The EXTRA 300 EXT Build Thread

[3dNater]

There is nothing wrong with running 6s. I don't think anyone is attacking it... it is well documented that 6s packs will work fine. The only point being made here is that the higher voltage systems are more efficient and don't have to add weight.

Since there are so many numbers flying around though, this has really gotten down to the nitty gritty. [MENTION=2280]Dr. Gonzo[/MENTION] has posted 75A repeatedly for the max amperage of the 12S setup. I would like to know where that number is coming from. Aeroplayin's highest amp draw was 68.6 Amps and we can see that the calculation is affected a great deal by the difference.

68.8 Amps x 33% power =22.704
2600mAh x 70% safe capacity =1820
1820mAh is 1.82Ah
22.704 Amps divided by 1.82Ah = 12.47C
60 minutes divided by 12.47C = 4.8 minutes

By using [MENTION=95]Aeroplayin[/MENTION]'s amp draw number you gain 1.2 minutes of flight time. So I guess the lesson to be learned is... prop it right and it works out nice. Get greedy on the power and you get a short flight time on either system.

The place where you win with 6s is if you have the packs already, but I'd probly spring for the 12s setup if it were me because I don't have any 6s 5000 packs. But on the other hand, if I had 6s 5000's that were being used on another size I might just spring for the 12s setup anyway because I like lots of power and cool running motors The 6s packs you have are a sunk cost, meaning they should not have a bearing on your decision if you view going another direction as being the better long-term choice. The fact they can be used in another size airplane is a big plus.

 

[Dr. Gonzo]

"The place where you win with 6s is if you have the packs already" That was my whole point! He said he had 6s 5000 in another post. I also got the 75 amp number from an earlier post. Aeroplayin's number of 68.8 was about the equivalent of a 4325 not the 4330 so I used the number from earlier. Either way the spread of flight times would still be very similar. No doubt more voltage is more efficient that cannot be argued. I just don't see big gains anywhere to justify dropping another $200 in a couple sets of packs. 40 amp average on 6s spinning a 20x8 looks pretty darn good in the extra video above. The Joe Smith extra 330sc videos he runs 6s. This made me assume this is a fairly standard setup? More efficient is not always better or practical. It just is not that simple. You are only going to get 3-5 watts per gram out of a motor no matter what voltage/prop combo you throw at it. A Motrolfly 4330 is only intended to get 2700 watts max no matter what voltage you throw at it or you will overheat correct? So I do not buy into the more power thing it just is not apples to apples. Max wattage can be achieved at any voltage. Select voltages and kv to turn the prop you need to turn for the given airframe. Do whatever blows your skirt. Just my take which I thought was pretty well thought out. My question goes right back to low cost airframe = budget build =save weight= 6s 5000 why not use them? I thought that was an obvious idea. I see a lot of contradictions here that seem illogical to me. I am wrong so let's get back to the build. I want to see this thing fly post stall. opcorn:

 

[3dNater]

Agree to disagree on several points... none of which have to do with whether or not a 6s pack will work just fine One thing I have learned in life is that perception is not reality and I am humbled everyday at work when I find out I'm wrong about something. Please don't take my arguments as anything other than trying to get at truth. I could care less what batteries people decide to run so long as they end up accomplishing their goals in a way that pleases them.

 

[AKfreak]

Ok lets try to move past this 12S setup stuff. here is what Ken said exactly in a recent email.

The higher the voltage the more efficient the system is. On 6s to get the same watts your current is much higher and current is what causes the heat in a motor for the most part.
Watts listed are the max watts that can be put through the motor and these are not the watts of work you get out of the motor. If a motor is 80% efficient then the watts out (work you get out of the motor) are 80% less of what you read going in to the motor with a watt meter.
Some are going to 12S on planes this size and I do have some 12S Kv for the 4330.
The 216Kv on 12s with a 20x8 prop pulls about 3200 watts for instance and is what I would recommend if you want the same power to weight ratio as the 64"
It can handle 3200 watts because the amps are only 72 max, but your average amp draw will probably be around 35 or 40.


When I asked specifically about added weight of a 12 S setup, This is what Ken had to say.

