EMAC - Electric ONLY IMAC Events

[Fliprob17]

We will add more to this but here's the deal in a nutshell:

One day a month for 6months there is currently a contest held down in San Diego, Ca at the Silent Electric Flyers club by Sea World. Same sequences as the IMAC, Electric Only, does not have to be a scale airplane, so pattern planes are more than welcome. Great group of guys, lots of good information and help. We typically get down there around 8am and the contest is over by about 3-3:30pm. You fly a morning session, and an afternoon session, each consisting of (2) runs through the sequence. Once score is dropped, so your top (3) sequences count for the day total. Overall "season" winner in each class is based on the best (4) individual day scores. So with (6) total events possible, you get to drop your (2) lowest days.

Again, lots of fun, this is our 2nd year competing down there.

 

[Aeroplayin]

I've heard about this and am interested in the whole concept. I'm currently building a 101 inch wingspan Godfrey Laser 200 for IMAC and it will come in at 24.5 pounds with a 4-pack 10Ah 12S setup with a Q80-6L that should deliver 6400 Watts and between 9.5 and 10.5 minutes of flight time. I'm hoping to get two full sequences out of the setup, and since this is a Godfrey, I expect performance to be top-shelf as well.

Although we don't live anywhere near San Diego, I'm hoping this plane will compete in the IMAC events here in the southeast, and perhaps promote some interest in an electric only event. I hope to learn something here...

Jim

 

[Fliprob17]

as long as you can get two clean sequences done with running out of juice towards the end of sequence 2. Most IMAC competitors fly gas. Sportsman and above can be tough on the packs. There's always someone every at every EMAC that runs out on that last upline

 

[Bigroger]

Nice idea.

I visited my first IMAC day last weekend as spectator only and thought, I could do that in electric.

But 10+ minutes on an electric 3D plane is a hard ask, especially the higher end of the levels.

Full throttle up lines with multiple snaps is a hard ask in any electric setup with large planes.

Mind you large 6s packs are getting more and more powerful and lighter and lighter these days, so a 6s6000 or 6s6500 packs are going to get you close to being able to run through the sequence twice I guess. As long as they aren't too heavy.

 

[Fliprob17]

for Basic, electric is completely feasible in IMAC

for Sportsman, it's a stretch but do-able. Anything past that is going to be tough

in the EMAC, the classes above Sportsman land and switch packs in-between sequences

 

[Aeroplayin]

Roger knows me for being a numbers guy, so here are a few from what I have calculate and compared to real flight time...

We are involved in IMAC with gas planes and from what we see, a full two-sequence Unlimited routine required 9.5 minutes which includes everything from wheels off to wheels on. We timed this several times, so if you feel this is incorrect, please let me know what you have found so I can add it to my information as even though we are not competing in unlimited, we would like to determine the time as accurately and as conservatively as possible.

For a 50cc size airframe in the 18 to 20 pound range, we found that 861mAh per minute is a relatively conservative estimate with 886 being the outside usage on our trials on a 10S setup (Q80-7M with a 24x10TH Mejzlik). This means that a 9.5 minute flight requires approximately 8200 - 8400mAh capacity. Safely using no more than 80% of the full capacity, we're talking about 10.08Ah capacity. With this understanding, we realized that going to a 4-pack on this airframe is virtually impossible without bring it to a weight that could easily be 2 pounds more than the design intended. With precision competition designs, like the Godfrey airframes we have, the design can manage the extra weight well, but we decided to look at bigger airframes where the weight differential is not that great.

The 40% Godfrey Extra 300, which Andrew used to win the TAS in 2011, comes in at 36 pounds, which is light compared to the other kit built competition airframes, which we have seen go to around 41 pounds. Therefore, it is a good option IMO. There is also a 32.5% Extra 300 that I am also running some numbers on, but this airframe is about the same size as the Godfrey Laser 200, which Tom flew for the first time in his first-ever competition, in which he finished 5th.

