Vectorizing old plans

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
1,712
Location
YMM
Isn't technology wonderful? ;)

My buddy sent me his legal Terf CD - was planning to start importing the VV into autocad...

Then the swearing started :roll: Hand drawn templates on hand drawn graphs, scanned in the 80s at looks like 16dpi on what appears to be a scanner that had some feed issues... :computer:

Been playing with inkscape - trying to even out the grid & lighten it, take away the fuzzy edges of the actual templates - and get a vectored line over it.... Needless to say, 3 days in I'm still on the first page of templates with no end in sight...

Is there an easy way to do this I'm missing?

Thanks in advance!
 

Dana

Super Moderator
Staff member
Joined
Apr 3, 2007
Messages
9,214
Location
CT, USA
Redrawing from scratch is usually easier and faster than trying to clean up rough scans.

Dana
 

Norman

Well-Known Member
Joined
Nov 28, 2003
Messages
2,948
Location
Grand Junction, Colorado
For the most part I agree with Dana regarding rough scans. There's a limit to how accurate a tracing can be. Orthogonal parts can be OK, especially if they're dimensioned, but if it's a full size template of a part that mates with other parts you're going to have to spend a lot of time comparing those parts for fit and tweaking your drawing. The first thing I'd do is set the user coordinate system <UCS> so that the x axis is even with a horizontal line on the scanned drawing. At least then the orthogonal lines would be easy. Well, theoretically anyway, what you'll find is that hand drawings weren't all that accurate. So parts composed mostly of straight lines are not hard and a few simple curves don't make it much harder but don't expect to be able to accurately trace the airfoil. When you get to that look for the name of the foil and download a set of ordinates from one of the online databases. Turning a coordinate file into an acad script is not at all hard. I've only done this kind of conversion with peanut scale airplanes so take my words with a grain of salt ;)
 

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
1,712
Location
YMM
Yeah know the airfoil is a GU - was planning to cut the wing cores on the CNC hotwire as it fits within the boundaries of my current (RC sized) unit. Just need to sort out thickness. But wanted to see about getting the fuse and center wing section modeled - was contemplating just building the original rutan design - even if I suck with wood construction...

Im just wondering if the scans were intentionally tweaked so they're unbuildable from the terf cd - like leaving out the ez's templates - or if I find an original printed set if they'll be a bit more accurate... I've got 2 sets here now - but they both appear to have been printed off the terf CD - not originals as claimed.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
12,860
Location
Memphis, TN
All depends on how they were scanned. Probably after the full size plans were scanned and then turned into 8 1/2 X 11; what they sell is the scan of the 8 1/2 X 11. All loftable but not enlargeable.
 

Dana

Super Moderator
Staff member
Joined
Apr 3, 2007
Messages
9,214
Location
CT, USA
The best approach is probably to use the scanned drawings as a basis for a new 3D CAD model, inputting any numeric dimensions on the drawings where possible, and importing and tracing the scanned drawing into a sketch or 2D wireframe only where necessary to construct the 3D model, correcting lines to straight/horizontal/vertical/even number dimensions where appropriate.

The advantage of doing it this way is that you can then easily verify the 3D model's consistent geometry and create new drawings from it. The new drawings, if done correctly from a good model, will likely be more accurate than the original and parts made from them will fit together better.

In over 25 years of using 3D CAD I've resorted to tracing a scan only a handful of times, but manually created new models from printed or downloaded drawings hundreds of times.

Dana

Resist militant "normality" -- A mind is a terrible thing to erase.
 

Apollo

Well-Known Member
Joined
Feb 7, 2010
Messages
301
Location
Southern California, USA
The best approach is probably to use the scanned drawings as a basis for a new 3D CAD model, inputting any numeric dimensions on the drawings where possible, and importing and tracing the scanned drawing into a sketch or 2D wireframe only where necessary to construct the 3D model, correcting lines to straight/horizontal/vertical/even number dimensions where appropriate.
As another 25 year 3D CAD veteran, that's exactly how I would do it. Trying to vectorize crappy scans will just lead to inaccuracies and you're gonna have to clean up the linework anyway. Even for 2D CAD, it's better to do it Dana's way. You want to clean up and fix those scanned plans as much as possible. I know this from personal experience when I tried to vectorize a Lycoming engine drawing 15 years ago. It was very time consuming and it appears the process hasn't gotten any better.
 

