motors and boat speed

[dbonomi]

Hi guys,

I'd like to get some opinions about 40 size brushless boat motors and straight away speed. I realize there are a lot variables in this question...What motor brand and kv. size would you choose for a v-hull or cat(about 35" size to get the fastest straight away speed possible using a 180 seaking esc, 6s batteries and drivers choice on prop. pitch and diameter(you make the call). I'd like to get some opinions.

Thanks,
Don

[dmitry100]

Is it a twin ?

[runningman]

Did you try search Google or YouTube for "fast RC boat" or similar? There are a of lot posts with setup description. Also depends on definition of fastest.

I own stock TFL Genesis and saw a lot of vids where this boat goes fast. Like one bellow.

https://youtu.be/KANUurXDupI

My personal record today 45 Km/h on 4s so far :)

[Fluid]

YouTube is one of the worst places to learn about FE boats. What you see is often not what you are told. Plus you don't know how many ESCs, motors and packs went up in flames prior to the video. Or, did the ESC grenade on the next run? You are already on the best resource for FE boats and will get better advice here, although some folks don't know what they are talking about. But a concensus of several should help.

No one can give you the recommendation you want without more info. We need to know the exact boat you have, the money you can spend and the use of the boat. How long is your pond? What speed are you looking for? What is your experience building a boat from scratch? I can tell you my race-winning combination for a 34" cat on 6S, but if not set up correctly it may blow in your boat.



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[dbonomi]

Hi Fluid,

I'm glad you responded to my request. I value your advice because of your successful experiences at the highest boating level competition. Here is the information that I can give you. One of my boats is a 33" mono fiberglass V-hull. I run a 40 size motor in the boat. Right now I have 4092 1390kv. Leopard motor, powered by a seaking 180v esc. I also use a 3/16 flex drive with a Octura 445 or 447 prop. I run this boat on 6s 5 or 6000 mah. The boat is really slow with this set up. I'm in the mid to upper 50's almost all the time. I would like this boat to really scream, especially in straight a ways. The pond that I boat in is large and I often share it with gas/nitro boaters. I have no experience of building a boat from scratch and would rather modify my present boat and make it faster. I am willing to spend money on esc's, motors and props and do almost all of this work by myself. Is it possible to get into the 80-90 mph range with this boat under the right conditions? I read alot about Lehner motors and am wondering if that is one of the areas I might look into. What are some of your suggestions to make this boat run much faster?

Thanks,
Don

[Fluid]

You didn't tell me the boat you have, but regardless you will be lucky to reliably reach the high 70s. The fastest official Q mono in NAMBA went 82 mph and that was by an experienced racer. If you are GPS racing then the speed will be higher, but when the boat crashes it will likely suffer severe damage. SAW racers concentrate on boat strength as much as they do the power system because they know that they will eventually blow over.

Your boat is running about the right speed for the motor/prop combo. You can go faster with a more aggressive prop like an x648, that should get you well into the 60s. An ABC 1917/17* would be even better. You will likely need to keep the prop diameter under 2" to avoid handling issues, with the ABC prop you should see ~70.

The quality of your packs (and their temperature) is a major player if you want the highest speeds. So is motor timing. The hull has to be well trimmed out and you will need to check temps often until you know it is a safe setup.


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[dbonomi]

Hi Fluid,

Thanks for the quick reply. I do a lot of GPS racing with the guys at the lake so I'm very interested in straight a way speeds. I haven't used the props you suggested so I"ll give those a try. I check motor timing often during my runs and I usually run under 10 degrees. I really don't like my motor/esc combo and I was hoping that you could suggest at least a different motor and kv. combo that might work better with my 180 seaking esc. I look forward to your further suggestions.

[Fluid]

If top speed runs are your only concern, then more Kv is your friend. If you are wedded to the SK-180 then I would use an 82 mm motor, you won't be able to use the extra potential of a 92mm motor. Ditch Leopard and try this motor: TP 4050-2100. It is a Delta wind so should run on 0* advance, or low setting. An ABC 1817/17* or x648 should give good speed, but be certain to make the runs short and check temps often until you know your setup is safe. You may have to raise the strut a bit to settle the hull into the water and reduce chine walk as speed increases.

I just don't know a decent ESC you can buy over the counter. Swordfish are a crap shoot, based on the luck my club has had with the normal ones I won't use them. The original T-180 was pretty stout, but the later versions don't seem to be as good.

Going really fast is not just about power, it is a combination of minimizing water contact while maintaining control and applying the available power efficiently. Anyone can buy plenty of power, but as the F1 adverts state - "power is nothing without control".


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[dbonomi]

Hi Fluid,

I agree about the esc's especially if you're looking for 200amp power or more. What about: "Alien" esc's? They're expensive but have tremendous power options. How come you didn't recommend : Neu motors or Lehner motors? Aren't they considered better than: Leopard, tp power, SSS?

[boredom.is.me]

They are on a much different price scale. He would have mentioned MGM ESCs if those motors came up, but then you'll be in the $1000 range for just a motor and ESC. And if you are asking a question like this here, you're not on that level.

[Tamelesstgr]

I'd like to chime in, I'm running a deep-v hull with a Leopard 4082 - 1450kv on 6S2P with the Turnigy Marine 180. Thus far I have run a best of 48mph on a relatively small X442 sharpened prop.

That resulted in the following parameters:

Max Amps: 105.4
Max Watts: 2,437
Motor temp and ESC temp very low
About 30k loaded rpms

There is a lot more left in the combo as I start going up in props and this deep-V doesn't turn for $hiT so I am pretty much only making straight line passes. I could probably go up in KV as well, but I'll be sticking with this motor for now.

Ken

[Newboater]

I have a proboat impulse 31 1750kv stock motor which is 40x68 can. Running an M545 prop it is at 51mph and very stable, though I did forget to check temps last time out on stock 120amp ESC. On the voracity thread one of the members is running a Leopard 4092 1750kv with 180 amp esc and is at 70mph or a touch over

[Fluid]

My stock Motly Crew with an m445 once gave a GPS reading of 160 mph. That's faster than the car I drove at that time (but I could do it now with the current ride). A single high speed reading may not be accurate. I read posts from guys who ran 60 mph with a certain setup, but on all trips after that they could only make 50 so they wonder where all the speed went. At least some were doubtless due to a faulty initial GPS reading.

The point to the above is that GPS speed claims are not always definitive. And that doesn't address flat out lies told by some. I believe no speed claims in YouTube videos unless I either know the poster or the video clearly shows the GPS reading before and after the run. Many speed claims are impossible with the setups claimed. And you never hear how many ESCs were burned up getting there, or that on the very next run the motor grenaded. I recommend YouTube as an entertainment source, not reliable boat setup and performance advice. Of course many posts are legit, but how to tell?

The mono in post #11 is wildly underpropped. With an ABC 1816-17* prop that setup should give speeds above 60 in relative safety. The limiting factor is either the ESC or Leopard. Or the tuning of the boat so that it runs clean and stable with minimum water contact. It's not all about power...


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[Gary]

Try...USE!! a Castle Mamba 1/5 ESC and water cool it. I have had FANTASTIC results from the ones I use on my SAW boats and pull over 250 amps with NEU 1530 2,200kv motors. I have dunked these so many times its not funny and not so much as a glitch....EVER!! They are the longest running esc'c I have ever owned in the 15 years of boating and I have tried many. Just spray them down each time with Corrosion X and good to go. Works for me!!