Techone Sbach 342 -1100, Update 1

Update 1, 4 March 2014

I had trouble on Sunday, 2 March 2014.
I had new Turnigy 3S2200mAh, 60C lipo and crashed in the morning from a failed hover. Motor mount snapped, broke the propeller, enlarged the spar hole in the central spar box, rudder hinge torn.
Went home, fixed it up with hot glue, flew again in the afternoon.
This time I fixed up Eagletree Guardian.
Barely 2 batteries later, lost a servo horn screw (aileron's), hard landing, motor mount loose again, undercarriage needs glue, to perhaps replace one aileron servo.
Maybe I didn't setup the eagletree guardian properly, because it didn't seem to work in the air.

16 February 2014

How it all started

Chris is the one at fault for telling me last Saturday that he would like the TechOne Sbach.



Why is the 11"x5.5" propellor on mine a different colour from the box?
Could this be the reason that I can't fly the Sbach with my set of 3S1300mAh 20C batteries?

15-16 February 2014

Last Saturday, 15 Feb 2014, I rode my motorbike to Rotor to buy ca kicker and 2 digital servos (Hitec HS-A5076HB Digital Slim Programmable Servo Motor (Karbonite Gear) [Torque at 4.8/6V - 2.5kg.cm/3.0kg.cm][Speed at 4.8/6V - 0.14sec/60° / 0.11sec/60°][Bearing - Top Ball Brg][Dimensions(HxWxL) - 27.6x10.8x29mm] [Weight - 14.3g][For Park Flying Models, Indoor planes, Small Glider, Micro Heli, MAV]to replace those of my Techone Katana (the blue one)).

So far I have bought five Techone models. The first was a Su-31 (from Rotor, subsequently given to Wong and he must have destroyed it completely) and two Katana (from Jet Hobby, after destroying the red I got the blue but the fuselage carbon reinforcement aft of trailing edge must have snapped after a crash because of damaged Hitec HS-65HB Mighty Feather Servo Motor (Karbonite Gear) [Torque at 4.8/6V - 1.6kg.cm/1.9kg.cm] [Speed at 4.8/6V - 0.14sec/60°/ 0.11sec/60°] [Bearing - Top Ball Brg] [Dimensions(HxWxL) - 23x11x24mm] [Weight - 11.1g] [For Micro Helicopters, Electric park flyers, Gliders, and 1/18 scale cars use]), both types are 1000mm wingspan and all flew well and the final two are Mini-Popwings. I liked the Katana better but I think that the Swift, being larger, will be much better.

I was thinking of buying a Techone Swift, wingspan of 1200mm. I think it will fly better because it is much bigger.

It is safe to say I trust TechOne.

Rotor had an assembled Sbach, all needed was plugging in a receiver and battery. The price was good, since the kit itself was listed as $153 and the assembled Sbach had 4 (Hitec HS-81 Standard Micro Servo Motor (Nylon Gear) [Torque at 4.8/6V - 2.6kg.cm/3.0kg.cm] [Speed at 4.8/6V - 0.11sec/60° / 0.09sec/60°] [Bearing - None] [Dimensions(HxWxL) - 30x12x29mm] [Weight - 16.4g] [For smaller Airplane, Glider or Heli]), 40A Flycolor ESC and two 12" servo extension lead.

So I bought it and had to return home to drive out again to bring it home.

On Sunday, 16 February 2014, after  some re-routing one servo extension, I plugged in my receiver and battery and got the ESC to respond.

First flight was on my 3S1300mAh 20C battery. My set of batteries is quite old, because they were used in the Su-31 and the two Katanas. I had my Hobbyking X1 Wattmeter and it was drawing ca 27amps, ca 330watts and considerable voltage drop. Well, 27amp divide by 20 is 1350mah, at the limit of the battery. The model has great potential in flight, but it only lasted ca 3 minutes when the model loses power. On retrieval, the motor was warm, and the battery too warm.

Wong loan me his almost new 3S1500mAh 25C (Zippy?), and it was ca 5 minutes and battery still too warm.

Freddy loan me his old 3S1800mAh 25C and it was ca 7 minutes and battery still too warm. I shall have to check with him if his battery is still chargeable.

Battery Consideration

Come to think of it, that's about right! 27amp divide by 20 is 1350mah. 60 minutes divide by 20 is 3 minutes while the actual flight was a bit longer than 3 minutes (excluding maybe 20 seconds for Wattmeter full throttle testing). If I get 5 minutes for 1500mAh and 7 minutes for 1800mAh, I shall perhaps have 8.5 minutes for 2200mAh.

But having too warm a battery cautioned me that I ought to buy better discharge rated batteries. And while I am at it, bigger capacity too.

The Sbach listed 3S1800mAh (to 2200mAh) 25C as suitable battery. I chose 2200mAh, even though it pains somewhat to add weight to the model and found on HobbyKing, Turnigy Heavy Duty of 60C with listed price just below USD 20.00 before shipping. This is priced better than the 35C battery at SGD 38.00 from Rotor.

For a 2200mAh battery, divide by the amperage drawn, 27amp divide by 2.2Amp, equals ca 12C. Yes, the recommendation of 25C is probably suitable for 1800mAh, but unnecessary for 2200mAh. So if I use 3S2200mAh 60C batteries, they ought to be long lasting (my definition of long lasting is 300 flights per battery, because my 2S500mAh batteries have to be replaced after 25-50 flights).

With the latest HobbyKing order of five Turnigy Heavy Duty 3S2200mAh 60C batteries, I also ordered a low voltage alarm (and Eagletree Guardian, but that is beside the point).

With the aim of achieving 300 flights per battery, I promise to look after my batteries better, new or old, by adopting this practice:

In the field

• using the low voltage alarm in the Sbach;
• not flying to less than 11.1v for 3S and 7.4v for 2S;
• to discharge unflown batteries at end of flying day unless the next flying day is the next day

Back home

• to bring all batteries to storage voltage, until the day/night before flying day;
• to balance charge the batteries the day/night before flying day.

Flying time of Sbach

Using 2200mAh batteries that ran cool does not solve the flying time issue I have.
I think 8.5 minutes is too short for my practice flights, I would like 10 minutes (or is that wishful thinking?).
To extend flight time, (not by flying gently or at low throttle throughout the entire flight), how shall I reduce the amp draw and still be happy?

First thought that came to mind is the propeller.
To fly 10 minutes, the amp draw has to reduce to, 27amp/10*8.5, 23amps. The battery discharge rate will be closer to 10C now and might help somewhat to their lifespan.
I shall try different makes, type, diameter and pitch of propellers and static test them with the X1 wattmeter.
Hence the leading question of "Why is the 11"x5.5" propellor on mine a different colour from the box?".