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Hello to all,
I am trying to understand how to install transducers for Depth and Speed.
I understand it should be forward of the keel.
If I drill from outside -> in where will I land on the inside and will I be able to reach the spot to screw the transducers down, and seal them?
Any help would be appreciated.
Thank you,
Roger Savain
C&C 27 Mark I, hull #3
There is a discussion of this topic archived as "transducer location" (see page two of the Forum topics).
Mounting a transducer forward of the keel is a good idea on a later style of hull, with flat and horizontal surfaces forward of the keel (see later C&C's or J-boats, for example). When the hull has a deep v shape, such as is used in the 27, you have to create that flat area - in other words, you have to expend a huge amount of effort to create a fairly large bulge in the hull in what is hydrodynamically the worst location for any disturbance in the waterflow.
Moreover, you have to consider what's inside the boat. Close to the keel, access could only be achieved by turning the head compartment sole into an access plate (and I'm not sure there would be enough room under it). Under the v-berth, you've got a tank in the way (at least on my boat) plus you've got to create a really monstrous bulge for the transducer due to the acute angle formed by the hull. (It also occurs to me that unless you really know what you are doing, you are creating a potential weak spot in the part of the hull that is most stressed in large waves.)
Everyone puts their transducers under the forward dinette seat. It's a good compromise and I've never heard anyone express regret at having done so.
David Weatherston
"Towser", Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
Offline
Thank You,
This is the place where the previous transducer is. however it does not seem to be a thru-hull type.
I am buying a NavMan Multi with 2 transducers.. do you think I can place both under the seat.. if so it is fine with me.
Thanks again,
Roger Savain
C&C 27 Mark I, Hull #3
Certainly there is room for both transducers. My boat had a depth transducer that was immersed in oil in a tube glassed inside the hull (I assume that's what you have). I ground the area smooth again and drilled a new hole next to the speed transducer (which I also replaced).
I can't show you the outside of the hull (at least for a couple of months) but I can send you a photo of my layout inside the boat (which I did when I bought the boat in '97). The speed transducer is mounted flush with the hull, but for the depth transducer, I made a fairing block that cancels out the angle of deadrise in the hull at that point. This ensures that the depth transducer is pointing straight down and giving a fair reading on both tacks.
I made the fairing block out of a plastic material called Starboard. It's shaped sort of like <o> (where the o is the hole for the transducer. I then split the flat shape on a saw to get two pieces, that when installed give the correct angle outside and inside the boat (for security, the retaining ring should lie against a smooth surface all around its circumference).
I drilled the pilot holes from inside the boat, then used a hole saw from outside for the full-size holes. The hole saw made nice neat holes, but it makes a colossal mess, so you want to do it from the outside and wear a mask.
David Weatherston
"Towser", Toronto
C&C 27 Mk IV
David Weatherston
Towser, Toronto
C&C 27 Mk IV
Offline
How thick is the plastic material called Starboard. and do you think it is availabe at West Marine.
Is the fairing block epoxyed to the hull?? how much build up is involved ? How thick?
Roger Savain
C&C 27 Mk I
I _think_ it's available in 1/2", 3/4" and 1". Check http://www.kingplastic.com/. West sells it in their catalogue, but as to individual stores...
You might have better luck if you check out local plastics outlets. There's an industrial supplier near here called Plastic World and they sell something very similar if it isn't actually Starboard. (You're making a fairing block, so perfection is not mandatory - you just want it to be dimensionally stable, easy to work with, waterproof and able to hold bottom paint.
My block is not epoxied on. I coated the mating surface with 3M 5200 and held it mechanically with the transducer while the 5200 set. Five years later, there's no sign that the seam is opening.
How thick? Don't remember. I think I assumed that the inboard side of the block should be at least 1/4" thick so as to be stiff, then measured out the width of the transducer plus an allowance for rounding the edges. Measuring from that point on the hull down to a level that touches the inboard point gives you the thickness of material that will allow you to fit a vertical transducer.
A page on transducer location and installation has been added in the Special Interest section (see the nav bar at left)
David Weatherston
"Towser", Toronto
C&C 27 Mk IV
Last edited by (2003-11-16 02:02:47)
David Weatherston
Towser, Toronto
C&C 27 Mk IV
Offline
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