Do CAD format Boat Plans still require Lofting?

[Gerhart]

Hello Everybody



I am planning to buy a design and plans for a 10 meters wood&epoxy motor boat

My intention is to build the boat myself in wood.


Does anyone know:

After purchasing from a Naval Architect the design files and plans;

do I need to perform any lofting to be able to cut the wood framing?

so that the hull would be fair and the planing does fit on each of the frames?.



Or should I expect the plans to be precise and accurate enough so

as to print them out directly 1:1 and cut my hull frames straightforward?





Thanks for all help ; all feedback appreciated.




Gerhart

 

[DCockey]

It depends on how the design and plans were created. CAD plans may or may not need to be lofted. Ask the naval architect.

 

[TANSL]

It is necessary to distinguish between project plans and construction plans. Not the same.
For the design, it is not necessary that the planes are smoothed, as the results of the calculation does not vary appreciably.
The construction plans should be based on good smoothing shapes. Also included construction details that on the project are not needed. May include files for numerical control cutting of the pieces, development of the plates, nested parts, joining systems, etc. ..
The basic engineering (design, CAD) and development engineering(construction, CAM) are complementary but different.
CAD : computer adided design
CAM : computer aided manufacturing

 

[PAR]

Unless you specify full size templates, it's very unlikely you'll receive 1:1 ratio drawings on a 10 meter yacht. Most can offer full size templates, typically for station molds or other items, such as fin sections, bow and appendage profiles, etc. Contact the designer and ask about full size templates or station molds.

 

[FAST FRED]

ask about full size templates or station molds.

And ask what the templates are made of , paper changes size & shape with moisture.

 

[gonzo]

I would not skip lofting. My reason for it is mainly cosmetic. Minor changes, which are too small to show on a computer screen, make a huge difference in the looks of a boat.

 

[TANSL]

in defense of the computer (although it should go without such a defense)

For many years, the smoothing of the shapes of the vessels are carried out by a computer and its display. It is true that a good screen for fairing may require much resolution (1900 x 1400 pixels or more) but it is also true that a computer screen can give many more details than can be seen with the naked eye of a scale model 1:1. They have tools to detect whether the curvature of the surfaces is or is not correct. That is, it analyzes the values ​​of the first and second derivatives at each of the points on any surface.
Today you can not do a smoothing accuracy without the aid of a computer and its display. Sorry, you can, but it is much more expensive and less accurate.

 

[DCockey]

Back to Gerhard's questions. He asked specifically about plans in "CAD format" for a 10 meter / 33 foot motorboat of wood/epoxy construction.

"CAD format" alone does not guarantee that the plans are sufficiently accurate and precise to allow building without any additional lofting.

As has been noted it is possible to develop a design on a computer with sufficient accuracy to build directly from the CAD design. I recently talked with a designer and builder of wood boats who has been successful for many years. He now designs using Rhino and goes directly from Rhino to having frames, bulkheads, molds, etc cut by CNC. He no longer lofts manually.

But there is no guarantee that all plans in CAD format have that level of accuracy and precision. For example hand drawn plans can be digitized and put into "CAD format" but would generally still need to be lofted before building. Or the deisgner may have developed the design in CAD but without sufficient accuracy and precision to build directly without further refinement.

So my response is there is no general answer applicable to all plans in CAD format. Some, perhaps most, can be built from directly without lofting. But lofting may be needed for others. The designer is the best source for an answer about whether a specific set of plans the best source can be built from directly or need to be lofted first.

 

[Gerhart]

Thanks everybody for your extremely helpfull feedback!

The Naval Architect I was talking to said he will deliver the set of lines; a construction plan in Rhino CAD format; as well as the 3D model in rhino Cad format
side top and front views; deck plan; interior and cockpit in 2D Rhino CAD.

However what appears to result from the above is that I may not/ should not expect is to just take each and every of the hull fames drawings from the Construction
plan print them out 1:1 and make patterns for cutting my hull frames from wood.

Unless there would be cutting files/frame patterns expressly specified in the deliverables design package.


Thanks and Best Regards

 

[Jarek]

I wrote a few answers, but deleted them in frustration, as they could be wrong - to many assumptions required.
You need to ask the designer, exactly, what he delivers, and how you proceed to use his plans to build your boat. It is his duty to make sure you understand the process before you pay.

 

[PAR]

It's not the designer's duty to make sure you understand anything. You have purchased a set of plans, it's the plans owner's responsibility, to come to terms with the plans and the details within. The designer is under no obligation to nurse maid anyone, through a set of plans.

Printing at 1:1 is should be costed first. Printing on a 60" wide printer isn't cheap, usually being about $5 to $8 a square foot, which simply means on a 60" printer at $5 a square foot, the first foot of plans costs $25 bucks. So, lets say a midship station mold, printed as a half breadth and only 5' by 5' (pretty darn small, for a 30' yacht), at $5 per sq. ft., the section half breadth drawing at 1:1 will be $125. Assuming station molds on 24" centers, you'll have 15 stations, so, likely a $1,500 to $1,800 printing bill, just for full size half breadth station molds. Lastly, as has been mentioned, paper changes dimension with environmental conditions and with how it's made (grain direction in the paper), so most prefer Mylar or acetate film for 1:1 drawings. This will push the costs up further. On the above hypothetical printing bill, add another grand.

 

[DCockey]

Thanks everybody for your extremely helpfull feedback!

The Naval Architect I was talking to said he will deliver the set of lines; a construction plan in Rhino CAD format; as well as the 3D model in rhino Cad format
side top and front views; deck plan; interior and cockpit in 2D Rhino CAD.

However what appears to result from the above is that I may not/ should not expect is to just take each and every of the hull fames drawings from the Construction
plan print them out 1:1 and make patterns for cutting my hull frames from wood.

Unless there would be cutting files/frame patterns expressly specified in the deliverables design package.


Thanks and Best Regards

Is there a reason you can not ask the naval architect if you can print the hull frame drawings from his plans set full size and work directly from them? For many designs it is possible.

 

[Jarek]

Par,
of course, you are under no obligation; it is a question of professional ethics.
I know, "buyer beware" and making a sale are the most important principles of making money.
In my own practice, I try to make the boat building process as easy to understand as possible, to stop unqualified dreamers from making a costly mistake, before I take their money.

 

[PAR]

I do things in a similar way Jarek, though you do have to draw the line someplace. The easiest way is to develop a good set of plans, anticipating build issues, based on experience. I know you know the difference between good and bad plans, so . . .

 

[gonzo]

I trust my lofting battens and eye more than any computer program. A huge advantage of lofting, is that you have the means to make full size patterns for any part of the boat. That means that you can pre-cut all or most of the interior if you so wish. As far as computer screen resolution, the amount of pixels is not as important as the pixel density. A larger screen will have more pixels but the pixels themselves are not larger. A pixel of .15mm, when enlarged thirty times will be 4.5mm. That is a huge bump.