Sonic Series | nnP-39

[andrej]

All the links to high-speed motors are dead, and the motors themselves are no longer in production. What motor is suitable for speeds up to 130 km/h these days? Will any 2206 2100 kv motor be suitable?
I'm planning to build a new NNP39.
Also, what do you think: should I choose 3mm or 6mm thick foam? Will the 3mm foam flex at speed?

 

[RickHunter]

All the links to high-speed motors are dead, and the motors themselves are no longer in production. What motor is suitable for speeds up to 130 km/h these days? Will any 2206 2100 kv motor be suitable?
I'm planning to build a new NNP39.
Also, what do you think: should I choose 3mm or 6mm thick foam? Will the 3mm foam flex at speed?

Yea. Those motors are discontinued. I believe the size for the sonic was a funjet 2825 1950kv. I don't think a 2206 will get you there for speed, but would work. Maybe a 2826 2200kv 40amp esc 3s setup might do it. It takes my swappable mustang to around 70mph(112km/h) with a 7x4x3 prop. Being this is a smaller plane, it should get you there.

Amazon.com

 

[andrej]

The 2206 2100kV on the nerdnicrc website says 70 mph on 3S and 90 mph on 4S. If those numbers are accurate, that's definitely enough for me.
I have an old Turnigy 2826 2200kV, I'll have to try it. Isn't the 7x4x3 overkill? I used a 6x4 propeller on one. For speed, a 5.5x4.5 would probably be even better.

 

[RickHunter]

Also, what do you think: should I choose 3mm or 6mm thick foam? Will the 3mm foam flex at speed?

At those speeds make sure to put a wing spar in. Nerdnic has a great aluminium one. Since your spar will be your strength, as far a thickness the 3mm will be lighter so I would go with that. Keep in mind the blueprints are for the Adam's or FT foamboard which is 4.7ish mm thick so you might have to modify (where the folds are ect....) the blueprints to fit whatever thickness foam you use.

 

[RickHunter]

I have an old Turnigy 2826 2200kV, I'll have to try it. Isn't the 7x4x3 overkill? I used a 6x4 propeller on one. For speed, a 5.5x4.5 would probably be even better.

Might be. I always forget that I live at high altitude, over 1600 meters, so I always bump up the props by a inch. The 6x4 was definitely slower for me. I use these cheap motors from the link, and they burn out really quick on 4s setup.

 

[andrej]

If I make the spar out of 4mm thick ply, won't it be too much? I can't find thinner plywood in my city.

 

[RickHunter]

I would think it should be okay. You might have to widen the channel to fit it in. The normal basswood he uses is about 3mm wide. I would pry not make it a super fast version with it though. If you have any type of hardware store around you, the aluminium spars he uses work great (it's what I used on mine) and are pretty cheap.

 

[nerdnic]

You should be good with 4mm. I didn't test that but the weight and strength will be close enough.

 

[andrej]

I decided to make the spar out of aluminum after all. The wing profile didn't turn out quite the way the designer intended. I don't know if it will fly. It weighs 257 grams with an 1806 motor and an 3S 850mAh battery. I used too much epoxy, and the wing turned out very heavy—around 90 grams.

 

[andrej]

The maiden flight didn't go very well. First, the motor tore off; the aileron rates were too high, and apparently one wing was significantly heavier than the other. Then it crashed into a tree, and a wing snapped off.

 

[Mr Man]

The maiden flight didn't go very well. First, the motor tore off; the aileron rates were too high, and apparently one wing was significantly heavier than the other. Then it crashed into a tree, and a wing snapped off.

What makes you think 1 was heavier?

 

[bisco]

that's how all my flites go , I thought it was normal

 

[andrej]

I glued the spar on one wing with epoxy, but I was too lazy to wait for the other one to cure, so I used hot glue. Tomorrow I'll try to take off using the flight controller.

 

[andrej]

I made another attempt today, and here’s what I discovered: there was a terrible torque roll to the right. The motor has a few degrees of right thrust, just like in the plans. Then I remembered I had installed a 5x4 3-blade propeller, and I think it rotates clockwise (to the right) as well... I trimmed the ailerons all the way over, but it still pulled hard to the right instantly and crashed. Could the right thrust angle and the different propeller have had such a strong effect on the flight?

 

[Mr Man]

I made another attempt today, and here’s what I discovered: there was a terrible torque roll to the right. The motor has a few degrees of right thrust, just like in the plans. Then I remembered I had installed a 5x4 3-blade propeller, and I think it rotates clockwise (to the right) as well... I trimmed the ailerons all the way over, but it still pulled hard to the right instantly and crashed. Could the right thrust angle and the different propeller have had such a strong effect on the flight?

Yes it can 👍

 

[telnar1236]

I made another attempt today, and here’s what I discovered: there was a terrible torque roll to the right. The motor has a few degrees of right thrust, just like in the plans. Then I remembered I had installed a 5x4 3-blade propeller, and I think it rotates clockwise (to the right) as well... I trimmed the ailerons all the way over, but it still pulled hard to the right instantly and crashed. Could the right thrust angle and the different propeller have had such a strong effect on the flight?

An incorrect thrust angle is basically thrust vectoring in a fixed direction- it can make a plane basically unflyable. Pair that with a high torque setup for speed and you have a recipe for disaster

 

[andrej]

I swapped the prop for one with the opposite rotation and resoldered a couple of wires in the ESC. Now it torque-rolls, but to the left..

 

[RickHunter]

Is it uncontrollably torque roll at all times, or just at takeoff? Mine does torque roll on take off as well, but nothing more than expected for the big motor I have on it. 3536 1450kv. I just use the alieron to adjust adjust for it. Once it's going though, it flys great. My maiden I did almost eat it, but that was due to too light of a toss with not enough throttle. If you can, or already do, have a buddy give it a strong toss (don't throw it yourself) it will be easier for you to correct the torque roll on launch that way. If it torque rolls at all times, not just at takeoff, then I'm not too sure.

 

[andrej]

I’m using a modest 1806 motor with a 5x4 prop, so torque roll should theoretically be minimal. It happens right at takeoff; basically, before I can even get my finger onto the stick, the plane is already in the grass. I suspect the airframe geometry might be off somewhere. I managed to take off a couple of times, but even after gaining speed, I still had to use the ailerons to compensate.

 

[telnar1236]

I’m using a modest 1806 motor with a 5x4 prop, so torque roll should theoretically be minimal. It happens right at takeoff; basically, before I can even get my finger onto the stick, the plane is already in the grass. I suspect the airframe geometry might be off somewhere. I managed to take off a couple of times, but even after gaining speed, I still had to use the ailerons to compensate.

A good idea for hand launching a plane for the first time (especially if it's likely to be sketchy for some reason) is to ask someone else to throw it for you so you can have your fingers on the sticks from the moment it's in the air (or if you aren't flying with others, then to throw with your left hand so you at least have elevator and aileron control immediately.

You can also fix some of it with thrust angle. If it's torque rolling to the left, add right thrust, if it's torque rolling to the right, add left thrust.