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Boat Build- Motor, ESC advice

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Boat Build- Motor, ESC advice

Old 07-19-2010, 02:43 PM
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MadManAndrew
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Default Boat Build- Motor, ESC advice

I'm building a 34" flat bottom boat, on which I plan to mount two Aquacraft EP-1's to push it around. I'm thinking of buying a Traxxas EVX-2 Marine to use as a speed control, but I'm not very knowledgeable in the electric motor market. What would be a good set of motors to pair with that ESC in the outboard application? Or maybe a different combo? I'd like to even find a brushless motor/ESC set I could pair together and stuff in there. Thanks.
Old 07-20-2010, 04:39 AM
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Default RE: Boat Build- Motor, ESC advice

Look at
There is a link to the instruction manual there, which states that it comes fitted with a 27 turn 550.  ESC manufacturers often use this rating - a smaller turn number is a higher power rating, what will control a lot (ie low turns) will control a little safely.
Old 07-20-2010, 12:29 PM
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MadManAndrew
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Default RE: Boat Build- Motor, ESC advice

I'm aware of what motor comes with the product. I'm looking to buy higher end motors to replace them as 27T seems a little slow from my experience with RC cars.

Questions:
[ul]
[*] What do y'all think of [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&W=001948440&I=LXJZN3&P=K]this[/link] or one of the higher turn motors in the series for use in a boat?
[*] The EVX-2 speed control is rated at 180A, while the [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&W=001948440&I=LXRJL6&P=K]Castle Creations[/link] one I found is rated at 240A for dual motor/dual battery. Is it anywhere near worth paying double the price ($255) for the extra amps?
[/ul]

Also, I've got two Parkzone 1800mAh 3-cell Lipo's from one of our electric airplanes. Would these be suitable for this setup too?
Old 07-20-2010, 01:09 PM
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Default RE: Boat Build- Motor, ESC advice

http://www.rcuniverse.com/forum/m_8769458/tm.htm read at the bottom page i also put two traxxas one revevers motor i got from e-bay
http://cgi.ebay.com/Traxxas-550-Tita...item5adacca53b

http://cgi.ebay.com/Traxxas-550-Tita...item2eae6e55a9
Old 07-20-2010, 01:49 PM
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MadManAndrew
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Default RE: Boat Build- Motor, ESC advice

I actually already have a set of Titan 550's from an E-MAXX, but those aren't the best of motors. The guy that recommended those only did because he didn't know what he was talking about You didn't need a reverse direction motor, as you have two seperate outbards and are not gearing the motors together, and any set of two of the same motors can be used in a dual setup, not just the Titan's.
Old 07-20-2010, 03:19 PM
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Default RE: Boat Build- Motor, ESC advice

Solidworks. The last one is an older drawing I painted up the way I want it finished.
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Old 07-21-2010, 06:02 AM
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Default RE: Boat Build- Motor, ESC advice

I'm looking to buy higher end motors to replace them as 27T seems a little slow from my experience with RC cars
First make sure the hull can handle the power on the water.  There are plenty of threads around asking "why does my boat keep flipping over" and similar questions usually followed by the admission that the boat was designed for much less power than it was given.
Old 07-21-2010, 08:13 AM
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Default RE: Boat Build- Motor, ESC advice

A couple of 27t 540 motors should push a flat bottom barge way faster than it should go! Take a look in the scale forum and see how people are powering their push boats. What you have in the pic is not a "high performance" design more of a putting about slowly kind of boat, you would probably be happier with it if you went with a single geared inboard 540 and turned a bigger prop. More scale speeds anyway and be easier to operate longer run times, lower amp draw etc. And cheap.
If you are after performance I'd look at some of the free mono hull plans available ( Wasabi 900, Wild Thing) you can scale these to whatever size you want to power it with!
Would look pretty cool as an airboat, basically what you have there.
No offense but that design would be worse than a crakerbox to operate, it will be skipping and bouncing all over the place if you give it to much power, and you would have no rough water performance what so ever. (hate crakerboxes! would rather drive a boat than retrieve it!)
If this is your first boat I'd recommend going with a tried and true design with setups that are known to work, as you get more experience go for the off the wall ideas. This way you can learn about the equipment and setting up boats without wondering if design flaws are causing the problems or just a set up issue.
So many people in this hobby start out with great ambitions then end up selling a half finished project 5 years later, There are many great ready to run and almost ready to run boats out there. Kits to build from and manufactured fiberglass hulls, (Fleabay). For not much more than that esc you can get a whole boat almost ready to run!
Just my own 2 cents, seen a lot of people leave this hobby after a short time, I'm sure some would still be here if they had chosen a first boat compatable with their skill level. Remember nobody starts anything an expert, this is a motorsport and has quite the learning curve, Lewis Hamilton didn't start in an F1 car, he started in a go kart! And we have to learn how to tune as well as drive these things!
Good luck, have a blast and keep asking the questions!
Oh ya that Castle esc is NOT FOR DUAL MOTORS. Also you linked to a brushed motor, that castle is a brushless esc, not interchangable! Brushed motors are antique technology in the boating world. For brushless you would be looking at 2 escs with a y-harness to the reciever. The double 10 guage wiring is to carry the extra amps not power a second motor! As far as I know there is nobody manufacturing an esc for dual motors.
That esc would also be way overkill for a low performance boat like that, if it had enough motor to require 240 amps the thing will be uncontrolable! Or the prop/motor choice is completely wrong and drawing way too much current. Then you'd burn something up, battery, motor or esc. $$$$$$
Those 1800 mah packs wouldn't give you much run time, good to run in paralell, more important what is the C rating on the cells? Boats draw a lot more current than planes or cars, you could cook those packs by discharging them too quickly. 25C is about the minimum to be safe with a boat.
Old 07-21-2010, 12:53 PM
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Default RE: Boat Build- Motor, ESC advice

