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)
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