampager

In Autocad,draw the boat profiles (sections) you want. Import these sketches into Solid Works, off-setting and positioning them correctly - reletive to your start point.
With these sketches floating in free-space. Use the 3D sketch tool to draw splines to connect the points you want - create a lofted surface between to splines (3d curves in this case ) - then click flat pattern button. Solid Works will flatten it - but say there is an error. Ignore this, and sketch on perimeter off compound flat pattern - extrude - and export back to AutoCad.

I have done this recently - it works.
However if you are to cast the hull - a huge polystyrene mould could be cut, this is what I have seen for carbon fiber anyway.

Picture Attached

Best of luck.

John

 

Interesting idea John, I will try that. Did you draw the sides of that boat you pictured using that method? I probably would rarely have much more curvature than you do there on that side panel, altho my boats will be of a much different style.

I'd likely have the panels for the model already drawn in Solidworks in 3d as a "shell" but could certainly do as you are suggesting.
If this worked and I could simply generate the flat panel nests for the CNC guys right in solid works and thats would be really ideal, only one software!

Thanks for all the suggestions guys, keep em coming. This is a really rough sketch of the method I want to automate.

 

Rampager, back in -73 or so, when a personal computer had a roaring 64 kb of memory, I wrote a simple program in Basic to do just the kind of rollout you sketch. I'll see if it can be printed to a modern machine; maybe it could give you some ideas on how to proceed (or maybe it's just neanderthal crap......). At least it could be rewritten to an Excel format which might accept coordinate inputs from other sources?? I'll be back......

 

I'm not gonna ask how old you are

My dad taught early computer science way back and I remember how big a deal it was when he could "borrow" a Commodore PET, what did that thing have like 8K I think? Ahhh the good old days of the casette tape drive that took what like 15 mins to load a game hahaha

 

The method suggested by johngilpin will work if the panels are flat but wont if you want some curvature - especially in a bottom plate.

If you have the logic you can always write a vba macro to automate the drawing process in autocad. Lots of books at amazon. Just search for autocad vba

Have a look at Inventor before you settle for Solidworks. I much prefer Inventor. Much more stable, less bugs, better drawing control, more features at entry level price, ie rendering, revision control (vault), standard component library and it comes packaged with Autocad Mechanical and Autocad. When you consider the cost of autocad, the bit more you pay for the Inventor package is a bargain. No matter what anyone says, you will still need to make 2d drawings at some stage and autocad is the best, especially now that is has parametric relationships. The 2D dwg editor that comes with solidworks looks like autocad but isnt as good. Go to the forum at https://forum.solidworks.com/index.jspa and see what other users are saying.

Again Solidworks, inventor, solidedge etc (which all use the same parasolid kernel) will not give you a DEVELOPABLE hull bottom, which is why I use workshop for this.

The other way is to buy the full versions of maxsurf and workshop, do your entire model in maxsurf, flatten everything in workshop and detail your drawings in autocad - but it wont be paramtric. Dont forget you will at least need to be able to do level hydrostatics to deterimine how your boat will float. Maxsurf does this fine for small boats, hydromax does it much better for larger boats.

The other cheaper option, rather than spending all that time and money on software would be to just buy a design.

Good luck.