JA37 Viggen EDF Build log

by RCExplorer | April 29, 2013 | (85 Ratings) Posted in Projects

The J37 Viggen is my absolute favorite airplane of all time. I've been thinking of building one for a long time, but I didn't just want to build a flat foamy. I wanted to do it's awesome curves meaty fuselage justice. So I decided to cut one out of 4 inch thick Bluecor using a hotwire.

Here is the plans to the formers used in this build: EDF Viggen Plans

Since Chad didn't have a hotwire in the basement, I had to build one from scratch. (How can people live without one?)

To do this build I didn't really need a big hotwire bow. I rather have a small, light one that gives me great control over the fine movements and doesn't make my arms tired.

Very basic shape. I didn't feel the need to glue 1/2" PVC pipe pieces together. The friction seems plenty strong.

The wire I use is 0.4mm thick Nikrothal 80. A nice thickness for this kind of work. It also doesn't expand as much as other hotwires when it heats up which is nice. Regardless of what wire you get you will most probably not going to be able to solder it. To get around this problem I cut a small piece of brass tubing.

I then slip the tube over the wire and clamp it down hard using a pair of pliers.

The brass is soft and makes a great electrical bond to the wire and it's super easy to solder to.

One thing you don't want on your hotwire bow is a slack wire. To achieve this I simply pushed the two arms inwards when I attached the wire. This creates an outward tension in the bow that keeps the wire taught even when it get's hot.

I wanted both wires to come out the same end so they don't end up in the way when I'm working. I simply fed a piece of wire through the inside of the bow.

Soldered toghether. Nice and clean.

Close up of the solder joint.

To control the temperature of the wire I used a BRUSHED spedcontroller and a servo tester. That way I can easily control the voltage aplied to the wire and thus control the current flow, which is what is turned into heat. I^2 * R = Heat dissapated in the wire

I started out by cutting two blocks of 4" foam

A tip is that the hotwire bow cuts perfectly straight down with the help of gravity if no external force is acting upon it. Just let it hang and make sure the power wire doesn't affect it. 

Used building needles to pin the formers down.

Started by cutting the air duct for the entire F-H and C-F first

Then I cut the big pieces into the individual sections.

And cut the contours of each piece.

The F-H piece was a bit short so I had to add a piece of foam to the end.

Nose cone before shaping.

I used a power drill and some sand paper to shape it into a cone shape.


All pieces glued together.

Nosecone fits pretty well

ChangeSun 10 Blade 70mm EDF unit

To get the CG correct I mounted the fan as far back as possible.

Time to fix the intakes.

Removed around 5mm.

Sanded away the material between the air intake and the fuselage as well as smoothed the intake edges.

Before and after.

The intake was way to fragile being that thin so I glassed the edges.

Now there nice and strong.

Sanded the whole fuselage.

Added a layer of light spackle.

Sanded it again.

Nice and smooth.

Cut the wing.

I strengthened the radar detectors on the wings with a 2mm carbon rod.

Installed the canards.

Notice the positive angle of attack.

Installed the wing.

Time for the servos. Glued using hotglue to the wing.

A detail that really transforms the plane is the wing fillers. Looks great and hides the servo wires.

Servo wires going into the fuselage.

Added the bottom details to the exhaust.

I added a plastic tube on the inside of the exhaust to minimize the drag an add strength.

Speed controller installed.

The bottom plate covers the wires nicely.

To add some scale detail I added weapon hard-points made out of balsa spars.

Installed the rudder

Control linkages in place and ready for the first flight.

It flew awesome! Time to hand it over to Chad and have it painted.

Just need some decals!

The numbers are cut from orange vinyl. All other decals were printed on normal sticky back paper used for shipping labels on a laser printer and then spray painted with a layer of clear coat.

Canopy held down with magnets.

