Depth Offset C34 MK II

[Tom Lanzilli]

I am looking for the approximate offset between the transducer and the bottom of a wing keel.  I have been using -4.3, however, this is obviously wrong because I seem to be plowing through the mud at low tide in certain areas of the channel which leads to my mooring area.  I assume with most C34 MII's the Depth transducers are in the same area.  Would anyone have this handy?

[Stu Jackson]

Tom

The offset can be measured by checking out a brochure and scaling off the distance that your transducer is located below the waterline.  Only you can tell how much above or below the designed waterline your boat actually is sitting, based on how much stuff you have on board.  And not all transducers were installed at the same place on all boats.  Ours is below the V berth, some have them as far aft as just in front of the mast.

Another way to approach this issue is to ignore the attempt to "zero out" the depth (trying to get the depth sounder to read zero when you run out of water).

It's simple, all you do is gently run your boat aground at a place you choose, and read what the depth sounder says.  On our boat, we hit bottom when the sounder reads 4.4.  That's all I need to know (in addition to being aware of charted depth, state of tide, etc.).

Try this:  http://archives.sailboatowners.com/pviewarch.htm?fno=20&sku=2006111081736.40&id=394478&ptl=#2006111124848.94

Part of this discussion, while not specifically mentioned during the threads, is this:  Do I measure the depth of water REMAINING under my keel, or do I measure THE DEPTH OF WATER from the waterline, and then have to subtract the depth of the keel.

I think my way is the simplest, but that's because it works for me.

Your boat, your choice.

[Ron Hill]

Tom : I have a MKI, and I don't know where your transducer is located, but I use 3.5 feet from my transducer face (just in front of the wing to hull joint) to the bottom of the wing. 
Hope this helps.   

[Tom Lanzilli]

Thanks for the advice.  I currently have the offset set to -4.3' (from spec sheet on wing keel).  My transducer is also under the vberth, my current worry is I did run aground last week comming out of a marina at low tide.  The depth finder read .9 which would indicate to me that the depth is 4'12" or 5'.  I know this can not be right so I am thinking of looking for another MKII which is sitting dry dock and do a little measurement.

Thanks again for the help, I am very worried about this situation.

[Joe Kern]

Do most people use actual depth or depth of water under keel?  The thought of sailing around with the depthmeter reading 2 feet just does not feel right.  I have the offset set up so the depthmeter reads actual water depth and alarms at 5 feet.

[Stu Jackson]

HOW TO USE DEPTH SOUNDER INFO

Joe,

In answer to your question, I suggest you read the referenced post in my last message, which I posted in anticipation of your question.

[Joe Kern]

Yep.  Understand the issue, just wanted to see what others did. 

As with most things there are good arguments for the various ways of doing it.  In 4 days I will be in the Bahamas and will want to know the actual water depth.  I expect a few sand bumps here and there, but as long as I stay away from the coral I should be ok.

[Ron Hill]

Tom : The 4'3" depth is from the water line to the bottom of the wing.  Your transducer is in the hull below the water line, that's why I suggested 3'5" as an offset. 
A Thought.