barney 5

My Feedback: (231)

ok so i decided i wanted to try a brushless boat, made a great trade here on rcu and got me a nice genesis twin cat. its got a brand new leopard 4074 2000kv motor. it needs a esc. he told me a turnigy 180amp would make it fly on 6s. i'm not a rich man now that i got married lol and can't really fork out 90 bucks for a esc. i'm open for suggestions. been looking at the seaking 120amp but they are sold out at hobbyking. i want something fast, not gonna race or anything. prolly drive it once and sell it like everything else. also i been rcing 30 years but mostly nitro so when it comes to programming and all the jibberish talk about amps x cells and so all that stuff i'm quite green. any help would be very helpful. thought i'd throw a couple pix at you. if someone likes it i am always willing to some horsetrading...its in great shape!

yellow-bird

Hi Barney

The usual recommendation for boat rpms is to aim for around 30,000rpm maximum. You can push beyond this but prop balancing and size become increasingly important.

With a 2000kv motor (2000 rpm per volt applied) to get to the 30,000 rpm target you would need 15 volts. A 4 cell (4S) lipo battery pack (or more commonly 2x 2S packs as they are easier to balance out the boat with) would give you a nominal 14.8 volts and would be a good starting point, especially as your prop doesn't seem to be sharpened and balanced (important for smooth running at high rpm). See the attached pictures for a better idea - the polished props have a shiny finish.

For the 2000kv motor a 5S battery pack (2S + 3S) seems to be the most common upgrade - 6S would be better for the 1400kv to 1800kv versions.

As the battery packs can be daisy-chained you could think about buying three packs - two 2S (7.4v) and one 3S (11.1v). Then you can start with the 2x 2Spacks and change to 2S+3Sonce you have got the hang of the boat. All the packs should be the same brand and capacity for best reliability - I would recommend packs with at least 5000mAh capacity for good performance and a reasonable run time.

-yellow-bird

barney 5

My Feedback: (231)

i'm glad to hear about lipos, i was gonna start right out on 6s. i am looking for a couple 2s lipos...do you have any? see my ads...thanx again and any help with boats will be appreciated!

yellow-bird

Hi Barney

For the Leopard 4074 2000kv motor the maximum current rating is 120A, so you need batteries which can provide this with some headroom - e.g. 150A minimum.

Lipo battery performance is classed by the "C" rating, the current multiple of battery capacity the pack can supply. For example:

- a 3000mAh "20C" pack can provide (20*3=60) amps of current safely
- a 6000mAh "10C" pack can provide (10*6=60)A of current safely - the same amount
- a 6000mAh "20C" pack can provide (20*6=120)A of current safely - twice as much.

For your motor you should be looking for a minimum of 150A current capability, so:
- 5000mAH 30C
- 6000mAh 25C
- etc or better is where you need to be.

There are two schools of thought when it comes to batteries:
- One group will buy the best available for ultimate performance and security
- The other group will buy multiple cheaper packs and accept that they may not last as long as the "expensive" units but can be 1/3 or even 1/4 the price.

Hobbyking is a very popular source of reasonably priced lipo batteries and has a USA warehouse for fast shipping of popular products - the rest comes from Asia. Something like a pair the 2Spack below would be a good choice - I have something very similar in my boats:

http://www.hobbyking.com/hobbyking/s...arehouse_.html

the hard case gives a bit more protection from water splashing around in the boat and boats aren't really weight sensitive. This pack can provide (30*5.2=156) amps continuously and (40*5.2=208) amps for up to 10 seconds to cover spikes on wide open throttle. THese packs are sometimes used four at a time to double capacity and double run-time for longer racing heats.



They do also have a range of 5Spacks if you wanted to upgrade later and don't want to mix'n'match different voltage packs - see below for an example:

http://www.hobbyking.com/hobbyking/s...arehouse_.html

-yellow-bird

barney 5

My Feedback: (231)

very good schooling! am i gonna get max performance from the 4s setup using the lipos in your link? or would it be best to run on 6s and give up some runtime due to lower mah? what would you suggest for 6s? also the 5s alone, this will this give max performance on just one lipo but maybe a short runtime. the runtime isn't a issue as long as i can get a couple top speed runs out of it...

barney 5

My Feedback: (231)

also i forgot to mention, the prop looks like a octura x642. is this a good or bad prop. it looks a little worn, been rubbed before...

yellow-bird

Hi Barney

The 4072 2000kv is designed for 4S to 6Soperation, but to some extent it depends on what you put it into. In a boat the motors work harder than a car for example because drag is much higher and you can spend more time with wide open throttle. With the Octura x642 (if that's what you have, if you take it off you may find some stamps on the hub to confirm) I think you would be fine with 4S operaton and this will be fast and reliable - the Octura props are very good.

As the battery voltage increases the boat will get faster - 6S will be significantly faster than 4S. You might get 40mph or so on 4S but 50-60mph on 6S.

To run 6S you might need a smaller propellor or the motor will draw a lot of current and everything will be stressed. This could be fine for one run but over time something could get damaged. The simplest way to try 6S might just be to get three the 2S packs in my previous link and just daisy-chain them. Alternatively if you had four you could use them as two boat sets, try 6S, or use them all together with two in series and two in parallel to extend your runtime depending on how you configure them.

On 4S you might get around 4-5 minutes of flat-out running on the batteries I suggested, depending on the size of your pond/ lake. Increasing the voltage will increase the power consumption and current draw and therefore reduce your runtime. With four packs together (2 parallel, 2 series) you could extend your runtime up to nearer 10 minutes of flat-out running.

-yellow-bird

barney 5

My Feedback: (231)

on 2 5200mah lipos i'm only gonna get less than 10 minutes of run time? wow maybe boating isn't for me. gonna take an hour to charge the lipos on my passport one at a time.

yellow-bird

Hi Barney

Welcome to the downside of fast electric......! - you can always potter around to extend the battery life With a fast electric boat you have much more drag at speed than a car, so spend much more time on full throttle.

More seriously, that's why many people like myself buy a few sets of the budget lipos, and a good parallel fast charger helps too. With 3 sets of batteries and a fast charger you can kep going almost continuously.

Do you live near water, or have drive to get there?

-yellow-bird

barney 5

My Feedback: (231)

i live about 2 minutes from a 10 acre lake that is almost always like a mirror. it has a big parking area where the guys come to fly there planes and helis...whats a good economical dual lipo charger, my charger is a passport dynamite. takes almost an hour to charge my 6400mah 3s lipo...

yellow-bird

Hi barney

Would you be looking for something you can use at home (AC powered), or in the field/ at the lake (12v powered), or both?

By the way, two single-pack chargers are usually cheaper than dual-pack chargers, so you could just consider getting another charger like the Pasport you already have.

At the budget end of the market the iMAX B6 family are popular in AC/DCand DC only versions - one of these will certainly be cheaper than a high-end multi-pack charger:

http://www.hobbyking.com/hobbyking/s..._GENUINE_.html
http://www.hobbyking.com/hobbyking/s..._GENUINE_.html

At the top end, Hyperion chargers are very popular and will probably charge anything you ever need in electric RC. These are single pack chargers:

http://www.offshoreelectrics.com/pro...mp-eos0606I-dc
http://www.offshoreelectrics.com/pro...-eos0606I-acdc

and this one is the "Cadillac" of chargers!

http://www.offshoreelectrics.com/pro...=emp-EOS720DUO

All of these would be able to recharge a standard pack in about an hour or less.

-yellow-bird