The Total F3A E-Setup
My usual first advise to put together an electric pattern model that is sucessful from the start is to look around your area for someone who you know has something that works......and copy it! I dont mean copy the top guys, trust me there are lots of times when a top guy is running gear that he works very hard at to make run perfect. I know because I have done it myself! Find something that you know works day to day in the trenches so to speak, and not something that you saw working at the Nats for 6 flights.
Now there are a number of setups out there that work good, and as time goes on there are more and more of them. What I want to do here is first, give you some questions you need to answer, then give you the setup I use which works, and works well if you stick within the guidelines I establish for you. I will try to keep this info general, obviously I have sponsors and I would like to everyone using their gear :) This is not realistic and whatever gear you choose I want to see you using it sucessfully!
1. Airframe - Pay careful attention to what model you planning on using for F3A! To go electric without a bunch of work my experience has shown that you want to use a model that with a YS 160 setup would be in the 10-10.25 lb range without fuel. Heavier than this and you are going to have to start paying close attention to your weights and equipment choices. Its definately do-able but more work in the long run. A light plane gives you wiggle room! However you go shoot for 10.75-11 lbs flying weight (with batteries) for you electric model, lighter than this feels really light and gets beat up in the wind. My first electric this Enigma was 10.29 lbs and was a nightmare in wind.
2. Motor - Here we go! In-runner, or Out-runner? I think what I will do is break this down into pro's and con's that I see from a practical perspective that I have gathered from watching both in numerous contests
Ok so what does all this mean? Well lets try and quantify a few things. First the maintenance, the planetary gearbox is a mechanical device with a lot of power running through a number of tiny planet gears. Without any forced lubrication other than an unsealed housing with some grease in it. In time these gears will fail, and most likely during a contest! So you gotta keep on top of it. No a huge deal but you gotta be prepared for this reality....I dont know about you but I never did that much work on a YS! Outrunners have no such gearbox, therefore no routine maintenance is required.
Current draw....this is a very important point. At full throttle the inrunner will spin the same prop at the same rpm for less current draw than the outrunner. However, typically you will prop the outrunner for more pitch speed with a smaller prop, giving up some of the large prop power (these things are already way overpowered anyways!) and dropping the current down in line with the inrunner. So in real world terms you will use a similar amount as the inrunner for the same duration of flight.
Props, most inrunner setups will use a particular size prop suited to the combination of kV and gear ratio in the motor. Generally running props outside of that does not work well, they either present too much load for the motor or the motor cant spin them fast enough to get power from them. The outrunners on the other hand will work very well on a wide range of props, spanning 2" in diameter at the same pitch range and giving good performance on all of them. The real advantage in this is the ability to increase pitch speed for windy days, something the inrunners have a hard time doing without changing to a different wind of motor.
So choose whichever motor you feel will suit you best, be careful with the outrunners as some of the cheaper options can be upwards of 150 grams heavier than the more expensive choices. Plettenberg and Cyclon are the only outrunners I know of that are equal in weight to the Hacker C50 inrunner motor that is so common.
3. Speed Controller - There are a few choices out there for controllers. I personally think simple is better, and the more bells and whistles that you add the greater the chance of problems. Castle Creations is one in particular that has had their share of growing pains in the software update department. I have witnessed HV 85's igniting in flames moments after being connected to batteries!
One thing is if you run an outrunner a proportional brake of some type is very handy to help control windmilling on downlines. Most of the controllers offer this feature now. The inrunners have the gearbox drag to help out on downlines and dont seem to benefit as much from a brake.
Go big on the current capacity if you can afford the extra weight, at least 85-90A minimum. As batteries improve we seem to push up our peak draw requirements to get that extra punch on tall manuvers.
Go with something opto-coupled, I am not sure if you can even get a BEC controller in these sizes, but you want to run a seperate Rx pack anyways.
If your controller needs cables, boxes or whatever to access more advanced features its probably worth the money to get. Not only will you have more options for setup, but it should make programming easier.
4. Connectors - Again, tons of choices. Go simple, bullets or Dean's Ultra's are my choice. If you go bullets get the Neu 5.5mm ones for the ESC to battery connectors. They can deal with tons of load (200A) are easy to solder, cheap and give you lots of hookup options for the x2 5s packs you are going to use. Stay away from Astro's or other "fancy" brands, they are more often than not expensive and dont work any better.
You want to use bullets between the motor and ESC as well to make motor or ESC changes in the field simple. Here use a high quality (Schulze or similar) 3.5mm bullet for each lead (there should be 3 of them!)
5. Batteries - Oh, boy! This can be very difficult to say because there are so few actual manufacturers and yet so many battery vendors....so many of them use the same OEM cell suppliers yet are assembled to such different standards. You can have two packs made of the same cells that perform completely different because of the assembly.
I will break my sponsor rule here for a second....unless you want an R&D project use a set of Thunder Power packs. Virtually all of the e-powered pattern models out there today use TP, and they have a huge success rate. When I first started out I used Apogee and it cost me a fortune in puffed packs and then another fortune to switch over to TP so that I could fly.
I will also back up for a second and say that there are a few others getting into the F3A market, Flight Power (Evo 20's) are one of them. However, be cautious, weight of packs can cause you stress, and TP is lighter for equal capacity than nearly all other brands.
If you are flying F3A P-07 sequence, use something in the 5000 mAh range that can deal with at least 70-80A continuous draw. If you fly shorter sequences, a 4200, or 3700 may be suitable. Balancing taps are a must, not only for safety while charging but to allow you to check out the cells individually to assess pack health.
Pay special attention to battery cooling, you want to keep your packs from getting up near 60° C
6. Chargers - Again, a lot of choices and it will probably depend on what you can afford. I would highly recommend going with a charger that is capable of charging a full 10s pack. This allows you to keep the packs connected in series all the time, and lets you treat them as a set for their entire life. The drawback to this is you need a very powerful charger, and if you want to balance you need a 10 cell balancer.
Currently the only options on the market for this are the Thunder Power 1010 and the Schulze 636. Neither are cheap, but both work very well. Both have the ability to run a balancer in the charge circuit such that should a problem with the charge occur (over voltage, over imbalance etc) the charge is terminated. As well it allows the charger to know exactly how many cells are connected, nearly eliminating charging at the wrong cell count. These safety features are invaluable in my opinion, and the cost of the chargers is a small price to pay when you look at the total investment.
One thing to beware of is the charger ratings. Very often a charger will claim it can do 10s with a max rate of 8A.....however what you need to pay close attention to is the max charge wattage. A 10s pack at 5A requires 210-220W from the charger, regardless of the amp rating givin by the charger, if its watt rating is less than that it will not charge a 10s at 5A.
Chargers at this power level also give you the ability to charge a 5s 5000 mAh pack at 2C, or 10A. Using a charger with the above safety features and new generation cells this is a great way to get the charge times at the field down to 30-35 minutes. Do be cautious though and even more so when charging at high rates.
7. Power Supplies - To power those huge chargers you need some serious power. Charging a 10s pack at 5A requires around 250W from a power supply. I strongly recommend getting an Iota, either 45A or 55A model. These are high quality supplies that can be ran continuously under high loads without failing and either of those will easily handle charging x2 10s packs at 5A. This really cuts down on the recharge time in the evenings after a flying session. As a plus they will also charge 12V batteries that you may use during field charging.
Enough for tonite, will try and get this finished up this week.
Chad