You would not add any weight if you sized the batteries accordingly. In other words if you use a 5000mah 6s pack for and get say 2800 watts and you choose a Kv for 12s that gets you 2800 watts (206Kv and 20x8) and use two 2500 (not that they make these) the weight and flight time would be very close.
If you use a 6s system in this plane I would think a 5000mah would be too small and only get you 5 minute flight times and not as much power as the 12S set up. You could go with two 2600 6s packs for 12s and be roughly the same weight. Personally I would use 3200 or 3700 or what ever you are using in the MXS and you just double the packs in the 75" Extra.
You are close to pulling the same amps in both planes if the 75" is 12s, you are just doubling the voltage.

And here some previous information that he gave when I told him I wanted the same performance from my 75" plane as my 64" MSX, this is what he said.

The higher the voltage the more efficient the system is. On 6s to get the same watts your current is much higher and current is what causes the heat in a motor for the most part.
Watts listed are the max watts that can be put through the motor and these are not the watts of work you get out of the motor. If a motor is 80% efficient then the watts out (work you get out of the motor) are 80% less of what you read going in to the motor with a watt meter.
Some are going to 12S on planes this size and I do have some 12S Kv for the 4330.
The 216Kv on 12s with a 20x8 prop pulls about 3200 watts for instance and is what I would recommend if you want the same power to weight ratio as the 64"
It can handle 3200 watts because the amps are only 72 max, but your average amp draw will probably be around 35 or 40.
Also it is harder to get the watts where you want them (2800) on a 6s set up as you are asking a lot more of the batteries amp wise and they may not hold their voltage under that load thus dropping the wattage.

hope that helps,

Ken Young

Now I hope we can all agree what Ken says is pretty much gospel right?

 

[3dNater]

haha... ya, let's move on. Anyomre progress on the build?

 

[Dr. Gonzo]

What ken said is pretty much true but not gospel. He gave you what you asked for. The application of this power system is up to you. The flight times will be close not longer than 6s. 12s 3300 would be the hot ticket if you got them. But again, if you want good post stall flight it is all about weight. You drilled the landing gear to save weight then add 4-8 oz of battery? That was more my angle plus using what you have would save some beans (I assumed that was why you got a budget airframe, my bad). Put a fork in me I am over it. On to the build!opcorn:

 

[3dNater]

"I just want to flllyyy

Put your arms around me baby

Put your arms around me baby..."

 

[Aeroplayin]

Sorry, I didn't even know what plane this thread was about, but I got an email telling me I was mentioned, so I came to see what that was about yesterday. Nice feature, actually. But just to clarify a few things before going back to Extreme Flight and 3DHS threads....

6S is fine for most guys at 2330W and 105A. I fly in the Florida summers and just won't do it on a Hacker. Maybe a Motrolfly but I would rather go with a 10S and now a 12S setup.

Flying at 2330W and 105A means that I'll be using more throttle, the upper limits of power, and therefore more capacity, compared to my 12S system that runs up to 3100W at WOT and only 69A. So I'll rarely visit the 70A peaks on the current system, and not that long when I do, and I'll probably frequently be visiting the 105A peaks on the 6S setup. This means that the 33% throttle level may only pertain to the 12S setup, while a 45% throttle level may be needed on the 6S level. When you run these percentage levels through the two calculations, you may see a difference.

With electric power systems, nothing is linear, and Watts-in does not always represent power-out and thrust. On hot systems, the margin between power-in and power-out is greater, so the 2330 Watts-in may not be linear when comparing it the 3100 Watts-in on the 12S system. So the power that translates to the prop on the 3100W system can be even more than the 1740 Watts-in you get when you subtract the two Watts-in values.

With that in mind, the bigger prop on a 6S system, like a 21x10 or a 22x8, will produce more torque and vectored thrust at lower and equal RPM levels than the 20x8, which will perhaps benefit low and slow 3D flight. But throttle response and prop acceleration will be better on the smaller prop on 12S, so there is more power there, and quicker, when you get out of position and need to power-up to stay out of the dirt.

The thing I like about the 215Kv motor is that I can put a 22x8 on 10S on the same motor and same plane and float around slowly on the big prop. There is no top-end compared to the 20x8 on 12S, but it's fun to do once in a while anyway. So if you have 6S 5000's, try them. You may like them enough to not spend the extra money for more power.

 

[AKfreak]

The progress on the plane is I hinged the wings, and I am ready for my motor and need to buy servos. I might have to take a few days off the build, but it will be done soon. AKf

 

[gyro]

The progress on the plane is I hinged the wings, and I am ready for my motor and need to buy servos. I might have to take a few days off the build, but it will be done soon. AKf

Which servos did you settle on?