prop tachometer

[gregk]

any of you guys use a airplane prop tachometer on your twin boat ? before I toss mine in the water I wanted to use a tachometer on the props to see if they are the same rpm (or close) soo im wondering if any of you guys tried this

[jstolz]

You can't tach a boat prop as you do an airplane prop. If you run the boat at full speed you will damage something. You could also get hurt. I have used my Eagle Tree system to tach my motor speed. With a mag pickup I have measured my motor RPM.

[gregk]

I see what you are saying I wasn't planning on running them up full throttle maybe 1/4 throttle anyway I just wanted to see if anyone has tried it

[Fluid]

Say you did tach the motors unloaded in the air. What would you do if you discovered that one motor was running faster than the other.....? Unnecessary information. Better to see what the boat does when running under load, that's what matters.


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[jstolz]

With my Eagle Tree data logger, I have measured motor rpm under load in the water. I think that I only used it one time.

Jay

[D for Dummy]

Knowing your motors RPM unloaded is worthless. 4.2 per cell X 4 cells (4s) x Kv of motor tell me that my Aquacraft Motley Crew can spin a max RPM of: 16.8 X 1800 = 30240. AND keep in mind that is only the first minute or less that the LiPos are at peak amp. If I could know my peak RPM while pushing the weight of the boat, with the particular strut height and angle, with a particular prop.... well then I could match max pitch to that RPM base on heat (Amp draw and volts).

Until then, quality batteries with a high C rating, a laser temp gauge, combined with my experience of which props work well with the desired strut position based on water conditions is the best I can do... Lets RACE!