Up, up and away



Todd K on April 29, 2013
Why not use blue core for the wings? Nice build!
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RCbacon on May 6, 2013
I think he didn´t use Blue core for the wings because it is much easier to just take some dollar tree foam board and cut it than hot wire cut it.
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wingnut on April 30, 2013
I love that paint job Chad, How about a how to video please.
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aidan284 on April 29, 2013
This is one of the best planes i have ever seen.Awesome build log as well.Thanks Flitetest crew for doing such an awesome job.
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lracnolip on April 29, 2013
best scratch build ever!
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iLoveRC on April 29, 2013
amazing work of art!!
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pitts special on April 29, 2013
THAT IS AMAZING.... great work.
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Krad on April 29, 2013
That is one sexy airplane. Great work, David!
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phoenix on April 29, 2013
Also can Chad please do a video on airbrushing techniques for RC models?
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liveyourdreamsRC on April 29, 2013
Yes PLEASE! that is just what I was thinking. It looks fantastic by the way Chad!
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tramsgar on April 30, 2013
Third that, a few plane painting episodes are way past due. I want to see the actual techniques and hear all the painting tips. Thanks in advance =).
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sokol on May 1, 2013
I would love to see some painting tips as well :)
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PlaneButcher on April 30, 2013
I love the plane!!! I built a mirage 2000 the same size and it was 950 grams! You really did a outstanding build! Keep up your good work, happy landings, - matt
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Villalji on April 30, 2013
Great build! Many things I was eager to see coming together: hot wire foam cutting, awesome ducted fan plane and air brush painting... If I only had time to put that to practice...
Great job as usual David!
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MrChrister on April 30, 2013
Skitbra David!
Apparently the name Viggen comes from "Åskvigg".
Some ole Swe word having to do with norse mythology and Thors lightning bolts...or something.
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RCbacon on April 30, 2013
Where did you buy that foam? Can´t find it anywhere :( Can you send a link? (if you bought on the internet)
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tramsgar on April 30, 2013
Great build, David! Where were you with that when the Ruskies came visiting the other day?

Maybe FT could sell the laser cut formers?
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jeffreyheslop on April 30, 2013
Yes laser cut formers PLEASE
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learn2fly on May 5, 2013
I agree! I would totally buy them

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dzbum on September 3, 2014
I am looking at this build thinking that it looks like a great project but I am not sure I want to cut that much ply for a foam airframe. I would defiantly buy a former set from FT!
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ashtodust2000 on April 30, 2013
What size brushed esc for the hot wire?, also 2 or 3 cell battery?
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eric on May 1, 2013
+1. Can we just do a simple V = IR to size the ESC? How many watts should we be pumping in this thing?
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NCC1701 on February 9, 2015
I used a direct linkage to a 2s battery for my wire. Just make sure to look up the formula for how long the wire needs to be in order to have a direct connection. If you make it too short it will get too hot. He used a 30amp Turnigy brushed esc from Hobbyking and a Turnigy servo tester from Hk as well.
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phoenix on April 29, 2013
Awesome Build David. Can't wait to see the video on build techniques.

When you built the bow, did you have add any insulation or do anything else to protect the PVC tubing from the heat of the wire?
Also when glassing the intakes did you use epoxy for this?
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Willsonman on May 1, 2013
When using a bow the heat is primarily in between the electrical connections. There will be some that dissipates to the ends but it is minimal and not near the melting temp of the PVC. This is a great solution.
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Willsonman on May 1, 2013
I use a simple car battery charger I had in the garage. I made a plug setup that I plug the battery charger into with a rotary dimmer. Then I clamp the alligator clips to the bow from there and just use the rotary dimmer as my on-off switch. Been building with hot wire bow for a few years now. Great for making wing cores.
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Fabiano on May 1, 2013
hi! fantastic aero, I'm from Brazil, always accompany you for the you tube channel, has started the construction of the mine would have a list of electronics?

sorry for my english, google translator ...

once again congratulations!
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jlt1968 on May 1, 2013
Outstanding plane David great work. How about some estes type rockets you could launch from the weapons hard points?
Great job on the paint Chad, please put together a painting how to video we would all like some tips and tricks.
And thanks FliteTest you are all doing a great job!
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cloud9photos on May 2, 2013
Very nice build! Have you considered building one with working canards? Although it looks to fly superb the way it is set up now. Would be cool to see the canards work and how it would effect the flight characteristics.

