Depth Sounder Installation

waternwaves · Post by **waternwaves** » Thu Feb 10, 2005 10:23 pm

Looking at those numbers for peel and shear.....

and thje vendor not describing them per particular ASTM tests....

and seeing that the numbers are lower than wood to fiberglass or pretty much epoxy to anything.... and the adhesive stays flexible...it is not a good candidate for ultrasonics...... it also is a poor material to shoot an ultrasonic beam through... A better choice... not as strong a material, but accoustically a better choice, would be stryene board, and a few more compatible adhesives.....

mtc · Post by **mtc** » Sun Mar 27, 2005 6:50 am

Bob,

How did your transom mounted transducer work out?

Michael

Bob Zoobricke · Post by **Bob Zoobricke** » Tue Mar 29, 2005 7:50 pm

I did ok, used a piece of 3/4 exterior plywood, expoxyed it to the transom then covered the balance of the plywood with epoxy, when dry I mounted the transducer/temp/speed sensors to the plywood ran the wiring up and drilled a hole for the wiring. looks good time will tell.

mtc · Post by **mtc** » Wed Mar 30, 2005 4:39 am

What epoxy did you use?

nemo · Post by **nemo** » Wed Mar 30, 2005 9:07 am

Blue Water Yachts pointed out the spot to me where the transducer should be mounted on an M transom (on starboard side between outboard and swim ladder). They said that this is over the ballast tank, so although I don't care if it leaks there, I did use the sealer they recommended. Seems to work fine so far.

Here's a picture of the transducer mounting..
http://www.brownz.com/transducer_2.jpg

And the Raymarine ds400x unit..
http://www.brownz.com/instruments-2.jpg
http://www.brownz.com/finder_wires_2.jpg

tidalwave · Post by **tidalwave** » Wed Mar 30, 2005 10:43 am

I have a 'shoot-thru-the-hull' transducer and am trying to figure
out where to put the unit.
It is very short in height (about two inches)...so it would fit underneath
most of my cabin floor.
Here are some locations I am contemplating:
1) In the port locker just in front of the daggerboard slot
It would give me some 'advanced' warning about shoaling rather
than having it attached to the transom.
Would it encounter turbulence just in front of the board?
I know behind the board would not work.
2) in the port locker adjacent to the cabin ladder
It is slightly off the center line...but not on the water ballast tank.
3) in the stern 'drain' area behind the aft bunks
I wouldn't be able to 'see' what the depth is at the front of the M.

Please comment about these interior locations...any other place some one
has installed a 'thru-hull'?

The manufacturer recommends seating the bottom and sides of the transducer in epoxy...I was thinking of using plumbers putty-epoxy...
any positive or negative comments?

Frank C · Post by **Frank C** » Thu Mar 31, 2005 12:56 am

This isn't intended to be critical - simply pragmatic. Depth sounders report the TREND of depth changes, not instantaneous examples of an outcropping that's going to pierce your hull.

Nobody will ever avoid an underwater obstacle by using the depth sounder for advance warning. Consider this ....

1. The transducer must be at mid-hull or aft, or it won't work at speed.
2. Therefore, we're debating a point at mid-hull or transom, a difference of 13 feet.
3. At a speed of only 3 knots, your boat is moving 5 feet per second
(..... and I can't remember when I've _ever_ motored at just 3 knots).
4. Your advance warning is 2.5 seconds (max), likely much, much less.
5. BUT, TAKING ADVANTAGE DEMANDS THAT YOUR EYES NEVER LEAVE THE SOUNDER.
6. Even if your head is in the sounder, YOU CANNOT STOP THE BOAT, or even change course, in that 2 seconds, even if just idling.

So, the only real determinants of where to mount a transducer are reliablilty of readings, and inconvenience of transom mounting. Honestly - there's simply zero practical "timing advantage" to placement of the 'ducer.

Depths can change more rapidly than the boat can be maneuvered, but fortunately we can rely on the the trend. When motoring and the depth drops to 5 feet, and trending less - it's time to chop the throttle! At this point I'd probably be steering to a a watch on the bow, not relying on the sounder, unless following a charted channel.

mtc · Post by **mtc** » Thu Mar 31, 2005 2:51 pm

Frank,

You didn't mention the potential damage to the plywood in the transom resulting from the trans mounting. Is that because you feel that it is not that big of a risk properly mounted and sealed?

I'm going to develop a hinge mounted unit that is secured to the transom above water line that can hinge up and out of the way for trailering and boarding from the water.

I can see it in my head, but just need to go out into the garage and do the mod.

Michael

richandlori · Post by **richandlori** » Thu Mar 31, 2005 8:40 pm

I have an M and have spent lots of quality time crawling around deep aft in the rear bunk and I could be wrong, but I do not think there is ANY plywood in the transum of the 26M. It all looks like Glass to me? But I could be wrong!

Rich

Frank C · Post by **Frank C** » Thu Mar 31, 2005 8:44 pm

Michael,

I cannot picture it either. I know my dealer originally installed the sounder to port and paddle wheel to stb of my outboard. IMO, those screws into the transom are the least of risks (but then my boat is dry-stored).

Not sure if the lower motor mount is in the water? ... if so, much greater risk, eh? For that matter, not sure the 'ducer screws are in the water?? ON balance tho, I think I'd like to TRY the hinged starboard. (Not sure HOW to stabilize it to remain vertical in the water? - probably a thumbscrew into the transom ... LOL!). Water speed is definitely useful, temp is handy, depth reporting was most reliable and consistent - seems best of all solutions, IMO.

Frank C · Post by **Frank C** » Thu Mar 31, 2005 8:46 pm

Rich,

I thought so too - no plywood in the transom. I even posted that recently, but it was from hearsay.

New hearsay from Capt Jim, the Mac dealer in Annapolis. He just posted to Sailnet's list server that THERE IS plywood in the transom of the 26X. Go figure.

mtc · Post by **mtc** » Fri Apr 01, 2005 3:22 am

Hmmm, . . .

Plywood in the transom, that would be the most cost effective way to build-up the bulkhead I'd imagine. Could be all glass, though. I'll do some core sampling to see and let you all know.

I was planning to stabilize the two hinged pieces with a sliding lock-type deadbolt arrangement that once down, the bolt would move into place and prevent the lower half from folding up. Ultimately, I'll get some cannon plugs or something like that to arrange a quick disco because that transducer (triducer, posh, posh) is pricy and too easy to cream with one bad oversight beaching or trailering.

By the way, I just found the e-store www.ahoycaptain.com where the Plastimo Contest 101 is sold for $147.36; a mere $78 under WM price!!

What's that, a 35% savings???

One's gotta shop.

Michael

Catigale · Post by **Catigale** » Fri Apr 01, 2005 3:42 am

Frank - your post on the limitations of depth sounders for depth safety was excellent.

While it is less of an issue on our relatively slow speed Macs, 20 mph is pretty fast to hit a hard grounding, its likely you will get hurt.

My favourite are the guys in the big powerboats on the Hudson who drag down the river at 45 mph (daytime speed limit in NY inland) and say "I have depths on my plotter..."

Imagine hitting someones chart plotter mistake at 45 mph....not to mention trees, sofas, and remains of Jimmy Hoffa

An inland river is a living, breathing thing and depths change every week, month, and season...

Kudos to Admiral Frank....use your depth sounder for TRENDS

MacGregorSailors.com

MacGregorSailors.com

Depth Sounder Installation

Where to place 'thru-hull' transducer on 26M