Brushless vs Brushed in a CC Runabout

[DavidMC]

Hi Guys,

Im still new to the boating scene having just put together a Vac-u-tug (modified for a 600 size can motor) and will be starting work on a Dumas 19' Chris Craft (28") I am still debating the power system and whether it is worth it or not to go brushless.

Regarding the stock dumas motor (or a traxas 14 volt marine motor) that I already have and plan to run on 2 emoli cells (8.4 volt):
1. What type of maintenance is required on these motors.
2. How long can I expect the brushes to last

I know there are other advantages to the brushed option:
Its easy to get a brushed motor with reverse
The brushed controllers are more efficient at partial power settings
It costs less (though maybe not in the long run)

The brushless setup I was looking at is the Aqua Craft.
You can get the motor and controller for about 110 dollars.
1. Is it possible to run this setup efficiently at 8.4 volts (7cell) or will I need to upgrade to a 3S setup of emoli cells.
2. At lower power settings (hopefully below 10 amp) will water cooling of the controller and motor be required?
3. Will running at these lower power setting at partial throttle put a lot of strain on the controller.

I did a search trying to find some stats on the aquacraft controller and they do not seem to be available so I am not sure what the peformance of the controller really is (I run my airplane speed controls at partial throttle all the time).

Is the technology of brushless still too new to the scale boating world.?

Thanks,

Cheers
Dave

[fleetmaster]

For scale performance there is nothing wrong with a brushed motor,any 700 size motor will last you years and a very cheap to boot.
They can also be bought retimed for reverse rotation or you can do it easily yourself.

[LtDoc]

Dave,
Brushless motors aren't exactly 'too new' for boats, but they do have a sort of limited application, in general. If you are looking only for speed, then a brushless motor is probably the way to go about it. The 'down' side of brushless motors is cost and fuel consumption (current draw). And like you pointed out, making a brushless motor 'back up' is sort of expensive.
If speed isn't the primary concern then a 'brushed' motor is probably your best bet. Common as dirt, not always expensive, you can make them 'back up' easily/easier.
RPM/speed isn't a great benefit for propeller driven boats because of cavitation beyond a certain rpm. Like spinning car tires, it may make a great show, but it doesn't do anything useful.
It just depends on the application. If it's scale, or sort of scale, I don't think I'd bother with a brushless motor...
- 'Doc

[Kmot]

David: I too am a proponent of brushed motors for scale boats. Brushless is mostly about all out speed.

A Titan motor from Traxxas is a long can 550 motor. It is a GREAT motor. I have lots of experience with those motors in E-Maxx trucks. In the harsh environment of an E-Maxx being run through dirt, the motors last seemingly forever. I installed one in a Kyosho boat and over a period of a couple years the performance did not change one iota. The boat has been sold but I expect that motor will never wear out. You can buy it new fairly cheaply or find it on ebay for practically nothing.

If you want lots more power a 700 motor is the way to go. Again, a brushed 700 will be a lifetime motor as long as you don't cook it by overvolting it 'too much'. However, 700 motors can be over volted and still live a long happy life. For example, a Graupner 700BB 8.4V motor can be run on 12 cells (14.4V) and it will blow your mind how powerful it is and it will live practically forever as long as you water cool the brushes and can. Easy to set up the water cooling on them.

[steveciambrone]

I agree a simple can motor can be fine for a scale boat.

But brushless motors are more efficient than a brushed motor. What makes this so, is no brushes means less friction, but the real bonus now is the timing on a brushless motor can be varied according to the RPM, the same as the timing on a car is varied through its RPM range. As the RPM is increased the timing is advanced. This makes a brushless motor really efficient at partial throttle settings, this is why model airplanes are getting some great endurance times compared to 5 years ago. You just cannot do this with a brushed motor. For a Chris Craft where you want a faster top speed a brushless setup can buy you a higher top speed and more efficient at lower speed. Selecting a brushless motor does not actually mean that it will draw more current but could mean less current draw at the same shaft RPM, which would extend the given run time per battery. It is all dependent on the selection of the motor, todays hobby market has dozens of motors available and little guidance on what and how to use them.
I worked on a project at work which had a powerful brushed motor used for propulsion, I changed it to a brushless motor and controller and for the same shaft RPM and resulting vehicle speed at partial throttle, the current was reduced by a factor of 5. Both were hobby motors.

