engineering CAD (solidworks / pro E) vs. boat software

[Kwolf]

hi,

i'm new to boats. I'm a mechinical engineer, and have access to professoin engineering CAD packages. For FEA, i use inventor simulation. For CFD, i use openFOAM. What's the advantage of the boat software people use over the real engineering code?

DELFTship is a lot less expensive than a professional CAD package, with stress analysis extensions.

I'de like to approach boat design with the tools I already know. Any thoughts? has anyone used openFOAM to model stability?

Single sculling rowing shells are the boats im interested in.

 

[Kwolf]

also, any good books on boat hydro statics, boat ladings, and composites you all would recommend for a BSME reading level?

 

[Ad Hoc]

Single sculling rowing shells are the boats im interested in.

Hi Kwolf, Welcome to the forum.

All the FEA and CFD in the world wont help you with the basics. Forgot them...just buy a good book on small boat design, its all you need. Unless your bidding for a world record, you wont be doing stress analysis or hydrodynamic calculations that shave off 0.0001% here and there.

If you can do basic hand calculations of stress, that is all you'll need for such a boat. The rest, hydrodynamically that is, is simple length-displacement ratio...i.e. make the boat as long and thin and as light as possible.

 

[DCockey]

also, any good books on boat hydro statics, boat ladings, and composites you all would recommend for a BSME reading level?

Principles of Yacht Design by Larsson and Eliasson would be a good book to start with.

 

[Leo Lazauskas]

The rest, hydrodynamically that is, is simple length-displacement ratio...i.e. make the boat as long and thin and as light as possible.

Further to that, I put a collection of length-displacement ratios for existing
rowing shells in another thread. See:
http://www.boatdesign.net/forums/at...chlet-godzilla-questions-extant_hulls_geo.pdf

 

[SukiSolo]

I have built shells in the past, not my design. However they were, and are pretty quick ones. There is a lot of stuff on design out there from Dr Bourne's two pennies on top of each other rolled apart to give the mid section to attempts at planing hulls.
It's like any small hull, build the real thing full size and try it. I have been told by naval architects with regard to small sailboats (4m) which do plane that no software currently will accurately predict all the behaviour. It might not be far off but there is only one way to find out. As a design engineer with 40+ years small dinghy racing in lots of different designs, of course I've built and designed a few boats now. Last one is genuinely quick as its a 'One Design' class with quite a bit in the tolerances....

Back to shells, if you row a lot, try different shape shells if you can. See how each one behaves in different conditions ie smooth/rough water wind etc. Understand the different shapes that are operating under the water and also as air drag, ie deck/riggers etc. Bear in mind the weight transfer of the body, I believe this is very significant in developing a fast shape. Trust your intuition with the shape and don't be afraid to modify it once you understand where it needs to be improved. It might be spot on, like right first time engineering without a prototype, ha ha. You might end up with a shell shape not unlike an AC72 hull, with white bobbin stuck up top! K1 canoes are not miles away but do not have that weight transfer/thrust cycle in the same way.

Software package won't matter, I've used both Pro-E and SolidWorks and I'd be quite happy doing a shape in Rhino alongside a 2D for dimensioned details drawings etc. The only real advantage in surface modelling is it lets you go through more options in less time. Most of the sweet shapes could quite easily be drawn by hand in 2D and many have been in the past. Software is just a tool like a plane or a chisel or a pencil.

 

[baeckmo]

Software package won't matter, ......... Software is just a tool like a plane or a chisel or a pencil.

To be copied into major scale, printed in red and nailed to the wall in front of every designers/engineers working station!!

 

[DCockey]

To be copied into major scale, printed in red and nailed to the wall in front of every designers/engineers working station!!

I complete agree that "Software is just a tool like a plane or a chisel or a pencil."

But it needs to kept in mind that the particular software packaged used does matter. "Software is just a tool like a plane or a chisel or a pencil" and like a plane or a chisel or a pencil there are appropriate and inappropriate tools for the job. Scrub planes and finish planes are suited to different tasks as are butt chisels and paring chisels, and carpenters pencils and mechanical drawing pencils.

My understanding is software for mechanical design such as Solidworks, Pro-E and Inventor are optimal for design work with regular, geometrical elements such as planes, cylinders and spheres, but are not particularly adept at arbitrary curved surfaces which are critical in much of boat design.

 

[Ad Hoc]

My understanding is software for mechanical design such as Solidworks, Pro-E and Inventor are optimal for design work with regular, geometrical elements such as planes, cylinders and spheres, but are not particularly adept at arbitrary curved surfaces which are critical in much of boat design.

Are you saying that aircraft and cars don't have curved surfaces?

It's all about investment/money. High volume large output products "tailored" for such industries. The same software can be used in the marine field. However, I cant image Joe Bloggs buying a bit of software costing more than his house just to draw (I stress draw not design) and build a boat.

Once the 'curves' are done, the rest, is child's play...and linked, or not, to a production schedule/procurement/admin system. Again, hardly suitable for Joe Bloggs, a company building vessels though, yes.

