Hydromite setup question!

[baldwinc]

Hello all,

I'm in the process of building a hydromite, and I'm trying to use existing equipment from my airplanes to power it. My question is, I am using a Typhoon 2w-20 from an EDF plane (3350Kv, 28mm can), what would be a good starting point for prop/battery? I'm planning on using 3s, either 1320 or 2100, but where should I start with props? Also, what would my run times be (approx) with either the 1320 or 2100? I appreciate any help you can give!

Thanks in advance!

[ReddyWatts]

I plugged it into FeCalc = 2S at 50amps on a 1437 prop, going 25 mph at 20,000rpm for a 16 inch hydro hull? Not sure which lipo you need, run time and heat on the motor? I would not use it in a hull larger than 19 inches.

2S at 55amps on a 1735 prop, going 30mph at 21000 rpm. Anything on 3S is using atleast 75 amps. I think that is a 50 amp motor.

Anyone can jump in here anytime if you have some experience with this. All i know is what FeCalc says about the motor.

[baldwinc]

From what the EDF guys say, this motor is a clone of the Mega 16/15/3. I've ordered 4 Octura X431 plastic props and plan to trim them down (one 28mm, one 29mm and so on...)

Does this still sound far fetched? I can't believe pulling 50+ amps on a 16" hull!

I'm still planning on 3s, but not if those #'s you said are correct!

[ReddyWatts]

Ok, that helped. FeCalc says for a X431:

3S at 45 amps, 40 mph, 34000 rpm

You can use the formula: mah rating (x) .06 / amps = run time

[baldwinc]

Now that's more like it!!!

But under 3 min run time?!

[ReddyWatts]

You cannot run a lipo battery completely down, so it will be a lot less than 3 minutes on a 2300 mah battery.

Can you water cool the motor and controller?

Probably a 5000mah atleast 20C.

[baldwinc]

Yes, I know you can't run a lipo down all the way- I just did the calculation and it said 2.8 minutes for the full 2100mah. Figuring 85%, that gives me a hair over 2 minutes run time. I will be water cooling the motor/esc, but there is no way possible to fit a 5000mah battery in a hydromite!

What if I were to use a Himaxx 2025-5300 on 2s?

Sorry for the questions, but I can't figure out how to add my own data to FEcalc and my motors aren't in the listing!

[ReddyWatts]

I ran into a new problem with FeCalc. It started giving me an error message when I added a motor. I guess it will only handle up to so many motors in the text list. I removed one and added yours and then it worked.

On 2S your speed really dropped.

I have attached the FeCalc text file with your motor in it. It also has the KB45 motors and Neu lipos. This data has not been calibrated yet. Rename the fecalc.txt file on your computer and then paste this file in its place.

[baldwinc]

Thanks for the help!

[baldwinc]

Ok- I've got the boat almost done, and I've decided to go with 3s 2150, and a x431 prop cut down to 25mm (to get a half way decent run time according to Fecalc.)

Is a 25mm prop too small for this boat? I found that in Fecalc, the speed only dropped 3mph going from a 30mm prop down to a 25mm prop, but you gained almost 3 min runtime! ANd lets be honest, 40mph in a hydromite is still BLAZING fast (may end up a little un controllable??) I'd like to be able to run for a good 3-4 min without drawing the batteries down too much, and going with a 25mm prop seemed the way to do it.

Is a 25mm going to be too small?

[baldwinc]

Bump it up!

[ReddyWatts]

I think you are treading new water with that one. Octura does not make a prop that small. The smallest is 27mm.

[baldwinc]

It is a X431 cut down to 25mm.

[ReddyWatts]

I was just saying that not many people have tried that.

[FRED]

hydromite setup

Go to Trents site. www. microhydros.com