Sonar Transducer Offset R29 Classic

[fishheadbarandgrill]

Anyone know the distance between the transducer and the keel on a R29 Classic? I want to set my offset On my Garmin. I’ve seen some discussion on the R27 but not the R29.

 

[fishheadbarandgrill]

Anyone know the distance between the transducer and the keel on a R29 Classic? I want to set my offset On my Garmin. I’ve seen some discussion on the R27 but not the R29.

Or should I be asking the distance from the transducer the waterline so I can have true depth?

 

[Scottfree]

I measured while on the trailer and applied my best guess and decided it was about 30 inches and set it to 36 inches. Do you really want to split hairs between "oh ****" and crunch? That being said while on the Great Loop I was in negative numbers and alarms ringing ploughing silt in shallow water. Now that we are back in the PNW boating around rocks I like 6 inches to spare.


Good luck, Leon

 

[fishheadbarandgrill]

I measured while on the trailer and applied my best guess and decided it was about 30 inches and set it to 36 inches. Do you really want to split hairs between "oh ****" and crunch? That being said while on the Great Loop I was in negative numbers and alarms ringing ploughing silt in shallow water. Now that we are back in the PNW boating around rocks I like 6 inches to spare.


Good luck, Leon

Thanks Leon. That’s 30” from transducer to keel? What I’d really like is true depth and then using 3’ as my draft. I’d set an alarm at 4.5 feet. That should give a nice safety margin with time to react.

 

[knotflying]

What I would suggest for accuracy is go into shallow water and place a fishing sinker on a line and lower it until it hits bottom. Reach down and hold line at the water line. Pull it up and measure from where you are holding it to the sinker. That will give you the water depth. Now go to your chartplotter and see what you are reading for depth. Go to the Keel offset page on the chartplotter. Now do the math, If you want actual depth add or subtract to get the actual depth reading or if you want distance from under the keel use your draft subtracted from the actual depth and then add or subtract to get the number you need for difference below the keel. As an example:

For distance under keel - Water depth measures 10 feet - Vessel draws 3 feet. You want your offset number to calculate so
you are reading 7 feet on the depth sounder.

For depth of water - Water depth 10 feet - Use an offset number that will give you a depth of 10 feet.

This method, IMO, is most accurate because your boat is most likely loaded the way you will normally have it and weight does make a difference on what you actually draw.

 

[fishheadbarandgrill]

It’s been a while since I asked the question about keel offset. Here’s what I did. I saw that the waterline was resting right where it bisected the engine exhaust outlet. I measured the distance from the hull (where the transducer is located) to the exhaust outlet. I did this from inside the boat. This came to 18”. I did not allow for hull squat at our typical cruising speed of 6-7kts. I’ve been using 18” as an offset (-1.5’ when inputting the value in the chart plotter). I guess I should add 6” or so of squat to that value. When we get to the Keys this winter I’ll do an accurate calculation. Mucky water with mellow bottom in NC.