If you go with 6 volts, still the most popular, at least in my area, you can get two 10 amp hour packs of D cell NiMHs in the ship. If you go with LifePo you might be able to get a little more power, but I don't think you'd have room. 20 amp hours at 6 volts is plenty.
Conversely, some of the modern batteries like the Headway lithium-iron cylindrical cells (6.6v, 10ah, 1.5lbs total weight) work and fit perfectly into smaller hull like an I-boat. They last upto 4 times longer than a sealed lead acid battery, gives more voltage under load, and has half again more capacity at half the weight of a comparable lead acid battery. Google "Headway LiFE". Going with a solid state fire control system (electronic firing boards and solenoids) not only eliminates servos that will eventually fail when wet, but gives far faster rates of fire compared to a poppet based system. The downside is usually higher cost but it pays off in ship reliability. If you would really like to go modern, then go brushless motors and electronic speed controls. They are usually up to 20% - 30% more efficient than brushed motors and don't have brushes to wear out. One of my ships still has a brushless drive system in it from 2 years ago ... and it is still going strong with zero wear. Brushless may cost a little more than brushed, but in the long run it pays for itself with longevity, power, and reliability.
i saw some batteries on strikemodels. i didnt spend much time on the page but im sure they have the right ones. btw i think ill go with brushless and esc's
http://www.batteryspace.com/ For a Colorado you can probably fit the 20 Amp LiFe cells (http://www.batteryspace.com/LiFePO4-Prismatic-Module-3.2V-20-Ah-10C-Rate-64-wh.aspx) buy this (http://www.batteryspace.com/LiFePO4-Prismatic-Box-Battery-12.8V-20Ah-256Wh-10C-rate-without-PCM.aspx) open and remove the cells for a better deal. 6.6v is pretty standard, 13.2v is better. brushless is the way to go if you dont mind the initial hassle
obviously, batteries are a sore subject to me as all the numbers and cell sizes is overwhelming sometimes. i was on battery space and saw this LiFePO4 42120e (M size) Cell : 3.2V 10 Ah, 50A Rate, 32Wh (3.0) its 3.2 volts at 10 amps. would to of them work? Snipe, your scaring me, what kind of hassle we talkin about?
Those batteries would work, I'd still recommend the ones in my previous post but either will work fine. Brushless setups are newer to the hobby so there is less institutional knowledge to draw on and fewer setups to copy. People are trying to predict what setups are the best and whatnot but at the moment they still require some trial and error to get the right size motors. It isn't really a big deal if you're willing to experiment and possibly try a few different motors. Basically larger props are better than smaller props and most of our boats use motors in the 400-1000Kv range depending on voltage/gearing.
the batteries you recommended are also cheaper. what kind of brushed motors are best for the invincible?
Then I'd start with something in the 800-1200kv range, probably 1000kv and then move up or down from there depending on how it performs.
Are they rating brushed motors in kv now? You'd think it would be kv + some calculus equation describing the load curve But I haven't looked back since going brushless.
doh, my mind is stuck on brushless. for brushed I'm a fan of Mabuchi's RS-540 if you can find them. but the "standard" johnson motors that BC sells seem to work fine for most people too. I think most people just find a motor that "works" and they like/can get easily or cheaply and buy a stock of those and use them for whatever and don't put to much effort into optimizing. Ideally for a drive motor a brusehd motor with a higher number of turns is probably best but then determining speed under load and all that jazz is even more complicated, however I have had better luck finding spec sheets for brushed motors so those can help. (If I quit buying cheap chinnese brushless motors I might have better luck with spec sheets but at this point I'm pretty comfortable without them so who really cares.)
Brushed motor specs can be a royal pain to find sometimes. Many manufacturers like Mabuchi has motor specs online. Many don't. The hard part is finding out exactly which motor model the motor is. It is common to see three motors made by the same manufacturer that look identical when side by side but have different windings internally with different rpm and voltages. Additionally, brushed motor specs tend to list rpm at a specific voltage versus a kv rating. And finally, many motors come with no markings at all. LIke Chris mentioned, most people fall back upon the most popular motors in use right now, such as the Johnson motors BC sells. They (the motor) has been around long enough that people know how they perform and what gearing works best with which prop.
Now that I think on it some ... the data we are learning from using brushless motors can be used with brushed. For instance, the 800 - 1200kv data can be used to try to pick a brushed motor. A brushed motor with 12,000 rpm at 6v run on a 6v geared setup will have similier prop rpm as a brushless 800 - 1200kv motor. It pretty much hinges on the bushed motor identificaiton and specs (if available).
I disagree on the generalization, Mike, as the brushed motors will drop their RPM under load until they reach a current flow that lines up with the torque required. A brushless motor will not, as it responds to the set frequency and draws more current to keep at that frequency as load increases. Totally different response to load.
Hmm ... yeah. You are right. Heh. That was the major thing that led me to overestimate the kv on the first brushless motors installed in the Erin and the first attempt at a brushless pump. For instance, a pump using a Titan 12t brushed motor vs a brushless motor. The Titan 12t runs around 21 - 23K rpm on 6v with no load. I did not have a way to measure rpm while pumping, so simply chose a brushless inrunner that would give slightly better rpm (a 4300 kv, 36mm inrunner). The result was an astonishing 81 amp draw while pumping and a crazy gpm (not measured in any way other than the getting the entire bathroom wet!). In hindsight, it was pretty obvious that the brushless motor did not have near the rpm drop under load as the Titan 12t brushed motor. You know, knowing the actual reason why the motors behave like that is good to know. Thanks Tug!
Wow I feel so dumb! Couldn't I just get the hardware pack from Strikemodels? Im pretty sure that comes with switches, shafts, pushrods, and some more little things, right? But knowing all of that about motors is very helpful thanks guys
Yeah, you can, perfectly legitimate option especially for your first ship. Getting a ship on the water is much more important than what motors you use.
