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Designing wings with Sketchup

#1
First post long time reader. I am an avid FB builder I enjoy designing and building almost as much as flying. Most of my builds are what you would call budget and I like duct tape. I have built a bunch of planes some fly great some crash great. I haven't followed a plan yet. I build KF wings and folded wings.
I wanted to make a thread explaining how I use sketchup and some other free tools to design foam board planes. My method of design and construction is a little different then the standard FT or armin wing methods. My design goals are usually easy to build strong planes.

My tools and materials
Sketchup make 2017 desktop edition
Sketchup plugin unwrap and flatten https://extensions.sketchup.com/sv/content/flatten-faces
wing cg calculator http://winglib.com/wings/create
3d printer I usually use PLA filament. A printer isn't necessary if your creative and can scratch build your motor mounts
packing tape
duct tape
shipping tape
hot glue
cutting mat I use a big piece of 1in foam insulation
my thingiverse page https://www.thingiverse.com/Flyersean/designs
youtube (lots of planes and quads) https://www.youtube.com/channel/UCMVGRjic9C8LW3GJStkgLLA

I am currently working on a wing that should be similar to an AR 900 in flight and size characteristics. I will do my best to document my process in this thread my hope is to share something that might help other scratch builders. I will update this thread as the design and build progresses

here are some of my planes some use just an rx some are running ardupilot all are fpv. If anyone wants specs or plans the spec wing is on thingiverse the others I can share some basic plans for.
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#2
The first things I think about when making a new wing is what do I want it to do and what parts do I have to build it with.
I have a bunch of 9g servos and tons of quad parts. I always aim for super simple builds.
in this case I want a wing that is similar to the AR 900 which is a very popular wing that can use the parts I have on hand.
I did an image search and found a nice picture of the wing.
I import the image into Sketchup and scale it to the proper size. The AR 900 has a 900 mm span. I draw a 900 mm line and eyeball the image as I scale it until the size of the line and the span in the image are close.
scale.JPG
Next I draw a profile on top of the image profile.JPG
from that profile I have drawn I can go to http://winglib.com/wings/create
and enter in the dimensions of the profile measured in sketchup at this point I round the numbers.
I now have a CG and an idea what the thing might look like. cg.JPG
Next is the wing fold and airfoil.

I like symmetric airfoils on wings. I pick a thickness that will fit the battery I am planning to use. In this case a 22003s it will almost fit inside this wing. I am planning on a small raised cover on this build.
In Sketchup I draw 1/2 an airfoil. The length is at the widest chord but does not include control surfaces. I dont bother using curves I use the line tool with many small segments to make up the airfoil. The thickest part is at 1/3 of the total length. This is the outer surface of the airfoil. airfoil.JPG
A little bit of copy and paste and flip in Sketchup and I get this. The inner line is drawn with the offset tool. its a 0.2 in offset this is the thickness of my DTFB. The inner area will be a wing rib. airfoil whole.JPG
Now a little bit of easy math
The widest chord is 9.58 in the tip chord is 3.35 in
3.35 divided by 9.58 is about 35%
If I scale the above airfoil by 35% I will get the correct size for the tip airfoil.
I want a center rib also so I will make a copy and scale it by 70% which is half as much as the tip.
The top is the wing profile with the rib section
the second is just the rib
third is a 70% scaled rib
fourth is a 35% scaled rib
scaled ribs.JPG Wing fold is next.
using a copy of the half airfoil I started with I use the extrude tool and extrude the part equal to the parts span. (check the wing lib image or measure it on the profile you traced in sketch up) If you have rounded any numbers use your new rounded numbers. In this case the wing panel has a 13 in span.
extrude.JPG
Scale the tip plane by 35% the percentage from the previous calculation. find the sweep of the leading edge. In this case its 10 1/2 in. Use the move tool and move the tip plane 10.5 inches back. Sketchup has snap functions that allow a straight movement. You should end up with a 3d version of one side of 1/2 a wing. half wing.JPG
delete all but the wing surface of your 3d wing part. select all thats left. Run the free plugin flatten and unwrap on the part. You should get a flattened out version of your 3d part that can be cut and folded out of foam board. We only made 1/2 a part so copy paste and rotate to get the whole part wing panle.JPG
next will be printing and cutting.
I am assuming a basic understanding of Sketchup if you are a new to Sketchup its very well documented and fairly easy to use. Please ask questions if you get stuck on a step. With this plane I am working from an existing model that I have traced. If I was starting from scratch my first step would be wing calc to sketch out the top profile.
 
