Transducer placement

C

ctort

New member
I am outfitting our new Cdory 19 and had several questions:

- where the bast spot is to place the depth/fishfinder transducer (the type that is placed on the floor and shoots the beam through the hull...I did not want to penetrate the hull)
- storage, rod holder suggestions and ideas

Many thanks,

Ctort
 
ctort-

The hull of the C-Dorys is cored, meaning that it has a layer of little 1" square balsa wood blocks between the outer and inner glass layers to build up structural strength by increasing the thickness of the laminate.

As such, sound waves cannot be transmitted through the hull, unless one is willing to drill out a section of the inner layer, dig out the balsa, and replace it with solid resin to render the resulting solid hull transparent to the sound waves from the transducer. This is a little scary for most!

Most folks therefore mount the transducer(s) to the outer end of the transom. In order to reduce the number of holes, a "transducer mounting board" is often used.

This is a piece of plastic (either Starboard or HDPE (high density polyethelene) (cutting board material) that is screwed to the transom in order to minimize the total number of screws placed into the hull. Once it is mounted, transducers can be replaced, a second one added, other hardware mounted, etc. Look up "transducer mounting board" in our Search engine.

The other possible alternative would be to mount the transducer on one of the trim tab plates. I know Red Fox has done this, mounting it within a hole cut into the plate to make it flush, but I'm not aware of any problems or cautions that might be involved.

One has to be careful not to get extraneous echos from surrounding underwater structures when mounting transducers. Also, it is important to get good, solid water flow at speed w/o a lot of air bubbles or extra turbulence which can cause problems with transducer performance.

****

The placement of rod holders depends a lot on what kind of fishing you'll be doing, and whether you'll be using downriggers, etc.

Rod storage can be done by adding "rocket launchers" to a radar arch, by adding a stand up rack on the starboard side of the rear of the bulkhead (side w/o the open door folded back), or by mounting them on the top of the roof inside the cabin (less common).

Tyboo has designed a great rack and cover for the bulkhead mount that you can see here (link comming after access to photo albums is fixed).

I'm sure others will add to this discussion soon. Congratulations on the new boat, welcome aboard the C-Brat ship, and good luck!

Joe.
 
I just purchased a very nice 1000W thru-hull transducer to go with my new Furuno fishfinder. Because my C-Dory does not have the typical space seen on most boats between the cockpit floor and bilge, the only possible place that I can actually mount this transducer will be in the space between the gas tanks just forward of the transom. Would then have to build some sort of box over the top of the transducer to protect the portion of it sticking above the cockpit floor. My other option will be to do what a lot of people do here in Hawaii with their transducers, that is, mount it on the end of a stainless steel pole which will be mounted off the transom on a sort-of swiveling mount that allows me to pull the transducer up when trailering my boat. Should be doing this within the next month and will post the results & pics on the website when done.

Bill S.
Big Island, HI
 
On my sailboat, I had a depth sounder with a through hull transducer. For journey on, I got an Interphase depth sounder with a transom mount. Put the transducer on a piece of channel bolted to the transom, between the outboard and the trim tab, port side as recommended. The transducer sticks just below the hull.

Works great, even up to 20 knts. Looks forward, finds fish, and will tell me when I'm going aground.

Boris
 
My new transducer is the Furuno 526T-HDD 1000Watt(W) Broadband Bronze Thru-Hull Transducer with Temp. to go with the Furuno BBFF1 Network Sounder. I believe that it is the equivalent to the Airmar 256 or 258. I wanted to get a really good 1000W transducer because here in Hawaii if one is going to bottomfish, you have to be able to see down to 150 to 200 fathoms. Otherwise, I think that a 500W to 700W transducer would be adequate. My sounder actually gives the choice of running it at 600W or 1000W, so I think that I will probably end up just running at 600W when I am not bottomfishing, since 1000W will be a serious drain on my batteries.

Bill S.
Big Island, HI
 
I have a SiTex color sounder...with a bronze through hull transducer...I mounted the transducer in the only spot that I thought would work...but I was wrong.... I mounted it between the fuel tanks near the drain plug...where the hull is not doubled.... but what I found was the keel when going at any speed makes bubbles in that area and I get lots of distortion (noise) at any speed..

One of the things I did was to buy a fairing block to move the transducer about an inch lower...and that helped lots...but it still looses it's signal above about 10 knots...so now I am going to make another shim out of starboard to lower the transducer another 3/4 inch deeper... (the shaft of the transducer is about 4" long) ....hopefully that will put the transducer deep enough so the noise from the keel will not bother it..

The better idea is to have a transom mounted transducer mounted out by the trim tabs...less noise from the keel.

Joel
SEA3PO
 
Capt'n Bill-

The wattage rating of the depth sounder is measured in PEAK wattage, meaning that the signal is equivalent to 600 or 1000 watts at the peak transmission of the sound signal, but that burst is only on for a fraction of the time (the rest of the time the sounder is listening for echoes), so the device doesn't consume anything like 1000 watts.

