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Old 04-28-2018, 08:13 AM
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How big scale electric can you go?

Having recently successfully migrated to flying 60cc equivalent electrics and been pleased with the performance, I thought I might study the logistics of a 100cc electric equivalent. Not too many about in the UK compared to you guys in the USA. Leaving aside the costs involved, largely because if the technology is unreliable or weights too much then the cost is immaterial. Anyway here goes. For example if we take a Turnigy CA120 150kv (100cc) motor the weight is 2.73kg. The Opto ESC being Turnigy FatBoy V2 300A which weighs chunky 4.06kg. So basic power plant comes in at a hefty 6.79kg. Using a 12S set up comprising 2 (6S) X 10amp lipos totals 2.5kg. This added to 6.79kg comes to a shade over 9kg!

Averaging the weight of three popular 100cc petrol engines (DA, GP and DLE) comes in around for one engine of 2.6kg! Okay so say an ignition battery 0.2kg and for arguments sake, 2 x 6v 3300 mAh nimh batteries plus Powerbox unit, equates to around 1kg so lets say 1.2kg in total. Add that to the engine makes 3.8kg. I think you can see where I am going with this. The ignition unit doesnít amount to much in weight. However, the one thing I have not included is the possible weight of the exhaust system/canisters. But based on the above numbers I canít believe it would be anywhere near the 5kg weight differences between the two systems.
Reading through the forum here in the USA the subject is a bit "Marmite". There are those who have done this successfully and those who dislike the idea with no middle ground. Clearly, duration is an issue with expectations no more than 8 minutes. Additionally, a quick calculation suggests 1 cc of petrol = .75 gram so say a 100 cc engine has a tank of 50cc say ( I stand corrected there, however) so fuel weight would be 50 x 0.75, say 37.5 gram or 0.4kg at the take off. Still a weight issue for electric I guess. I would be interested to hear from you guys who fly 100cc electrics and the reasons why it works successfully. Thanks
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Old 04-28-2018, 08:29 AM
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Sorry bit of a dope here!
The Turnigy FatBoy ESC weighs 406 grams so that's just under 0.5kg not the 4.06kg I quoted. That makes the numbers much more sensible.
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Old 04-28-2018, 11:20 AM
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What? Lower? OK!
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Still, reasonable and meaningful realizable size is 2.2 m wingspan. Something bigger is a logistical, economic and weight challenge.
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Old 04-28-2018, 08:14 PM
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Depends on the model. I suspect you could build a ginormous J3 or B17 on electric fairly well due to the glider sized wings, low dynamic loads, and typically dismal power to weight required. A big overpowered acrobatic Extra 300 is going to be MUCH harder.

Edit: search and ye shall receive Here is a 50% (4.6m) clip wing Cub on a very reasonable power setup.
Epic RC Plane giant scale Electric 50% Scale Clip Wing Cub HUGE (6 min 24 sec)
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Old 04-28-2018, 09:16 PM
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Here's one for you......saw it fly, truly incredible....of course the pilot is very proficient too

https://www.flyinggiants.com/forums/...light=Ultimate
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Old 04-28-2018, 10:36 PM
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this just happened

Emmaselle II by Damon Atwood - MAIDEN FLIGHT! SEFF 2018 (4 min 54 sec)
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Old 04-29-2018, 04:47 AM
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Nice video clips there, guys.
I would love to know the power/equipment specification on those aircraft.
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Old 05-03-2018, 09:49 AM
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The 50% Cub has the info in the video description if you watch it on youtube.
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Old 05-03-2018, 10:57 AM
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Here's a good comparison for you.
I set up a 93" Laser with a Hacker Q80-9n. It weighed 21 pounds with 2 6s 5,000 mah packs.
I set up the same identical Laser with a DA70 on a pipe and it weighed 20 pounds.
Both planes flew identically the same however, the electric was limited to 6 minutes of flight time.
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Old 05-03-2018, 12:28 PM
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Just Here For The Comments
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All the way to 100%.
Electric aircraft: World-record electric motor makes first flight. (1 min 2 sec)
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Old 05-03-2018, 01:27 PM
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Thanks for the input gents, appreciate it. Plenty of food for thought I must say!
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Old 05-03-2018, 02:09 PM
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Interesting Thread - just commited to all Electric. 60cc size 95" EF Extra and 93" AJ Laser. Building both at same time. Using the Extreme Flight 60cc, Castle 160 and Graphene 6000 6-cell x 2.

It's not exactly economical and flights are shorter, but so is my attention span. I have been flying 10 cell F3A and 78" Extra for several years. Electric - for me - is the way to go. I go to the field with 3 sets of batteries charged and ready. I charge used sets while I fly.

If you need sound - add playing cards in the prop. I think the local residents to the field love electrics too.
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Old 05-03-2018, 02:18 PM
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One more thing - I have a H9 Decathlon 100cc still in the box. I am waiting for a good story around 120cc electric alternatives. May take a year or 2. Might have to use big comercial drone batteries rather than stuffing up to 4 5000s in the nose.
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Old 05-03-2018, 02:35 PM
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Thanks RC - Jeffrey. Like you I have reached the stage of 60cc electric conversions which I am happy with. However, I am interested in trying a 100 cc conversion and just looking at the logistics of it all. I have identified the motor and ESC of interest, but I am not sure of the aerobatic frame to go for or the level of battery power to utilise.
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Old 05-04-2018, 10:46 AM
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I did a 104" EF Extra a couple years ago. I used a Hobby King Turnigy Rotomax 100cc electric motor, Castle 160 ESC and a 12 cell 8000 lipo. (two 6s 8000 batteries). Everything else was used from the gas setup the prior year. This was about the same weight as the take off weight using a 120cc gas engine.

With a 28x12 prop power was amazing but flight times were only about 4.5 - 5 min. I don't remember the amp draw but the temps were within the range for the ESC. I tried a 27x12 and a 26x12. The 26x12 kept the amp draw down closer to the 160 range, power was close to a 100cc gas and flight times were about 8 minuets if I was careful.

I intended to fly this for IMAC Sportsman that year. Problem I ran into was flight time. 8 minuets is just enough for two sequences a take off and a landing on a calm day. With no cushion for error I opted to go back to gas.
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