H & M Spider Hydro

[G Doggett]

My H & M Spider is having its maiden voyage tomorrow and I would appreciate some info on what prop to run.
It is powered by a Feigao 8XL with 12 IB3800 cells and a Hydra ESC.
I am guessing an X442 or X642 to start with.
What is the usual prop for this motor/cell combo ?
Graham.

[ReddyWatts]

This is what FECalc says.
X642 should use about 80 amps and runs in the upper 40's.
X640 uses about 70 amps , upper forties.
X637 uses 60 amps, upper 40's
X442 uses 65 amps mid forties
X440 uses 55 amps mid forties
X438 uses 50 amps mid forties

[Fluid]

I would suggest starting with an x440 or m440, or even an x438. My P Sport Hydro runs faster (48-50) with the m440 prop than it does with larger, higher pitched ones. Seems counter-intuitive, but letting the motor unwind produces higher speeds with lower temperatures for several of us racing 8XLs on 12 NiMH cells.


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[Jeepers]

My H&M Lifter has posted runs on my GPS in the mid 50s on 4s lipos and an 8xl turnin a m440 prop which Jay had suggested to me.

it also had ran better on a x438 on 12 nimhs for me.

[Fluid]

This is what FECalc says....

The more advanced the power we have the further away FECalc becomes when predicting amp draw or speeds accurately. It was great in its time, but it's speed and amp predictions are based on data from boats a generation ago, and the program has not been updated. Reliable information from boaters who actually run the same setup is more accurate.


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[ReddyWatts]

Oh I agree, it will just get us in the ball park. Smoke is not cheap and FeCalc has never let me down to find a prop to start testing with...... FeCalc is still a great tool.

He asked if a X442 or X642 would be good props to start with. From the FeCalc information, I would say not to use the X640 as a prop to start out using. I would try it later, after I got a bench mark from using some props with less pitch.

This is one thing that makes this hobby enjoyable for me; discovering which prop works best.