converting nitro to FE, confused on hardware and parts....

[Steven Vaccaro]

I will look into your motor/esc suggestions. My picks were passed on cost. I'm looking to go cheap china stuff. Then in the future upgrading to better gear. you think If I do my combo with 2 3s packs will be any better run time?
.

No, it will be faster, but only so long before if burns the esc or batteries inside the boat.

[JIM MARCUM]

I must be missing something here. Why not run 6S2P (2) 3 cell packs in series, and another set of (2) 3 cell packs in parallel with the other? That would be a total of (4) 3 cell battery packs VS (2). Won't that double the run time? JIM

[Steven Vaccaro]

I must be missing something here. Why not run 6S2P (2) 3 cell packs in series, and another set of (2) 3 cell packs in parallel with the other? That would be a total of (4) 3 cell battery packs VS (2). Won't that double the run time? JIM

Sure that will double the runtime, but double the cost. With the 2150kv motor he's picking, it will also cause a meltdown of sorts. i suggested a 6s setup with a lower kv motor because the amp draw of the 6s setup is much lower than a 4s setup with the same speed results in most cases and more runtime. 6s is a win, win situation over a 4s setup. Unless you are restricted to a 4s setup, like a racing class.

[JIM MARCUM]

I agree with Steve. I was going to use a Leopard 5692-1090 and 8S3P. All of my battery packs are 4 cell 45C, so after doing the math I changed to a Leopard 5692 730KV running 12S2P. The 1090KV 8S3P would use 135 amps at 32,264 RPM. The 730KV 12S2P only draws 90 amps @ 32,412 RPM. Both setups will use (6) battery packs so cost is the same. Should also increase run time with less heat stress on the motor & ESC. JIM

[crudeau]

I am not limited to anything other then money. I like the motor I had picked because it is only $49 and almost identicle to the leapard motor. This boat is just for me to run at the lake. I've never owned a boat so I want to start cheap and get a feel for it. I do not however want the boat to burn down. I'm really looking to get stuff from hobbyking or hobbyparts as they are both cheap china stuff. But I really don't know what I need and what works with what.

Motor/esc/batteries/prop are where I'm stuck at. I want the thing to be fast. 10 minutes run time is as long as I care for. 6-8 minutes works for me to. I'm more just looking to build the initial boat with cheap stuff. If I love the hobby, then the next steps will be better gear. For now I just want safe and fun. I know that I may just get something that's faulty since it's china stuff. But I don't want the cause to be because I had matched the wrong gear. There's no battery bays in the boat, so I don't see why I couldn't run four packs, other then the weight.

Based on what I read, would that 200 amp esc work with 2 3s packs and then find a motor that has around 1000kv and is 40xx in size? or what about running a 36xx size motor. Remember i have no motor mount or esc mount. So Basically I have a blank 32" hull. I can run whatever. but I'm looking to go china budget stuff.

[JIM MARCUM]

CRUDEAU: From what I've learned in this forum, start with a target RPM, then get a motor that will meet that target. Get batteries with the voltage (number of cells in series) & max amps required. Get an ESC that's rated at least 10% higher than the max amp draw. I use Chinese stuff (Leopard motors, Red Dragon batts) cuz I like both the quality & price. Except for the ESC. I needed 12 cell capacity & bought a Castle. JIM

[crudeau]

that's part of the problem. i have no idea what target rpm I need. My motor pick was 2150 rpm per volt and only 120amp. My esc was 200 amp. So I thought I had it pretty well covered. But I was wrong. so now I have no idea. Jim suggested a motor that was only 1000kv and another that was only 780kv. So I'm really at a loss trying to figure all this out.

[Chenige]

Take a look at this chart: http://forums.offshoreelectrics.com/...ight=rpm+chart

But from what I have learned here it looks like something around 30k rpm.

I am also new here and trying to pick electronics for a 20" mono and getting confused also.

Anyway you mentioned going to 6s above with the 2150 motor. That would be 47,730 rpm which is too high and the next commenter(Steve) was right in that it would cause heat issues.

His next suggestion would give longer run times (1600, 6S= 35,500 rpm) and a better boat overall but may cost you more money than your first proposal. I think it would work but just not optimum.

There just seems to be many ways to do these boats and these guys know all the ins and outs and different possibilities.

[crudeau]

KB45-10XL 1200kv Brushless Inrunner
Kv: 1200RPM/V
Weight: 557g
Shaft: 6mm
Size: 77x45mm
Voltage: 36v
Highest rated power: 2880W

what about that motor, with 2 6s packs in parrellel? With a 45mm prop. And using the 200amp esc that I listed above. Am I at least getting somewhere. The above motor is only $49 and seems like it wants way more then 6s so I would think it would stay pretty cool.

that motor and battery puts me at 26,640rpm according to that chart.