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Bondo 604 on May 3, 2013
great build, you need to add measurements to the plans for the size of the templates to be made please. thanks guys and keep you the great work love the show
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Jghanson25 on May 3, 2013
you know... I've built a hot wire foam cutter before, but I had no idea about the crazy awesome tricks that could truely be unleashed with the darn thing! this is absolutely astonishingly fabulously incredibly realistically radically amazingly beyond explanationly awesome! Thanks David!! This scratch build is amazing and seems so simply doable! I need to build a cub or taylorcraft with these techniques when my schedule opens up. YOU GUYS ROCK!!! keep up the awesome work! I seriously hope to meet you guys someday.

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dzeanfly on May 3, 2013
Marvellous !
I am going to study how I could build it...
Dzeanfly from France.
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RaptorJesus on May 7, 2013

i am just blown away about this build. i cant stop watching the episode. you have to do FPV with this and put an afterburner in it.

Also please laser cut the templates and sell them i WILL buy them.

next project a Gripen maby? :P
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brandx on May 1, 2013
Hi David, Josh and Chad. Why don't you make a copy of this plane by effectively 3d printing it from your dollar tree foam board in layers, remove the paper then simply glue and sand and paint. There are some cheaply available 3d scanners you could scan the outside with and then refine the design. With some clever orientation on the sheets it could be quite efficiently cut with your nice laser and could not require much re-working and world be far stronger but a bit light than the blue.

What do you think?
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x3mperformance on May 9, 2013
The amount of glue would make it quit heavy.
There would be like 20 layers (or more) of 6 mm foam, thats 19 layers of heavy glue...
Pulling paper of, glueing, cutting...
Make it out of 4" Blocks in stead, you will get a much better result.
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NCC1701 on January 13, 2015
I agree. Not practical with all that glue.
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Marker on May 8, 2013
Does any one know where I can buy 0.4mm thick Nikrothal 80 wire (the wire that he used on the hot wire)?
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magnespins on June 26, 2013
Try this on eBay:

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Coops on June 15, 2013
Please please please dimension the plans, or remake them in a tiled format like those for the swapable series i am so keen to build this plane it looks amazing. i am in the process of building my hotwire and am sourcing the foam for it
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magnespins on June 26, 2013
Yes, please do. Or maybe make subplans for the formers and the wings part. Thanks!
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RCbacon on July 11, 2013
There is another way :) 1. Download posterazor. 2. Open the file with the plans. 3. When you come to the scale settings set it to 100 %(it will be like 40 pages so i recommend that you use gimp or another photo editing software) If there is anthing you wonder about let me know :)
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Gal 2:20 on September 4, 2013
Or using version11 of AcrobatReader you can take "snapshots" of the formers and print them out actual size. You can get 1-2 formers per page. The wing and canards can be done all together in one snapshot and posterized to 12 pages within Acrobat as well.
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Lokhu on July 4, 2013
I would love to see a list of all the electronics, as a newbie it would really help me get what I need.
And the ChangeSun seems to be out of stock at hobbyking :/
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RCbacon on July 9, 2013
I thing that i have learned is you dont really have to have exact the things that he/she has when they are bulding something :) Heres comes the list! 1. One ten bladed 70 mm edf fan unit! 2. A motor that fits with that unit(some fans have already built in motors)! 3. Two servos(normal 9 grams will do the job) 4. One esc! A fast tip! Dont use an esc with the same rating as the motor use an esc which is rated for more amps :) 5. One rx and tx! (6. Maybe some connectors)! Hope i helped you and good luck!
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hart on May 1, 2013
Hi David,

