mean machine

[tertim]

I am finishing my mean machine 29" . I am planning on running a 7 XL with 4s-4000's supplying the power. running them in parallel. My question is , where do i find the balance point, and will a 642 be the right prop to start with ?
any help would be appreciated.:D

[saleens7]

the balance point is different with every boat, but there usually somewhere between 25-35% of the boats length from the transom...with some cats the balance point is around the middle of the space between the first step and the second step. i would suggest an 8XL instead of a 7...may have less rpms, but you will be pulling less amps and it will have a little more tourque, so you can run a larger prop....i cant really tell you wat prop will work, but i would suggest getting carbon props (can be found here) around the size you think will work best...(i.e. between 40mm-48mm) and test out each one....try the smallest first...if the motor is cool or only slightly warm, you can prop up...keep on using a bigger prop until the motor starts getting warm...once you find the right one, buy a metal version all balanced and sharpened up....this is a good way to find the right prop without spending a lot of money on a buch of metal props...

[NorthernBoater]

I would also go with an 8XL or 9XL. The 7XL will be drawing over 100 amps with the 40 mm carbon prop. What is the C rating on the batteries you are using? RMZDadaddy would be able to recommended where to place the COG since he runs a mean machine.

[Piranha2]

I'll be running a 9XL with a Hydra 240 and an 11XL with a Pulso 100 amp, so.......a 7XL? not sure

[saleens7]

if you still decide to use a 7XL, the hydra 240 is the only affordable esc that will hadle tha large amount of amps youll be pulling....like northboater said, an 8 or 9XL will be a better motor choice...

[steveo]

unless you use a gear drive

[RMZDADDY]

I run the COG on my MM at 8.75" from the transom, that seems to give the best combination of speed and handling. Like Saleens said, middle of the flat between the first and second step is a good place to start. That's pretty close to where mine is. I also agree with the other guys, with that voltage you'd be better off with a 8 or even a 9XL. My boat is making 45.7 mph turning 31000 rpm at the prop in a 7+ pound boat, with lipos yours would go considerably faster. If you want to see how mine handles, check out my member gallery at rcflix, vid titled MMX642.

[RMZDADDY]

I hear ya steveo, I love my gear drives!

[Piranha2]

RMZ......c'mon......handles? the vid I saw showed that thing on the edge .....not that there's anything wrong with that, she just screams.....I don't know why you even worry about COG, the hull doesn't touch the water....:D

[Piranha2]

tertim....lferguson has a Neu 1512....that would be nice!

[RMZDADDY]

Did it look that bad to you Piranha? LOL, I thought it turned pretty well in the vid I mentioned, the earlier vids had the COG further back, didn't turn so good:rolleyes:

[Piranha2]

oh, it didn't look bad....it looked TOO fast....if that makes any sense....but I lose control at 20 mph....

[Fluid]

if you still decide to use a 7XL, the hydra 240 is the only affordable esc that will hadle tha large amount of amps youll be pulling...

Simply not true. I've run a 7XL in my P Sport Hydro 12xIB3600s) for heat racing and while the 7XL is overkill, a BK9920 worked just fine as long as the prop is reasonable. The Barracuda 125 worked great for unreasonable props that cooked the packs to over 160F....no watercooling either.

My MM ran too slow with a 10XL, IB3600s and an m645 gave just 35 mph with amp draw around 50-60. On 4S the draw was over 70 and the speed near 40. With an MGM16024, 4S2P/3300/25C with a Neu 1521/1D and x438 prop it was ballistic but amp draw was well over 120....no problem. Personally, for fast sport running an 8XL or 9XL is probably about right. In another cat I got nearly identical speeds with an 8XL and a 7XL and 12xGP3300s - 45 mph.


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[tertim]

Mean

I would also go with an 8XL or 9XL. The 7XL will be drawing over 100 amps with the 40 mm carbon prop. What is the C rating on the batteries you are using? RMZDadaddy would be able to recommended where to place the COG since he runs a mean machine.

20C FIREFOX PRO MATCHED RACING SERIES. I HAVE 2 SETS , 3700 & 4000

[tertim]

I really appreciate the help. I have already bought the 7 xl and I guess I will try it. piranha, you are talkin greek to me on the 1512. I am fairly new to the scene of cats. all of my efforts have been with the sv27. I take it it is a special motor??????who makes it?
thanks rmz . I have been told it was approx 38 % of the length. will check out your vid. thanks again