CURTISSP40

My Feedback: (27)

I need some help here. Am in the process of converting some of my Nitro Planes to Brushless and Lipo.Am ok with 1/2a so far but am stumped on 40 size airplanes of all types High wing trainers to low wing Sport planes.Example 40 size low wing,Weight Loaded 5 lbs.wing span 54 inches.Normally would have a 40 size Nitro motor and about a 10x6 Prop.Now what size Brushless,Lipo and Prop should I use?
I have avail a Brushless OK-C3530c ,6-12v-1100Kv, Lipo 2200 3s, 40a ESC Prop Size ???????? will this be anywhere close to what I need?
Another Question:Have also avail. 4s (4 Cell) Lipo 14.8V-2650 MAH ,and Above described Brushless (6-12v),can I use the 14.8v Batt with 6-12v Motor?(40a ESC).Need plain answers please,No technical stuff. Thanks for listening. Jack Curtis (CURTISSP40)

subzJC

volts x amps = watts

you need a certain amount of watts to carry 1lb of plane.
I think its like 75 watts/lb.
You will have to get a watt meter to test your various setups.
Your readings will change if you switch props or batteries.
Some sites will list the potential of a motor and hopefully
they show what prop and battery they used.
You wont want to run a motor at the max rated watts for very long
as well as you wont want to push your speed controller to the max
rating.
I would be willing to bet that 3530 will not produce the watts your need
That seems like more of a 2lb motor.
Like I wrote 75 watts/lb to carry a plane but I like to get around 150 to jam.
dont quote me on 75 but its around there.

Good luck

jester_s1

That motor is way too small to power a .40 size plane. The specs say it can handle 22 amps on a 3 cell apck, which makes it a 275 watt motor roughly. You'll need more like 600-700 watts to fly a 7 pound .40 size sport plane. If you want to make it easy on yourself, many of the manufacturers have recommendations for glow to electric conversions. I've linked to one such guide below. Alternately, you could study up on all the variables in choosing electric power and become able to produce such a guide for yourself in a few hours. www.wattflyer.com is an outstanding resource for gaining the technical knowledge for that. In a nutshell what you have to do though is choose a system that can handle the watts you need along with having the right motor Kv to turn the prop you need with the battery voltage you'll need to get the watts you need. A lot of getting that right is knowing the amps that a given prop will draw with a given motor, then knowing if the batteries can deliver those amps under load. But if you're not looking to become the guy who can answer these questions on his own, going by the guides that the manufacturers have produced will serve you just fine.

http://www.maxxprod.com/mpi/mpi-264.html

In this example, you'll have 3 choices based on their recommendations of their products. There is a .40 equivalent that makes 500 watts of power, which would be a minimal system to fly a .40 size plane. It would be fine for most scale models or for a .40 sport plane that is fairly light. You wouldn't get unlimited vertical out of it, but you would be able to do smaller loops, hammerheads, and any "on the wing" maneuvers like rolls and such. The big advantage of that system is that you'll come out lighter due to the lower battery capacity that will be required. Then there are 2 different .46 equivalent systems, both using the same motor but with different ESC's. ESC's don't affect your power at all, but if you exceed their amp ratings they will melt on you. So for flying hard, you'd want to spend the extra $25 to upgrade from the 45 amp to the 75 amp ESC. Either of those systems are 850 watt systems, which would be great for an aerobatic .40 size plane or a sport model that you want to be a little overpowered to handle high winds and such. The negatives of this system are its increased cost (both the system and the batteries it requires) and greater flying weight.

Then there's the question you haven't asked yet but nearly everyone does- can you get these parts any cheaper? The answer is a tentative "yes," but at the cost of durability. ESC's in particular vary widely in quality with the same amp ratings, so just understand that a $25 one isn't going to last as long as a $75 one will. Motors are less of a worry, but the higher quality ones will be a touch more power efficient giving you longer flight times. Cheap batteries are very popular due to the fact that you'll be buying multiples so the savings add up. The trade off there though is that low cost batteries generally don't give you as many amps at a given load as good ones do, and they definitely don't last as long.

Jetdesign

My Feedback: (8)

Take a look at E-flite power series motors (horizon hobby) or the Rimfire motors (tower hobbies) - and now the OS and Futaba motors. These motors all have a 'glow sized' equivalent number - Power 46, Power 110, etc. Look at the numbers of the size motor you need and get something similar.

Motors are usually designated by 3 numbers: Length-Width-kV (I think length/width are size of the stator, but not 100% certain) and the kV is the rpm/volt.

This is a great way to start. Once you get something running, you can experiment with props and different motors to see what works for you. I suggest avoiding experimentation until you understand how the system works - stick to something that you know will work the first time out (I wish I listened when I was told this a few years ago).

jester_s1

One really neat thing about electric power is that changing the prop can totally change the way the plane flies, much more so than with glow power. Electric motors will turn the RPM they are supposed to turn no matter what the load is. The amp draw will simply increase to carry the load, which of course means that with really overpropped planes the batteries might drop some voltage and lose RPM that way. But what's really cool about it is if you feel that you're a bit overpowered and would like longer flight times, you simply go down a prop size. And it works the other way too- you can bolt on more power by putting on a bigger prop. That's all within the watt and AMP limits of your system of course.

acdii

If you do what jester suggests, my only advice, use a separate battery for the RX and servos. Dont use the ESC BEC as you can get brownouts if the voltage drops too fast, which an ESC that gets too warm can do.  Been there, done that, have the scrap plywood and balsa to prove it.

Gray Beard

My Feedback: (-1)

Really!! Last week we were doing some prop testing on the eflite Taylor Craft {Fantastic little plane!!} and we went just one inch up in length and one inch down in pitch. I would have thought that would have given the plane a bunch more thrust and lowered the speed. That combo did slow the plane down but there sure was no added thrust! At full power the plane was very slow but it would hardly fly at all under 3/4 power. Electrics are a bunch different then wet engines! I was very surprised at just how much different they are.

Sport_Pilot

Why bother, you will just have wait on or  keep track of charging all of those batteries.