depth calibration

[George Pyrpiris]

I have a fin keel 1986 and was hoping someone would know what the distance is from the depth fitting to the bottom of the keel.  I wish to recalibrate it to show actual depth from the water line and not from bottom of hull which is on starboard side at front end of the bilge.
thanks
George

[Steve Hansen]

George,

What I ended up doing was taking an old steel tape measure and stuck it down in the water until it hit bottom, then recorded the number off the tape at the top of the water, which gave me the depth to the waterline. Our dock was only 7-8 feet of water. Washed it after to get the salt off.

steve

[Sundance]

My depth gauge is set to 2.3 or 2.4 feet below the waterline.  Seems pretty reasonable.

[Larry Robertie]

The PO did a marvelous job calibrating my depth.  He set it to show -0- at the bottom of the keel.  You might want to consider that.

Sorry i can't actually answer your question, but I suppose a quick dip in the water with the first mate holding a lead line and you checking the depth would work. 

[Stu Jackson]

George, this "philosophical" discussion has been going on all over the Internet and in boating ever since they invented the digital depthsounder.  Some say they want to show 0 when the keel is about to hit.  The other train of thought, one that I find is just as easy, is to run the boat gently aground at a known spot with soft sand and read the sounder.  On mine, it's 4.4 ft.  When I get near there, I KNOW I have zilch under my keel.  If you only have rocks where you live, this won't work.   

Arguments about being able to better monitor tide heights from charts I find unconvincing, because tide changes of from 6 to 12 feet in most of our waters aren't going to be any more easily read if your keel is 5 feet deep and your depthsounder is set at 0 or like mine at 4.4 or any other number.  It's easy to do it in your head, regardless of what method you choose.  And, for years, we lived with lead lines and analog depthsounders.

[Mike Vaccaro]

That location is approximately two feet below the waterline on our 1988, Hull 563.  I'm of the "depth under the keel" school, but most folks are of the "depth at the waterline" mindset to assist in contour navigation.  Ether way, a bit of mental math is involved!

You can then adjust the displayed depth to show either value, by adding the two feet up to the waterline or subtracting the 2 feet to the bottom of a wing keel or 3 feet to the bottom of a fin. 

A lead line (or tape as above) should be used to confirm your adjustment in suitably shallow water. 

Cheers,

Mike