Notices

Tru-hull ducer ?

Old 10-16-2011, 05:50 AM
  #1  
Senior Member
Thread Starter
 
Join Date: Jul 2009
Location: Peoples Republic of New Jersey
Posts: 6,783
Default Tru-hull ducer ?

Is there any difference between a flush mount ducer like the b20 vs one with a fairing block ?
jerseysportfisher is offline  
Old 10-16-2011, 06:19 AM
  #2  
Admirals Club Admiral's Club Member
THT sponsor
Marine Advertiser
 
Join Date: Oct 2009
Posts: 21,746
Default

To answer your question:
The transducer element itself can be exactly the same but depending upon the size of the boat, performance can be different.
Flush mounted transducers are recommended on boats under 30'. (See note below)
A fairing mount can be use on almost any size but is not recommend on a trailered boat but can be used depending on the bunk configuration.


Transducers of the same element can be mounted in many different configurations.
For example:
The Airmar P66, P79, B60 and B744 all have the same single element and sonar paramaters.
They all have a different mounting styles which does affect the sonars performance.
The P66 is a transom, the P79 a in hull, the B60 a through the hull flush mount, the B744 a fairing mount.




A flush mounted transducer is excellent for trailered boats and its placement in cleaner water than a transom mounted produces less noise in the sonar signal.
Flush mounted transducers are not recommended on boats over 30' because the boundary layer of the vessel will cause added pressure on the transducers internal elements thus affecting its performance. *
On boats over 30' a fairing block is recommended.




A fairing mount has dual purpose.
Years ago many boats used the thru hull stem transducers but if not properly sealed they tended to leak...and they was difficult to use then on areas of deadrise more than 10 degrees. That is because if mounted directly to the hull the transducer would not be pointing directly downward.

So they started using a fairing block because it provided a seal and could be shaped to conform to the hull deadrise but still have the transducer shooting directly downward.
Also, it was found out it improved the transducers ability to track the bottom in deep water and at high speeds by minimizing aerated water flowing over the transducers face by mounting it deeper in the water.




* Note on flush mounted transducers on larger boats.

The process of converting sound waves into electrical pulses and vice versa is called transduction...thus transducer.

The internal arrangement of the piezoceramic element (Crystal) with their positive and negative poles lying in the same direction is the key element.

Pulses of current from the echo sounder activate the crystal element. This is normally an AC current, and as the current changes direction the transducers elements will expand when a positive voltage is applied and contract when a negative voltage is applied.
This expansion and contraction changes the electrical pulses into sound waves.
This is the sound pulse that is sent out from the sonar system.

When a target echo from these sound waves returns to the transducer the pressure of the sound wave will act on the crystal element and produce a very small voltage as the element expands and contracts with each cycle of the return sound wave.

If a flush mounted transducer is mounted a very large boat over 30' the boundary layer caused by the mass of the boat could produce added pressure on these internal element thus giving false sonar readings...this is why a flush mount is not recommended on larger boats over 30'.

Last edited by semperfifishing; 10-16-2011 at 05:50 PM.
semperfifishing is offline  
Old 10-16-2011, 07:09 AM
  #3  
Senior Member
Thread Starter
 
Join Date: Jul 2009
Location: Peoples Republic of New Jersey
Posts: 6,783
Default

interesting thanx for the info. So in reality, as long as both are in the laminar flow, with no turbulence they should both equally perform the same
jerseysportfisher is offline  
Old 10-16-2011, 07:23 AM
  #4  
Admirals Club Admiral's Club Member
THT sponsor
Marine Advertiser
 
Join Date: Oct 2009
Posts: 21,746
Default

The fairing mount "could" perform slightly better at speed and for deeper bottom tracking.

(Sorry for the long reply above but many times others are looking at sonar and transducer information for the first time and your question was a very good one.)

What is the reason you are asking about these two?
semperfifishing is offline  
Old 10-16-2011, 08:00 AM
  #5  
Senior Member
Thread Starter
 
Join Date: Jul 2009
Location: Peoples Republic of New Jersey
Posts: 6,783
Default

new to me boat has 3 fairing block and alot of other underwater apendages that need to go. They all seem to loose bottom at anything over 10knts anyway, so i'd rather llose the drag.
jerseysportfisher is offline  
Old 10-16-2011, 05:30 PM
  #6  
Admirals Club Admiral's Club Member
 
Join Date: Feb 2010
Location: Boynton Beach, FL
Posts: 1,826
Default

I went with the fairing block on my 27ft boat that goes on a trailer. I did this because I wanted to mark bottom well at speeds and b/c I mostly use it in 1500ft plus. I have never been on a boat with either a shoot thru or flush mount that marked very well at 30 knts.

Good info Semper, as always.
laythewood is offline  

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