Thursday, August 25, 2011

Knocked up

This is a common sight in many marinas. The "Steel Forks" of the lift snatch your boat out of the water, and place it onto a storage rack, or the ilk. The forks always end up generally in the same place, sort of, and that is the outboard edges of the hull, give or take. Running these machines takes practice, hopefully not too much on your boat, and a lot of skill. There are always signs around dry storage marinas that say something to the tune of, "Make sure your antennas are lowered, and the trim tabs are all the way up." Loosely translated, this means it ain't our fault if you end up with broken, or bent stuff on your boat, or any of the other possible variants such as "Tell it to the judge", "We told you so", and my favorite, "What, you can't read? So given the fact that these huge metal hydraulically operated prongs are going to snatch your boat from its undersides, why would you mount your transducer where the forks can knock them up?

















The  following examples took all of five minutes to find in a high and dry facility, and are all examples of poor transducer installation location choices. Now just to be clear on the subject, there are instructions on how to install a transducer in the box when you buy it. For a transom mounted transducer this is what Airmar has to say in their instructions, "Mount the sensor as close to the centerline (keel) of the boat as possible to ensure the sensor remains in the water when the boat is turning." What a revelation. 
















I think some people must just think they're experts, and don't need to read the instructions. They seem to be often re-written to say something like, "Mount the sensor as far as possible from the centerline (keel) of the boat as to ensure the sensor remains out of the water when the boat is turning, and so the lift truck forks can knock it up."
















So for transom mounted transducers, the rules are simple:

Place it as low as possible on the hull.

Avoid upstream hull protrusions such as intake scoops. (Read more about this here)

The bottom of the transducer must be lower than the hull, not just even with it. I think about a 1/2" if possible to get below the boundary layer turbulence.

Avoid placing the transducer next to trim tabs, and hull strakes.

Try to get it onto the the starboard side if possible.

Oh yeah, take a couple of minutes to read the instructions.

What you can't read? Hire someone who can.

Remember installing the transducer on the hull is the easy part, pulling the wire through the #$#!@&!! boat's hull to the console is often the most difficult part.

You can cut off the connector to pull the cable, despite the manufacturer's wails of anguish, just do a good job of re-splicing at the other end.















A prudent boat owner should have a sample of the fork truck's DNA on hand for the possible paternity suit if their transducer does get knocked up, but practicing safe forking is always advisable. Please contact your attorney for any legal advice.

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