Awesome model! Josh was clearly impressed, I don't think I've seen him quite as excited when flying a model before :-)

Quick question regarding the foam you used - obviously it is Dow blue core Styorfoam - but are you able to tell us which style of foam was used? I deduce from the Dow website that it was either Roofmate, Deckmate, Panelmate custom or SM (based on it being the only variant availbale in 4" thicknesses)? Oh, and which PSI rating was the foam? Just trying to understand what type of equivalent foam to look for here in the UK...
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RCbacon on July 9, 2013
I think it doesnt matter :) But if you choose a foam with higher rating it will will have a higher total weight but it will hold longer and vice versa with lower rating! Hope i helped!
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yanivme on August 6, 2013
Awesome looking plane. I have the PDF plans. Trying to make sense of them and struggling a little. Is there perhaps some more details instructions, i.e.
Dimensions for each foam core segment, recommended electronics, etc. I have looked at the original German article and cannot translate too well.

An otherwise incredible looking plane.
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yanivme on August 6, 2013
Also, is it possible to get the original plans in Freehand or AI format before being converted to PDF to better plot the stencils on a laser cutter?
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mrscale on August 23, 2013
please sell the laser cut templates. what IS YOUR LOCATION.
Panama City FL
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Gal 2:20 on September 2, 2013
Awesome, awesome EDF. Love all your videos and am envious of your jobs. I've had two EDFs so far and love 'em. I definitely want to try and challenge myself with this build (have never used hotwire). I will echo many others and ask for some templates for the cutting guides.Your laser cutter will do a way better job than I could do on a scroll saw. Keep up the great work and God bless.
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TonkTonk on September 11, 2013
What a great plane you made, it really does look awesome!
You guys inspired me to start making one for myself - even though it will probably take a year or three before I feel confident enough to try a fast plane like this...
Laser cut templates for this model sounds like a great idea btw.
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mrscale on October 30, 2013
Hello Josh can you tell me where the CG is on your Saab Viggen
Thanks Brother
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Trident on October 30, 2013
I'll try to build this plane. What setup do you recommend? EDF-unit, ESC and LiPo? Any idea where the CG should be?
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Gal 2:20 on November 10, 2013
So is this the wrong place to ask questions and get answers from David? I keep coming back to see and there are no replies.
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RCExplorer on November 10, 2013
CG is roughly in inch back from the where the wing meets the body.
The Fan is a Changesun 10 bladed 70mm running a 2300kV hacker motor and a 60A ESC on 4S2200mAh if I remember correctly.
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Gal 2:20 on November 22, 2013
Thanks David, wasn't sure if I was looking in the right place for response. Had other questions a while back but was able to figure it out between your blog and Johan's. Got most of my foam cut, had to order some hotwire, guitar strings did not last long for cutting. Can't wait to start putting it together. Will post pics when done.
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Scale-German on December 11, 2013
How much for a set of the Laser-cut formers so we can build our own?

