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Moxis

Scanned bulkhead drawings into vector format?

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Every time I start a new project I have wondered how easy it would be to scan the bulkheads from drawing, have them converted into vector format and then scale them in CAD & finally cut the bulkheads with a CNC mill. But all the programs I have studied need enormous work to clean all the unwanted pixels from the drawing. I wonder if there exist any programs that make this cleaning automatically?

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As far as I know there are no programs that will give you a 100% conversion without some manual touch up.  I found it was easier to scan what you want insert the scan directly into CAD, scale it, and trace over the underlay.  On bulkheads and frames etc you only have to trace half and mirror the other side.  This way you can correct any errors in the original.

 

Don

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Hi Moxis

I have used this in the past and it did a pretty good job. It seems to have a lot more features now than my older version and claims to be able to distinguish between characters and object shapes. They have a free trial that you can use to see if it does what you are after so you don't have to put any skin in the game to find out.

https://www.scan2cad.com/

Cheers Pete

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Yes Bill, I have tried that. However the result was that there were so many rubbish pixels even in the drawing of one bulkhead which had to be cleaned one by one, so that it was not worth the work. So I did my bulkheads in the old school method by making first a template of all bulkhead halves, drew the complete bulkheads on plywood using those templates, and sawed the bulkheads away. Much faster than clean those rubbish pixels.

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There is an intermediate method: scan the body plan with sufficient resolution and then import the picture into your (2D) CAD-program. You then can draw in another layer each bulkhead/frame half by tracing the scan with a vector line. It is useful, if your program has a spline-function or similar to smooth the hand-drawn curves. A graphics-tablet is also useful, but I have done it with the mouse or even a track-ball/-pad. Making the drawing big helps to even out the inaccuracies of tracing.

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Hello Moxis, 

 

I think there is another way to look at this problem, which expands on the post above, that will be much easier for you and more accurate.  From your .pdf scan, you can take PRT SC of the various views you have and simply insert these in your favorite 2D or 3D program.  You can then set the dimensions you want for the part and use the spline features to simply trace out the lines. This will give you much better accuracy than any scanning of the lines themselves. You do not count on the dubious algorithms of the scanning programs; you make your own decisions. 

 

Also, remember the originals are based on the outside lines of a ship and don't compensate for an offset that you will need since you are making the bulkheads and then planking over those. You really need to plan for that or your end product will be bigger than the scale you are considering. 

 

Plus, you will need to design a keel into the structure. The lines you have end in the original keel width. One way or another you need to cut a new keel into the bulkheads while keeping in mind the offset for the planking as well as the thickness of the wood you will use. 

 

Having done close to a hundred of these projects, I can tell you it's easier to forget about scanning technology and just go for it on your own. 

 

FANCY IMPROVEMENT:  If you want to go crazy with these projects, you can start with 3D software and use surfacing techniques to increase the number of bulkheads.  You simply make up the few bulkheads that are included in your lines and then simply loft a surface between the bulkheads. From there you can easily cut the surface and create intermediate bulkheads. For the sake of keeping things square, you can create waterline parts that run all the way along your ship, setting absolutely everything square.  This helps a lot if you are making a really big model. 

 

Have fun!

 

Rick 

 

 

 

 

 

Edited by rshousha
addition

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Thanks a lot Rick for an interesting method. I have to try this when starting a new project. Very interesting feature is also to add more bulkheads if there are not enough them at the original plan. For this I should however get some sort of 3D cad and learn to use it, but that is another story.

 

Interesting is also the fact that the bulkheads shown at the drawing represent the outer surface of the ship. And when you make the bulkheads after the drawing, you have to deduct the thickness of planking from them. I wonder how many of us are doing that. It is very difficult to redraw the bulkheads so that the outer form remains unchanged. So far I have made only 2 or 3 models and have made my bulkheads exactly as shown on drawing, so resulting to slightly larger hulls than they should be. But who will notice that? But you are right, when building a museum model, you should take also this fact in consideration.

Edited by Moxis

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Whether plans show the outside of the planking or the frames depends on the kind of plans. 'Real' plans are typically drawn to the outside of the frames, as they were used by the shipbuilder, who is not interested in the outside of the planking at this stage. Model reconstructions and the likes are usually drawn to the outside of the planking, on the other hand. It also depends on whether you talk about wooden or iron ships.

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Greetings,

 

With any good 2D or 3D software there are offset features to move a line one way or another. So, with a couple of clicks you can move the spline the exact thickness of your planking. Generally, I decide how many layers of planking will be used and I estimate 30% of each layer will be sanded off when faring a model. This gives me my offset dimension. 

 

Actually, very few of the models I make are for museums. Most are for racing sailboats and the dimensions need to be quite accurate to conform with class rules. Generally, also, the lines for these models are quite spartan and one has to be creative to get a nice shape. With about 45 years of experience racing sailboats I have a good eye for what will be fast. It's all good fun!

 

Regards, 

 

Rick 

 

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I ran into similar issues as Moxis did- scans of paper plans are full of stray pixels to clean up. I was trying to create a vector based image that I could send to the laser cutter...