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#3
Here are some assembly pictures. A video showing how I'm putting my wings together is here
I am using 2 pieces of cf arrow shaft as spars. The wing is plenty strong enough without them but once you cut big holes for installing the electronics the spars help a lot.

Layout of the wing template.
I draw half a panle and cut it out. trace it then flip the template for the other half. I cut out the whole panle then use it as a template for the other wing panle. This wastes a little foam but tracing is easier than measuring and laying out 2 symmetrical panles.
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Taping and creasing. I just guess at the crease locations. I use a blunt object to crunch the foam on the crease lines.
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Tape like an armin wing
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Test fold
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Assemble the panels
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Spars glued in
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Cut outs for servo wires
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Fold it over and glue. A very strong smooth wing with cf spars ready to be chopped up for electronics and a battery hatch. 20190727_231110.jpg 20190727_231037.jpg
 
#4
I forgot printing and layout from Sketchup.
I create a 20x30 rectangle in Sketchup I place my wing panel on it and snap it to an edge of the rectangle. I use the dimension tool to get relevant dimensions. Always pull the dimension tool from one edge of the rectangle. The real world sheet of DTFB might not be exactly 20x30. If you layout a piece based on Sketchup dimensions from both sides and the sheet is not 20x30 it will not come out correct.
wing dimensions.JPG
I use a ruler to layout 1/2 the panel I cut out the half to use as a template.

The airfoil profiles need to be printed at a 1 to 1 scale. Sketchup will print the view on the screen so you need to have only the airfoils in view. The camera must be set to parallel projection and aligned with the camera alignment tool button. Set the printing preferences to 1 to 1 (see image)
print settings.JPG
You will have to do a few print previews and pan the camera around to get the airfoils on a single page or at least not cut in half. Once you get a good preview print it. For some reason there are always blank pages.
I lay the print out onto foam board and trace the outline of each airfoil. this dents the foam board. I trace the dent so I can see it and then cut out the airfoils. There is some of this in the video I linked in the post above.
 
#5
A few small things today. A 3d printed motor mount. Thats not the prop im going to use. Thats an emax 2208 2000kv should be good for 6 or 7 in props on 3s.
Im using PLA which can melt from motor heat. I haven't had any problems with pla if i use a motor base. I have raised the motor a little above the center of the wing. The center of mass will be above the wing. The gopro and batteries are just a bit thicker then the wing. I try to keep the center of thrust through the center of mass. This can be done with thrust angle or moving the motor up or down.
Control surfaces are taped on, and I taped the seams.
My helper wanted to be in the pictures. 20190728_181105.jpg View attachment 137346
 
