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Old 26-11-2010, 08:19   #1
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Two Depth Transducers for Multis ?

I am toying with the idea of mounting a 2nd depth transducer in the other hull of our catamaran. And having a second display at the helm.
Reason would mainly be to find the deepest spot when going through shallow passages by observing the depth difference between port and starboard soundings.
Plus avoiding to dry out on a slant surface.
I would like to know experiences and opinions:
- Is this a good idea?
- Who has done this, what are your experiences?
- Do you get interference between the two transducers? Do you need to take different brands, using different sonar frequencies? Is the selectivity when receiving high enough, so that you get no interference?
Thanks,
Jef
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Old 26-11-2010, 08:37   #2
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The only times I have wished for a depth sounder on the other hull is in narrow channels like the ICW or doing the inside route down the Exumas.

If it was free, I would do it, but not worth spending my boat dollars on.

George
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Old 26-11-2010, 08:54   #3
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I see no reason other than cost and another hole in the bottom not to have a second transducer and display on a catamaran. Many times negotiating coral off of Belize I've wished for such. It just hasn't risen to the top of my upgrade list. Exiting a narrow cut from Belize City, I touched bottom (soft, thankfully) with my port hull while my stb depthsounder showed several feel of clearance. I would put the frequency interference question to Raymarine or whatever brand you currently use.
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Old 26-11-2010, 08:57   #4
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Good Idea, cat's are wide enough that you could have significant depth difference when in a narrow channel or even up close to a beach.
-- I have 3 depth sounders on a mono-hull. On the bow is the Interphase scanning sonar depth system. On the starboard beam is the Raymarine ST-60 depth - which refused to read anything more or less than 30 feet for 3 years due to a faulty transducer. I was not going to haul the boat just to replace a faulty transducer and waited until a regular scheduled bottom job.
- - In the meantime I glued an speedboat depthmeter to the portside beam inside the hull. It shoots through 1.5" of FRG and works great. So now that I have fixed the ST-60, I have 3 working.
- - That comes in handy as sometime cavitation or for other strange reasons one or the other midships depthmeters refuses to get a reading.
- - You can Google the inside the hull installations to see how it is done. But basically I had a speedboat transom mount little 0-99ft depthmeter and mounted it by removing the paint and smoothing the FRG inside the hull where I would going to mount it. Then I purchased a PVC cleanout adaptor from a plumbing store and ground it to fit the hull. then epoxied the two together. I cut the screw cap to allow the cable to pass through. Then put the transom transducer into the PVC adaptor, filled it with mineral oil (baby oil); then screwed the cap on to hold the transducer tight to the inside of the hull. System has worked great for over 10 years.
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Old 26-11-2010, 10:26   #5
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If you bought a dual frequency transducer you would not have the same frequency problem. With a cat the transducers may be far enough apart where they do not hear each other in shallow waters, if you think about how the cone widths are narrower in shallow water.
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Old 26-11-2010, 10:28   #6
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I think a spare depth unit is very sensible in a bluewater boat.
Depth information is vital.
I fitted a B&G depth and a Simrad fishfinder on my monohull. The B&G will display both. So I have port and starboard depth displayed if I want.
They are only a foot apart so naturally and reassuringly both read the same, but one will usually read correctly in reverse where the other is effected by the bubbles.
The reason for both, in my case, is redundancy, but on a cat the difference in the readings may be useful.
I have no interference, but I selected the units so they had a different frequency.
Something that will read to 200m + is also handy.
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Old 26-11-2010, 16:22   #7
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I have one in each hull. Raymarine and Furuno, the Ray is depth only on the nav gear and the Furuno is a fishfinder on the chartplotter so the frequencies are different. I did it as much for redundancy as for tight areas.
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Old 26-11-2010, 22:40   #8
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We have three depth sounders on our boat. One on each hull and a handheld sounder. The two hull sounders are both Simrad but are of different frequencies so they won't interfere with each other. The handheld comes in REAL handy for charting out shallow routes and anchorages using the dinghy. Depth sounders are pretty cheap as boat equipment goes and it's always a good idea to have at least one backup to a crucial piece of equipment.
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Old 27-11-2010, 09:05   #9
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When passing through some narrow cuts in the Bahamas we at times use a leadline.........i2f
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Old 27-11-2010, 13:49   #10
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I installed 2 Datamarine sounders in our first cat (one subsequently replaced by an SM Mariner Nav 10), and 2 Raymarine ST60s in our current cat. They don't interfere with each other at all.

I find it VERY useful. You don't have to assume or guess where the deeper water is. Also, as has been mentioned, redundancy.
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Old 30-11-2010, 14:45   #11
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I have a normal Raymarine depth in one hull, and an Echopilot forward looking sonar in the other. They are both 200kHz units, but they don't interfere with each other.
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Old 01-01-2011, 06:12   #12
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I installed a second depth sounder in my cat which has a 7.6 meter beam. Reasons
- for redundancy.Ithink for coastal cruising a backup depth sounder is vital.
- for navigating narrow mangrove channels

One is a tacktick that came with the boat that sometimes suffers from cavitation and when the alarm goes off reading zero metres, it is reassuring to see a nice hunk of water under the other hull that is not cavitating. The other sounder is a fish finder and is helpful to gauge bottom make up.

There is frequency interference at times below 3 metres of water under the hull but when that depth gets less than one metre the tacktick seems to read more often and I get readings back from it and the other as well. Over 3 m, there is no interference. The fish finder reads accurately all the time, so I tend to watch it. With two sounders, I don't need to worry about being stuck in some remote area without a depth sounder.

Having said that, I met a guy in a a home made ?Boldger designed mono that drew 18 inches. He said that he did not install a depth sounder because he could see over the side when it was getting shallow. I suggested that if the water was dirty then he would lose that option and it is noce to know what the bottom depth trend is.
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Old 12-01-2011, 08:48   #13
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Hello, I do have a Raymarine ST 60 depth- with an in-hull transducer- and speed witch is not connected. The deep sounder works good for weeks as long I'm in the marina and don't move, ones in open water it fails after 20 min. It say "LAST". Somethimes it comes on again after houres, somethimes after minutes. Has someone advice please. Best regards. Willy
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Old 12-01-2011, 09:01   #14
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Originally Posted by mbu745 View Post
Hello, I do have a Raymarine ST 60 depth- with an in-hull transducer- and speed witch is not connected. The deep sounder works good for weeks as long I'm in the marina and don't move, ones in open water it fails after 20 min. It say "LAST". Somethimes it comes on again after houres, somethimes after minutes. Has someone advice please. Best regards. Willy
I have the same problem with my st60 I do know a little growth kills it I was thinking a bad transducer ?
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Old 12-01-2011, 09:12   #15
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Originally Posted by mbu745 View Post
Hello, I do have a Raymarine ST 60 depth- with an in-hull transducer- and speed witch is not connected. The deep sounder works good for weeks as long I'm in the marina and don't move, ones in open water it fails after 20 min. It say "LAST". Somethimes it comes on again after houres, somethimes after minutes. Has someone advice please. Best regards. Willy
Has it always worked like that? It could be that underway you're getting aeration or turbulence beneath where it's mounted. Bubbles interfere with the signal. Can you correlate the failure with speed or wave conditions?
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