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Tomas Thomsen on December 3, 2013
Im about to start cutting the foam, but, i dont understand how to use template"E2-b" and "G2-b".
Please help!
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Gal 2:20 on December 23, 2013
Its what you use to cut the flat spot for the wing in sections E and F, after you cut the outside profile of those sections first. There is an F2-b as well. I suppose you could just go straight to the flat profile template but that may be more difficult and not come out as flat when worrying about the curved part.
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micilo01 on April 30, 2013
Snyggt bygge! Any chance that Gripen becomes a buildproject? I agree with tramsgar; FT selling the lasercut formers?
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Matt Mountain on January 3, 2014
Agreed again! Lasers all the way ;-)
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RoryKennedy on January 12, 2014
Hey David,
I was just wanting to know if it would be possible to scale up the plans on this and make it larger with specialized foam sizes and cut it out of solid piece of foam without cutting a slit through it like you did and adding an after burner to it would be awesome!!
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NCC1701 on January 12, 2015
What glue do you use to glue each section?? Surly not hot glue.
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sleepy1956 on February 9, 2014
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flbbcb@hotmail.com on April 3, 2014
The build video shows a completed airplane with landing gear, but only briefly. Has anyone installed landing gear? How did you do it?
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Gaurav on March 6, 2014
Where do you guys get the 4" foam?
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Gal 2:20 on April 18, 2014
Rcfoam.com has 4" x 12" x24" blocks for $10.
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Gal 2:20 on April 18, 2014
Hey David, finally got mine finished, check it out under Mad scratch builders forum under Rcrazy.
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Jcrankshaw on February 12, 2014
Where's the CG and how do I print these plans to scale
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Gal 2:20 on April 18, 2014
CG is approx 1" behind where the wing meets the fuselage.
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NCC1701 on January 13, 2015
I have the same question; How to print????
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kerrycorcoran on June 21, 2014
Can someone tell me how to scale the drawing? Looking at the PDF I don't see where the scale is. Unsure how to enlarge correctly. Any help appreciated.
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latios2468 on August 11, 2014
How do you make the wooden templates? Thanks!
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jfbrubaker1969 on August 28, 2014
It would be great if you could share the CAD file for the laser cut templates!
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arbiter on September 9, 2014
Wow that is awesome, looks easy to fly aswell!
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NCC1701 on January 7, 2015
Hur gjorde du det ? Jag vill ha en ...
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onebladeprop on April 30, 2013
David is a genius. Thankfully he usually uses his powers for good.
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NCC1701 on January 12, 2015
The world would be instantly vaporized. I am actually Swedish but using "Google translate"
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Fire1 on August 30, 2013
What is the motor in this monster?
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NCC1701 on February 9, 2015
I used a 14 blade 70mm 3000kv edf from a Hobbypartz motor and esc combo, and a 14b edf unit from Changesun. He used a 10b edf, though I don't know the kv rating.
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tlshrum1949 on March 21, 2015
David, I must be missing something. What are the lengths of each section of the cut foam?
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chase on May 15, 2016
Hey guys, I realize it's been a few years since this build. I'mFirstly, great build David. Since seeing it a few years back I've been wanting to build it and I'm back looking at it again.

Despite the time lapse since you posted about this build I'm hoping you could either add a link or send me via email to the cnc/laser cutting file for the cut-outs for those of us that would like to either diy or have someone laser cut them out?

As well, you stated in the video with the battery used she gets around 6 minutes flight time. Have you tried a bigger battery in the Viggen to extend flight time and if so, how was her fight characteristics with the larger battery?

Any changes to the build three years later you'd make? It'd be nice to see the Viggen and other top builds revisited. (Like your tricopter)... given the advancements in the industry, longer flight times being the norm etc and improvements or gear changes you'd make if any...

- chase -
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grahamm on April 5, 2015
I dont know the section sizes either!! :'( Please help
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Kostas on August 5, 2016
Hi guys!!I think....that F part is the point that it says how exactly you should find the diameter of your suitable motor guys!! i want to build that bird with changesun 50mm 11 blades and i study a lot and i noticed that this is the exact point!! the F point is the right point to get some serious info about your length of your bird! The lenght of the bird for 50mm motors are 68cm long! i will build this and i will show you pic of my attempt
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spikey on August 2, 2013
Hi, would you be able to make an EDF flying wing, maybe a WW2 Horten HO 229? i've been wanting to make one for a while now, but I dont have any experience in scratchbuilding foamies :)
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ScottgrayNZ on December 3, 2016
I'm a newbie from NZ and I'm looking to make a ww2 Horten HO 229 EDF using the same principles as this plane for construction, if you wanted to collaborate on Designs that would be a great help :)
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Scar17s on April 24, 2017
Great work team, we need a build video on this! Call it Advanced Builds. A small kit with the plywood forms and pieces laser cut would be cool as well as some of the electronics in another kit
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