Do CAD format Boat Plans still require Lofting?

Thank you, Groper. I was beginning to think I was the weird one ;-)
Seriously though, one point I forgot to make.
The industry has changed over the years, probably thanks to computer development.
As you guys point out, a lot used to be the responsibility of the builder, which made the designer's work easier. Technically, the designer only needed to produce the paper lines drawing(which did not even heave to be perfect because the builder would scrutinize it and fair it, if necessary) and layout concept drawings - a capable builder could do the rest.
Nowadays it is different. The designer does everything, from the proverbial scratch to the cut parts, which are not meant to be tampered with - or else things will not fit.
In essence, I am also the builder, and the builder's role is reduced to being the assembler/welder/fitter - in case of aluminum boats - but also in case of cold molded wooden boats and FRP ones, where construction frames (and other parts) can be CNC cut, thus eliminating the need for lofting.
There is a cool video on YouTube on how they build the A380 Airbus; the plane sections are built all over the world, then shipped and assembled in France, needless to say, with a fraction of a millimeter accuracy; no place "sweet" battens here.
And here is a link
http://www.superyachttimes.com/yachts/details/1016
to Antonisa, a wooden sail boat designed by Bruce King and built by the famous Hodgdon Yachts yard in Maine. I may be wrong here, but I doubt he would let them re-fair his computer lines.
Incidentally Mr. King used the same 3D software(Multisurf) I am using. I am not dropping names here, I mention this simply because when I was at the Landing School, he came to give a lecture on Multisurf use and we went on a field trip to visit Antonisa during construction.
I am sure all you wooden boat guys will drool when you read the boat's description and see the photos. I think, at the time, Antonisa was the largest wooden sloop in the world.
Cheers.

 

Jarek: what I mean is that if you have never used splines to create a curve or built a boat by eye, the program is all you know. I find it difficult to accept the limitations it imposes compared to the infinite points of a batten or spline. Also, for smaller boats, by the time I'm finished designing, I would be half way through the build. Building by eye is a method that has sharp limitations, but is very fast and efficient for an experienced shipwright.

 

What are the limitations of software such as Multisurf or Rhino compared to physical splines? A spline in Multisurf or Rhino can be defined by as many points as you want, same as a physical spline (assuming you have enough ducks or nails).

 

The limitations of the software are probably more correctly called the limitations of the user. To be truly proficient in a design programme to the extent where it can be relied upon to produce fully faired lines that need no lofting needs a time & learning commitment from the user that for most builders isnt available.
I know in my own experience with Delftship this is the case. However it got me to the point where with a swift & pleasureable lofting job for what i am building its going well.

 

Although discussions are very healthy and often serve to clarify concepts, in the XXI century is absurd to have to explain the advantages that a computer done work has on handwork. On the other hand, if you do not know both ways of working, you have no moral authority to ensure that one is better than another. Of course, no matter what anyone says, the computer is much faster and more accurate than manual labor. I can not imagine that anyone would dare to discuss this.
I wonder where is the advantage of smoothing shapes using splines (bi dimensional element) on smoothing by means of NURBS surfaces (which as some of us know are three-dimensional elements)?

 

I completely agree that "To be truly proficient in a design programme to the extent where it can be relied upon to produce fully faired lines that need no lofting" requires the investment of considerable time to learning both how to use suitable software and how to work in the virtual world.

 

Surface quality standards in the auto industry appear to be considerably higher than for most of the boat industry, and final surface development in the auto industry (at least the major companies) has been done completely on computers for years.

 

I totally agree that not everyone has some skills, like vision in space, to work in the virtual world. But this quality, the vision in space, was also the most needed when the smoothing was done "by hand".

 

Include me in the roster of people who believe lofting has been largely superseded.I have spent enough time crawling around and if a more accurate and faster job can be done in other ways,why would anybody but a hobbyist do it the traditional way?If the designer has the proficiency to develop a fair shape,and with porcupine curves,gaussian shading and environment mapping tools-he should,the outside surface is likely to be orders of magnitude fairer than anything from a drawing board and pencil.From this fair surface its easy to accurately offset a skin thickness and arrive at true frame shapes.At which point the frame data can be given to the man with the appropriate CNC machine.The resulting frames can then go the boatbuilder.Omitting the CNC stage moves you back to the old ways and almost certainly costs more in time and money.Its up to the builder to select an efficient way to translate the designer's lines into a finished boat and it would be unwise to eliminate a method solely because of a lack of experience.The world will quickly leave you behind.As to fairness from a CAD model,how many large plugs are directly milled from CAD data?

 

How long does it take to loft and create files for a 65' powerboat? I usually take about two days on the lofting table and about three or four to mark and cut the molds, with a helper. As the guys on the floor set the molds I would start laminating and cutting bevels on the timbers. Perhaps I, like most shipwrights, envision the shape in 3D, color and building process in my head so the computer system is not an advantage in those aspects. Renderings are a great selling tool though. Customers can then see what their boat will look like.

 

My experience is with smaller boats for strip planking using Rhino.

Starting with a typical table of offsets and a lines drawing, it takes me less than two hours, usually less than an hour, to have the offset points displayed in Rhino and the corresoponding spline curves (sheer, rabbet, sections, waterlines, buttocks, etc) through them. Then I initially fair the curves and reconcile them. Length of time for that depends on the quality of the offsets but is typically another hour or two. Next step is to create a 3D surface. The time for that step depends on the complexity of the surface. A typical hull takes less an hour or so, sometimes considerably less. Then final fairing on the surface.I

At this point the surface is equivalent to what can be achieved with good manual lofting and depending on how the boat will be built may be adequate. Additional fairing for a higher quality surface adds anywhere from another hour or so to the best part of a day.

Once the hull surface is finished, it is offset to obtain the inner surface. This takes a few minutes. Then the inner structure is added which depending on complexity takes anywhere from an hour to part of a day.

At this point files can be created for CNC cutting molds, bulkheads, stem forms, etc. The time required depends on the complexity but is usually an hour or two.

So, depending on the accuracy needed and complexity of the hull shape the time from lines and offsets to files for CNC cutting can range from less than day to two or three days.

 

The only reason I know not to use a computer in this work is that one considers himself unable to do so and therefore have no other way to do it with pencil and paper.
I've done the work by hand and find it beautiful but it is absurd to claim that it is faster and more accurate than the computer.

 

i dont think anyone is suggesting for a minute that the computer is in some way less accurate. What method a builder uses depends on what sort of boat you are building & the budget, price, numbers to be produced etc.
In an ideal world i would love to spend the time to become really really proficient with a design programme like delftship (though it could be any other suitable software). The reality of life & trying to earn a living means i do not have the time to become that proficient (it would probably cause a divorce!)
Likewise i fully appreciate that CNC mold cutting could produce a superb job.
However for a very limited run of two or three boats as i am doing at present it is cheaper for me to do it the old way. Every job is different.

 

I understand perfectly what you mean. But my experience leads me to tell you to try to learn how to use software. It's not as difficult as it sounds, trust me. Find help, perhaps a friend, or in this forum. I assure you that even for boats that only built a model, and especially in this case, it is worth.

 

There are other reasons to design with pencil. There is the pleasure of the smell of cedar as I sharpen them for example.