|Jul 10, 2014, 10:41 PM|
85mph 480mm FT Viggen
After the FT Viggen was released I wasted no time getting it built. I really enjoyed how stable it flew and was pleased with my first EDF. After a half dozen crashes I had to retire her and have been wanting to rebuild ever since. I have been on a roll lately building 80% FT planes so the Viggen is up next!
I had originally planned to use the 2700kv NTM motor but it was damaged in a crash so I have opted to use the 2200kv NTM instead.
I have added the plans here.
Motor 87g 700w 2200kv
Prop 7x6 APC
ESC 70a Dynam
Battery 2000mah 3S
The plans fit on 2 sheets of DTFB, and that would include making 5+ noses as well.
The build went fast, a lot faster than the full size. I was able to get everything cut an assembled in just a few hours.
Weight with just servos is 151g - not bad at all.
80% next to my beat up full size.
ESC is mounted in the duct for max airflow.
Plenty of room for my 2000 3S and TX.
Control rod is running through a straw and motor powerpod is mounted with two BBQ skewers.
- Very fast and stable at high speeds
- Tracks really well, no dipping or loss of altitude
- Very small
- Motor caused tremendous torque roll that is uncontrollable at low speeds
- Very unstable at low speeds due to weight
- Difficult to land due to instability at low speed
- ...basically you have to fly fast, always
Boy is she fast! There are 5 other videos that I have not posted of my maiden of this plane. I didn't post them because they are all 4 seconds long and include the Viggen immediately death spiraling into the ground even when giving 0 control input. The torque roll is just that bad. I was very lucky to land each of these attempts on the belly so there was no damage sustained. Each throw I would adjust the angle to try and gain altitude right off the bat, the 5th attempt was the keeper and I actually got airborne.
I can't launch this bird without doing at least 1 roll from the motor torque. This makes take off very tricky and stressful. Once I got up to speed it does handle very well, though. A lot more stable than I had originally thought it would due to its compact size. If I bring the speed below 40% throttle it becomes unmanageable and doesn't respond to control inputs, it just kinda starts doing it's own thing. This makes landing tricky as I have to set it up perfect in a downward glide and set it down fast and hot otherwise a nasty crash will be inevitable. My maiden landing was awful as I hadn't realized how finicky it would be, but I was able to set her down okay.
All in all
Would I suggest you build an 80% Viggen? Yes, but don't use this motor. Get a lower KV and bigger prop that will give you more thrust. I have a few other motors I'm going to try and will update my review with the results. I am hoping a larger prop/more thrust will help to alleviate at least some of the bad tendencies.
|Jul 16, 2014, 02:54 AM|
Good post. I am building a Viggen as well but I am limited in my choice of motors. I was going to put 1000 kv nom in it but am concerned about torque.
I thought that a slow large prop developed more thirsty than a small fast on, am I mistaken?
|Jul 19, 2014, 03:56 AM|
Hey I just saw the motor you are using - wow, that is a beast of a motor!
I am going to put in the same brand and size motor (NTM 28-36) in the full size motor but mine is only 1000Kv. do you think that will be enough for the full size viggen?
|Jul 19, 2014, 10:04 AM|
Others have successfully used that motor on the full size Viggen so I think you'll be fine.
One of the things I found interesting was how long my flights are on this plane. I get over 4 minutes at WOT. With the same power set up on my 800mm Spitfire I get 3, and 2.5 on my 800mm Mustang. The only real difference I know of is cooling. The better cooling matches with the longer flights.
Is this normal?
|Jul 19, 2014, 05:39 PM|
That is good to know about my motor - it was the 1000kv version they we using and not the beast you have? I am only checking as once I put the motor in I can't easily take it out as I do not intend to use a power pod and am instead putting in a Cross Piece of foam at the back for a pusher configuration.
As to battery life, I am sure that the temperature plays a part but it is also a function of drag and effort. Of course I write this but I am not sure how much more drag if any a 800mm Spit or P51 would have. Probably the temp.
Just FYI I was in the middle of buildig the viggen and discovered a Draken that really turned my head and that is the one that I am concentrating oon right now. I think you would really like it.
Prop in a Slot Draken
|Jul 19, 2014, 08:34 PM|
85mph 480mm FT Viggen
Cool I'll definitely check that out!
So I doubled checked and I don't know anyone with the 1000kv version but with a 4S and 9x6 it produces about 1kg thrust which is enough for Viggen but it's not going to be very fast. You'll probably have to hold 75% throttle to stay stable.
|Jul 20, 2014, 09:35 AM|
No problem - once I have maidened it and assuming it is still in one piece I will buy a 2200Kv version. Persosonally I still try to fly all planes on a 3s 2200 as it is much simpler that way.
I am not yet experienced enough to go really fast - you bird is way out of my league.
To quote Dirty Harry - "Man's gotta know his limitations" (now one of my motto's).
|Aug 07, 2014, 12:45 AM|
Hey man did you get to maiden yet?
|Aug 07, 2014, 09:02 AM|
Anyway I was a little put off building the Viggen due to my "weedy" motor - not sure if I should go EDF or just buy an NTM 2700 or even put one of my many 2826 2200kv in it (they are supposed to be pretty powerful).
|Aug 07, 2014, 02:23 PM|
Joined Nov 2012
for the same power system (battery)
|Aug 07, 2014, 07:01 PM|
OK will do - thanks fr clearing that up as I was toying with the idea but all the 70mm EDF's need 4S batteries etc.
I think I will build the Viggen with the 2826 2200KV motor now - I can always swap it over later to another.
Time to start building. BTW I am pretty certain Torque roll is exacerbated by larger props and slower motors as there is more mass involved. If you want your baby viggen to not roll on hand launches I would thing the 2700KV and 6 x4 or 5x5 prop would do the trick.
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