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Aug 05, 2019, 08:21 PM
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Designing Foam Board Flying Wing Plank

I have tried designing an RC airplane before and my designs usually were drawn to scale on a piece of paper and then measured and cut out of foamboard. I got lucky a couple of times and the thing actually flew pretty well. But the process was tedious and I couldn't really share my plans with anyone without lengthy explanations of the details I kept in my mind. It was discouraging. So I decided I wanted to do some CAD style drawings like the guys at Flite Test.

When I saw the Nano Drak from RitewingRC I knew it was time to give it a shot. From the pictures I found it looked pretty small and basically like a plank flying wing. That's when I put 2 and 2 together and I knew exactly how I was going to do it. The FT Goblin!

I downloaded a copy of the full page plans and started wondering how I was going to make the necessary edits to get the shapes I wanted. I needed some software. I had heard of people using Inkscape to draw plans before so I downloaded a free copy and when it was installed I started playing around with it. Pretty soon I had figured out how to import PDFs, make new layers, measure correct distances, and all those good things that you have to know to use the software. I dove in head first.

Here is how I did it:

Download the plans from FT.
Download and install Inkscape.
Open the PDF of the plans in Inkscape.
Create a new layer over the one the plans are on.
Set the transparency of the layer to 50%
Use the panel on the left to select the “Draw Bezier curves and straight lines” tool
Don't start drawing just yet though.

Now you are going to need some experience building FT style planes out of foamboard to get the next parts right. There are a couple of things you need to know.
Foam Board is somewhere between 4 and 5 mm thick. So you have to take that into account when making pieces that fold or intersect.
Center of gravity or CG. You are changing the dimensions and shapes of the airplane you are using as your foundation. So the CG on your airplane is going to change too. Head over to and browse their library. That is where I found the basic shape I wanted to use for my Drak. This wing design in particular is the one I chose for these plans:

OK! So now that I have plans, software, and a wing design I am ready to start. Remember that layer I added to the plans in Inkscape? Make sure you have that layer selected. Look at the bottom of the program window and you can see your current layer in a drop down box.

Now paste a copy of the Drak wing design on that layer. You set it to 50% transparency so that you can see through the wing to the plans below it.
Next you need to resize the wing to fit the FT plans. What I did was lock the aspect ratio of the wing and drug the corner around until I was happy with the size. I lined up the right wing of the Drak with the wing of the goblin.

Here is a picture of the button you have to click to lock the aspect ratio.

Now that the Drak wing is the right size, I wanted to get a higher resolution outline of the shapes. So I traced over the Drak wing shapes until I had the design copied to Inkscape. Doing this gives you anchor points for the rest of your drawings. Some good tips when making this outline is to make sure you are using perfectly vertical lines with 0 degrees of angle in them. Its easiest to make all of the vertical lines first. Then connect the angled horizontal lines to the vertical lines.

Here are the results:

Notice that I only did 1 half of the Drak outline. This is to ensure a perfectly semetrical airframe. Once you have ½ of the plane, just make a copy and flip it hoizontally and connect it to the other half. Make sure you capture that CG marking as well.

Here is a shot of the Drak shape overlaying the Goblin plans.

Use the plans you are copying to draw all the necessary markings you will need on the new plans.

These are the plans I created using this method.

The hardest piece was the middle wing section. I wasn’t sure how I was going to fold the wing together using the FT build methods. I will go into more detail on this part in the build video.
Other parts that took some extra thought were the Nose piece, the spar, and the Fin. The nose and fin required learning how to create curves in Inkscape to my liking.
This is the button you use to put a curve on straight lines. It takes some experimenting but it makes sense the more you use it.
The curves on the back of the nose piece that connect to the fuselage seemed too difficult to reproduce. So I changed those to straight lines. The spar was made by simply putting the outer wing section next to the inner wing and tracing the two wing folds on the rear of the wing.

Well you get the point. If you want to know more PM me. I am happy to help anyone who wants go further.
These are the results of my efforts.
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Aug 05, 2019, 08:22 PM
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Aug 05, 2019, 08:23 PM
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