Using Inkscape for model airplane plans

pedwards2932 · Postby **pedwards2932** » Tue Aug 19, 2014 9:08 pm

I am using inkscape to trace over model airplane plans to create .svg files that I can use with a sure cuts a lot program for cutting out parts. The plans are usually pdf but require a fair amount of accuracy. The ribs on the wings have notches that need to be precise. I saw a measuring tool was under development but it didn't seem to be included with latest download. How do you get that tool? I can create a 1/16" box (actually I can only get it to .060 which is slightly small and use this to create notches by combining it with the upper curve of the airfoil but I am not sure how to delete one side of the box to make it open ended. here is an example of a rib drawing:

drawing-test.svg: This is an example; (2.07 KiB) Downloaded 419 times

Lazur · Postby **Lazur** » Tue Aug 19, 2014 9:38 pm

Hi.

Some tips on a more accurate drawing:

Draw everything in big, scale down them at the end.
Inkscape can produce about 0,05 pixel inaccuracy in some cases, no matter the size of the actual path.
By scaling down the result, the errors will be scaled down too.

Change the inkscape's preferences to a higher precision.
Shift+Ctrl+P to open the preferences tab, go to svg output settings, increase values and restart inkscape.
(Keep in mind that this will result in a bit bigger svg files than with the default settings.)

Use filled shapes with no strokes, or work in outline mode (Ctrl+5 twice on the numpad),
and maybe even change the bounding box settings to geometric one in the preferences.
If working in outline only display mode, you may change the background colour from white in the document's settings (Shift+Ctrl+D).

Now, focusing on those notches.
By drawing one box over the curve as separate object, you can set a snapping to path intersection points at the snap bar,
and trace over the right part or duplicate the wing profile and use the node editor tool to add four new nodes, position them right to the intersection points and adjust their handles.

Also, you can drag guide lines of the top and left rulers with the mouse, and use those with snapping enabled to make sure segments are horizontal/vertical.

Postby **heathenx** » Tue Aug 19, 2014 10:04 pm

Interesting. I just did this a week or two ago. I have a 2w laser diode attached to my 3D printer. I traced a business card balsa glider picture that I found on the net and cut one out for myself. Fun.

pedwards2932 · Postby **pedwards2932** » Tue Aug 19, 2014 10:13 pm

Ok I will try what you are suggesting. One difficulty is I am using pdf's to trace so if I scale it up really large I need to be able to scale it back to original and the notches need to be exact because 1/16" square strips are glued into the notches.
Also I was able to create an airfoil and then created a 1/16" box that I positioned in the proper spot then I think I used Path division and it combined the box with the airfoil then I used the eraser to take out the unwanted segment. This seemed to work. A measurement tool would be a great addition to this app. Also is there anyway to make the grid 1/16" inch squares? When I tried reducing them down it seemed to stop at about 1/4 inch?

pedwards2932 · Postby **pedwards2932** » Tue Aug 19, 2014 10:18 pm

Wow that is cutting pretty accurately! I am using a Sizzix eclips which uses roland blades to cut. I didn't realize that low a wattage laser would cut balsa. I wonder if there would be a way to incorporate that lazer with the Sizzix blade holder. That might work better than the blade. I have to put tape on the balsa and make 3 passes to increasing the depth to cut 1/16" balsa.

Postby **heathenx** » Tue Aug 19, 2014 10:46 pm

pedwards2932 wrote:Wow that is cutting pretty accurately! I am using a Sizzix eclips which uses roland blades to cut. I didn't realize that low a wattage laser would cut balsa. I wonder if there would be a way to incorporate that lazer with the Sizzix blade holder. That might work better than the blade. I have to put tape on the balsa and make 3 passes to increasing the depth to cut 1/16" balsa.

My laser will nearly cut 1/4" thick acrylic. I can easily cut up to 1/4" thick balsa. I'm using an L-Cheapo laser kit (https://www.indiegogo.com/projects/l-ch ... attachment). JTechPhotonics sells a kit as well (http://jtechphotonics.com/). They can be attached to just about any CNC-type machine. Another that you might be interested in is the LazerBlade (https://www.kickstarter.com/projects/15 ... r-engraver). The inkscape gcode extension that I use can be found here: http://polakiumengineering.org/1000-por ... er-cutter/

Anyway, if it's the measurement tool you're after then try using a development version (http://sourceforge.net/projects/inkscap ... /inkscape/). You can install these (or unzip) along side your stable version. I run both versions quite often when I need an extra feature or two. As for your grid spacing, set your document units to inches first then adjust your x and y spacing for .0625.

pedwards2932 · Postby **pedwards2932** » Tue Aug 19, 2014 11:02 pm

hmmmmm when I use the same settings as above I still get the grid with what looks like about 1/4' squares?

Postby **heathenx** » Wed Aug 20, 2014 12:02 am

Have you tried drawing/snapping to the grid and looking at the size of your object? You don't need the measurement tool for that.

hulf2012 · Postby **hulf2012** » Wed Aug 20, 2014 1:44 am

Hello:
Just thinking:
You are showing just a section of one wing. heathenx made an easy airplane, but the wing is plane. What are you trying to do is an aerodinamic wing like:

http://en.wikipedia.org/wiki/NACA_airfoil

which is a LOT of work!!

Maybe it's better use a CAD program like, LibreCad:
http://blog.librecad.org/
And, if you want, export it to Inkscape in a DXF format.
The trouble that i found with this work it's the wide of the outline. You demand accuracy, but since you are using a PDF, that accuracy is relative. It depends of the quality of the Document, if it is just an scan or a vectorized document. Also because those lines in the PDF have a wide, perhaps measured in fractions of an inch.

Giving another read to your post, i think you are requiring is learn to do a boolean operation. See here:

If you have problems:
1.- Post a sample (or samples) of your file please.
2.- Please check here:
http://tavmjong.free.fr/INKSCAPE/MANUAL/html/index.html
3.- If you manage to solve your problem, please post here your solution.

tylerdurden · Postby **tylerdurden** » Wed Aug 20, 2014 2:39 am

I suggest using points as grid units, as they can be easily divided into fractions compatible with inch units.

viewtopic.php?f=29&t=16005

You can still use inches as the ruler units.

pedwards2932 · Postby **pedwards2932** » Wed Aug 20, 2014 2:40 am

Thanks for the link in the manual. Those are the functions I was playing with and it was working pretty well. The pdf's plans are more designed for you to build the model over top of them. They were hand drawn not computer......I think as long as I get the notches right the rest will fall into place with sanding. Generally once you assemble all of the wing components then you block sand which will correct any small deviation on the ribs. The airfoil is already done in the plans so you just have to trace around them. I have added an example, it was hard to find one that was small enough file size:

C.A.B. GY 20.pdf: Plan Example; (173.22 KiB) Downloaded 297 times

pedwards2932 · Postby **pedwards2932** » Wed Aug 20, 2014 2:53 am

Using points works great now I have 1/16 inch grid. That should make the tracing much easier. Everyone has been so helpful on this forum. Thanks.

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