Thanks
Steve

[CG Bob]

The AquaCraft BL ESC doesn't have reverse. If you want reverse check out the Novak XBR (http://www.teamnovak.com/products/brushless/ex_systems/index.html) line, which features a "Marine Brushless Mode" with 25% reverse.

[quicksilver]

I think the choice anymore is mainly dependent on your wallet. A simple brushed setup with a 700, could run you 100-$150. Where a brushless setup is a bit more quirky, yeah the aqua craft system run about $150, but maybe be to high a kv, depending on the boats size. If you get in feigoa motors, then the controller costs a fortune compared to the brushed equivalent unless you buy a cheap Chinese esc, which may or may not come by the end of the summer. Unless you find one of these, you're looking at between 200-400 for a setup. To me brushless is close to the mainstream but maybe not close enough yet, to fork the money out. Maybe I'm wrong about the SV27 setup working and then maybe you could say I'm cheap, just my 2 cents.

[DavidMC]

Hey Guys,

Thanks for the feedback.

One more question - how often do you guys use reverse?

So its seems the brushed motors I have on had will last quite a long time. I assume I will need to oil the bushings every so often. I do like the looks of the traxass 14.4 volt marine motor I have with the built in fan. It does seem like a fairly high quality piece of kit.

I guess I am wary of brushed motors because I only have limited experience with astro brushed motors and the rest of my motors (100 to 3000 watts) are all brushless. With the airplane motors and controls the stats are very well laid out. It seems a lot more difficult to get things like the KV and internal resistance of the motors many people are using in their boats.

If I look at the stock motor Dumas recomments, it is suppose to turn 10000 rpm on 6 volts, so thats about 1666 KV
At "8.4" volts which is probably closer to 7.8 under load, and at a 5 amp draw we are looking at about 40 watts from the batter. The brushed can motors from what I understand are only about 60% efficient so we are going to loose probably 24 watts to heat, which is pretty low for a 6 or 8 oz motor to deal with.
At 10 amps and 50 watts of heat thats probably something to start to be concerned about in a closed hull.

From the research I've done I have found some reports that the KV of the aquacraft is 1800KV. Judging as how the motor is about the same size as a 600 can motor but likely with bettery magnets, I could expect a similar amp draw, with more power going to the prop. As I suspect the aqua craft is a cheap chinesse version, efficency is probably only around 80% with most of the losses from the controller. Again, these are just assumptions based on limited info.
So on 8.4 volts, the Aquacraft would make a decent 1 to 1 conversion, drawing likely the same amps. But the problem is I don't know if the aquacraft controller can handle only running on 7 cells when it was designed for 12 cells or if there is a low voltage cutoff. Certainly at these power levers water cooling wouldn't be required. So just the motor and controller would be 110 dollars - a tower hobbies discount - we'll say 100 dollars.

How often do you guys use reverse? (not counting tugboats)

Right now Im leaning towards a Proboat brushed controller. Its 40 dollars and I already have the motor. I could use the "brushless money" to upgrade the drive train to MACK products and a bronze prop. Its always possible to convert later down the roat the engine, but its a lot hard to change the frame.

Hmm, what to do, what to do :)

[Kmot]

If you have reverse you will use it occasionally. If you don't have reverse, you will get used to it and not even think about it.

[steveciambrone]

Reverse is highly overrated. Besides a CC looks best when it is up on step running fast.

Steve

[green-boat]

Castle Creations makes a nice ESC that will work on brushed and brushless motors and has reverse. http://www.castlecreations.com/products/mamba.html

As for the ProBoat esc, well I will say this, I used to be a fan of them but I and other fellow boaters have had tooo many problems with them. Life is too short too put up with a problematic ESC, spend the few dollars more and never have to worry again.