#7
This mess is the parts from a recently decommissioned giant delta.
image002.jpg
The delta actually should have its own thread. It was an experiment to see how low I could get the amps on a big heavy triangle. I have been thinking about a solar plane. solar cells are square should the plane also be square to fit as many cells as possible? It flew ok at 3 1/2 pounds on 3s with a 4108 600kv motor. Defiantly under powered but it stayed in the air. The coolest thing about it was how quiet it was.
image001.jpg
This is the seanhawk V2 or seanhack V2 depending on how you look at it. Its a omnibus f4 pro v2 and a 6s capable PDB in a 3d printed stack. Its running Ardupilot its got 3 servo outputs, barometer, current sensor, OSD the add ons are gps, compass, and 900mhz telemetry. The 5v rail on the FC is powered from the ESC BEC or the PDB not the weak 5v on the board.
It gets ripped out of one foam plane and hot glued into the next. I have made 2 of these. The add on bits are due for a rewire I have exceeded even what I consider an acceptable number of splices. I am going to clean this up and see if I can get it into the wing I am currently building. I am planing on using a small quad 35 amp ESC not the big plane ESC in the pic. image003.jpg
A very fun part of the RC hobby to me is making stuff work. I like that with my 3d printer and a box full of cheap parts I can come up with an idea draw it build it test it.
I do like looking at beautiful builds and expensive quads and planes. I dont have the time or patience for that as a hobby. My day job is often detail orientated fussy work Im a general contractor that does a lot of interior finish work. Its nice to just throw something together and send it. Sometimes they even fly.
 
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#8
Ive been really busy this week with stuff thats not foam planes. I did cut a hatch and glue in servos. I think I'll get it in the air this weekend. the huge 50amp esc Is still wired up I may just leave it. I know the setup works. 241850_c3038f977922dd8702c6333f3f1d1630~2.jpg
 
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#10
The maiden flight went ok. It was a bit to windy 20+ mph gusts. It flew alright but needs some aerodynamic tuning on the winglets. Its got some wag. The CG hit spot on with a 2200mah 3s I got lucky with that.
I discovered the colored packing tape I used to cover the foam board is not good for hinges. It does not stick well to itself. I cut off the elavons and re taped them with heavy duty packing tape. I will skip the electronics install its a mess of hot glue shrink tube and tape. There are much better ways to do it then my cram and glue technique. I did get everything in and working after a polarity swap on my fpv system I cant believe nothing smoked. The pdb got so hot it remelted the hot glue holding it in.
The gopro is really tight in the foamboard cradle and its got double sided tape holding it in.
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here is the video. most of the flight is 3rd battery the toss is the actual first toss. I used ardupilot auto take off. Its not tuned in ardupilot and just oscillated up and down on climb out but it went up and stopped when it leveled out.
next will be tuning this bouncy waggy thing. Control throws seem smaller then I like, the winglets are keeping it straight but the wag at low speed is bad, CG might be a little far back Ill experiment with it. I like a nose heavy wing they seem to track better.
 
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TEAJR66

Flite is good
Mentor
#11
Wings are all about the drag. More at the tips than the center is better. Maybe consider a longer tip chord and / or, try toeing in your winglets 1 degree.

Just my two cents.

That's a very good looking build.
 
#12
I usually start with winglets that are bigger then I think I need. I dont tape them they are just foam board. The have a small toe in. If it tracks at speed but wags in any cross wind or at low speed I will cut the winglets down some. A cross wind hitting the winglet behind the GC pushes the tail around. My goal is to have the cross section behind the cg just a little bit more the in front of the cg. This means small winglets. If I cant get it tracking and behaving in a cross wind I cut them off and add more toe in. Toe in = parasitic drag so I try to go with as little as possible to fly smooth. To much and it will act like a fishing lure with a fast side to side oscillation but a straight track over all.
I need to 3d print some adjustable winglets.
 

TEAJR66

Flite is good
Mentor
#13
You can drop the winglets all together. Blunt leading edges at the tip will do the trick. Parasitic drag at the tips that over come the induced drag at the center will keep out the waggle. And no winglets will reduce cross wind interferance. Hence, a longer tip chord or more constant chord.


From the video, it looked like you were using a flight controller. If this is the case, give the winglets rudders and let the FC counter the waggle.
 
#14
I have done drag tips a few times. I think the winglets add elavon authority. My drag tip wings didnt have larger controll surfaces and felt weak in the sticks to me. My smoothest flying wings have all had the small triangle winglets with a good amount of toe in. So basically a triangle drag tip that helps keeps air on the elavons. Most of my wings do have a larger tip chord. This particular build was a rough copy of an AR900 wing. I didnt realize tip chord affected wag that much but it makes sense.
 

