Monday, 8 October 2012

Weekend of test flying!

We had a busy weekend of playing, I mean working!!- We test flew two planes; the New Air One Electric under power and the prototype of the Hurricane, our new 2m sports plane. More about this one later.
First the electric powered New Air One. This project was specifically aimed at F3B electric which as a quick recap meant it needs to be a slippery largish 3m airframe and light for duration but enough power in the electric set up to haul up 4kg + when fully ballasted. The original motor, Hacker FAI was taken out and replaced with a Hacker B50 12s geared running a 16x13 but still with a Castle Creations 100 lite and 4s TP 1800mah 65c. This saved 50g but reduced the static power to around 1.2kw. AUW is now 2.45kg without ballast. Current thinking is that around 700w is the minimum required but will require a longer motor run. I wanted a fast climb and short motor runs to allow smaller lighter lipos and besides it’s more fun this way! The numbers look good with the new set up, the original 1.7kw+ set up was a bit too close for comfort for the esc and lipos especially as I wanted to use a Ubec to power the radio gear saving the weight of a separate RX battery: static tests now showed 93a.
Remotored with B50 12s geared running 16x13 with CC100 lite and 2+2s TP 65c 1800mah

The first reflight was on the slope. Power on and it went scolding away with a short speed up whilst the delayed start up kicked in and the motor and prop began to bite. The thrust line was set up with 3.5 degrees down thrust which meant it didn’t automatically climb on power. A small dab of up and after only a few seconds it was very high above the slope. Power off and the brake worked a treat with props folding back immediately. Of course with all that height it was pointed down and screamed across the slope with some F3F practice pulling some very high speed turns- what a laugh!
To be fair the conditions were good and needed ballast so the New Air One was light but the power was nonetheless impressive.
Later we down loaded the logged data and saw around 1.1kw dropping to 1kw after a few climbs. Current at this power was around the 80a+. Not silly but very safe for all the components.
The next day with very little wind we tested the New Air One on the flat. The conditions were thermic and variable wind directions but predominately from the S/E. A straight throw and power on after release saw the plane speed up and with a dab of up point 70-80 degrees. It needed less than 5s to get to 250-300m and power off saw the New Air One continue on it’s trajectory gaining even more height. Vertical climbs are effortless and the longest logged power run was just over 6s. The high pitch prop gives good speed so much that we did one power run at around 20 degrees and pulled to vertical at the end after power was off gaining nearly as much height as all the other climbs! At over 200w per lb- it’s definitely hotliner territory! It makes me think about my other hotliners of the past which had more power but considerably more weight too, perhaps they did climb faster but this is no slouch and obviously a very efficient use of power for such short motor runs being required. It doesn't make that contorted bark of cavitating props though! It just pulls without fuss and very little noise. Of course a loud prop isn't efficient but it does sound great and very scary! Thing is though doubling the power doesn't give double the performance when dealing at these levels. Which isn't the case at lower power levels say 500w to 1000w as the difference is huge but 1kw to 2kw is much less than you might think and even less from 2kw to 4kw.
1kw for this plane as we have found is very nice indeed.
The New Air One Electric felt very buoyant and cruise speed could be slowed down due no doubt to it’s low weight. It was thermalled away several times and even once when coming in for a landing when it hit a bit of low level active air- very satisfying! We drained 3 packs with about 20 climb outs but cautiously only using about 500mah per pack. There is definitely an opportunity to reduce the pack size to 1300mah saving another 50g or so. For F3B Electric you only need one climb, may be 2 per flight if a relaunch is necessary so 10-15s motor run time is ample, with 1800mah there is 60s available if you dare consume 1500mah, leaving 300mah for the radio.  
All in a very promising model and set up. As a do everything 3m electric sports model if your thing is the gliding and not tearing around under power then it’s pretty much optimized for about 10 climb outs per flight. Top up climbs when already up will get you more. Then you can tear around gliding and have quite a thrilling time doing it!
Now 2.45kg, approx 200w+ per lb in old money! That's real hotliner territory. 

We’ll have to see what it can do in F3B but what we can say definitely is that it makes a good practice model without the fuss of a winch to haul around.

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