[JIM MARCUM]

Thats a cool chart that gives you some basic knowledge about LIPO batteries, voltage requirements, motor KV & RPM. Because it's for cars, substitute pinion gearing for prop size. The larger the prop the more amps the motor will consume and generate more heat. Also, FE boats perform best between 25,00 - 33,000 RPM. That's why I suggested targeting RPM first, match LIPO voltage to the motor, and get an ESC that can easily handle the # of cells & amp draw. A Seaking from Hobbywing is a great quality & cheap Chineese ESC that will handle up to 6 cells & 180 amps max. But, as the chart explains "High Voltage is your friend & Heat is your enemy". More amps more heat. Less voltage = more amps = more heat. I'm running 12S2P - 44.4 volts - & a Leopard 5692 730KV w/50 Volt max motor. So I went with a Castle ICE HV 200 12S LIPO & 50 Volt capacity to reach my 32,000 RPM target. The down side of exceeding 6S is you'll need a high priced ESC & more battery packs with more weight. My setup runs a total of (6) 14.8V (4) cell LIPO packs to reach 12S2P with a max 90 amp motor draw. You could use a 5694 1090 KV with 8S3P @ 29.6 volts and get the same RPM. But that would draw a max of 135 amps, resulting in shorter run times. As I have heavily invested in 4S 45C LIPO packs, using a combo of 3S LIPOs is not pratical for me. There are as many ways to skin this cat as there are cats. This is mine. JIM

[crudeau]

so that everything is on one post. Using all the advice and suggestions I have received. How does this combo look as far as temps and run times....

Sky-wing 200A Water-Cooled Brushless Motor ESC for RC Boat
Constand 200amps, max 210amps, Bec 5amps, 2-6s or 6-22.2volt

with two motor options...

$69 Tacon 4475-9T Brushless Motor 1600KV for 1/8 Car Buggy Truck
ROHS/CE Yes
Watts 2350
No-load Current /7.4V 3.1A
Load Current 115A
No-load RPM 4W
Load RPM 3w
Net Weight (g) 543G
Diameter (mm) 44MM
Length (mm) 75MM
Shaft Diameter (mm) 5MM

or

$60 Tacon 4465-13T Brushless Motor 1400KV for 1/8 Car Buggy Truck
ROHS/CE Yes
Watts 1860
No-load Current /7.4V 2.4A
Load Current 88A
No-load RPM 4W
Load RPM 3w
Net Weight (g) 450G
Diameter (mm) 44MM
Length (mm) 65MM
Shaft Diameter (mm) 5MM

with 2 of these in series for 6s $28 each
77P-SL3300-3S1P-40C-3333-HardCase
Capacity: 3300MAH
Voltage: 11.1V
Size: 138.21 * 46.56 * 31.38mm (L * W * H)
Weight: 317.2g
IR (mohm) 30
Discharge rate: 40C Continuous, 80C Burst.
Plug: 4.0 Banana Plug

I would swap out the 4.0 banana plugs for either 5mm or 6.5mm. But I would get 35k rpm from the first motor and 31k rpm from the second. But the second motor seems to draw less amps. No idea what prop, but that doesn't matter yet, since i can finish building the boat with out it. Does it make sense to also get a BEC and not use the esc? I feel like every where I look everyone says to do it. And they are only a couple bucks. Above is about $150 bucks.

[JIM MARCUM]

All the BEC - battery elimination circuit - does is provide power to your servo(s). Some ESCs - electronic speed controllers - come with a BEC built in some don't. But you MUST have both an ESC & BEC to run any electric boat. If your ESC doesn't have a BEC you will need a 4-5 cell AA size NiCad battery pack to power the servo & receiver. Be sure to use a 2.4 Gig radio system with a failsafe built in. If the transmitter signal is lost or turned off it will shut down power to the motor/ESC. No runaway boat. JIM

[crudeau]

I thought people were saying to use a dedicated bec so that the esc doesn't have to deal with the heat of dropping 11-22 volts down to 5. I figured since I was going with cheap china stuff I would be safer using my own bec.

What do you think of those two motors and esc's running on 6s? Am I safe going with them as far as heat?

[JIM MARCUM]

The ESCs with a BEC don't mind the small draw to run the receiver & servo. Most High Voltage ESC don' have a BEC so you need to use a 4-5 AA batt to power the R & S. I'm not sure how your motor/batt/ESC choices would work out. All I know is have everything in balance with a saftey margin of at least 20% on all components. The math is eazy, but actually running your boat will tell you if you are overproped. Short runs - then see if the batts/motor & ESC are not running too hot. The motor should be hot/warm but if you can't keep your hand on it it's too hot. If your solder connections melt you are pushing too many amps. Been there. So many variables - just got to test & adapt. JIM