Look at your owners manual and it will tell you how many amps the device draws. Multiply the amps by the volts, and you'll get the real wattage.

For example: 3 amps x 12 volts = 36 watts.

And 3 amps on your two 90 amp hour batteries would have to be on for a lot of hours to run them down.
90 x 2 = 180

180 x 65% = 120 usable amp hours

120 amp hours divided by 3 = 40 hours. (to run the battery down to 65% of its full charge.)

HTH, Joe.
 
On my tug...I installed the Interphase forward looking sonar....it's kinda a disappointment... maybe if it was in color it would work better, but even though it has dual screens it really does not give much useful information.....I once had a Hummingbird 3-D sounder that worked much better...it was not forward looking and so everything was kinda backwards but at least you knew what the bottom looked like in shape...if they made that in color it would be really nice...(to show the bottom hardness) Interphase now has a sounder that runs through your personal computer that has much better definition...but kinda pricey.

Joel
SEA3PO
 
Thanks, Joel. I will try to find that on their site. John Maybe that is because you operate in such deep water? Does it fail to warn of shallows ahead?
 
I just finished making a lowering block to add to the transducer fairing block.... the bottom of the transducer was originally 1" off the bottom of the hull....and that would loose signal at almost any speed over idle...then I added a 2" fairing block...so the bottom of the transducer was 3" from the hull surface...but still got bubbles from the keel...it would work up to about 10mph fine,...and on up to 18 but at speed it would often clutter up from bubbles (turbulence).... NOW with my 1"
Starboard spacer added to the fairing block the bottom of the transducer will be 4" from the bottom of the boat....should be well clear of keel turbulence...and in clear water...(I hope)...we'll see...We are leaving for the Delta cruise on Tuesday and should be able to give it a real test...

Joel
SEA3PO
 
I love the Interphase depth sounder. I know I don't have a 6" keel now, and I'm not on the East Coast, but I still dearly want to know what is ahead. On my boat, it puts out good info, in black and light green, but so far it's good info. I've run it up to 20 knts, with good readings. At ~25 knts, the transduce mounting unloads, and pops up. I just slow down and push it back down.

I'm happy.

boris
 
Yes...I do admit it is nice to see what's coming up....the amount of forward "look" depends on how deep the water is...... in water less than 40' it is only looking forward two boat lengths ahead...which is fine...I would like to see it in the ocean where the water is deep.... maybe someday I will trade it with my color sounder on the C-Dory ....
I use a sounder to locate things on the bottom... usually I can tell what they are by the squareness of the image and the hardness compared to what the bottom is made up of... so the Interphase is not what I need on the tug...if I had the $$$ I would sure look at that model that runs using a lap top computer...it looks really neat.

Joel
SEA3PO
 
Wow - two others with the interphase forward looking sonar! I thought I was the only one willing to drop about $1k on that. I must admit, I'm not too happy with it. Mine throws static on the radio and the definition on the bottom is not near what I had hoped for. While I can spot fish, I never see the nice arc that one sees on most other finders. Any of you other two have these problems?

Roger
 
Hey Roger.... Yep there are other folks out here that bought that junk too... I don't fish so I don't notice much about what those critters look like... what I am looking at is the bottom...looking for structure..for diving....it barely does that... the definition is poor...I see the new models are available in color.... But if I were going to buy another I think I would go back to the Hummingbird 3-D sonar units...I would love to have a real sonar unit... like I used in the Navy.... now thats detail..

Joel
SEA3PO
 
Many thanks for all the advice and comments. From the replies, I am assuming the transom mount is the most typical/practical place for mounting transducers on Cdories.

How and where did you run the wire into the boat?

Thanks again CBrats !

- Ctort
 
Roger, my old Interphase Probe caused radio static when the line from the transducer was tied adjacent to the radio antenna cord. I re-ran the Interphase cord to stand by itself and the radio static went away. I had the Probe on my old houseboat for years and became accustomed to easily trolling next to shallow shelves without fear of running aground by using the forward scanning function. I mainly purchased it to help in finding overboard victims withou having to run directly over them with standard transducers.

The neatest hi-def thing I have seen in the catalogs is the Hummingbird side-scan which purportedly will give photographic quality pics of bottom structures. The ads show neat 'photos' of a sunken dam and fish swimming over it. I bet something like this would work well for salvage..... if it does what the ads imply. Anybody tried one of these yet? John
 
SEA3PO":fqezzit1 said:
I would love to have a real sonar unit... like I used in the Navy.... now thats detail..
Joel
SEA3PO
Click to expand...

Hey Joel, REAL sonars are passive, can tell the difference between a whale fart and those durn "carpenter fish," and can hear those ASW type sonars braying from 40 miles away! :lol:

Seriously, Ctort on a C-22 it's easy to route the cable straight up, over the transom, then into that big cable bundle, through the transom boot, and up through the present wire run. I have a stern photo in the "Jenny B" album that shows what I did, most everyone is similar. The Airmar P66 transducer kit even has the right size cable clamps. Save the clamshells for something else.

Don
 
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