A, B, C, F Power Pack?

[Inq]

I've been reading in some of the forums and finally found the reference to the plans page... and just now coming to realize how extensive this foam building process is and how great FT has been to provide all this. I'm pretty much dumb-founded that they've done so much for this hobby. I downloaded my first plans and I have to ask what must be a really obvious question to everyone else. I've searched in the menus and the forum, but I can't find the definitions to this :
"Works with A Power Pack", B, C, F. Is this some industry standard or FT standard and can someone point me to the proper reference?

Thanks,
Inq

 

[Mr NCT]

I've been reading in some of the forums and finally found the reference to the plans page... and just now coming to realize how extensive this foam building process is and how great FT has been to provide all this. I'm pretty much dumb-founded that they've done so much for this hobby. I downloaded my first plans and I have to ask what must be a really obvious question to everyone else. I've searched in the menus and the forum, but I can't find the definitions to this :
"Works with A Power Pack", B, C, F. Is this some industry standard or FT standard and can someone point me to the proper reference?

Thanks,
Inq

That was one of my first questions, too! These power packs are FT's way of making things easier to order. Here is the link to the power packs in the FT store and they very helpfully include a description of which components make up each power pack.
https://store.flitetest.com/complete-power-pack-kits/

 

[AIRFORGE]

I've been reading in some of the forums and finally found the reference to the plans page... and just now coming to realize how extensive this foam building process is and how great FT has been to provide all this. I'm pretty much dumb-founded that they've done so much for this hobby. I downloaded my first plans and I have to ask what must be a really obvious question to everyone else. I've searched in the menus and the forum, but I can't find the definitions to this :
"Works with A Power Pack", B, C, F. Is this some industry standard or FT standard and can someone point me to the proper reference?

Thanks,
Inq

This chart might be helpful, as well.

 

[Inq]

NICE! With my available gear (from the last wreck) I can see which planes I can build auger-in next. Now, if that chart just had pilot skill level, it'd be perfect.

 

[WillL84]

The power packs are FT's way of bundling motors, props, servos and ESC's into an all-in-one package. So if the build plans for your plane call for a power pack C then you can just go to the electronics section of the FT store and add a power pack C to your cart. Then all you'll need are a TX/RX and a battery

 

[Andy.T.]

Very similar question to original, I've been trying to wrap my head around why one plane needs a power pack B versus power pack C, etc. Some of the power packs product pages include specifics of "works well for planes weighing 1-2 lbs". However, last I looked, they don't all have that info.
Does anyone either have that info in a chart or some recommendations on how to know why a certain plane needs a certain motor?

One specific example that I've questions on, is it possible to just use the motor from power pack C's on planes, like the FT Explorer, that recommend a pp B.

 

[AIRFORGE]

Very similar question to original, I've been trying to wrap my head around why one plane needs a power pack B versus power pack C, etc. Some of the power packs product pages include specifics of "works well for planes weighing 1-2 lbs". However, last I looked, they don't all have that info.
Does anyone either have that info in a chart or some recommendations on how to know why a certain plane needs a certain motor?

One specific example that I've questions on, is it possible to just use the motor from power pack C's on planes, like the FT Explorer, that recommend a pp B.

I have an A-tail, twin boom Explorer with a C motor/2200 3S, and it's a blast to fly.

 

[Tench745]

Very similar question to original, I've been trying to wrap my head around why one plane needs a power pack B versus power pack C, etc. Some of the power packs product pages include specifics of "works well for planes weighing 1-2 lbs". However, last I looked, they don't all have that info.
Does anyone either have that info in a chart or some recommendations on how to know why a certain plane needs a certain motor?

One specific example that I've questions on, is it possible to just use the motor from power pack C's on planes, like the FT Explorer, that recommend a pp B.

I don't think there's a quick answer to what motor works best for a given plane. You need to match motor performance with prop choice and balance that with the needs of the airframe.

One factor to keep in mind as you move to larger, more powerful motors is CG. Per your example, if you put a C pack on the Explorer you will likely need a larger battery to balance out the motor. More battery means more weight means a higher stall speed, but also more energy to carry into maneuvers. Also, because of the motor location relative to the tail boom, the Explorer is limited on how big a prop it can fit, so you won't necessarily be able to put a big enough prop on to take advantage of the extra power the C pack can theoretically provide.

 

[Andy.T.]

I don't think there's a quick answer to what motor works best for a given plane. You need to match motor performance with prop choice and balance that with the needs of the airframe....

Thanks for the replies, guys! It makes sense that there's not a simple answer to the question of which motor / ESC / prop for an airplane. Picking the prop is also something I don't understand yet how to guess. How does one know if a 9x4.5 or 10x4.5, or something else entirely, is the right choice? Are there any rules of thumb for at least a starting point? When I'm looking at various motors, ESCs, etc, I don't even know how changing the motor would affect the mix. KV seems to be a thing that describes...something...about motors, but what? How come some motors are smaller but have higher Kv rating?
Sorry, there's a lot of questions...I don't even know if I've found the right questions to ask...

