Is It Possible to go Fast on Brushless Power??

[Tuslow1]

What I'm thinking my next Project is to take a 30+ inch hull and get a sturdy and reliable 40 to 50 MPH out of it on upto 16 cells... Bad thing is I still have no clue of what Brushless power is all about... I look at the motor charts and it all looks like bad math to me... The ESC's are really out of pocket so I don't want to get one not up to the task nor one that will fry the motor.... Also picking a good prop for me is asking someone what works well for them... pitch is something that happens in Baseball... I need help, and hopefully I will learn to help others along the way... I got tons of vids but all they really tell me is that others know how to make FE work, and I don't.. I also don't want to call a shop and ask too many questions, they might sell me anything because they might think "Hell, he don't know he's doing anyway"
Please help me to not make a very exspensive entirely tu-slow boat??? :confused:

[Rex R]

the short answer is; yes. ok a slightly longer one includes several questions, some of which are; what do you consider fast, what sort of run times, which hull, etc. etc. the namba speed record is 140+ mph on brushless power :). normally its the other way round the motor will turn the esc into charcoal(and turn batteries into oven heaters). I'll let the other folks get into specifics(since I'm new at this too :))

[Kirker]

Well I'm a newbie myself but my first thought is I think it might be tough to get 40-50 mph out of a 30+ inch hull on 16 cells max, unless it's a outrigger or maybe a hydro. I'm sure there's people that do it though. My two places to start would be, first, offshoreelectrics.com. If you read the "6-cell/7-cell" thread you will see some e-mail exchanges I've had with Steve at offshore. He seems helpful and they're defiantly racers that cater to guys that want to push the envelope! Another suggestion is finedesignrc.com. I've never dealt with them personnaly but if you look around their site it's obvious that those guys have "the need for speed". Everyone is a retailer so they all want to sell you something, BUT, those outfits (and I'm sure a few others) want to sell you something that does what you want (which is get nasty letters from your condo assc. :D ).

Pitch really is a fairly easy concept. Greater pitch = more topend BUT less holeshot. A larger diameter prop will usually have a greater pitch just because it's bigger. But, if your prop is to big the motor won't be able to spin it fast enough and you end up with a dog that you'll want to give to your wife as a "present"! :D Have a basic prop recommended to you and then just experiment from there. I'd try to stay at the same diameter or maybe a little bigger and try ones with more (or less) pitch depending on how the boat is running and how you want to change it. :teacher:

[Fluid]

Here is a recipe that works:

29" Aeromarine Titan
9XL motor
Fine Design gear box
18 cells
Hacker 77 controller
x442 prop

Set up correctly this gets 40-45 mph for 4 minutes depending on gearing and cell quality. "Set up correctly" is key, but the parts work well together. :)

Brushless motors are generally rated by size and Kv(rpm per volt). A rough guide to chosing a motor:
* For 12 cells and up - a larger format motor (XL, or Xtra Long in the Hacker and Nemesis BL motor lines)
* For a sport running Kv, divide 20,000 to 25,000 by the number of cells to get the Kv for direct drive. For 18 cells that's 1111 to 1388 rpm, so a motor with a Kv between 1100 and 1400 would work well in direct drive.

For extended run times in a large boat a gear drive is a great way to go, and you can use a motor with a higher Kv for better efficiency. The key is choosing the right gear ratio, and that depends on the hull design, weight, prop and desired speed. You can go from fast with short run times to a bit slower with long run times just by changing the gears - a two minute task. The ideas are a bit complex, but they can be learned like anything else. :teacher:


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[lferguson]

Hey thats my setup!! Only I run 14 cells. It is a sweet setup. THe man is right.