Merv

Well-known member
#15
I use packing tape to cover all my planes. For the hinge, I use hot glue & packing tape. Put a small bead of glue in the hinge, smooth it out with a hot iron, apply the tape over the hinge, then use the hot iron to reactivate the hot glue to seal the tape. I use an old covering iron but an old clothing iron would work just as well.
 
#16
I had a chance to mess with the winglets. This is where I am at. wing tip size1.jpg
wing tip toe in1.jpg
I reduced the overall size and put about 3/16th of an inch of toe in. It mad a big difference. The wing tracks better, it still has some wobble wag on some turns and tends to drop the nose in hard turns. The wing loading is high and Im only running 3s. I probably have to live with the nose drop. I guess its not a spec wing dont try turning that hard.
I havent tried moving the CG around. Wing calc shows 20% cg at 5.1 inches from the nose. I am at about 5.2 so its really close. I tend to like wings cg to be less then 20%. On this build the only way to change it is to add weight or change the way the gopro is mounted and push it forward.
The plane with a gopro and 2200mah 3s weighs 740g. It cruises at 45 to 50 mph on 5 to 6 amps, tops out about 63mph. Its got a 7 or 8 mile range (total distance not radio gear).
Over all I am pretty happy with it. A 900mm plane with auto pilot and the ability to lug a session on the nose is not bad. Its got few flying quirks pitch is pretty unstable worse then other flying wings. ( I think this is the CG). Still has some wag in turns and the nose drops in hard turns. I think the nose drop is due to wing loading. more power or flying less aggressively will fix that.

Its hard to get a scratch built to fly great on the first iteration. I wanted to show the process from design to flying great. Since I haven't built this plane before I may not get great but Im already to good. CG is next.
here is a video from today.
 
#17
Ive moved the cg forward without adding much weight. Usually I will allow for moving the battery around to get the cg where I want it. I cant do that on this plane the battery is right up to the front spar. I opted to move the cam vs remove the spar. haven't flown it yet. Its going to rain for a few days here.
This is the process I go through every time I build a new plane. Add tape, add foam, cut off foam.
On this plane I want as smooth flight as possible on a small wing.
The hd pod is visible in my fpv cam that is not ideal but its not a show stopper yet.
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#18
I got a chance to fly. Its definitely getting a lot smoother.
The hd pod in the fpv view is not nearly as bad as I thought it would be.
Im getting some twichy movements. It may be the cheap mg90s spazing out.
I have another theory also. I didnt taper the trailing edge of the wing foam. The elavon is one layer of foam the back of the wing is 2 layers. It makes a 1 layer step right at the hinge line. Its on the bottom of the wing.
I think this step is making a vortex or buble of turbulence on the control surface. I have made a lot of kf wings and if the step is to tall or to close to the control surface it can get squirrely. Little movements do nothing a little more movement and it feels like full throw.
Im going to make some 2 layer elavons that taper down to a propper trailing edge.
I also tried a 1500mah 4s. It was pretty fast. Im running a 6040 prop.

A funny thing happend when i was making some adjustment in ardupilot. I pluged in a battery heard a sizzle smelled the smell. Everything still works I flew it right after. Must have been an esc cap? I haven't checked it yet.
Here is the latest video. As you can see moving the cg up definitely helped.
 
#20
Ah well sometimes mistakes are made.
The plane is actually not bad the spars are fine and the electronics are all good. Its dented and needs some tape. I added some Rightwing style fins and fixed the control surfaces. No more twitch on the controls. Both things moved the cg back. A little hunting on the sticks to maintain pitch with the new not yet adjusted cg. Clipped the grass at speed. No damage. The failsafe test did not go well. the RX didnt output a low enough PWM value to trigger Ardupilot to fly the plane. It was a RX configuration mistake.
Before
image001.jpg
After image003.jpg image002.jpg
The gopro session is pretty impressive.
Im going to fix this up and fix the failsafe. . Then probably build another with a few changes that will make it fly better.
The video