I love the smell of heatshrink in the morning

by RacerX | March 1, 2015 | (8) Posted in Projects

What does heatshrink smell like? Victory.....eh, something like that.
When starting into this hobby and purchasing some parts, I bought a 64mm EDF unit just to have around. Didn't really know what I was going to do with it. The EDF was a cheapie off-brand thingie that I eventually used in a delta wing style scratch build. It was an easy design for me to put together. The EDF was an (8) blade fan with a 4500kv motor rated for a 3s battery. It seemed like a nice unit. 

Sonic Boom!
Well, maybe it wasn't the best EDF. I was spinning it up for testing, after I had it mounted in the plane, and it shredded! Absolutely exploded! Luckily, none of the shrapnel hit me and my eyes were protected since I always wear glasses. That was my first experience with EDFs. Not a good start but now I've proven that I can destroy a plane without even flying it. (below is a photo of that first EDF that shredded)

I was sent a replacement unit but in the meantime, I had ordered a different EDF to put in the delta wing. I was able to get that plane to fly but had some other issues with it, namely servos. I still need to rip those defective servos out and replace them. While in the air, the plane would twitch at different times and the elevons wouldn’t act properly. That’s another story.

Does EDF stand for Extra Difficult Flying? Or maybe, Easy Doo Fuss?
It was last year when I put that first EDF plane together and I was able to fly it about 10 times. Enough to get the CG close and get a feel for the characteristics of flying an electric-ducted-fan propelled plane. I definitely needed to keep the speed up and also had to give a healthy hand launch every time.

I liked the way it flew and the way it sounded. EDFs are definitely unique. This winter has been pretty harsh and there has been no opportunity to fly. So, I decided to try and put together another EDF scratch build. This time I wanted to make a proper fuselage.

The latest winter project: my second EDF
I have bought a few other EDF units since that first one exploded. What I'm using in this build is actually a replacement part for a Freewing jet model. I've tested this new motor and it seems to work great. I pulled the fan off the motor and balanced it as best I could. I have one of the small magnetic balancers. It helped but the fan was fairly balanced from the factory already.

 

 

I use some really old CAD software to draw up the plans. None of it is in 3D, just straight plan view design. I also use several different online CG calculators to get things balanced to start with. I realized with this latest design that the CG was going to be difficult to keep from being nose heavy. So, I shifted the wings forward to help out. I think I should be able to get the CG right with the battery in a reasonable spot.

I'm fond of delta wing planes since they only require two servos – elevons! It makes for a simpler build. I have an idea for a rudder that would extend down into the thrust wash. That would actually give a little bit of yaw thrust vectoring. I show that alternate rudder on the plan but I haven't tried it yet.

 

EDF could be Speedy F

I'm hoping this little plane can fly fast. I named it FLF703. Fast Little Flyer 703. Give it a fast name, it will fly fast, right? And maybe I need some flame decals. No one ever accused me of being smart.

Here's the specs:

Build material: Dollar Tree foam board
Wingspan: 27.6” (703mm)
Length: 20.7” (525mm)
EDF size: 64mm
Fan: 5 blade
Motor: 4300kv Freewing
ESC: 30A HW w/ SimonK firmware
Battery: 3s 1800mah (or 1300mah)
AMP draw at full throttle: 27A (measured)
AUW: 440 grams (measured)
Thrust: 430 grams (measured)

 

Here's some build photos:

 

3.....2.....1.....Doh!

Why did I have to try a maiden when it was only 19°F and a bit breezy? Cabin fever and RC fever make a deadly combination. I muffed the hand launch and the wind caught the plane. It headed straight up and then straight down. I believe it was a slight bit tail heavy. However, I'm not sure I could make a good judgment from the three second flight. As you can see from the progression of screenshots below, the flight was a bit short.

The combination of the cold and still having the throttle up when it hit the snow made the blades crack off the EDF. That was the only damage to the plane. I already have the spare fan installed in it. I'll wait for a better day and shift the battery forward to ensure it's nose heavy.

 

I used my Mobius that was taped to my hat but it really isn't worth uploading the entire video:

(just say "oh poop" when you look at each frame - that's pretty much what I said)

 

COMMENTS

81zapper on March 2, 2015
I'm not into edf yet still playing with pushers but this is a beaut nice job
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RacerX on March 2, 2015
Thanks!

I really wanted to have a good maiden and post the video of it. We need some warm weather to roll on in.
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RickN on March 2, 2015
Be sure to get back to us when you get the nuances cleared up and can get some video. That is one cool little plane. Crazy thrust to weight ratio; ought to go like a bullet !
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RacerX on March 2, 2015
Thanks for checking it out! I'm itching to get it flying.

I also just bought a cheap radar gun. Here's hoping I can get some speed readings on it.
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jkahn on March 2, 2015
The plane looks great!! I took your plans and scalled them down so the plane could fit my 28 mm EDF fan from my Eflite micro Mig 15. I am still building it out of Dollar Tree, but I took off the paper and am not putting a step foil.
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RacerX on March 2, 2015
Awesome! I can put up a higher resolution PDF if you like? I wasn't sure if anyone would be interested.
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jkahn on March 2, 2015
The plans are fine. My planes are never very precise anyway. :)
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RacerX on March 3, 2015
OK. My planes are all fudged up, too.

I'm glad you're good at improvising because the plans I generate are very sparse with details. And I don't know how to incorporate the "A fold" or "B fold" joints like FliteTest makes for their plans. I just do what I know or make it up as I go.

I'm really interested in your build. Please post it when you're done. But don't cuss me out if my plans suck! Haha!
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jkahn on March 3, 2015
I will post when I am done. Hopefully it will be finished this weekend.
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RacerX on March 3, 2015
Sweet! Any chance you are attending Flite Fest this year? I'm planning on bringing this plane there and I'd love to see your micro version.
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jkahn on March 3, 2015
No, sadly. I live in California so I can't just drive over, but it is definetly something I am thinking about going to in the future.
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jkahn on March 8, 2015
Maiden flight of my mini today!!!
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RacerX on March 10, 2015
Awesome! Get any photos or video?
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RacerX on March 10, 2015
AND how did it fly??
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jkahn on March 10, 2015
It didn't really fly. The tiny EDF did not have enough power keep the plane in the air. I got about a 100 foot full throttle launch before the plane touched the ground. From the few short flight, the plane seems like it needs to have a lot of speed to maintain lift. It's going to be really fast. I am going to change it to a pusher, and well see how that goes.
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RacerX on March 11, 2015
Sorry to hear that, I was hoping it would work for you. The weather here is starting to turn around. Once the snow melts, I'm hoping to get my EDF in the air.
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Yogenh on March 2, 2015
I have two 70mm edf I think that it would really be nice with a 70
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RacerX on March 3, 2015
Thanks for reading!

It would probably work with a 70mm. The EDF would need to be shifted forward where the fuselage widens. That would probably offset the weight difference between a 64mm EDF and a 70mm to help with a adjusting the CG.

The other thing is that some EDF shrouds have the flared intake that makes for a larger diameter. The Freewing EDF shroud was designed with a removable flared intake ring which, when removed, made it easier to fit in the tight space.
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Marnix on March 3, 2015
That plane looks really cool !
With what software did you make this plan ? I am also scratch building a plane, and I would really like to have pdf-format plans, to perhaps being able to share them.
Thanks !
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RacerX on March 3, 2015
Thanks!

I use DoPDF printer to make the PDFs. The design software is a super old version of ACAD. It won't run on Windows Vista or 7 or 8.
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I love the smell of heatshrink in the morning