1/4 Scale Outboard electric

[Wayne Johnstone]

Hi, just wondering if anyone has set one of these 1/4 scale hulls up as an electric boat? After some set up advice

 

[LohringMiller]

I've never set up that big a tunnel for electric power, but I've setup moderately large electric boats as well as several different sized tunnels. I would need to know a lot more about the motor in the picture for better advice. As a start you need a 3,000 to 4,000 watt power plant to be equivalent to a stock to mildly modified gasoline engine. That means something like 140 amps with an 8S battery. A Castle Phoenix 200 will handle this easily, even without added water cooling. You might consider a less expensive system running a 6S battery with a Turnigy 180 Marine ESC, but that will be close to the limit of the speed control.

Next you need to know the KV of the motor. A modified Zenoah develops peak power at around 16,000 to 18,000 rpm so you need a KV of around 950 on 6S or 700 on 8S. You can easily turn more rpm with a smaller prop, but with similar rpm to a gas engine, you can run similar props and the hull will handle much the same.

Electric motors have more torque, especially at low rpm, than IC engines. The boat will seriously torque roll, burying the sponson, if the prop runs too deep. The current draw will be high as well. I've found that running the prop higher than with an IC engine helps. You will need to experiment with several props to find the combination that works best. Also, the outdrive looks like a geared unit. I'm sure that it is torque limited, but I've never run a gear drive on a model boat. An electric motor's smooth torque delivery will help the gears live.

Lohring Miller

 

[Gilbert Pun]

I have set up a Zippkit F1 tunnel for electric, using a 400A ESC running Castle 2028 800KV motor for 10-12S batteries, running on Lawless drive leg, the run time is very limited. Cause 8S would never push these boats to a acceptable speed.

For my Baba 1/4 scale hull (it just came in a couple of weeks ago from Holland) I would consider to use Quickdraw gasoline engine for either in or outboard driving.

Lohring, using 180A for big boats is definitely not adviceable, I have about 4 sets of 180A burnt to pieces in my 40"+ bigger fast running boats.

 

[LohringMiller]

The Turnigy 180 has a burst current of 1080 amps but can only handle 6S. That makes it a lot tougher than its continuous rating would indicate. The Castle controllers are similar. The Phoenix 200 can handle 8S. I've seen over 300 amps on a Castle Phoenix 200's data logger without damage to the controller. Water cooling raises the continuous rating. Again, I emphasize running the prop higher than with gasoline engines. That will reduce the current draw without reducing the speed. Props are everything in electrics.

The 8S setup in a 1/8 scale boat registered the currents graphed below while setting a NAMBA 2 lap record. We only ran 2 4S packs for that record, but ran 4 packs for heat racing. That setup won the class and T sport hydro at the NAMBA Electric Nationals. See the pictures below. The boat has similar speed to a 11 cc nitro powered boat which has similar power to mildly modified gasoline engines. The torques are a lot different, though. A Quickdraw has over 8 hp which is around 6,000 watts. I think people are running gas tunnels here with modified Zenoahs.

I have a lot of experience with gasoline engines. The best modified Zenoahs develop almost 7 hp which is a little over 5,000 watts. That's a little less than 170 amps on 8S. The gasoline engines should be heavier than an electric setup and the batteries put the CG in a better position. Of course 10S would be easier on the ESC and give longer run times, but more batteries require more expensive components.

I defer to your actual experience since my estimates are not based on experience with big tunnels. The analogy holds up with the smaller tunnels, though. A 4S spec motor tunnel is almost as fast as a 3.5 cc mod tunnel. A record comparison is 55 mph for 3.5 stock, 66 for 3.5 mod, 65 for P limited, and 73 for P tunnels. The limited P output is around 1,000 watts while the full P is probably twice that. OS rates their outboard at 1.28 hp or a little less than 1000 watts.

The 6S power plant in a Leecraft XT-460 is faster than a 7.5 cc modified tunnel, but the Leecraft is a little too small for that power. I ran a 45" long 1/4 scale tunnel with an 11 cc mod K&B. It was reasonably fast but used a lot more fuel than the 7.5 cc tunnels that run similar speeds.

