ESC Recomendation

[thomaska]

Hi all,
This is my first post so let me introduce myself. I used to run in rc cars races since 2005 but i am completely new in boats. I saw the UtilityShip project in thingiverse and i liked it so i started the printing process immediately. The ship is almost 1 meter long and the width is about 30cm. The weight might be something like 5 to 6 kilos because i am planning to add two motors SSS 56104/420KV with water cooling (the designer of the boat is using two AvrotoLIFT 3520 400kv). The props that i have already order (like the ones the designer of the ship is using) are 55mm Diameter M4 Thread 4 Blade Brass Props with Pitch 49.0mm. So these are the existing hardware. I would like reccomendations on ESC's and batteries. I read that Flier ESCs are great. But which type for these motors and these props? I read a lot of calculations that you are doing which i cannot understand. It will be very helpful if someone explain to me and suggest me some good esc's in order to avoid burning my boat.

One last thing, this is a ship, so i don't want to see it flying, i just want torgue, not speed.

Best Regards

Thomas

[Nevs]

On 4s a small 20A ESC will do. Calculated speed, (if it was a planing boat) 420x14,8x49 =...0,304x60 = 18,2.... x 0,7 = 12,8 kmh/ 8 mph

https://www.youtube.com/watch?v=qLksIWYpI88

[thomaska]

I appreciate your fast reply. As a newbie can you please explain me the numbers on the calculation?
As i understand:
420 = Motor KV
14,8 = ??
49 = Props Pitch

I am a bit lost. I am sorry for asking but i am completely new and i like to know how to do it

[Nevs]

420 kv x14,8 volt, (4s lipo) x pitch = 6216 rpm x 49 mm pitch = 3045884 mm = 304,584 meter / min.....1000 meter a minut is 60 kmh. so its (60x 304,584) : 1000 = 18,2 kmt or 8 mph... That is the teoretic max speed at nominal volt. Normaly you can expect a planing mono to reach 70-80% of teoretic speed.
A calculator you could use. ( 436 has a 36X1,4 = 50,4 pitch..close to what yours are).

http://www.radiocontrolinfo.com/information/rc-calculators/rc-boat-calculator/#Brushless

I do not know the calculations for not planning boats, but at these speeds I think there are no big differences.

[Nevs]

...The 20 A ESC. I never tried anything close to that kind of setup, (BIG motor/small esc/medium prop) 20 A is fine but there could be issues when the motor "starts up". Maybe a heli esc, (they have to turn big rotor blades) would be the best choise ??

[thomaska]

That will be my next question... With that configuration (SSS 56104/420KV and 55mm 4 Blades Props with 49mm Pitch) and the results from the calculator how do i decide which esc to use and what size of battery considering that i will use 4S LiPo.
I was thinking Hobbywing SeaKing but with what A? Also i read that some users had overheating problems. Turnigy Marine? Flier? But again what A? I am completely confused. And also should i use two batteries one per esc and motor?

[NativePaul]

56104 motors are totally inappropriate for this build, they are FAR too big, if you use these you will use more power just to spin the motors themselves than you would otherwise use to push the boat at its scale speed.

You may think you want the weight to ballast the ship down to its waterline, but you would be much better off using batteries or even lead as your ballast. much longer runtimes with lead ballast due to the motor running much more efficiently at the power level you are after, and hugely longer if you use bigger batteries for ballast instead.

What sort of running do you expect to do, brushless motors are much more efficient at high throttle loads, but brushed motors are more efficient at low throttle loads, so if you intend on spending most of your time with just a sniff of throttle on and plenty of power in reserve (as is often the case with tug boats) you might want to consider a brushed alternative.

I can see why you don't want to use the motors Peter Sripol used in his, $130 each is a lot of money for tug motors. I think he only used them as he got them for free, even they at under 1/5th of the mass of the sss 56104 they looked like being way too much for the hull at full throttle. I would consider something even smaller like the 3510 he mentioned designing it for, if you can find one with as low KV. YGE and their Chinese YEP clones have a very smooth throttle, which will be more important to you than it is for many FE runners.

[larryrose11]

you may consider water cooling. It will wont take much, but the marine ESC all need water cooling.
A small diaphragm pump to pick up water from the hull, and out to the hull below the waterline may be in order. That would prevent any issues. you could easily water cool the motor too.
As far as an ESC is concerned, running on 4s means the smallest marine ESC rated for 4s you may find is over 100A. Seaking make quite reliable ones.

[thomaska]

56104 motors are totally inappropriate for this build, they are FAR too big, if you use these you will use more power just to spin the motors themselves than you would otherwise use to push the boat at its scale speed.

You may think you want the weight to ballast the ship down to its waterline, but you would be much better off using batteries or even lead as your ballast. much longer runtimes with lead ballast due to the motor running much more efficiently at the power level you are after, and hugely longer if you use bigger batteries for ballast instead.

What sort of running do you expect to do, brushless motors are much more efficient at high throttle loads, but brushed motors are more efficient at low throttle loads, so if you intend on spending most of your time with just a sniff of throttle on and plenty of power in reserve (as is often the case with tug boats) you might want to consider a brushed alternative.

I can see why you don't want to use the motors Peter Sripol used in his, $130 each is a lot of money for tug motors. I think he only used them as he got them for free, even they at under 1/5th of the mass of the sss 56104 they looked like being way too much for the hull at full throttle. I would consider something even smaller like the 3510 he mentioned designing it for, if you can find one with as low KV. YGE and their Chinese YEP clones have a very smooth throttle, which will be more important to you than it is for many FE runners.

The only reason for not using Peter's motors is that these motors are for drones and are not waterproof. I was looking for waterproof ones using also water cooling. That is the only reason.

[NativePaul]

You are right to be thinking about start up if you do go for the 56104, I bet it will pull well over 20A totally unloaded on acceleration, just trying to spin the big heavy rotor up to 6k rpm instantly, an ESC with a soft start feature would definitely be advisable to reduce that current. The YGE / YEP ESCs are programmable with several different strengths of stop start to reduce the start up current.

[thomaska]

So, considering that i will not use 56104 (i will cancel the order), how about these motors
1. Multistar Elite 3510-350kv Carbon Case Multi-Rotor Motor
2. TURNIGY 4258 BRUSHLESS MOTOR 400KV

As you can understand i am trying to build a nice setup for Peter's boat

[Nevs]

I almost forgot about it. But some years ago I made a small 3 pound mono (rtr). running on 6s/5000 mah. I used a small 200 gram outrunner 500kv and a 51-1,4 prop = pitch 71,4.. I was running 1 hour and 40 min at half trottle, (10 mph) with some 40 or 60 A esc. Average consumtion was... 3 A... and afterwards I could not feel any temp. though I saved the watercooling on both motor and esc. So with your props you do not have to worry with a pair of "200 gram" outrunners.
And Yes The YEP are the smoothest ESC I know of. At least in the HV editions

[thomaska]

How about this?
YEP 120A HV (4~14S) Marine Brushless Speed Controller (Opto). This ESC requires BEC as optional. And how about this motors?
1. Multistar Elite 3510-350kv Carbon Case Multi-Rotor Motor
2. TURNIGY 4258 BRUSHLESS MOTOR 400KV

[Alfa Spirit]

What hull is this exactly?

1 meter and 5 kilos ?

[thomaska]

Yes.