[steveciambrone]

The Castle Controlers are really easy to program using the USB interface and updates to the software are available by free download.

Others with blinking lights and throttle stick movements are sometimes impossible to program.

Steve

[CG Bob]

Almost all of the scale boat regattas I've been to require a reverse manuever somewhere on the course: sometimes it's leaving or entering the start/finish pier; other times it's backing away from a fuel barge or dock. Reverse can be used to stop the boat quicker than coasting to a stop.

[tsenecal]

having completely refitted most of my boats (and all my subs) i can say that the only reason you have for not going brushless is cost.

all other reasons these guys have listed as to minus qualities of brushless motors is plain false.

brushless motors have more torque (meaning a smaller brushless will have the same amount of usable horsepower), higher efficiency (longer battery life, or smaller batteries) and lower maintenance (no need to replace/turn brushes, etc.) than a brushed motor used in its place.

for your chriscraft, I would recommend a Castle Creations Mamba ESC, and something like an AXI 2816 or 2820 that runs somewhere around 1200 to 1400 rpm per volt, using your 2 cell lipo. the Aquacraft supervee 27 is designed to go 40+ mph out of the box, which is twice as fast as you need to get your CC going.

the secret to brushless on boats is to use outrunners, and not inrunners, due to the massive amounts of torque the outrunners generate.

as far as your amp draw is concerned, the propellor is going to make the biggest difference. smaller prop spinning at higher rpms will draw fewer amps on the same motor.

[DavidMC]

Thanks for the info guys.

The mamba ESC looks pretty good. And I hear that you can get Castle to put some sort of permanant waterproofing on all their ESCs for like 5 dollars (or so Im told).

Outrunners definately have their place, but I think they would not do well in boats, at least in higher power applications (this wouldn't really be one of them though).
With the coils in the core of the motor, you really need to have some sort of forced air being blown through them (look at all the fans being added to them for heli use) so in an inclosed area of a boat thats not too good I would think. Inrunners are inherintly more efficient (watt per gram of weight) and would be easier to cool with heat sinks or water cooling. But generally inrunners cost more so you cold always upsize the motor on the boat since weight is less of an issue.

Probably the best motor would be an ORK. I have a 1910 and 1912 for my planes and they are very well made. The large diameter of the ork gives them lots of torque to run direct drive and are easier to cool with the coild being against the outside case.. There is a 1907 and 1905 which seem to have KV's high enough for scale boats.

From the discussion though, I think you are right in that cost is the deciding factor as to whether or not to go brushless.

[steveciambrone]

I had thought about using an outrunner for a boat and it would have needed cooling. My thought was to incorporate cooling water through the face style motor mount, made with aluminum it should conduct the heat away from the armature. I decided to use an old aveox motor instead so I did not get a chance to try out this type of cooling. I am sure it would work.

Thanks
Steve

[tim slocum]

I have a Proboat Classic Runabout which is approx.29in long or about the size of boat your talking about. The boat came with a brushed 550sized motor that really made the boat quite fast.About a month ago the motor emmitted the mystical blue smoke, so I shopped around for something "a little hotter". I decided on a Traxas Stinger,since its for 7.2v and I didnt want to buy new batteries.I installed the Stinger and WOW :D it added several MPH and really split the waves nice. The only downside was it made the motor very hot after about 20min. of runtime,but what a fun 20min, :) In order to cut down on the hot motor problem, I installed a Octura x430, which is 30mm compared with the stock 33mm prop.I didnt really notice any drop in speed and the motor didnt get quite as hot.(still too hot for me) With watercooling, I believe this setup is about right.One point Id like to make,and Im not sure if anyone has yet, is scale runabouts like this are really not made to go insanely fast.This isnt just because its not scale speed to do so.Theres a limit to how fast these hulls can go,unless you like to retrieve upside down boats. The bottom of the hull is mostly flat,and you may notice that in a high speed turn the boat tends to slide sideways, kind of like the drifter cars so popular with the young people these days. If you are sliding sideways and hit a wave wrong :censored: over she goes. I just think that if you want something REALLY FAST, get a deep v , hydro or something specifically DESIGNED to go fast. Just my 4 cents worth.