Lohring Miller

 

[Randell Doane]

I've been wanting to run that setup for some time now, I've heard good things about that gear driven MHZ outboard lower. Saw a video a couple years ago of someone running that lower on an MHZ tunnel with one of their Scorpion motors, looked pretty neat

 

[Gilbert Pun]

The Turnigy 180 has a burst current of 1080 amps but can only handle 6S. That makes it a lot tougher than its continuous rating would indicate. The Castle controllers are similar. The Phoenix 200 can handle 8S. I've seen over 300 amps on a Castle Phoenix 200's data logger without damage to the controller. Water cooling raises the continuous rating. Again, I emphasize running the prop higher than with gasoline engines. That will reduce the current draw without reducing the speed. Props are everything in electrics.

The 8S setup in a 1/8 scale boat registered the currents graphed below while setting a NAMBA 2 lap record. We only ran 2 4S packs for that record, but ran 4 packs for heat racing. That setup won the class and T sport hydro at the NAMBA Electric Nationals. See the pictures below. The boat has similar speed to a 11 cc nitro powered boat which has similar power to mildly modified gasoline engines. The torques are a lot different, though. A Quickdraw has over 8 hp which is around 6,000 watts. I think people are running gas tunnels here with modified Zenoahs.

I have a lot of experience with gasoline engines. The best modified Zenoahs develop almost 7 hp which is a little over 5,000 watts. That's a little less than 170 amps on 8S. The gasoline engines should be heavier than an electric setup and the batteries put the CG in a better position. Of course 10S would be easier on the ESC and give longer run times, but more batteries require more expensive components.

I defer to your actual experience since my estimates are not based on experience with big tunnels. The analogy holds up with the smaller tunnels, though. A 4S spec motor tunnel is almost as fast as a 3.5 cc mod tunnel. A record comparison is 55 mph for 3.5 stock, 66 for 3.5 mod, 65 for P limited, and 73 for P tunnels. The limited P output is around 1,000 watts while the full P is probably twice that. OS rates their outboard at 1.28 hp or a little less than 1000 watts.

The 6S power plant in a Leecraft XT-460 is faster than a 7.5 cc modified tunnel, but the Leecraft is a little too small for that power. I ran a 45" long 1/4 scale tunnel with an 11 cc mod K&B. It was reasonably fast but used a lot more fuel than the 7.5 cc tunnels that run similar speeds.

Lohring Miller

@ 2012 Electric nats 2.jpg

T_Sport_Hydro 2012 Nationals.jpg

Scale Record Runs more cup.jpg

Lohring,

Very knowledgeable information, thanks, and very good observations.

Big boats are very different stories and they are heavy and draw a lot of current, at an instant, which normally caused the burnt out especially when using 2P batteries with larger amps for bigger boats.

When I said burnt 180A ESCs, i didn't mention that I had a couple of 240A and a 200A original Castle water cooled controllers burnt as well, during running of big boats.

But so Far, I have no bad experience at all with MGMs 300A & 400As for 10+ plus and also some Chinese made 300As on 8S, as I normally run them in less than 800Kv motors for 10S and above for larger propellers.

As for gasoline engines, I have run a lot of Modified Zenoah engines in different boats for several years and then I began to switch to Chungyang, Tiger King and Quickdraw engines for better power and performance, since we have different racing rules here for engine power so we are allowed to use whatever power we have.

Gilbert

 

[LohringMiller]

I built a two bolt Chung Yang that set a G2 hydro record but was disqualified for illegal fuel. ( I'm a proven cheater.) I love the Quickdraws even though I haven't worked with their Pioneer yet. I have a future project in the shop, though. I also am concentrating on the 4S electrics so I haven't needed high amp controllers. After all, Brian Buaas can go 140 mph with a 4S rigger and Castle controller. Again, props are the secret to high speed with low current draw.

Lohring Miller

 

[Gilbert Pun]

let's not sidetrack away from the original question and hijack Wayne's topic any more.

Please focus on his question about how to set up a 52" 1/4 Scale F1 Tunnel boat for Fast Electric.

 

[Gilbert Pun]

Here is some of MHZ OB legs pics for bigger models for your interest :

The Green boat is Insane Tunnel boat with Pioneer 30.5cc Lawless OB leg

The White/Green is Zippkits Tunnel boat with Castle 2028 Motor and 400A ESC for 12S1P Lawless OB leg

The White hull is the 52" 1/4 scale F1 Baba hull.

 

[Gilbert Pun]

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