Go Back  The Hull Truth - Boating and Fishing Forum > BOATING FORUMS > Marine Electronics Forum
Reload this Page >

Transducer/Depth Question for SemperFi or others

Notices
Marine Electronics Forum

Transducer/Depth Question for SemperFi or others

Old 03-01-2012, 06:11 AM
  #1  
Senior Member
Thread Starter
 
Join Date: Mar 2010
Location: Orlando, FL
Posts: 1,546
Received 104 Likes on 50 Posts
Default Transducer/Depth Question for SemperFi or others

I hope someone might have an answer for me...

I have 2 transducers on my boat, an M260 hooked to a GSD22 and a small Airmar P79-235-N2K transducer. Normally, when running in seas 2' to 4', I start to loose depth reading around 35 MPH, due to the step hull nature of the boat on both transducers. I am fine with this and understand it.

I went out this week and the gulf was just absolutely flat. I was running at an easy 50+ MPH cruise speed and had just the P79 transducer on. It held bottom the whole time since the water was so flat. The depth I was running was anywhere from 25' deep to like 9' deep.

Here is my question...due to the speed I was going, since it takes some time for the sound wave to travel down to the bottom and then bounce back and be heard/processed, is the depth accurate? Since I was running in what showed on the the gauge to be 9' deep, but I was going 50 MPH, was it actually shallower? Is there a formula that will compensate depth readings based on speed. Or is the sound still fast enough that 50 MPH wont really change the reading.

I am fine if it changes the reading by a couple of inches due to the speed. But if the 9' was really 6' or something like that, I need to know that the speed can throw the depth reading off that much.

Thanks for any input.
Old 03-01-2012, 06:59 AM
  #2  
Admirals Club Admiral's Club Member
THT sponsor
Marine Advertiser
 
Join Date: Oct 2009
Posts: 23,889
Likes: 0
Received 1,695 Likes on 928 Posts
Default

At a water temp of 50 degrees F. the speed of sound in water is about 4,748 f/sec...or about 3,237 mph.
(Sound travels approximately 5 times faster in water than in air)

And if you boat is travelling at 50 mph it will travel approximately 73 feet in 1 second.
Your boat is not going to outrun sound at only 50 mph in 25' of water.

So your reading will be very accurate...even to the fraction.








But of course if you dump all the beer ,tackle etc to lighten your boat..add a few nice jet engines and get your speed up to a respectable 4000 mph or so.....well, thats a different story.

Last edited by semperfifishing; 03-01-2012 at 07:28 AM.
Old 03-01-2012, 07:01 AM
  #3  
Senior Member
Thread Starter
 
Join Date: Mar 2010
Location: Orlando, FL
Posts: 1,546
Received 104 Likes on 50 Posts
Default

Sounds good, wont worry about it then. I thought it was only like 720 mph...much slower, maybe that is in air. Thanks Gil
Old 03-01-2012, 07:33 AM
  #4  
Admirals Club Admiral's Club Member
THT sponsor
Marine Advertiser
 
Join Date: Oct 2009
Posts: 23,889
Likes: 0
Received 1,695 Likes on 928 Posts
Default

Originally Posted by SaltyG View Post
Sounds good, wont worry about it then. I thought it was only like 720 mph...much slower, maybe that is in air. Thanks Gil
Of course if I am wrong ...
You may run aground, hit some rocks or such and make a real mess of your boat....spill your beer etc.

You could always stop every 100' of so, take lead line soundings to verify depth...and then proceed at speed.
Old 03-01-2012, 11:52 AM
  #5  
Senior Member
Thread Starter
 
Join Date: Mar 2010
Location: Orlando, FL
Posts: 1,546
Received 104 Likes on 50 Posts
Default

I try not to stop until I run out of gas or beer, which ever comes first....

Thanks for the info, I appreciate it.

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 On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.