[DavidMC]

Hi Tim,

Not really trying to go super fast as mention by the amount of wattage im looking at. Its more a question of efficiency vs cost. Is the extra cost of a brushless motor and controller worth the increase in efficiency (and thus battery time) and reduced maintenance vs the increased cost of the system and slim selection on reversible controllers.

What controller did you have in your proboat? How is your motor holding up?

Anyways, right now I am leaning towards brushed. I can can always swap it out later if I feel performance is lacking or as cheaper options open up.

To me this was an exercise in efficiency, and thinking again about how much efficiency I actually gain at the lower power setting, it really isn't worth the cost.

[DavidMC]

Here's another good controller option. Waterproof too.

http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LNRXX6&P=G

[tim slocum]

David, I replaced the stock unit(forward only) with a blue Proboat esc with reverse. I have to have reverse! I like to get out of trouble as fast as I get into it!

[rlboats2003]

You asked the question "How often do you guys use reverse"

More than on a real boat, because on a real woody you have docking lines, material covered fenders, boat hook, and usually someone else in the boat willing to use there body in any way possible to keep from getting a scratch or a brunish mark in the finish - put on 10- 12 coats of varnish and you will understand.

Sooner a late you have to bring a model boat back to shore - If you are in a club with a lake and a dock you will do the same thing to a model wood boat
as a real one - don't let it brush or run into the dock because you get to repair the finish. And usually to maintain unfimority of finish that means a wet sand of the existing surface finish and a recoating of the boat. So here is were reverse is your friend. It acts like a brake - if done properly. In docking forward speed is not your friend (unless you are in a current or lots of wind) as you enter the dock area start giving minimial short duration burst of reverse - if the boat walks left the burst was to hard and to long. By the time you come to the end of the dock the speed shuold be near zero.

Well that's why you need reverse,
Rich

[785boats]

If you operate on a busy lake (like ours is sometimes), crisis situations can arise. A sub pops up in front of you. A sailboat tacks across in front of you. A little kid too close to the edge grabs your attention, & when you look back up your pride & joy is about to spear that battle cruiser on her maiden voyage. :eek: REVERSE! can be your best friend. It's easy with brushed.
You can get into trouble quickly with a fast scale boat, It's good to know that you can get out of it even more quickly. As Tim said.
Kind regards,
Paul,

[jmolwitz]

I second the Castle creations mamba . It makes an awesome scale speed control.I have 3 boats running mambas . I use a gearbox to help match the motors to the prop and keep the speed down . I would be more than happy to help you figure out your power system right down to how many mph you want your boat to go . No problemo :) heres one of my boats

http://www.rcgroups.com/forums/showthread.php?t=591656&highlight=my+dumas+osprey

[DavidMC]

Guys, you have me sold on the REVERSE. I have though about the reverse too much because I will be using this boat is a fairly big lake (not always smooth water).

jmolwitz what gear box do you use?

[jmolwitz]

For cheapie I use great planes gd600 has ability to have 3 gear ratios 2.5 3.0 & 3.8 by changing the pinion . My latest project is getting M.E.C superboxes ( got a deal on a pair) any gear ratio up to 7 to 1 and can handle 5mm pinion's .

[DavidMC]

Hey Guys,

Well, I have a couple Mambas on the way that I got for almost the same price as a cheapie brushed controller.

Now its motor and prop selection time....

I would like to use a 2S lipo setup (emoli cell) for this.

Any suggestions?

[Rex R]

a suggestion, if you don't already have one, buy a 'castle link' programming kit. its the only way to properly set the low voltage cutoff for lipo's.

[pimp_squeak]

Did you order mamba 25s? or mamba maxes? the Mamba max can be used with brushed, as well as brushless motors. So if you'd prefer to try brushed first then you can, otherwise you just need to pick up a brushless motor down the road for the upgrade.

[DavidMC]

Hi Rex, yes, I will be getting a castle link. Seems like a good idea to invest in one.

I got mamba 25's. They should provide sufficient current capacity for my intended use.

Dave