Hephaestus

Well-Known Member
Joined
Jun 25, 2014
Messages
1,712
Location
YMM
Yeah, I'm seeing the light... Just daunted by the scale of that now ;) I'm OK sketching a part out in 2D - 3D requires some upgrading and learning...

Mind you I can export my RC stuff from sketchup and I'm using the same cnc stuff... (Yeah yeah not real cad I know :D)

This should be interesting.
 

jetboy mike

Well-Known Member
Joined
May 12, 2013
Messages
56
Location
Everett Washington
I use a number of CAD tools and have some experience dealing with scans from days gone by. Many times it has been faster to build the model in 3D for the parts you can and have details for and design what fits in between yourself. I have also spent hours pasting scanned pages together in GiMP to re-build A0 size drawings.

Side note: A new version of FreeCAD has come out. Looks like it might be worth a shot. ( price is right )

Jet
 

bmcj

Well-Known Member
HBA Supporter
Joined
Apr 10, 2007
Messages
13,360
Location
Fresno, California
Graphic Artists have programs that convert raster images to vector graphic, but it takes finesse to set up the parameters to get a decent result. It's best to let the graphic artist set it up for you, but even a good conversion of. A poor graphic leaves a lot of tedious cleanup to do to make it a truly optimal product.
 

Apollo

Well-Known Member
Joined
Feb 7, 2010
Messages
301
Location
Southern California, USA
If you want to see an example of a rastor-to-vector conversion, you can download the Lycoming O-360A Engine drawing from the link below:

Downloads

The 2D drawing was created by scanning the Lycoming installation layout with a drum scanner to create a huge TIF file. Then I ran some raster-to-vector conversion software to create the drawing views. The end result was hundreds of short polylines that do a decent job if you don't look too closely. Curves were especially difficult since the software didn't recognize circles very well. And straight orthogonal lines from the hand-drawn Lycoming drawing often ended up as multiple polylines. I spent about 40 hours cleaning up the drawing views.

I used a 30 day demo copy of high end conversion software, but that was 15 years ago. I suspect the right software could do a much better job today, but I have no idea which software works best.
 

Topaz

Super Moderator
Staff member
Log Member
Joined
Jul 29, 2005
Messages
14,109
Location
Orange County, California
Graphic Artists have programs that convert raster images to vector graphic, but it takes finesse to set up the parameters to get a decent result. It's best to let the graphic artist set it up for you, but even a good conversion of. A poor graphic leaves a lot of tedious cleanup to do to make it a truly optimal product.
Yeah, I've got experience with most of them. The one built into Adobe Illustrator is as good as any, and that's about "not at all" for engineering purposes. You either end up with lots of extraneous points, or you have to set it so loose that it no longer accurately follows curves. Or it throws a cluster of points and line segments in the middle of a smooth bezier - which falls apart when you pull them out. There's rarely a happy medium between the various unacceptable end conditions and, if there is, by the time you've fiddled with the controls enough to find it you could've redrawn the thing more accurately from scratch anyway. Every time the Warhol-ésque posterization look comes back into vogue you hear a lot about these filters and programs but, even in the graphics world, it's about all they're good for.

For graphics, I'll usually take a quick scan of the linework, and then use it as a template layer in the file, which I then redraw over by mouse using the scanned template only as guide to speed the work. I'll take measurements to confirm critical dimensions and proportions (desktop scanners are notorious for X-Y axis distortions) and redraw the piece with proper lines and curves. Much faster and more accurate than trying to clean up a vectorized scan, IMHO.
 

TinBender

Well-Known Member
Joined
Mar 4, 2010
Messages
218
Location
Charlotte, NC, USA
+1 for not attempting to convert. I tried for too long tweaking B737 airframe TIFFs I needed into vector art. The Boeing prints were high resolution, but with extraneous shadows and spots. (And way too much info on the sheet for my needs.) It was much more efficient using it as a background layer in autocad and squaring it up, stretching as necessary to match the grid or known dimensions. I then drew over it, using known dimensions where called out.
 

dirk_D

Well-Known Member
Joined
Sep 22, 2010
Messages
93
Location
Victoria, Australia.
I've used microstationJ from 1996 for tracing photos for the last 16 years.
Simple, easy, rolling circles out tangentially to other circles always gives you a good basis for solid modelling the contours in other more advanced cad packages.
You will spend more time cleaning up vector art and still wont have lines and arcs, lines and arcs form the basis of a coherent cad model.
Splines and poly lines are the exceptions but they are certainly not the rule.
 
Top