Avanti's Armada now has a Delta Force 33"

[highndry]

Let the experts chine in. Lets start with a conservative prop. I have some you can try.

[hebner]

X640 would be a good prop decent run time 3 + mins and about 54 mph I have one you can try on the 20th.

[RayR]

A 33" boat running a 7XL turning an X640. I agree with Dr. Jet. Lots of barbQ. Motor, cells and speedo. Three for one. Smells nasty.

[ReddyWatts]

Your build is looking good, but I am concerned about your setup. The Feigao motors are rated for 600 watts. I have run them up to 1600. Your setup is going to use 2,452 watts and 180 amps.. That motor is going to heat up real quick. It could cause failure of other components. A KB45 or Neu motor would be better for handling this kind of power and speed.

[Avanti]

a different motor is not in the budget please help me with a setup for what I have.

Thanks

[Avanti]

btw I have all the parts in hand now.
OSE rocks with some fast shipping.
only waiting on the second battery from tower.

Time to start drillling holes

[ReddyWatts]

This is the best I can do and dont really recommend it. You will have to use very small props. Not sure if any of them are big enough to push your 33" hull.



Feigao 7XL max effeciency is 95 amps.
@4s1p
Water cool the motor.
Keep your run times short!

Y537/3 120 amps 1600 watts
X438 112 amps 1500 watts
X437/3 113 amps 1530 watts

All run around 30,500 rpm.

80% = 125 amp limit on your battery.
If you calculate it using 2p your amps and wattage increase out of the motor limits.

[Avanti]

thanks RW

so what you would suggest is to start with a X438 on 4s1p on go from there?

how do you calculate the amps and watts?

I don't really care to much about the motor, but I will be upset if I lose a battery or controller. I am a long time R/Cer but this brushless and lipo stuff is all new to me. you never had to calculate anything when I was a kid, just plug the batteries in a run it to death. Now things cost more and seem to be a lot more scientific, not to mention temperamental.

Thanks again to everyone helping out with this build.

[ReddyWatts]

Yes, you can try a X438 4s1p with a short run and check your amps and keep a close eye on the temps. Be careful!!! This is just an estimate.

I use FeCalc to estimate the props, amps and watts.



http://forums.offshoreelectrics.com/...ghlight=fecalc

[blakybob]

how do you calculate the amps and watts?

fecalc is okay for ballpark numbers. Here's some general electric formula's that may help too.

Watts = Volts x Amps
Volts = Watts / Amps
Volts = Current x Resistance
Amps = Watts / Volts
Ohms = Volts / Amps
Current = Volts / Resistance
Power = Volts x Current
mAh (.06)/amps = run time

Number of cells in series times 3.5 volts = reference voltage
Reference voltage times Kv = Reference rpm
Desired Kv = reference rpm/reference voltage

Reference RPM for 2-pole motors:
Sport boats - 15,000 - 20,000
Oval boats - 23,000 - 28,000
SAW boats - 35,000 - 40,000

For 4-pole motors, add 15% to 20% to the above values.

Example for a fast P-class 2-pole oval boat: 4S x 3.5 = 14 volts
28,000/14 = 2000 Kv

[Avanti]

thanks for all the help guys.

for logging which eagle tree would be best for my setup?

[Avanti]

I just got the transom laid out minus my turn fins (as they are not here yet)
I will drill it out tomorrow at some point.
also a few hardware and power shots

[Avanti]

ok I have all the hardware dry fit. Now I need to make some backing plates.
should the rudder be extended back past the prop like some guys have been doing?

[hebner]

I have seen several DF33 where the stinger was shortened about 1" to put the drive dog even with the leading edge of the rudder, that is how Grant's boat was built.
Hugh

[highndry]

Looks great. You have alot of set-back there. The leading edge of my rudder is ~ .5" behind the prop