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How to turn plans into a cad plan?

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Hi Spencer,


There is an excellent article in the MSW database written by Wayne Kempson on drafting ships plans in CAD (which is what you are asking about, I think).


Of course, it requires a CAD program of some sort. There are many available at a range of prices. I use TurboCAD and it seems to work well for a reasonable price.


Here is a link to Wayne's article:




Hope this is what you were after.

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  • 4 weeks later...

Hi Spencer


I'm pretty conversant at CAD so I'm sorry of some of this is technically a bit complex. I'm going through the same thing - except that I use CAD a lot in my job so I know the commands fairly well. 


My first step was to scan the plans I have of the yacht & them insert them as jpeg files into the CAD drawing. The original drawings were too large in area to scan in one go, so on screen I had to rotate & line them up etc in the CAD file. Put the scans on a separate layer (named jpegs, for example) as you want to be able to turn them on & off; they can also be a cause of programme crash so being able to turn them off when not in use will reduce this problem.


I started by drawing in the setup lines (horizontal lines, station positions etc), using the lines on the drawings (the horizontal section lines, whatever they are called), & I coloured them yellow, except the LWL blue & one green one. The partial view below shows some of that. The numbers are the stations, I'm adding in additional ones  - the "a" numbers. Stations in red.




Most programmes will have a polyline function & a number of alternative ways of doing a polyline. The one I use is where you click a series of dots on the curved shape of a hull section & the programme will automatically join them in a "best fit" curve that goes through the points you have clicked. You can zoom right in & click a lot of points if you are sure the drawings are accurate. For me, the drawings I am working off have a lot of poetic license so the correspondence between the plan, side view & sectional shapes is a bit off.


The short vertical pale blue lines were checks - checking the plan drawing against the sectional shape.


You should be able to tweak the polylines, but it's a fiendish task, I recommend printing pages off & sketching with a pencil to help make adjustments & then do it on screen. I then offset the final polylines by the planking thickness. On the drawing below the red represents the outside planking line & the black the mould shape to be laser cut from plywood. I will have to redo this as I'm going to build it a slightly different way, but the gist of it is there. Station #4 is shown below.




CAD programmes are pretty big, lots of commands, but you will only need maybe 10 or maybe 15 max. If you are going to work off paper prints that would simplify things, but I will need files that a cutter can read so I have to assemble lines into a connected shape - the mould shapes are one continuous line each, but that's starting to get difficult.


The conclusion I have reached is that if I make the plywood forms NOT part of the final build then I can make adjustments when I set them up - shave off as needed or add laminations of timber & shape to suit. The drawing above was for planking straight on plywood moulds, but I now plan to put ribs on the moulds & then planks on the ribs & remove the plywood moulds . The sheer clamp cutaways will be adjusted but in principle they will be inside the ribs as they would be on a yacht.



Does this help?


best, Mark



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