I'd set the depth sounder to read actual depth making it your
responsibility to keep track of board up/board down considerations.

==========================================

On Fri, 27 Aug 2004 11:02:27 +0100, "Phil Stanton"
wrote:
Most people I sail with in the UK set their echo sounder to depth below the
keel. Great idea. Doesn't matter whose boat you are sailing on what the
draft is, if it says 1m then that's the depth of water you have to play
with. Here on the East Coast there is very little water and frequently we
are getting in and out of rivers with 0.2m under the keel.

OK my problem is I have now bought a lifting centreboard boat, "Feeling 39",
draft is 2.3m with centreboard down, 0.7m with centreboard up. Transducer is
0.4m below the waterline. So what do I do. If I set the offset to below the
keel when the board is down (1.9m), and then go into shallow water and have
to raise the centerboard the echo sounder will continue to say "0" in
anything under 2.3m depth.

If, on the other hand, I set the offset to depth under the boat with the
cenreboard up(0.3m), I have to remember to subtract 1.6m to get the depth
under the centreboard if it is down.

The solution would appear to be an echosounder that could show negative
depths. You could then set the offset to below the keel when the board is
down (1.9m), and if you raised the keel and went into shallower water (say
2.0m) the echo sounder would say -0.3m.

Does such an echo sounder exist, or has anyone any observations

Thanks

Phil