Thanks for the tips. I guess I'll just give responses in the way points came up in your post...Lol. To start, I really wasn't after scale orrr performance with this. I just wanted a project to take up my time until my family got money, and I could afford a nice hull or even an RTR. Not having any experience shaping balsa, I wanted to go with something with no curves. I guess I coulda gone with a shallow vee or something, but I started the boat before I did my research. I'd love to build something like that, or even a deep-vee after this, and maybe rip one of the outboards off of this build for it. Trust me, I'm not gonna skip out on boats just because my mini-project failed through lack of knowledge. I'v got passion for the RC hobby, just as much as it seems you do. I've learned everything there is to know about nitros cars over the last few years, and nitro planes before that, and it was neverrrr easy, Lol. Isn't that how it's supposed to work!? You start out with the worst, and move up and up to the best ifff you the ambition to pull through and get better? At least, that's what Iiii thought Thanks for the tip-off on that esc, I really wish they would specify that in the description, ya know? I guess Traxxas iss actually the only ESC designed for dual motors. Lastly, the Lipo's I have are rated at 15C. Way too low? They'd still be better than six-cell packs, though, wouldn't they?
Old 07-22-2010, 06:33 AM
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Default RE: Boat Build- Motor, ESC advice

The thing with the batteries is that boats really draw allot of amps, its the amps that burn stuff up not the volts. The C rating tells you the max amperage you can pull. For example a 15C 5000mah pack could provide a peak discharge of 75 amps. That would be cutting things a little to close. A 40C 5000 mah pack could provide a peak of 200 amps! Of course that depends on the motor you choose.
The other thing is voltage, you double the volts of the pack you half the amp draw! I think volts are easier on equipment than amps.
Bending the thin plywood and balsa used for boats of this size is so easy! On a couple of my small sailboats I've bent some crazy compound curves in 3/32 x 5/8 balsa stripping! Saoked the strips in water for a few minutes then bent and twisted it over a hot pipe. I just used a piece of copper pipe slid over a 25 watt soldering iron.
Recently I've gotten into the small nitro boats, Cheap! If you have a radio you can build a small mono with a 100$ supertigre marine engine for about 200$ total in water cost! I have a JAE .12 outrigger and am getting bits and pieces together to build 3 wildthing monos with the supertigre engines for the "Cottage Racing Team"! Thing I like for kids is no charging batteries! Bring it in fill it up, throw it back out! I'd spend more on li-pos and chargers to keep them interested and on the water that building all 3 nitro burners will cost me!
I also think kids believe that the louder it is the faster it is going!
Wait a minute thats me!
Old 07-23-2010, 06:30 AM
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Default RE: Boat Build- Motor, ESC advice

The other thing is voltage, you double the volts of the pack you half the amp draw! I think volts are easier on equipment than amps.
Not with the same load, you dont.  You get twice the current draw and four times the power (Ohm's various laws).  If you use motors intended to give the same power at twice the voltage, then yes, the current draw is halved over that of a lower voltage motor run at its rated voltage.
Old 07-24-2010, 05:33 AM
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Default RE: Boat Build- Motor, ESC advice

Could you please post the formula for figuring that out? I always assumed to get the same rpm out of half the volts required twice the amperage! INteresting!
say with something simple
say 1500 kv 4s vs 3000kv 2s. same hull, same target speed. Keep the same can size magnets etc, just change the kv. Both motors would have to do the same amount of "work".
I know there is much more to getting the same performance out of the two! I'm just interested in the electric motor theory here.
Old 07-25-2010, 10:07 AM
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Default RE: Boat Build- Motor, ESC advice

Plenty of formulae here,  http://www.sengpielaudio.com/calculator-ohm.htm, covering pretty much every combination of calculating whatever is wanted from whichever information is available.  (Not totally accurate for motors because they introduce plenty of their own variables, but near enough)
It is a sad fact that although electricity is fairly simple and logical, most people regard it as incomprehensible black magic, mostly because its invisible.  My comment was brought about because your post read (to me) as if it was promoting the same mistake that has appeared elsewhere many times that "twice the voltage is half the current" without mentioning that that was to get the same power out of differing loads.  Your more recent post mentioning different motors clarifies your intention.  Thanks.
Old 07-25-2010, 10:27 AM
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Default RE: Boat Build- Motor, ESC advice

LOL no problems! don't want to lead anyone in the wrong direction! LOl I'm pretty good with ttl and cmos based stuff but I know there is a pile I don't know about motor theory.
Thanks for the link! knowledge is power!

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