The plane came in at 21.5 pounds (101 inch wingspan) with a DA-85 all up. With a Q80-6L with a 4-pack of Sky Lipo 5000 6S batteries, it should come in at a little over 24 pounds. This is still 4 pounds lighter than most 101 to 104 inch planes out there. I'm estimating the flight time to be 9.5 minutes, and this will give me some leeway with regard to capacity because 5300 Gens may not change the weight too much and maybe increase the flight time by 20 seconds if the mAh per minute consumption is not different. It can be argued that it will be different since we'll be generating more Amps, but the difference in Watts due to the difference in volts should make up for it considering the Watts to weight. 19 pounds at 4400 Watts and 119A compared to 24.5 pounds at 6400 Watts and 143 Amps. We'll see.

 

[Bigroger]

JIm,
you can also save some weight by using a BEC setup like the cc BEC Pro.

I spoke with james at length the other day about electric 50cc planes, you know he has 3 or 4 now running that Q80-8M setup and in all of them he runs the Rx setup only off the BEC connected through the flight packs.

He has never had a failure and saves heaps of weight.

His EF 50cc edge comes out around 18.5# with 65C Nanotech 6s5000 packs and he gets full 5 minutes pounding or 7 minutes general 3D depending on what he is doing.

His flying has moved into the more extreme style recently after some first hand mentoring from the likes of Daniel and Chris at one of the events he attended, so much so that he is now breaking airframes in the air with the amount of energy he can get into the airframe.

 

[Aeroplayin]

I can save 10.8 oz (306g) by dropping the two 2S 2300 A123 batteries I have going into the AR9100, or 7.3 oz (206g) by going to the single 1100mAh A123. Taking them out brings the 50cc size down to 8.3 pounds (3773g). I also did some checking and the Thunder Power batteries, in this application, may actually make the crazy price worth it. If you check out the weight difference, it is huge, relatively speaking.

Here's something to consider... a 2-pack of the 45C 6600mAh 5S TP comes in at 61.25 oz or 1763g. If Tom is flying his IMAC routine at the 861mAh per minute range, then the 6.6Ah means a full minute more than my 5Ah setup. If I pull my two Rx batteries and run the straight BEC from the TP's, I'm getting the added minute at a cost of 3.25 oz or 92.1g of added weight. The only thing is that I'm using just under 60mAh per minuted powering the Rx and my five JR8611A servos, so I end up picking up only 42 seconds taking them out completely. So I may be better off sticking with the extra 1100mAh A123 at 3.5 oz, which means I pick up a full minute and add 7 ounces.

The bottom line is that since I'm not coming anywhere close to the two routines with 6 minutes, I may as well keep the 5000mAh batts and drop to one 1100mAh A123 on the Rx, save a half-pound and be happy with the 5 minutes on a lighter plane. Then finish the Godfrey Laser 200 and set it up with the 12S 10Ah 4-pack for 10 minutes. The 35% will present better anyway.

 

[Bigroger]

Here's another question about recharging.

I'm a little confused at this point.

Got me a 30A iCharger now.

Got me a deep cycle marine battery, 12V 87Ah battery.

Was hoping if I went to 2x 6s5000 packs that I could maybe charge up 2 pairs at home (4 x 6s5000), go the the field and fly then recharge at 20A from the deep cycle battery 2x6s5000 at a time and maybe get 4 or six flights before I depleat the deep cycle.

I think I read somewhere that you should only pull a deep cycle down to 50% ie, 43-44Ah extracted.

As we don't have live power at my club, just wondering if anyone that has large packs has any input into this?

Do I need to get either a good inverter generator or maybe more 6s5000 packs.

As over here a good Honder 2kv or Yamaha 2kV generator will set me back about $1600, and that's a lot of 6s5000 packs I could purchase for the generator cost.

 

[3dNater]

I'll take a stab at this...

*disclaimer: I have no personal experience with this... just telling it how my mind is thinking about it.

The way I see it. A 6s 5000 pack is going to take about double what a 3s 5000 pack would take in terms of actual power. Makes sense... Now, your 12v battery is similar in voltage to a 3s pack. So when you put in 5000 mah into a 6s pack it is like putting in 10000 mah into a 3s pack. You just used up 10 Amp hours. The good news is that you will not be depleting your packs to zero so I don't see why you couldn't do what you are trying to do. I'm guessing you could do up to 5 flights the way you described it. You just need to keep track of how many mah you put back into the packs. Then double that number to see how many you have pulled out of the deep cycle.

Someone correct me if I'm wrong You can also confirm if I'm right. Either way I'll learn something