Paper plans to computer-plotted?

Hello there fellow boat people,

I have some excellent boat plans on paper, in the traditional sectional view, with one half being the stern and the other the bow. What's the best and most accurate way to transform these into computer drawings that I can print out and use to cut my molds? I have CorelDraw, HullForm (freeware edition), access to CAD, and other various facilities.

Any help would be appreciated.... these plans represent the absolute best shape for the kind of small boat that I am building, and don't want to attempt redrawing them for fear of worsening the beautiful lines.

Eliza Camp
Italy

 

Eliza,

It’s an easy thing to do; you can scan the image and open it as a background into a CAD program. Scale it as large as you can and still have detail. Place points over the lines, then connect the points. Then scale so that the known dimensions are right. You now have something close to your image, digitalized. That was the easy part. The hard part is to use this information to build a fair hull. This can be a long and difficult job, even with good software.

It would be easier to take careful measurements off the lines you have and loft it full size. This way you can correct for errors as you go and be reasonably certain to have a fair hull even if it is not a duplicate of the lines you started with.

Gary

 

Probably not relevant but TouchCAD 3.5 enables you to import separate high resolution, in scale background images for the Front, Top and Side views and accurately place them relative to the 3D model.Also useful is that it only displays the image associated to the view and it chnges image whan you change view. Very useful when modeling based on 2D drawings and even photos. The import dialog also allows you to control measure, rotate, skew, deform, scale both horizontally and vertically to calibrate the image for accuracy relative to the 3D model.

www.touchcad.com

 

Thanks...

Thanks for your replies.... the TouchCad thing sounds neat but REALLY expensive! I think my best solution is just to find a way to make perfect distortion-free photocopies of these drawings and use them to cut the molds. Probably faster although I would really rather have them digitized properly, so that I can scale if I need to. Any more solutions out there?

Eliza

 

Ok, you need a BBC micro, a 2 channel A-D converter, or two multimeters...

Baiscally build yourself a digitiser with a 'shoulder' and 'elbow' joint. This is easiest to do with rectangular aluminium. Put one variable resistor (about 10K ohms) at each 'joint' and a needle at the far end. It is easiest to put the variable resistor for the 'elbow' upside down, then the 'elbow' will be supported.

Electrically, connect one end of each track (track ends are usually outer most pins) to the positive terminal of a supply (5 volts to 10 volts is reccomended (5 Volts from a computer power supply (that's the red wire))) and connect the other end of the track to the negative terminal of the supply (nb. The BBC micro supplys +5volts and 0volts through the analogue port for this purpose).

The middle pin (the 'wiper') on each is connected to a channel, or multimeter. You will note that the voltage readings change as the needle is moved. It is now a case of converting the voltage readings into angles, and, knowing the lengths of the arms (centre to centre) one can work out the exact location of the pointer.
I will post a few diagrams tommorrow, when I have drawn them. I will also post the maths to work out the position in cartesian co-ordinates. Incidentally, this system can be extended to 3 dimensions simply by adding a variable resistor to the 'shoulder' so the needle can pivot vertically and add another multimeter.

Cheers,

Tim B.

 

If you’re interested in Do-It-Yourself digitizing arms this a good read.
http://cnczone.com/forums/showthread.php?t=4424

Gary

 

Eliza

Please download the Maxsurf academic version from the Academic site listed below, as well as the tutorials on digitizing and fitting designs.

Basically if you can scan the lines plan into a jpeg, you can bring it up as a background image in any of the Maxsurf views. You can then create 3D marker points and then use these as a guide for fitting a NURBS surface.

Hope this helps.

 

Maxsurf

OK, this Maxsurf system seems like what I was looking for... boat design software (and therefore no need to draw out full scale to check for fairness) that lets me put points along my lines. I just hope my scanner is doesn't do any funny warping that I'm not aware of! Though making a digitizing arm sounds like some good pure fun.

I'm off to download Maxsurf... thank god I just had ADSL installed.

Eliza

 

It depends of what you compare with.

$795 ($ 248 - educational) for an integrated hull fairing program with unlimited number of surfaces, all control points on the surface (useful for tracing shapes), very powerful integrated unfolding features including stretch and image unfolding, integrated basic marine calculations, offsets, OpenGL rendering/animation/walk through/fly-over, weight / surface area / center of gravity calculations.

The unlimited number of surfaces, and the fact that TouchCAD is an excellent general-purpose 3D modeler, means that you essentially model ALL major components in TouchCAD and it therefore allows you to keep track of the weights and center of gravity as the work proceeds.

 

Cost.....

Of course you are right.... it is not expensive as in "it costs too much for what it is", it is merely expensive in the sense of "for what I need to do it is more money than I wish to spend." The boat I am building is a rowing shell which will consist of roughly 27 feet of wood weighing around 14 pounds before the metal bits are added. It may be that one day when I have a nice profitable shop running I will require that kind of software, but for now I can barely afford a bandsaw!

Eliza

 

You might also consider Rhino v3 (there is an evaluation available which should cover what you need to do) the system is similar to Maxsurf, but I found more intuitive. The On-line help is superior as well (sorry Andrew).

Anyway, those sums I promised...

Call point A the 'shoulder', point B the 'elbow' and point C the needle. Then with respect to point A the following is true...
length1 is the 'shoulder' to 'elbow' distance
length2 is the 'elbow' to 'needle' distance

theta is the angle between the X-axis and the 'shoulder'/'elbow' arm
phi is the angle between the two arms (with the 'elbow' at greater Y than the 'shoulder')

Bx= length1*Cos(theta)
By= length1*Sin(theta)

Cx= Bx + length2*Sin(phi-(90-theta))
Cy= By - length2*Cos(phi-(90-theta))

I'll post the schematics when I can find a scanner that works!!!

Cheers for now,

Tim B.

 

Ok, I've finally found a scanner that works, so here are the appropriate pages of explanation.

Tim B

 

go to www.cadalyst.com and look at digitizing and scanning services.

 

Eliza,

You may find this an interesting read.

Gary

 

This is a good thread, but a few questions.. Im also looking to take my paper plans to some electronic format for slight altering. My problem is that the plans are quite old, have been folded over and over. I made some copies of them and the copies show dark lines where folds were. Also some parts are faded and didnt copy well.

So.. if I scan, what format should I save as? jpeg? tiff? not sure??
Then I need to getmyself maxsurf or Rhino or other and open it as background? What is best format to save my scanned designs as for either of these two software?

Then.. the question is can I remove the imperfections that will likely be there (from the fact the paper is old and in not so good shape)?

Really what I am trying to do is get a good clean copy stored. I need to send to the yard and I think it easiest if they had a clean version. I really do need to update some also.

Any suggestions on this? Am I on the right track here? There is a dizzying amount of different software out there. I dont even really know what it is I need. I would like to get some calculations from these plans, such as stability, ab ratio. Can maxsurf or rhino give this info?

Thanks!!
James