Critical curved surfaces are easily addressed and quickly in marine/boat design it is just requires experience and understanding how such shapes are made. Which is what most of the softwares are attempting to do...take that "experience" and make it part of the software.

There were no computers in the dusty old mould loft shed when i first started, just highly experienced professionals. But they would work their magic just once per boat....hardly an "industry" worthy of major investment for anyone with a PC to play with.

The softwares that are cheap/accessible that exists today do the job well enough. They just don't link together very well nor parametric linking. That's what most people appear to want..which is more about processes, fabrication and admin and saving production time, not design per se.

 

[FirstLight]

Solidworks and Delftship - Works for me.

My two cents are that use what you are used to if the pieces will fit. I too am an ME and have spent thousands of hours in Solidworks. It does a good job with the structural elements of yacht design. I use Delftship for the hull design and hydrostatics and move from Delftship to Solidworks with .iges files. There are several simple tricks you can use to tie the two together in the event that a hull modification is made in delftship so the corresponding changes in SW are made.

There are so many ways to get this job done with all of the tools available. It's about picking one and sticking with it. And I think the one that you pick should have elements of what you have experience with.. Just in the interest of minimizing the learning curve.

Here are a couple photos from Delftship (freeeship) and Solidworks. There's a bunch more at www.mildrice.ellavickers.com




Again.. Just my two cents..

 

[DCockey]

Are you saying that aircraft and cars don't have curved surfaces?

Aircraft and cars have curves. In the auto industry at least (I'm not familar with current practice in the aircraft industry)software such as Solidworks, Pro-E and Inventor are not used for designing the curved surfaces of exteriors and interiors. Rather software more suited to that task such as AliasStudio is used.

 

[Ad Hoc]

In the auto industry at least (I'm not familar with current practice in the aircraft industry)software such as Solidworks, Pro-E and Inventor are not used for designing the curved surfaces of exteriors and interiors.

These 2 babies:



were designed used Inventor.

 

[DCockey]

These 2 babies:

View attachment 85220

were designed used Inventor.

Good to know.

 

[SukiSolo]

Main point is the advantage of Marine software lets say Maxsurf or whatever is they are geared to design a hull (or multihull) shape. They are dedicated tools and give you the necessary information straight away. General engineering packages are more geared to complex products (say washing machine full assembly model) Parametrics, production, drawing issues, revisions etc

The ability to push and pull surfaces, give curve of areas, Prismatic Coef etc is all part of a dedicated marine package. You can write addons to things like Pro-E to do this, and it has been done for some America's Cup boats.

If you can get your more general modeller to give you the shapes and information you need go ahead use it.

I hope you have seen the stuff about the Foiling Scull developed by Yale University. You will also find reference to a foiling scull developed in the UK in the early 1980's... it apparently fell apart whils airborne or should that be foilborne


Boeing use Pro-E for their planes. We had all the data from them necessary to design the interior of the First Class cabin area for the 777. Mock up full size built in Studio. You need the surface extension package in Pro-E to design almost anything in all honesty. Good package, but not easy to fully learn because of multi nested menus. Capable of very complex surfaces, good with draft tapers and fillets (test of any modeller) and updates 2D drawings fast.

Airbus use Catia (Dassault product) for all their collaborative design work. A CAD 'ergoman' was used developing the 380 to ensure access to all necessary parts for maintenance etc. SolidWorks is also owned by Dassault, and as their 'cheaper' product has Rhino as a 'Gold Partner' to handle parametrically editable complex surfaces.

In the UK Microstation is used by our Rail Industry, and quite a few architects too. Foster Associates did the Swiss Re (the Gherkin) building in London with it. Ironically it struggled with stuff both Pro-E and Rhino could do easily, one of my colleagues got involved and helped write some routines that allowed the shape (external panels) to be developed.

Both Pro-E and Catia are very capable packages but too pricey for most marine users. Horses for courses, as long as the software you use can do the job well, the package or a combination of, should not be a problem.

Alias is probably the most common car exterior/interior design package but is popular because it gives better material finishes and textures to the surfaces.
Freelance Alias operators rates are probably £50+ per hour if they are good.
There are quite a few good modelling packages out there and they have got an awful lot better over the years.

Autodesk have never been able to develop their own 3D product but have been clever enough to buy quite a few decent 3D packages. I cannot recommend early versions of Inventor (buggy and not competent) later ones are much much better, Maya is good for surfaces, 3D Studio Max is rendering only with meshes and it took years for them to add an IGES import.... AutoCad 2D is OK if clunky, not a personal favourite, but it does the job.

 

[Joe Petrich]

In my experience solid model/mechanical design packages are great for systems and structural design but most (not all) are limited in their ability to model complex compound surfaces. Most of them are fine for developable surface work.

Marine specific packages like Fastship, Delftship, and Rhino+Orca among others are better suited to creating surfaces with compound curvature and have built in routines or add ons for hydrostatics etc.

Example of a vessel with surfaces which would be extremely difficult to create in a mech design package but which was easy to create in Rhino+Orca: