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Old 06-04-2018, 06:28 PM   #34
garycasey
Veteran Member
 
City: Holland, Michigan
Vessel Name: Emerald Isle
Vessel Model: Nordic Tugs 32
Join Date: Jun 2017
Posts: 47
Cost of time

The discussion on speed vs. range was very interesting. I went a step further and calculated the cost of time. The calculation gives the answer to the question, "What would it cost me to save an hour on this trip?" For example, we usually cruise at 1300 rpm, which give about 7.4 knots. If I increase the rpm, I'll get there quicker, but will burn more fuel. Turns out at $3/gal. it will cost me (approximately, of course) $8.42 for every hour I save. I'm not spending that much per hour, but that's the incremental cost for every incremental hour I save. Is my time worth $8.42? That's the question to answer. As the speed goes up the cost also goes up. At 1400 rpm it's about $10 an hour. At 2500 rpm it's about $30 an hour. Just to put it in perspective, the sailboat I sail sometimes gives about $5 an hour at 7 knots. My airplane figured out to $200 an hour at 165 knots. A car at 70mph calculates out at something like $20 an hour, depending on the mpg. Make sense?
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