This post might be a little premature in that I'm just getting started, but after hanging out at DIY Drones for a few years and doing little more than adding editorial comment to other's posts, I'm anxious to share my real DIY Drone project. Since all of the hard work has already been done by others in this community with regard to the autopilot, this blog will focus on the airframe.
I decided to turn my DIY Drone project into my first attempt at designing an airframe from scratch. I have built from plans before, but never went this far. I chose the IAI/AAI RQ-2A Pioneer to model. First, I like the simplicity of the design and felt it would be fairly easy to model. Second, I prefer a more traditional tail to the v-tails that seem so popular with UAVs. I'm sure there are very good aerodynamic reasons for that, but they just don't appeal to me aesthetically.
My plane will be a 1/3 scale model of the Pioneer. That gives it a wingspan of 67-1/2". The design of the main wing and empennage assembly is pretty much done. Next I'll move on the fuselage. My plan is to have all ribs and formers laser cut.
I'm using Google Sketchup for the design work. It has been very easy to learn. The most difficult thing so far has been figuring out how to get 2D plan-view prints out of Sketchup. It's not really geared toward basic engineering. It's primarily a 3D modeling platform. However, with a little playing you can get the printouts you need.
When finished, the plane will be equipped with APM, telemetry and on-board video (of course). I will most likely learn APM on a smaller ARF, though, before risking this airframe.
I'll post a few more images in this blog, them move over to just posting progress photos in an album on my DIY Drone page. The first one below is the real thing hanging in the Air and Space Museum in Washington DC (not my photo).
Thanks.
Paul
This is my current design for the boom saddles that will attach to the horizontal stabilizer. I'll try to shape them from a layer of four 1/4" balsa ribs. The channel is for servo leads.
The boom attachments for the main wing will be a little different and will be integrated into the wing itself. All three spars will pass through the supports. The wing sheeting itself will also add strength to these supports.
Ribs will be 1/8" balsa. Spars will be plywood with 3/32" balsa webbing. Main wing sheeting will be 3/32" balsa. Tail feather sheeting will 1/64" ply.
Vertical stabilizer and rudder.
Finally, a little fun I had with Google Sketchup before starting the plane design. I modeled the CCD camera I'll be using and figured out how to model the clear dome.
Comments
Hi UFO-MAN,
Thanks for your comments. There's a lot to cover, so I'll start with a few questions then get back in a bit.
Regarding the curved surfaces, they were formed in different ways depending on the part. Without question, the hardest curves to model were the rounded edges of the fuselage. There is a plugin for Sketchup that will put rounded edges, inside and outside, on fairly simply shapes such as a cube, but it didn't work well at all when I tried to apply it to the fuselage. I ended up creating a wireframe model of the fuselage and working with that. There were so many steps I took to create the fuselage that it will be hard to state them all, but I'll give a (sort of) brief outline. Also, if you aren't already familiar with Sketchup, some of this might not make sense.
First, I drew up both top and side plan views of the fuselsage. The top view included an outline of the shape at the bottom of the fuse and an outline of the top shape. As you probably see from the pictures, the fuse tapers in from bottom to top. I then used the push/pull tool in Sketchup to drag that inner, or top, shape up to the height of the fuselage. What I ened up with looked like an elongated top hat.
The next step is to use various skinning tools and/or plugins to join the lower, wide, outline to the top, narrow ouline. If the four corners of any given area are coplanar, such as the long flat surfaces on the side of the fuselage without any curves, Sketchup will automatically skin that surface when the four sides are drawn. Skinning the complex curves gets a bit more difficult and I found that I had to use different tools or plugins at different times.
What you end up with now, using the top hat analogy, is a an elongated cone with the top cut off (that would be the flat upper surface of the fuselage. Also, at this stage, the uppper and lower edges are sharp. Now it gets fun.
Next, you import the fuselage side profile. You use the axes in Sketchup to make sure everything is lined up. With the side profile sitting next to your top hat, you use the push/pull tool to drag the side profile across that shape. You now have two 3D images merged with each other. Now, you "select all" and using the "intersect faces" tool to combine the images and get hard lines wherever the two 3D model touch. Finally, you use the erase tool to get rid of all of the extraneous stuff around the final shape.
Well, on the one hand this gets complicated real quick. On the other hand, this is actually quite simple in practice. If I had a screen capture program like Camtasia (not free), it would take me about 2 minutes to show you what I did above.
I gotta go (wife wants to go out for breakfast). Anyway, at this stage my fuselage looked pretty much like a shoe with sharp edges.
More later...
Thanks again,
Paul
Nice model!
I was under the impression that Sketchup is difficult to use for any serious engineering type of work, but it looks like you have managed to do exactly that.
Is it possible for you to write up the steps in you went thru in Sketchup when making the model?
Some questions:
How did you manage to get the curved surfaces done?
How did you import the X/Y coordinates for the Wing profiles?
Did you do the cutouts inside the fuselage?
How did you separate the balsa parts into the "stack" we can see in some of the pictures in your gallery? (Wingspars)
Did you use several parts that you made separately and then merged them together in an assembly?
What procedure do you use to print 3D to 2D paper?
Would you mind sharing the Sketchup file so we may try to learn some tricks by looking in your file?
ufo_man
Since first adding this post, I have changed my design for the Pioneer from 33% scale to 42%. I found that the individual parts, particularly the tail section, were a little small. I was actually having trouble placing the servos in the tail. So, I redesigned everything I had done to date and then made some additional progress. I updated all photos on my album, but I'll post a few here as well.
@Rory -- The laser cutting service I used once before is no longer in business, but I have another in mind that I'll be contacting for a quote. The first time I had to send in the plans and they scanned them. I doubt the new service can use Sketchup files without some kind of modification, so I imagine I'll have to send prints again, but we'll see. I will definitely post whatever service I end up using.
@Doug -- Good to know. Thanks.
Hi Paul,
I'm using that transmitter, there dual output receiver, one output for my goggles and the other for a monitor. I'm also using "RangeVideo's" DX201 camera. Everything works great.
@Psycomaxter -- Thank you. I appreciate your comments.
@Justin -- Here are the video system components I've zeroed in on. Please don't hesitate to make other suggestions.
Camera
Transmitter
Receiver
Pan/Tilt Mount (although I like that $6 SparkFun mount)
Paul
@Paul
Have you found a decent laser cutting service? When you do can you post something on the process please?
I am looking at a small wing modification project and I would will use this to run through the process of designing a wing segment in Sketchup and having the parts cut.
One word : AMAZING
That's looking like what I have in mind for my next build, so I plan to use 2 motor on wing instead of one pusher propeller. Maybe I will use pine wood and fiber glass.
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