Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 08-05-2011, 04:35   #46
Certifiable Refitter/Senior Wannbe
Wotname's Avatar

Cruisers Forum Supporter

Join Date: Jan 2008
Location: South of 43 S, Australia
Boat: Van DeStat Super Dogger 31'
Posts: 6,324
Re: True Depth or Depth Under the Hull ?

Originally Posted by doug86 View Post
Obviously, this is a personal choice, ...............

To me, it seems to make the most sense to be able to compare the actual depth as reported on my depth sounder to the charted depths. I think one should be in the habit of thinking of the actual depths rather than how much is under one's keel.

my .02
Originally Posted by wolfaroo View Post
exactly! whichever method you use will either involve a quick sum to get total depth or a quick sum to get clearance under keel.

As many have said before it is purely personal preference... I prefer clearance under keel too because that's the most important number!

If you hate 'math'(well, sums!)... When you are using for navigation you have to add datum+current tide regardless of how your sounder is calibrated so you might as well chuck all the 'math' in together (datum+tide-draft = sounder, and sounder=clearance)

It can be a useful fix line (contour) and is VERY useful in heavy fog.

Happy sailing
Yes, of course it is personal choice but those who say they want to compare the indicated to the charted depth always have (as wolfaroo and some others point out) to do the maths of charted depth plus current tidal stage. Calculating the state of the tide can be difficult in some areas so having to add your draft into the equation surely is not that difficult.

Personally I use depth under the keel as this is the most important number for me and the one that should be crystal clear in an instant. A quick glance at the sounder tells me right away what I need to know.

If I am navigating by charted depths, I always have some time up my sleeve to do the sums of charted depth, datum, current stage of tide and observed depth.

All men dream: but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find it was vanity: but the dreamers of the day are dangereous men, for they may act their dreams with open eyes, to make it possible. T.E. Lawrence
Wotname is offline   Reply With Quote
Old 08-05-2011, 08:50   #47

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 12,083
Re: True Depth or Depth Under the Hull ?

If you're gunkholing or running shallows that frequently shift, depth under the keel is probably what counts because the charted depth is obsolete before the ink dries on the chart.

Of course if you're trying to run a contour or use depth for piloting, depth under the keel isn't as useful as total depth, but if you're in tidal waters, you're going to have to do some simple path to offset your depth from the chart, according to tide state, anyhow. Six of one, half dozen of the other, makes no difference as long as you know just what the numbers are reflecting.

hellosailor is offline   Reply With Quote
Old 09-05-2011, 14:12   #48
Registered User

Join Date: Jul 2008
Location: Marietta, Ga
Boat: Leopard 46
Posts: 35
Images: 1
Re: True Depth or Depth Under the Hull ?

Thanks everyone for your thoughts. Sounds like the "bottom" (sorry couldn't resist) line is know how the equipment is set. A good point was made regarding anchoring and the amount of rode needed particularly since the more shallow the area the more variance you would have and potentially less holding power.
LifeJacket is offline   Reply With Quote
Old 10-05-2011, 13:10   #49
Registered User
knottygurl's Avatar

Join Date: Feb 2011
Location: Picton, ON
Boat: Grampian 26
Posts: 227
Re: True Depth or Depth Under the Hull ?

I have the original depth sounder that just spews the depth from the transducer which i need to add my keel, and I just installed a new one that is hooked to my chartplotter which I set to my keel plus one foot I draw 4'3" so it goes off when I am in water shallower then 5'3", so I know my safe limit at a shoreline lunch.
This way If someone reads the number to me while I am on the bow it will be exact depth under the keel.

knottygurl is offline   Reply With Quote


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
water depth Red44 Atlantic & the Caribbean 23 28-12-2011 20:20
Changing a thru-hull depth sounder in the water SeawindGirl Marine Electronics 15 31-03-2011 15:09
Good non-Through-Hull Depth Sounder unbusted67 Product or Service Reviews & Evaluations 5 24-02-2011 17:11
removing a Depth Sounder Thru Hull Transducer chuck711 Construction, Maintenance & Refit 14 19-02-2007 15:29
Depth Sounder Thru-Hull Alternative? markpj23 Marine Electronics 17 16-05-2006 22:34

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 07:59.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.