Why ???

**JimClark** · 03-29-2009, 05:03 PM

Did you think to start on a smaller prop until you check things out?

**pompebled** · 03-29-2009, 05:32 PM

Hi Mike,

For a monohull that size I aim for 30.000 rpm at the prop, with your 6S set-up you have almost doubled that!

My first thought was that the boat was slow because the 48mm prop is way too large to be able to let the motor rev out, drawing a massive current, frying your ESC.

Was your ESC watercooled? Most chinese data for ESC's are ornamental, unless you sand the Fets in one plane and add watercooling.

If you read the building reports on this (and other) sites, 'we' always start with a small prop and work our way up, keeping a close eye on the components temperature.

Regards, Jan.

**Mickey7312** · 03-29-2009, 06:17 PM

Hi Jim and Pompebled,

Thanks for replying, I didn't think I had to try smaller props because on YouTube, I saw someone running an AquaCraft SV27 with a 36-56 BL motor, a 6S Lipo and a Graupner 48K prop and it was a torpedo.
So I thought that with my bigger BL motor I would have no problems and I don't understand why my setup does not work well with a similar setup.

Sure that the stock ESC water cooling was very unsatisfying.

So which(es) ESC with good watercooling and Amp rate should I buy ?

Thanks a lot for helping.

**Mickey7312** · 03-29-2009, 07:26 PM

One last thing : do you think I have to buy an high voltage ESC for a 6S Lipo ???

Thank you very much for helping.

**Xzessperated** · 03-29-2009, 07:50 PM

Mike let us do some mathematics here. You say your motor is 2726kv and you want to run that on a 22.1 volt battery. That is 2726 multiplied by 22.1. That is 60,244 revs per minute.
You should be aiming at 30,000 rpm. In other words 6s is too much battery for that motor. You are spinning the motor too fast and you are running a big prop. Something has to give and it looks like it is the esc. I hope that helps you see the problem.

Paddy

**Mickey7312** · 03-29-2009, 08:34 PM

Hello Paddy, thank you for your mathematics lesson,

Regarding the motor, i didn't use the 9L 2726kv, I used the 11XL 1516kv.
So on a 22.2v battery we get 33,655 revs per minute.
So, the revs rule is respected, but I why did I fry the ESCs ?

And I don't understand why an AquaCraft SV27 with a 36-56 BL motor, a 6S Lipo and a Graupner 48K (I've seen on YouTube) works well, with the stock ESC, which is only 60Amp I think.

And what kind of ESC I have to use ?

If you have any idea, please let me know.

Thanks to everybody.

Mike.

**Xzessperated** · 03-29-2009, 09:05 PM

Originally posted by Mickey7312

Hello Paddy, thank you for your mathematics lesson,

Regarding the motor, i didn't use the 9L 2726kv, I used the 11XL 1516kv.
So on a 22.2v battery we get 33,655 revs per minute.
So, the revs rule is respected, but I why did I fry the ESCs ?

And I don't understand why an AquaCraft SV27 with a 36-56 BL motor, a 6S Lipo and a Graupner 48K (I've seen on YouTube) works well, with the stock ESC, which is only 60Amp I think.

And what kind of ESC I have to use ?

If you have any idea, please let me know.

Thanks to everybody.

Mike.

LOL. Yes I did not read it well did I!!!
Your prop is still too big.
Does your shaft spin free and is it well lubricated?
If you do not have an Eagle Tree data logger do as the others suggested and start with a small prop. Check the temperatures of battery, esc and motor after just a short run and then start making your runs longer but keep a good eye on temps.
I have never messed with anything except Castle Creations or YGE controllers so I will not comment except to say get the best you can afford. My YGE never gets any more than just warm but I do have to keep an eye on the temps of the CC controllers. Some of the guys that have used other controllers will put you on the right path.

**EPower** · 03-29-2009, 10:50 PM

way too much prop for that setup and esc

**Fluid** · 03-29-2009, 11:45 PM

And I don't understand why an AquaCraft SV27 with a 36-56 BL motor, a 6S Lipo and a Graupner 48K (I've seen on YouTube) works well, with the stock ESC, which is only 60Amp I think....

Your first mistake was believeing everything you see and read on YouTube. Many of the "setups" posted there are only good for a short time before something burns up - or else are entirely made up by the poster. Believe me, the setup you quoted would not last long - either the boat would be upside down, or burned up. And your 32" mono is larger and heavier than the SV27 - that makes a difference.

Next, IME very very few ESCs can actually handle the amperage they are supposed to - including the Castles. The cheaper chinese ESCS are the worst, many of them can't handle half the quoted amperage. Check with the members here if the ESC you are interested in is worth buying. BTW the Aquacraft ESCs seem to handle their rated amperage just fine - but they are limited to 4S for reliability.

The prop you used is really too large for that hull anyway. My 33" mono runs 50 mph in racing trim with a 45mm prop, and just 2 mph slower with a 42mm prop. Never never never start your tuning with a large prop!

.

**Mickey7312** · 03-30-2009, 12:10 AM

Ok, thanks to EPower and Fluid for their advices,

To reply Paddy, yes, my shaft is clean and well lubricated.
Regarding what Fluid has wrote, I realize that there probably was a mistake in the setup I saw on YouTube.
Finally, I'm interested in ordering a new new ESC and Power Analyser from ETTI at Offshore Electrics :

- Etti Brushless Navy Race 150 Amp ESC,
- Etti Power Analyser.

I will try this setup and I won't forget to start with smaller props taking care about temps.

This way, I hope my boat will reach satisfying top speed (50-60mph) and the ESC will live a long long time, lol.

Thanks to everybody.

**EPower** · 03-30-2009, 01:29 AM

Hi The Etti 150 race is a very good esc buy yourself the capacitor bank for it, it's good insurance
http://www.offshoreelectrics.com/pro...tti-cap-bnk-lv

Cheers Adrian

**Mickey7312** · 03-30-2009, 03:28 AM

Ok, thanks Adrian, but what is the capacitor bank for ?
Changing ESC's capacitors when they fry ?

**ED66677** · 03-30-2009, 03:30 AM

9L on a 32" doesn't work for long!
6S and 11XL is just perfect to be in the 30000rpm range, start with a 45mm prop, the 11XL is rated for 60A max but that doesn't mean you can't pull more, if you pull above 60A the motor cooling will have to dissipate a lot more heat.
120A esc works fine but I have had a bad experience (don't take this as reference) with the HEX120 at high rpm's, not sure it resist high ouput frquency!
ETTI seems to be good according to user's feedback, I wouldn't say as Fluid, that chinese ESC are the worth, some work very well but they are inconsistent in quality.

**video200** · 03-30-2009, 03:36 AM

Originally posted by Mickey7312

So I would like to know what is the problem ?
In the datasheet of my 11XL there's a data named : Max Amp : 60 Amp.
My Li-po delivers 20x5=100Amp, does this means my Li-po delivers too much Amps for the motor ?
Mike.

just need to add a little on this.
MAX AMP is max reccomended amp on the motor. its is NOT max of what the motor can draw. a 11XL can draw alot more then 120 amp your hextronic is buildt for. and those batteryes is probarly 20/30c meening that it wil give you 150 amp burst.

klaus

and ED beat me to it lol

Why ???

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