On 02/05/2016 07:42 AM, Thomas Buzzi wrote:
Hi John, What do you find works as to a compass? I have read about handheld but I wonder if their reading would change depending on where you were on the boat when you used it due to battery, ob or other chunks of metal.
If I get a "nice" compass, I am leaning towards the Plastimo Iris 100, which can mount in a clip in most any orientation, removable for handheld, clipped on for hands-free reading. I can also use it on my kayak if I need it there, so more versatile. Compass sensitivity to ferrous hunks of metal falls off quickly with distance - cube of the distance I think. At least, magnetic field around a magnet falls off as cube of distance. Not sure if it's the same for the effect of hunk of ferrous metal on compass magnet but I think so. Just take a hand compass and hold it close to your car, then move it away...you'll see the effect fall off within a couple feet (and that's a big hunk of metal). In other words, if you are taking a bearing off the stern and steady your hand on top of your outboard, you will have issues with the reading. But if you rest your hand on the other side of the transom, or just lift it up a couple feet, probably no effect. I can think of lots of mounting points with visibility from cockpit that would be fine WRT metal objects on the boat. Being able to do a hand bearing with the same compass I can mount on a fixed clip makes a lot of sense to me for coastal (including inland coastal) navigation. If I've only got a fixed mount compass I have to either have another hand sighting compass with me, or, point the whole boat at my sighting points to get a bearing line.
When you fashion your block consider someday a line, mooring or whatever may have to slide over your block and stern light so be sure it will not catch anything and cause damage to your boat.
Good point, thanks! I will look at that...think it will be OK, it is aft of the cleat and below it as well and the light is that smooth round Perko dome type. cheers, John S. -- John Schinnerer - M.A., Whole Systems Design -------------------------------------------- - Eco-Living - Whole Systems Design Services People - Place - Learning - Integration john@eco-living.net - 510.982.1334 http://eco-living.net http://sociocracyconsulting.com