Swap Airmar Depth Transducer and STW Transducer

[dkinzer]

On my 2007 H41AC, the water speed transducer is near the centerline of the boat while the depth transducer is slightly offset to starboard. Because of the hull shape, this results in the depth transducer beaming along the hypotenuse of a triangle rather than directly below the hull. Has anyone swapped the depth transducer and water speed transducer in a similar situation?

I'm being hauled out tomorrow and will be on the hard for about a week. I intend to see if I can swap the transducers while out of the water.

 

[dlochner]

If the transducers are the same diameter it should be an easy swap.

Transducer locations, either depth or speed, are always a compromise. Water does not flow at an even speed over the hull, there are places where is faster and places where it is slower additionally the further the speed transducer is away from the centerline the greater the variation is speed readings from one tack to the other.

Most transducers have an offset range that compensates for the dead rise in a hull. Airmar knows the bows of most hulls are not flat and design their transducers to compensate for it. Check the manual for this information. Additionally, once the boat heels, the "problem" you are trying to resolve appears again. On one tack the reading will be different from the other tack.

Move them if you want, just don't expect a big change in the accuracy of the speed or depth readings.

 

[jssailem]

Those are not that far apart. Yes, there is some difference when the transmission is at an angle rather than vertically down, which can be modified by adjusting the angle of the transducer attached to the hull. Check the transducer data in the manual about angle adjustment.

It is typical to set the depth transducer further from the keel to reduce interference (shadow) from the keel. Also, locating the transducer forward of the keel helps. Sometimes it is not possible. One must consider the real concern about the depth is from 50 feet to the bottom of your keel. The power of the transmission in clear water overcomes the issue of location and angle in most situations.

Note that the signal is not straight down from the hull. It starts as a small cone and expands as it goes deeper. By setting the transducer further from the keel, the constricted cone mostly misses the keel as the signal is propagated through the water.

In this image, you can see a Garmin flush mount transducer that has the angle adjusted to address the angle of the hull.

 

[colemj]

You want your speed on center line, for the reasons described above. A depth sensor is designed to handle up to 10* deadrise, and yours doesn't look more than that. Airmar makes each model of depth transducer with three different tilted elements - 0*, 10*, 20*. Check your specific transducer model to see if it has a tilted element.

You cannot adjust the tilt - only the installation angle of the housing. But you don't want to do this for several reasons.

Are you sure the depth isn't performing correctly where it is currently located? What issue are you having?

Mark