deppth sounder, transducer location

[Tom L.]

I am planing to install a depth sounder. I will be using a transducer that I intend to glue in place on the inside of the hull. Where have you installed the transducer?

The Hawkeye manual says to use slow cure epoxy. Is that what you used? I thought you could use silicone which wouldn't be so permanent. What say all you Sun Cat sailors.

Tom L.

[capt_nemo]

While you are gathering information I'll let you borrow my lead line.

Otherwise, when the centerboard touches OR you start to see the bottom, bear off.

capt_nemo

[Tom L.]

Never been a fan of the lead line especially when beating up a channel. Too much time between soundings. I wouldn't recommend using the board as a sounding method. It would be ok when motoring slowly but not while sailing with any degree of heel. I snapped a CB on my T-37 doing that. The board touched I tacked of course the centerline of the boat went deeper into the water during the tack and a wave just at the wrong time bang. On a Sun Cat it would maybe just bend the board.  I have always used a sounder to get a good average so I know how far out of the channel I can sail before tacking. Very useful in the ICW.
I suppose the board could be used under power in very calm conditions. Upon contact raise the board and head off.

[FireDrill]

Tom'

I was discouraged from using silicone from several sources including the folks at ComPac and at a couple of marine stores.   The big problem is getting rid of air bubles in the adhesive which is why slow cure epoxy is always recommended.  Furthermore, the signal wire is easily bumped and would exert pressure and easily pop a silicone mount especially if it exits the probe horizontally as mine does (My system is a Humminbird 385 Ci).

I mounted mine on the inward most part of the floor inside of the starboard locker, a few inches in front of its large access hatch and as close to the footwell wall as I could find a flat space with no ridges - about an inch - (system is still under winter tarp but could get exact measurements after the snow melts - would you believe it - we still have snow piles and some more forecast)  This position gets it in front of the keel just far enough, is fairly thin fiberglass and points the transducer only a few degrees from vertical. (do the trig, the error is a percent or two in depth)  Further foreward and the hull angle is too steep. (and difficult to prepare properly as well)  I was cautioned to remove the paint from the locker floor where it would be glued and to sand it as smooth as I could.. The fiberglass fabric has quite a texture.  I removed much but not all of it.  I used a vacuum and a damp rag to pick up sawdust to get it very clean.    A slow two part epoxy,was applied to the probe and firmly pressed it in place, placing a spacer between the footwell wall and the probe to keep it from sliding over a raised seem near the wall. I applied a couple of sandbags made from freezer bags to weight it down so it would not move.  If I recall, I waited a couple of minutes to let the epoxy set up a little before sticking  probe in place. I did not want it shifting around from sliding on runny epoxy.  Each epoxy is different so read the instructions carefully and work hard at minimizing air bubbles. (the slow cure helps this)   

Finally I created a type of bumper, shaped like an L,  with the short stem bolted to the inside wall of the under-the-step locker.  The long part of the L reaches out  past the probe and is designed to keep cargo from bumping the probe. The wire runs under it to protect it from accidental tugs 

The sounder has worked quite well for two seasons giving signals to depths well over 50 feet, sometimes nearly 100.  It has weathered one very cold winter- some sub zero days - and still seems locked tight . (will report if it fails this spring)

[Tom L.]

Thanks Don for the information. Sounds like a good location.

Tom L.

[mikew]

Tom, just a tip on transducer location- where ever you decide to install it- you can do a very easy temporary install to try it out. Pick up some "Duck Seal" putty at a local hardware or electrical supply store. This is a grey no-hardening / no-toxic clay-like putty used to seal around cables in electrical boxes. It is dense enough to pass the transducer sound pulse through the hull but can be easy installed and removed to find the best location .
You can work the putty into a 1/2" thick pad and stick it down to the hull and then push the surface of the transducer into it. I used it on my
Cp-16 to find the best location which is in the lazarette area between the cockpit drain tubes. After you find the proper location clean off the
hull and transducer surfaces with a solvent ( alcohol ?) before gluing as the duct-seal leaves a slightly oily film.

Mike

[hoddinr]

Previous Owner Dennis installed our depth transducer in the port locker as far forward as he could.  No, it's not forward of the keel, but it does give you an idea how the bottom is shoaling.

Ron

[Tom L.]

Thanks guys,

Ron, How far off center do you think the transducer is. I am concerned that the side of the  keel may interfere with the transmission.

Mike thanks for that information. I remember reading about something like that now I know what it is. I would think you could actually sail like that for a really complete test.

Finally I was thinking about cutting a 4" dia. hole in the forward end of the berth. There is already a small hole there where the builder injected foam. I was thinking about enlarging that hole to 4" and digging out the foam. I think that would be in front of the keel a few feet.


Tom L.

[hoddinr]

The location is probably 14 - 16 inches off of the center of the boat.  Does seem to give good information though.

Ron