A few radar comments:
First, radar is not required by law and if installed it is not required to be turned on.
Second, radars PRIMARY function is avoiding hitting something. A secondary function (and a poor one at that) can be used for weather avoidance. However, that will work best in open water and may allow one to maneuver to avoid some weather.
Third, radar does NOT see around corners. It's a line of sight device, very high frequency, and does not penetrate hard objects, trees, land or even heavy rain. (AIS is significantly better for tow avoidance on curved rivers).
Fourth, radar is a poor navigational tool (sometimes). The ONLY thing radar will show is a reference to land or markers. It does not show depth or channels. However, it's invaluable for "correcting" a charting error. Modern GPS is MUCH more valuable for a nav tool, and almost never fails. Now, charting errors DO happen and that's where the radar can find uncharted markers and prevent one from driving the boat over land. But it won't keep you from going aground.
Fifth, it doesn't take years to learn, Paul. Modern digital radars can be leaned in a few days and a few months of practice can give one the necessary skills to make it a valuable tool. Yes, the old analogs were a bitch, but I'd doubt there are any more of them out there, other than in a museum.
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Now, is it a necessary tool for the Loop? I'd bet that 99.9% of all prudent mariners would say yes. It's so cheap in the whole scheme of things that it's a non issue to just have one. AND DON'T MESS WITH A USED ONE, PERIOD. For $2000 the high end dome radar can be purchased, and yes, you can install it yourself with some skills.
Larry,
Just FWIW, I could strong argue that if you get a boat with electronics much older that 15 years, dump the whole mess of them and install a new radio package for your Loop trip. There's nothing more frustrating that a useful piece of electronics that just doesn't work or quits. I bought a complete Simrad package (less the VHFs) for a little over $12K, including 3 9in displays, depth finder, forward sonar, autopilot and radar. The whole package worked fine, with fine tuning made enroute, excepting the forward sonar, which is a POS. I later added a Vesper XB8000 AIS transceiver which I should have purchased with the package.
When you compare that with the price of the boat, other appliances, and all the other stuff, it's not a huge deal, and make cruising MUCH EASIER.
Also, I could argue that a prudent mariner would avoid heavy fog and night operations for the most part, but they can be navigated "reasonably" safe. However, if that were one's SOP a FLIR unit might be an additional tool to consider.
Would I value my radar high than my chart plotter or autopilot? Heck no! The chart plotter and autopilot is SIGNIFICANTLY more useful, and most of us use them on every leg, even short ones. While the radar may be on, we rarely need it much more than 5% of the time. If it day, VFR, you don't need radar, but you will need the chart plotter and AP. However, as SAFETY item, the cost of the radar for that 5% IS A BARGAIN.