So I finally got my new speed/log and depth sounder
up and running.
They are both Nasa brand, Clipper range. I bought them brand new, in the box, on eBay for a fraction of the cost from the local agent. I have the displays fitted in a box on the cabin
The depth sounder
transducer is fitted to, not through, the inside of the hull
, which I was a bit worried whether the signal would get through thehull ok because the hull
is not just GRP, but kevlar & GRP. But it seems to work reasonably well... actually, it goes a bit "loopy" (i.e. intermittent) in deeper water
(say 50' or more), but it works fine in shallow water
, which is where it matters, so I am happy.
The speed log transducer is a standard paddle wheel
type with the through-hull positioned about 15" forward of the frone of the keel
and about 12" starboard of the centreline. This location was chosen for it's accessibility - I only use the log for racing
, and remove the transducer when not in use. The speed displays fine and having calibrated it, seems pretty accurate under motor
. The problem is that under sail, when sailing to windward, it reads about 10% high on one tack and 10% low on the other tack. It seems to me that this must be a result of differences in water flow above and below the keel
when the boat is heeled, and, if this is the case, there is probably nothing I can do about it.
It is particularly frustrating because I can get my speed reasonably accurately from the GPS
, but I like having "thru-water speed" to monitor
the effectivness of sail trim and other small adjustments.
Any thoughts / suggestions (or you can just laugh at me)?