 

I use Inkscape as my drawing program, because it is open source (free) and can create and export .dxf files that the laser cutter wants. It also has a "bitmap to vector" conversion utility-- but that really struggles. Most paper plans we start with are not that good, quality wise-- and when you scan them, you get all sorts of stray or missing bits. I found I had to go into each image file and use an editor like MS Paint to erase stray dots, and to fill in the little white gaps, to try to create a continuous black line.  
Was way more time consuming than doing it the old school way!

So now to the reason for my post-- it occurred to me that maybe a blend of the two methods would be more efficient. If only there was a way to take the easy-to-make paper templates and then trace around them using the free hand draw tool in the program......

So I looked online, and I see that there are a lot of (fairly inexpensive) drawing tablets, that come with a stylus - I'm thinking one of these would be perfect for tracing around a paper pattern. They are primarily marketed to artists, for drawing and creating sketches and other artwork-- can't find any reviews that talk about the use case I'm envisioning. But they seem to give you a lot more control than you'd get trying to draw with a mouse....

Anyone using one of these in a model building application??

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Or, you can do it the hard way, manually (on the computer).  Scan the image, open in appropriate program (I use CorelDraw) and manually trace what I want.  Takes time but no artifacts, no clean up.  And a sense of satisfaction when I pop on the laser and cut.

 

I'm just cheap so my method is good for everyone.

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With some plans I recently had scanned, I used Gimp to do the clean up. Fairly time consuming but did a great job.

I then turned some of them into vectors using Inkscape. The cleaned up images from Gimp made a big difference to Inkscape's ability to do the bitmap to vector conversion.

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59 minutes ago, torpedochief said:

I use this to change stuff to vector. Online and I think it is still free.

https://vectormagic.com/

 

Doesn’t appear to be free- online version subscription  is $10/ month, or you can buy the desktop version for $295....

 

Don’t think I would use it enough to justify buying it, but might be worth  signing up for a month or two when starting a new project...

 

Thanks for sharing the link!

 

-Bill

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14 minutes ago, Rcboater Bill said:

Doesn’t appear to be free- online version subscription  is $10/ month, or you can buy the desktop version for $295....

 

Don’t think I would use it enough to justify buying it, but might be worth  signing up for a month or two when starting a new project...

 

Thanks for sharing the link!

 

-Bill

Give RapidSizer a try. Free and does qite a good job.

 

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For clean up, I use the polygonal selector tool to outline what I want, invert the selection and CUT.

The close in junk still needs attention, but everything else is gone.

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A lines drawing done in pen and ink or even a print-out has a finite line width and a certain contrast ratio against the paper. Scanning these approximates the lines with pixels, resulting effectively in a loss of contrast, as line is degraded into a more or less wide cloud of dots. Any software that is supposed to convert the cloud of dots into a chain of vectors has to interpret this. The precision of this interpretation will depend on the angle the original line had respective to the axes of the scanner. So you are bound to have lots of artefacts and deviations. The worse the smaller the original drawing was.

 

Personally, I am going down the same route as mtaylor. It may feel tedious in the first place, but it is probably more efficient than trying to remove all those rogue pixels before sending a drawing through a vectorising program. You, as a shipmodeller, are also much better in deciding what is a reasonable line and what not than the vectorising program.

 

I have done this for years using a mouse. As I will be getting an iPad with a stylo for Christmas, I am looking forward to do this kind work now on a tablet. Still have to find the right CAD software, as it seems that there is no iOS-version of my favourite EazyDraw for the MacOS.

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If one spends already a whole working day in front of the computer, one may want to look at something different and may want  to have a different haptic experience ...

Spending 600 $, even Canadian ones, on a model seems to be an awful lot of money ... never spent more than maybe 100€.

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I use the scan, then trace method using DesignCAD and the Curve function (a type of Spline curve). After that I use the 3D feature of my CAD to place the frames in position, and draw in the horizontal water lines connecting the frames. By viewing them from the top, I can see any deviations from a smooth flow of the lines. I then redraw the curves skipping the frame with the "bad spot". Then I bump that part of the frame in/out to meet the new line. I then redraw, and check that the lines are now smooth. Generally a couple of iterations will give me good frames.

 

This works well where you are just given the frames drawn, but no body plan. I was able to generate all the aft frames of an old kit, where the frames did not even come close to making a hull, as drawn. If the drawing was acurate. I think the manufacturer deliberately distorted aft frame drawings, so that you had to buy the kit, to build the model.

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I have been using Inkscape for that purpose, it's not perfect but very helpful, saves to svg extension.

Then I import it into Fusion360 and the tracing is easy. 

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542 class LST working from imported photos, sized from known dimensions. Trial and error around curves then tested in another program. General Cad 10 and Traverse PC, software I used in surveying for comps and drafting. Have used 2D programs to obtain 3D coordinates by shifting x and y coordinated to different planes. Slow method and my computer lost the hard drive, just back up and running.blob.thumb.png.8780589b0fe53911624f6307d86a12f1.png

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