Re: WOT
We use a couple of ways to determine slip. One is a formula on the computer that you simply plug in the numbers and the other is a calculator wheel (portable -- used for on water testing). <br /><br />The computer says theroitical speed is 56.6 mph. With the little wheel calculator it came up at 58.5 mph. Both use a prop rpm of 2741.9354 at 5100. Most likely its not exactly 5100 rpm. It may be 5140 or 5060 or whatever. Without a digital tach or something like a Digitron its impossible to tell. The % is what we're after so we give a little, at this point, just to get a rough idea. Thats why it's about 59 mph at best.<br /><br />If you run your numbers thru and it comes out at, lets say, 12% slip then you know youre looking at a fairly good set up. If it comes out at say, 25% then you know it can be better -- most likely thru props.<br /><br />If the rough numbers come up with something better than 0%, which is highly unlikely, then perhaps an instrument is off. Most likely the tach in this case since he's using a GPS (fairly accurate but not perfect). What if we find out the tach is defective in a way that it wont read past 5100? What if its on the wrong setting and the motor is really turning 6100?<br /><br />Many times the owner rechecks and finds the rpm was different than what he remembered. Or the prop was a 24, not a 22. <br /><br />At this stage all the numbers do is send up a red flag or not. If you start with an incorrect baseline all your work to improve the set up may be misdirected.<br /><br />In this case experience, and the numbers, tells up to recheck our instruments.
