At about... 25cc displacement.....



Except for the lack of "proper sound" and low flying time... whatever suits your mood (and wallet).

Practically speaking, I believe there is a difference between planes designed for precision flying and all others. Precision aircraft are weight sensitive and as a result there is a critical line where added battery weight for longer flight times begins to compromise performance. I am generally speaking.
On other planes that may have a light wing loading, You can add additional battery capacity to extend the flight time.
A prime example of this is the new H9 Folker DVll. It's not exactly an IMAC plane so aerobatic
performance is limited but the wing loading permits adding Gobs of battery for reasonable flight times. Some of these planes are running on 2 6s 7000mha batteries in series plus an additional Rx battery.

Originally Posted by Flybye Steve

Practically speaking, I believe there is a difference between planes designed for precision flying and all others. Precision aircraft are weight sensitive and as a result there is a critical line where added battery weight for longer flight times begins to compromise performance. I am generally speaking.
On other planes that may have a light wing loading, You can add additional battery capacity to extend the flight time.
A prime example of this is the new H9 Folker DVll. It's not exactly an IMAC plane so aerobatic
performance is limited but the wing loading permits adding Gobs of battery for reasonable flight times. Some of these planes are running on 2 6s 7000mha batteries in series plus an additional Rx battery.

Maybe so, but I tend to disagree. The gas engine, exhaust system, flight battery and or ignition battery and a full fuel tank can wind up weighing as much if not more than the electric motor, ESC and battery packs. So it is hard to say for sure anymore. The Lipo batteries have been steadily improving and getting more capacity with less weight over time.

I have a good example for you. I set up my first 93" AJ Laser with a DA70. It weighed 20 lbs. dry.
It was a great performer with uncompromised aerobatic capability.
I set up another one (same plane) with a good Hacker Q80 with a 6s 5000 mha battery and a 3300 mha Rx battery. Both planes came out with the exact same 20 lb weight and the performance was the same. In fact, I used the same radio program for each plane with very minimal trim and mix differences.
Problem: I could not get more that 6 minutes of light time out of the electric set up and that wasn't enough time for two IMAC sequences.
I would have to double the battery capacity in order to get the required flight time and that would have boosted the weight up to 24 lbs. The additional weight would have a significant impact on performance.
I should mention that this experience is not unique. There have been many examples on the IMAC site as well as here on FG's that prove this out.
Until we get a significant improvement in battery tech., giant scale performance planes will have limited flight times.

I had the same duration problem with my P-51B Mustang. Two 5300mah 45c 6s lipos in series flew it 4 minutes with about a minute of reserve for 1 go around. For an experiment I built a 24 cell pack using 3300 mah 30c lipos wired 12s 2p, (6) 4 cell packs. Flight duration jumped to 7 minutes with 2 minutes reserve for go-a-rounds. The electric power system's current draw was 160 amps when the gear and flaps were down for take off or landing.

Changing the prop from a 22-12 two blade to a 4 blade varioprop (16d) dropped the current draw to 120 amps for take off and landings and level flight current dropped from 90 amps to 65 amps (at over 130 mph). Top speed and vertical flight was vastly better with the 22 inch 4 blade prop set at 18 inch pitch. Gross weight of this Mustang using a DA 50r for power is 24 lbs. with fuel, 29 lbs. electric. I had to limit the 4 blade prop's top rpm to 5000 rpm (Ramoser factory recommended), by setting the throttle servo limit lower. I flew the plane 200 flights with gas, 100 with electric power. I also had to turn the esc over-amp setting OFF, advancing the throttle quickly from idle will pull over 200 amps instantaneous, shutting the esc down.

When I used the 5300 mah lipos they reached 140 F in 4 minutes and need to cool for an hour before recharge. The 24 cell packs reached 110 F in 7 minutes and could be put on the charger as soon as it landed. I credit the better 24 cell performance to each cell only seeing half of the current that the 12s packs saw.

The entire experience was a lot of fun, and I got asked to bring the plane to club events all over Florida to show to non-believers. I am currently working up a new air frame designed by Jerry Bates, and a glass fuselage by Vic Catalasan with plans-built surfaces. I have 30 flights on the new plane using a new DA 60 for power, it out performs the TF (5) and H9 Mustangs (2) in every way, and is much easier to land.

I have started building a second J. Bates Mustang, it will probably be electric and use a 25i series 4 blade Varioprop rated for gas (8000 rpm) or electric, (much higher). I have already flown the new plane with a 2 blade version of the 25i Varioprop. It is only slightly less performance than a 2 blade 22-12 gas prop. The difference is 1/2 a roll less in vertical flight. The two blade Graupner 22-12 pro will do 3 vertical rolls to 800 feet. I have tried almost every brand and size two blade prop, the Xoar 22-12 and Graupner props were the best, but the Xoar props will throw a blade if it nicks a blade of grass. The varioprops just bend with no damage.

The B model in level flight is the electric TF, the second plane is the J. Bates Mustang.

That is pretty interesting and neat too. Thanks for the information and sharing it.

If any one is interested, here is a link to the video of the TF electric flying with a two blade Graupner prop and the 24 cell pack.

Giant Scale P 51 at Ft White flt 2 720p (4 min 12 sec)

I have been on here on and off for a while now with different planes and set ups and I am now flying a Hanger 9 Extra 300 35% with a Hacker 150 - jeti/hacker spin 200 27x10 Mejzlik using 4x 6s 5000 40c packs and I am getting 8 min flying and then land with 23 % left in the packs on average
I am loving it other than the supper soft UC it seems to have but I am sure I will find something for it in the end
I also have a couple of 16000 6s packs I have been trying
the 2 of them weigh exactly 1 6s 5000 pack more which I think for an extra 6000 mah is nothing and it really is not that noticeable flying wise other than it comes in a bit faster to land when no wind about but on a windy day like most are here its no difference
but it dose seem strange flying for 12 mins with an electric plane
I keep checking my timer to make sure its on lol
I love electric always have and 12 min flight times plus landing is plenty for me,to long in fact 8/10 mins is more me so I think some 12000 packs would be spot on
I don't think there is to big now in my view
with 6 plus C charging you can have a quick charge and be flying again
I still only charge at 1c my self as I tend to take at least 3 sets of packs and a couple of different planes so I fly the one then while a sets on charge fly something different that way I fly all day and don't have to wait for a setoff packs to be charged
Its nice to see more trying bigger electric models now
I love how much prop noise and airframe noise you get so its not quiet as such
I think over time the motors will get more efficient and the packs lighter so we will see longer flight times
but more than happy with 8-10 min flights :-)

Originally Posted by Flybye Steve

I have a good example for you. I set up my first 93" AJ Laser with a DA70. It weighed 20 lbs. dry.
It was a great performer with uncompromised aerobatic capability.
I set up another one (same plane) with a good Hacker Q80 with a 6s 5000 mha battery and a 3300 mha Rx battery. Both planes came out with the exact same 20 lb weight and the performance was the same. In fact, I used the same radio program for each plane with very minimal trim and mix differences.
Problem: I could not get more that 6 minutes of light time out of the electric set up and that wasn't enough time for two IMAC sequences.
I would have to double the battery capacity in order to get the required flight time and that would have boosted the weight up to 24 lbs. The additional weight would have a significant impact on performance.
I should mention that this experience is not unique. There have been many examples on the IMAC site as well as here on FG's that prove this out.
Until we get a significant improvement in battery tech., giant scale performance planes will have limited flight times.

My 95" 3dhs extra on 2 5200mah packs can easily do 8-9 minutes of imac flying and weighs 19lbs with batts of your flying a 90+ inch plane on 6s your killing your efficiency.