Without a knot meter it can be very difficult to estimate the current. This matters, particularly in situations where it is useful to know something about the power being used to drive the boat. GPS of course sees velocity over the ground, but the boat - and whatever is driving it - experiences speed through the water.
I had occasion to proceed from Titusville to Ft. Lauderdale down the ICW on a friend's boat with a dead speed log and no tachometer. As it happened, the wind was against us the entire time and so we were powered by the diesel. Those of you familiar with these waterways will know that there is a considerable current generated by the tides in several places along the way. These currents can reach 2 knots or more in some places, and predicting exactly where, when, and how strong is educated guess work at best, even for those with local knowledge, which we did not have. At one point on our trip, while bucking such a current, it seemed to me that we were over working the engine since there was steam coming out with the exhaust, but the owner insisted that we should be able to make 5 knots (by GPS remember) no matter what. He was having some sort of mental block, and flatly rejected my analysis of the situation. Anyway we cooked the engine pretty good, the oil thinned out, the oil pressure dropped and at that point he started to understand that something was wrong. Long story short, this event led a lot of problems going forward, and if we had had a working speed log the situation would have been clear to everyone involved. By guess and by gosh is always a poor substitute for actual numbers. A tach could also have helped in this particular case, and we later installed a "Tiny Tach" that worked fine. Steve Thomas C&C27 MKIII ----- Original Message ----- From: John Pennie via CnC-List To: cnc-list@cnc-list.com Cc: John Pennie Sent: Sunday, August 09, 2015 22:07 Subject: Re: Stus-List Electronics upgrade Thanks for the input. Fred - my thoughts on the iPad dependent issue (and I fully understand your point), this all assumes a semi-permanent iPad installation with built in charging. Beyond that you have your spare iPad, smart phone, pc in the cabin, etc. Very interesting thought on the VHF serving as gps and ais receiver. Will give that some thought. Any thoughts on the reliability of the Furuno unit itself? It's a bit of an oddity but has been on the market for a while. Radar is not a critical function to me (except when it is) but I view this more of an offshore tool than anything else. Just my opinion which I'm sure most would disagree with. As usual I am in the minority. I still see no need for a knot meter. John
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