 

[Tench745]

The simplest way to choose a motor combo is to look at all the FT designs, find which one is closest to the plane you're building, and then use the motor and prop recommended for that design. If you want to get more in-depth than that, we can help.

Kv is a mostly theoretical number. It tells you how fast the motor should spin for every per volt applied when it isn't under load. So, if you put 1volt into a 1000kv motor with no prop on, it should turn approximately 1000 RPM. If you apply 10v, it should spin 10,000 RPM.

Your battery determines the voltage applied. A 2S battery has two cells wired in series. A 3S has 3 cells wired in series. Each cell puts out an average of 3.7v (4.2 when fully charged, closer to 3.4 when fully discharged). When you wire batteries in series, you add the voltage up, so a 2S battery puts out around 2x3.7= 7.4V and a 3S puts out 11.1v.

When sizing a prop, the bigger the prop you put on or the higher the pitch, the more amps it will draw at full throttle. It takes more power to turn a 10x4.5 than it takes to turn a 9x4.5. Similarly, it takes more power to turn a 9x6 than to turn a 9x4.5. If the prop you put on is too big for the motor it will draw too much amperage and cook the motor. If you choose one that's too small you won't be getting all the power that motor could potentially give you.

Volts x Amps= Watts, which is a measure of power. A rule of thumb for sizing your power system is 100 watts of power per pound of airplane. Then you have to figure out what motor and prop combination can effectively deliver that amount of power.

 

[Andy.T.]

Great info, thank you again!! I appreciate knowing and understanding. This actually also answered another question that's been bugging me that I hadn't dug into yet (how far I can safely discharge lipo's). I've been flying my 3S packs down to about 3.8v per cell, but figured I had more juice I could pull out of the battery but wasn't sure how much more.
But, original line of questioning is better understood now too. The volts for battery packs, I understand. The Kv rating now makes sense as approximation of RPM given a particular voltage input. I like knowing the formula of ~100w / Lb of plane. But, how would I know that when I am swinging a 9x4.5 9x6 (ex), what the amps are? Is that, basically...try it out while hooked up to a watt meter? I've wondered if a bench test really IS a good test. In theory, holding a motor/plane on a bench while running up the power, has almost infinite resistance, while a plane flying thru the air has a finite amount of resistance. I would think that would affect the amp draw. But maybe I'm over-thinking it, or maybe the difference, while not zero, isn't enough to be a factor.

 

[Tench745]

Great info, thank you again!! I appreciate knowing and understanding. This actually also answered another question that's been bugging me that I hadn't dug into yet (how far I can safely discharge lipo's). I've been flying my 3S packs down to about 3.8v per cell, but figured I had more juice I could pull out of the battery but wasn't sure how much more.
But, original line of questioning is better understood now too. The volts for battery packs, I understand. The Kv rating now makes sense as approximation of RPM given a particular voltage input. I like knowing the formula of ~100w / Lb of plane. But, how would I know that when I am swinging a 9x4.5 9x6 (ex), what the amps are? Is that, basically...try it out while hooked up to a watt meter? I've wondered if a bench test really IS a good test. In theory, holding a motor/plane on a bench while running up the power, has almost infinite resistance, while a plane flying thru the air has a finite amount of resistance. I would think that would affect the amp draw. But maybe I'm over-thinking it, or maybe the difference, while not zero, isn't enough to be a factor.

A bench test with a watt meter is a good way to get real world data for your specific setup. It is, essentially, the worst-case scenario as you will see the lowest thrust numbers and highest amp draw with a stationary motor. But if those numbers are within your motor and battery specs, you know for sure it can handle whatever it will see in flight. And if you do any kind of hovering flight like 3D pilots do, that bench test is almost exactly what the motor sees in a hover.
Personally, I like to use an online calculator to see how a setup will theoretically perform. I have two bookmarked. Both use data pulled from testing actual motors and ESCs.
https://rcplanes.online/calc_motor.htm
and
https://www.ecalc.ch/motorcalc.php

The first one is free but has a pretty limited selection of motors to choose from. Pick something close to the size and KV you have.
The second has a free trial which limits the selection, and a more involved paid version for about $9 a year. I always used the free version, but just sprung for the paid one a few days ago. I figure I owe it to the creator for the amount I have used it over the years.

Edit:
There is a third, more basic calculator I have called Web-O-Calc. It's a formula based calculator to help pick the best prop for a given setup. The website is expired, but you can still access it thanks to Archive.org.
https://web.archive.org/web/2016102...re/webocalc_1.7.6/html/webocalc_imperial.html