How many cells can I run with my Leopard?

[keithbradley]

So what are these guys doing in these Genesis cats blazing over 60 70 and 80mph? One guy was running 9s on a 4082 leopard.

Pulling 300A +.
...although most of them have no clue because they dont bother data logging it. They just gloat while it stays together and then get quite when something breaks.
Usually when people run ultra high voltage they are either new to the sport or just accepting that everything may catch fire and burn in the name of all out speed. Many of us have ran crazy voltages when we were new to FE, sometimes they last a surprising amount of time too, but its not something that I would reccomend you run if you arent in the stage of throwing caution to the wind.

[Travis]

Hi Guys,

Just back to the original question which I think was "Can I run this leopard on 8s?".

I'm reasonably new to boating but basic electrical theory supports Kookies argument.

Motors are capable of converting a certain electrical energy or power into motion. We rate this in Watts.

Watts is simply volts x amps. (ignoring any power factor considerations and any motor will has some inductance)

If the motor is rated at 3500w and you run on 22.2v you must take steps to limit current draw to 158A.

If the motor is rated at 3500w and you run on 29.6v you must take steps to limit current draw to 118A.

Current draw is dependant on load which in a boats case is mainly influenced by weight and prop size / style.

So yes, providing your speedy is sufficiently rated, you can run your leopard on 8s providing you limit current draw to within the kw rating of the motor. (this being said, no system with last long running at it's rated limit, you would drive your car on the red line all day!)

Cheers,

Travis

[keithbradley]

We all understand voltage, current, and power Travis. What seems to be continually overlooked is load. It is NOT primarily a factor of prop size and weight, it is greatly influenced by prop SPEED. if that wasn't the case, we would all have 100mph + boats and haul them around in our 200mph cars. It takes more power to move the same object faster. That is physics in it's simplist form. No amount of discussion will change it.

[Travis]

Granted, everything is a compromise and you can't produce extra energy from nothing but the question was "can I", not "should I and will it make it go faster".

Personally I base my power systems around 4s and this works for me but if this guy wants to try 8s on the leopard, he technically can if all other factors are taken into account.

As I said, as you said, current is limited by load and this needs to be considered. At the end of the day the resultant prop size may not be practical for the hull.

I understand many know the basic electrical principals but the original poster may not. Merely tried to offer a explaination, not an opinion.

Remember, high voltage means higher efficiency, jist maybe also higher cost!

[Skullcracken]

How do you know prop size?

My 37" Drifter cat ran with the same combo using an x445 and was running 62mph. I don't remember temps, but I remember having room to prop up. I'm confident it had the capability to run 65mph reliably. I'd run what you have and tune with props and strut settings.

More than one of you mentioned x445 prop. Can I run an x460 with leopard 4082 on 6s. (I've canned running 8s idea).

[keithbradley]

That would be a big prop for that motor and for a 34" cat. What would make lead you to that prop? Is this something where you are playing with a speed calculator and thats what gives you the speed you want, or is there a reason for the big prop? Most likely if the motor and esc were ok with that prop, you would have a hard time keeping the boat on the water. Too large of diameter prop will give you headaches trying to get your boat to run without crashes.

I know its not what you want to hear, but if you work on your setup you can get more speed without setting it on kill.


(to be clear. to anyone who may want to interject, you "technically can" run as big of a prop as you want, or as many lipo cells as you want...Im guessing you're asking because you want to know how well it will work though...)

[Skullcracken]

Two reasons I asked about the X460

[QUOTE=keithbradley;314871]That would be a big prop for that motor and for a 34" cat. What would make lead you to that prop? Is this something where you are playing with a speed calculator and thats what gives you the speed you want, or is there a reason for the big prop? Most likely if the motor and esc were ok with that prop, you would have a hard time keeping the boat on the water. Too large of diameter prop will give you headaches trying to get your boat to run without crashes.

First I just don't know in general how you size the props appropriately according to boat size, powerplant/motor etc.
The other reason I asked was I can only find and X460 that is sharpened and balanced. Can't find any X445's that are sharpened and balanced. So a larger prop would overtax the motor or esc?

[Skullcracken]

Prop size...

As I've been asking about upping the cells on my boat setup and the consensus is "bad idea," what is the upper prop size for a 34 inch cat. Most recommendations were X445 and X460 is way too much. What is the upper limits for a boat this size? Not wanting just a spoon-feed answer. Is there critieria, or just plain experience from you fellas' with trial and error? Thanks for the feedback, Im sure some of my newbie questions have been answered a lot on these forums.

[keithbradley]

Your best bet is to get a datalogger. Every hull is different and can get away with different combos. What prop are you running now?

[bbosncali]

My buddy's running a 4082 1500kv in his genesis with an x642 and he runs consistant 60's with a best of 63.7. He has his strut so high up that a 445 just won't fit unless he lowers his strut which he didvand lost about 8mph

[Insaniac]

Try 8S and let us know what happens (be sure to take some video)...

[bbosncali]

He's running on 6s and at those speeds its fast enough. Just found it a little odd that it runs so good with such a small prop as apposed to a bigger prop

[sailr]

The more the cells, the higher the RPM, the smaller the prop must be!

[Brushless55]

As I've been asking about upping the cells on my boat setup and the consensus is "bad idea," what is the upper prop size for a 34 inch cat. Most recommendations were X445 and X460 is way too much. What is the upper limits for a boat this size? Not wanting just a spoon-feed answer. Is there critieria, or just plain experience from you fellas' with trial and error? Thanks for the feedback, Im sure some of my newbie questions have been answered a lot on these forums.

prop size really depends on rpms
more cells means more rpms and the smaller you will want your prop

[fastblack]

you can run the leo4082 1500kv at 8cell, but you will have too use a x440 40mm prop or a x438 38mm prop.you will also need a high volt 120amp esc minimum, you should use a datalogger too find out the current draw. your flex system must be upgraded too 187. or it will break. if you cant get a decent ampdraw at 8cell you can also try 7cell.

i run a df 33 with leo4074 1400kv at 8 cell and x440 castle hydra 120amp hv all summer with amp dra about 95amps. speed 95kmph