Beneteau 34 Depth gauge offset
- Thread starter leonmalmed
- Start date
Don't know for sure, but
http://forums.catalina.sailboatowners.com/showthread.php?p=1038731&highlight=philosophical
http://forums.catalina.sailboatowners.com/showthread.php?p=1038731&highlight=philosophical
The sensor that measures the water depth is located below the surface somewhere on the hull. What is the distance between the water line and the sensor position on a Beneteau 34?
B boats typically have several different keel options so careful about using someone's quick answer. Easiest way was to measure the boat on the hard. Alternatively - quick dive below with a tape measure.
I took our actual measurement and added 6" for safety - but even then I get nervous when we get a reading of 1 foot.
Not sure where you sail but as a last point remember rocks don't follow the contour of the bottom.
If you can find one of your thru-hulls and it has clear-ish hose, you can see the water level in it and measure to the hull for the offset. A sink drain should also have water in it at sea-level. Or, use a spirit level (I think it's called? )
Our 99 361 has a Autohelm tridata and it shows a "depth offset" somewhere in the scrolling thru menu, it can be changed to whatever you want. For us its set to 10 feet which I think is from deck height as we have 6.5 draft plus 4 for the deck height, for anchoring I suppose.... Previous owner set it and I never changed it.
Update: I probably didn't answer your question, I got confused with the offset and the waterline to sensor depth question #2. If I didn't, my apologies and please ignore.
Update: I probably didn't answer your question, I got confused with the offset and the waterline to sensor depth question #2. If I didn't, my apologies and please ignore.
Last edited:
On our 37 I've measured the thru hull at 18" below the waterline. Yours is probably slightly less.
Everyone has a preference for their depth setting. Rather than concern myself with offsets for transducer location or depth below the keel, I chose actual water depth. That seemed to be the easiest. Just dropped in a lead line, and took that measurement from the water level. That way, knowing my draft is 5'6", it is easy to determine when the water is getting too thin. Knowing there could be a lag between the depth reading, bottom contour, and boat speed, we set the shallow warning accordingly. I use an extra foot, The admiral would set it for an extra 30 feet if she had her preference.
Check your owner's manual for draft, and check your instruments to see what they are set for in terms of offset. Your instrument offset could be anything. If your question is what the difference between the waterline and the bottom of the transducer... In my owner's manual, the total draft from waterline is listed as 6.23 ft. for a "Deep keel". Given the quote above, that doesn't seem quite right... And, I think our waterline to bottom of transducer might be more like a foot or a little more. The other possibility is that our 6 ft. keel isn't actually 6 ft. from the bottom of the hull. Anything is possible, and I haven't actually measured the keel...
Our offset is Zero on the instruments, and I've seen a depth reading of less than six feet (maybe 5.75?) and I wasn't noticeably dragging at the time, but maybe it was my thinking about helium that prevented that who knows, and I don't want to do it again.
Back to the "offset" number. According to my instrument manuals, a positive offset would indicate that your instruments are probably reporting a depth measurement from the waterline, and a negative offset would indicate that the measurement is from something like the bottom of the keel or the prop... Zero offset would be depth measured from the bottom of the transducer in the hull.
As said, you can set it for whatever you want. From the factory it will read depth below the transducer. You can set it for depth below the keel, or actual depth of water. I prefer to set mine for actual depth. To set mine I put the boat into a trailer launch well so I had a hard bottom, then measured the depth with a lead line at the transducer location, then set the offset to match. To set to depth below keel you would need the distance from the transducer to the keel bottom, and that's most easily done out of the water.
I don't know why in the world anyone would set the reading from deck height
Maybe it's a catmaran and he plans to turn over?To get the offset of our 331 while it was in the water, I measured the height from the depth sounder (inside the boat) to the deck height. I then went outside and measured the distance from that deck edge to the water. The difference would be the offset.
What I wish I had done this past winter when the boat was on the hard was measure the actual distance from the keel bottom to the actual waterline. Sure I've got the published draft, but inches matter on the Chesapeake!
What I wish I had done this past winter when the boat was on the hard was measure the actual distance from the keel bottom to the actual waterline. Sure I've got the published draft, but inches matter on the Chesapeake!
I don't know, I've seen it say 2.5 feet which made me think there was an offset, our 361 is shoal draft but...I don't know why in the world anyone would set the reading from deck height
It did prompt me look thru the menu for a setting and it was indeed set to 10 feet, maybe it was a round nice number or perhaps a compromise between previous admiral and skipper, like others suggest my admiral prefer to see over 30 and completely ignored my explanation of having an offset....
On some days in some waters I see a flurry of impossibly small depth numbers considering we aren't aground. I chalk this up to the sonar seeing a thermocline.