Transducer and Hull Deadrise

[pwillems]

Hi all. At my upcoming haul out, I will be replacing an ancient in-hull depth transducer with a shiny new through hull one that will work with my new electronics. The issue I'm finding is that it seems all the Raymarine transducers are rated for a maximum hull deadrise of 22° while it seems that my hull has a minimum deadrise of 24°. So I have two options, either I do some fiberglass work on inside and outside the hull to offset the angle or I say too bad, it's only a 2° difference, it is not going to matter much and install it as is.

Surely, this is a common issue on many full keel cruising boats.

Any advice?

[Pete7]

Yep, before you lift out, put the transducer and any plastic widget which varies the angle in a large clear plastic bag filled with water. Put it in the best place you can on the inside of the hull and go and see what the image is like. I am willing to bet you can't tell any difference. After all you hull may lean 2' and you not know about it.

Pete

[puffcard]

If you have a dual frequency xdrc, run it at 50khz not 200khz. The 50khz has a beam width of 10 degrees with a cone of 20 degrees. The 200khz only has a beam width of a couple degrees. Dockside hard to get a good test with the shallow water.

Some good info here, most xdrc are made by Airmar.
http://www.airmartechnology.com/uplo...ide%202009.pdf

[a64pilot]

In all honesty I would glass in the hole and install a shoot thru the hull transducer.
This one can be had to fit any model of sounder I believe as only the cable ends change.
http://www.airmar.com/productdescription.html?id=3

My thru hull Raymarine in my boat only tells depth and quits at about 600’. My P79 shoot thru the hull is connected to my Zeus and is an actual bottom machine and easily works for 1000’ deeper. Seemingly there is no advantage to having a hole in the boat.
On my boat it wasn’t too difficult to find a spot less than 22 degrees, although as Pete has brought up, it works still when the boat is heeled over 20 degrees, so it must not be a hard limit

[pwillems]

Originally Posted by a64pilot

In all honesty I would glass in the hole and install a shoot thru the hull transducer.
This one can be had to fit any model of sounder I believe as only the cable ends change.
Airmar

My thru hull Raymarine in my boat only tells depth and quits at about 600’. My P79 shoot thru the hull is connected to my Zeus and is an actual bottom machine and easily works for 1000’ deeper. Seemingly there is no advantage to having a hole in the boat.
On my boat it wasn’t too difficult to find a spot less than 22 degrees, although as Pete has brought up, it works still when the boat is heeled over 20 degrees, so it must not be a hard limit

Yes, I was looking at the P79 originally, but decide I want speed through water data. So now looking at the DST800.

[a64pilot]

In that case, your combining two holes into one hole, still eliminating a hole, accomplishing the same thing in a different manner.
I don’t have experience with a DST 800, I assume it’s removable like a regular speed paddle wheel?.
I’d try to stay within The 22 degrees, can you make a tapered shim?
I’d just hate to cut a hole, mount the Xducer, launch the boat and then find it doesn’t work as it should, or worse yet, it works but it’s degraded operation.
Sometimes limits are to ensure best operation, not that it won’t work outside of limits, just not as well.

[CarinaPDX]

I would avoid the triducer products. My approach is to shoot through the hull with the P79 smart N2K transducer for depth, mounting it with the puck pointing straight down. Then separately mount a smart N2K speed/temp transducer through the hull. I have exclusively used interior depth transducers for three decades with good results.

While it is possible to buy or make a fairing block for a thru-hull depth sounder I see no benefit, just extra work and another hole.

IIRC the cone angle is the point where the signal is cut in half (-3dB); the signal doesn't just stop there but continues to attenuate. So steeper angles mean weaker signals and hence reduction in maximum depth range. Under sail, at - say - a 15º angle of heel, the signal pointing straight down (relative to earth) from a 22º cone (mounted flat) is actually 4º outside of the cone. That is why it is important to get the puck horizontal.

My old depth sounder on rare occasion read 1000' or more, but in practice thermoclines or other interference will probably limit the max depth to half that or less.

Greg