mean machine

[Piranha2]

I'm talking greek? Did you read fluid's post??? ...and Fluid, since when is 35mph TOO slow?

[Fluid]

...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?

Neu Motors makes a variety of 15xx motors. They are 4-pole motors (most other BL motors are 2-pole) they have greater torque and efficiency. But you pay for that efficiency and for sport running they are extravagant. I have a handful of Neu motors but all are really racing motors.

I have been told it was approx 38 % of the length.

The exact CG position will depend on the speed and weight of the boat. I run mine at 9.5" but I have not tried it further back, it may run better. Strut depth and angle matter too - the bottom of mine is 3/16" above and parallel to the sponson bottoms with the boat flat on a table.


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[Fluid]

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

Be very careful with the 7XL and those cells. With maximum continuous draws of 74 and 80 amps you will want to run a small prop - start with something like an x438 or carbon 38mm. Much larger and you will certainly pull too many amps and risk damage to your cells.....I assume they are not 2P?


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[tertim]

Be very careful with the 7XL and those cells. With maximum continuous draws of 74 and 80 amps you will want to run a small prop - start with something like an x438 or carbon 38mm. Much larger and you will certainly pull too many amps and risk damage to your cells.....I assume they are not 2P?


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what exactly is 2p?
I bought this MM in a box and have never messed with lipoly before. I am running dual cooling and really want to protect my investment. I have a s&b 438 octura 3 blade as well as 440 3 blades and a 440 2 blade, then I get into the 642, 645, and CF 45 and 48. which one should I start with ?
I run the 645 on my sv27 with no problems in 7 lap races of course I am using nimh not lipo.
Thanks
TIM:D

[RMZDADDY]

I can't comment on the lipo question, but I do know one rule that always applies- start with a small prop. I've never smoked anything by following that rule. I am curious about one thing, what esc are you using? (or planning to use).

[Skunk Works]

7XL is not enough torque in my book. My bud select mean machine motivates well with a hacker 9XL.

[tertim]

Hydra

will be using hydra 240 with the 4s 4000 wired parlell

[Fluid]

what exactly is 2p?...

If you have a pack of 4S/4000mAh LiPos (14.8 volts, 4000mAh) that are 20C cells, you can safely pull 80 amps out of it continuously. If you take two 4S/4000mAh packs and wire them in parallel (positive to positive, negative to negative) you make a 4S2P pack - 14.8 volts and 8000 mAh. Then you can safely pull 160 amps continuously from them.

An x438/3 is too much prop to start, you will probablly pull more than 75-80 amps and you will risk damaging your pack if you run for very long. Get an x438 or x440 2-blade prop - these will be large enough to push the MM - I have run an m440 on mine - but will help reduce the amp draw. If you parallel your packs (2P) you can run any reasonable prop since the cells will no longer be the limiting factor....the ESC might be though.


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[tertim]

thanks

I will be running tomorrow very carefully. I have the lipos wired parallel so that makes them 4s2p . I have a 440 2 blade. I will start with that. what should I set the cutoff for ?
Thanks
Tim
PS I am using a hydra 240

[Rex R]

if you are refering to the low voltage cutoff I would not go lower than 12.8v

[Fluid]

I set mine at 3.4 volts per cell where I can. This is ThunderPower's recommendation too. Wired 2P you should be pretty safe if your cells are at least 20C. I'd start with the x440/2.

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[tertim]

first run

started with the 440/2 and ran it for a quick two runs. brought it in and checked temps. motor 105, esc 110-115, batterys cool. hull was running in a nose down attitude. raised the strut a 1/16th and moved the cells back 1/2 inch. next run switched to 642/2 and ran 2 quick runs. brought it in and all temps were the same.however the hull was still in a nose down attitude. weather got rough and called it a day. The guys I run with said it looked like the meanie was running around 35 to 40 mph. I never had it wot for it to really get up to speed. the nose down attitude had me worried. plan on trying it again next weekend.
PS , the meanie weighs in at 5.55 lbs with everything on board. pretty light I think.
Thanks,
Tim:D

[Fluid]

If the boat was indeed running 35-40 mph that is fast enough to carry the bow, so something is not set right. The nose-down attitude can be from a CG that is too far forward, a strut that is too low, or a strut that is angled down at the prop. Set the boat on a setup board or a flat table resting on the sponsons. The default setting is the strut bottom flat on the tabletop....where is yours? Where is your CG? Once we know where you are then we can adjust from there.


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[tertim]

whoops

I checked the strut like you suggested. I found it to be at least a 1/4" below the hull.
I tried to get it level with the bottom of the hull and ran out of adjustment. it is down approx. 1/16" . to get it level I will have to deepen the adjustment slot or ???
I mounted the batterys to balance the boat at 9 1/2 inches from the stern. Am I doing something wrong.
I am going to take it to the pond tomorrow and give it a trial run. I am in no hurry to get this boat up to speed. just gonna take baby steps. and get it right. I will be trying for a record at the saws event in Ga. in Sept if this baby will go as fast as I think she can.
Thanks,
Tim:D

[RMZDADDY]

I have my strut set so that the centerline of the prop shaft is even with the bottom of the hull, I seem to only have to move the batteries fore and aft to get the results I'm after. I usually set cog at 8.75". If the bow still rides low, move the cog back some and try again.
I'm sure you'll get it, and when you do, look out, that's gonna be one fast cat!