Modelling Hull + Internal Components

[Rupes]

Hi,

I know there are probably a lot of threads that answer this question to some extent, but Im after some quick opinions.

I am due to start a project to implement CAD capability in a small boatyard producing 20-40" GRP boats. The initial phase is to select the appropriate hardware/software and then to model both the hull and internal mouldings of the yards' newest design. I have used Maxsurf and appreciate its benefits in surface modelling (i.e. for the outside surface of the hull), but what is going to be appropriate for 'solid-modelling' the deck and internal mouldings? I understand they are currently working from 2D Autocad drawings.

I know the benefits of CAD systems are not as far-reaching for the production of smaller craft as they are in larger shipyards, but the company is looking to achieve a 3D model of the complete construction, component by component - is this achievable and which software would you suggest?

[Andrew Mason]

For composite hulls I would suggest your choice is probably going to be from the following five programs -

ProEngineer - good parametrics, but surfacing could be better.
SolidWorks - very good, widely used.
Solid Edge - similar in functionality to SolidWorks, with addition of some excellent surfacing code.
AutoDesk Inventor - widely used program from authors of AutoCAD
CATIA - powerful, but very expensive.

All will import IGES NURBS surfaces directly from Maxsurf, although ProE sometimes does unpredictable things with them.

[Rupes]

Thanks for the quick reply Andrew.

Funnily enough it's going to be my first job in the sector (just finished my Degree) and I had to present at the interview on the transfer of lines plans into CAD systems - your tutorials on the Academic site were infinitely helpful.

Cheers!

[MikeJohns]

Rhinoceros is another good contender that shouldn't be overlooked. It imports IGES too cost is low, it's easy to use has good surface tools and works seamlessly with the FEA packages we use.
Pro Eng. costs too much to be a candidate for your needs.

[Andrew Mason]

Rhino is a good general purpose surface modeller and is useful for doing additional detailing of surfaces that come from a naval architecture system such as Maxsurf, but it is not in the same class as parametric solid modellers such as Solid Edge, SolidWorks and Inventor.

[eckmuhl]

Rhino is wonderful to design deck and it is really cheap . But it is not really useful to draw hull & structure , for interior design you can try if you're ready to spend days &nights on it cause it's not a parametric software so after every little modifications you just have to do it again and it's happen a lot in yacht design . I have tried to do it for my final school project, it was nice, but hopefuly the yacht wasn't for building cause i will have to spend too many time on modifications ;-) to make it realistic.
If you have money (a lot) and time to learn to use it you can use Catia it can bring you every tools you need to design a full yacht (deck,interior,structure, FEA, electricity , water , people moving on it... ) I think maybe Pro Eng do the same , some people must know...
For the hull shape Maxsurf Pro is really great especialy if you have the package with Hydromax, Span etc.

[MikeJohns]

Parametric solids modellers and 3D Wireframe/Surface Modelling are two utterly different appraoches. Neither is superior they are quite different tools. For a "surface" oriented project a surface modeller is best. For a mechanical part the solids parametric modeller is superior. Surface modellers are more open to free-form manipuluation of the design. There is no hard and fast rule here.

Having used a plethora of packages over the years I find Rhino the most intuitive 3D design package and Autocad the standard draughting package of choice. Neither of them are parametric but engineers produce results just as well with any reasonable package. Once it gets past reasonable its just icing on the cake.

Have a look at
http://www.cad.com.au/cad/Mechanical%20Design.html
and beware of opinions based on vested interest.

[Andrew Mason]

Mike

As the principal author of a surface modelling program, I am more than aware of the differences between and relative advantages of surface modellers versus solid modellers.

I am also aware of the deficiencies that Rhino has for real production work - it lacks any true parametric functionality, its solids modelling is rudimentary, it doesn't even have the dynamic surface trimming that Maxsurf has.

What Rhino has going for it is price, it is a powerful program for the money. But there are programs that are 5-10 times more expensive that are better value in a production environment. In real terms, the cost of SolidWorks relative to the cost of the item being produced and the man hours that are expended is not a factor unless you are operating on a real shoestring budget.

As you say, engineers produce results with just about any reasonable package, but at what cost? If you are happy using a less capable package and putting in the extra hours needed to do the modelling, followed by any required rework of the model, that is your prerogative, but others possibly place a higher value on their working hours.

On the subject of vested interest, I clearly have a vested interest in Maxsurf and I think that is clear from my stated affiliation. In this case however we are not discussing Maxsurf and I do not have any relationship with the developers or resellers of any of the parametric solid modellers I previously listed.

Please note that I do not recommend solid modellers for vessels built of sheet materials such as steel and aluminium, in this case the solid modellers are overkill for what is really a surface model with implied thickness. For these vessels a dedicated system such as ShipConstructor is the best solution.

[MikeJohns]

High end tools can be useful, but we only model really complex 3d models for FEA input.Otherwise its simple std 2d draughting.

The most used tool in an engineers arsenal is a spreadsheet, and this is where we put the bulk of our hours. Only when the numbers add up do we start generating the drawings. Revision rates are then low.

So tongue in cheek I can say we generate hull shapes mathematically using the wonderfully high end marine package from Microsoft called Excel.

We then generate script files to generate the surfaces in the CAD package of choice ( used to use Autocad and tried Solidworks and others, now use Rhino).

All the internals frames etc can be easily represented as surfaces , its simple works well and I recommend it.

What you tend to overlook perhaps with Rhino is its powerfull plugin facility and the growing base of very usefull addins that extend this package well beyond its packaged disribution .

As an aside we have tried a few of the solids modellers with regard to FEA input (FEA on the PC is where we really save the hours ) usually end up re-generating the whole thing in the FEA packages modeller cause the import screws up big time, no matter how much the FEA authors claim it works. So you end up importing nothing more than some points from the CAD package to use as guides. End up pretty jaded about high-end solutions.