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Tomcat transom transducer placement

 
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JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Sun Aug 19, 2018 8:28 am    Post subject: Tomcat transom transducer placement Reply with quote

Where would the best placement be for a large multi-function transducer, GT51 and the panoptix PS21 on the back of a TC 255?

I like Dr. Bob's transom saver, but I'm also reading several articles on "transducer saving" too.
There are several adjustable aluminum brackets that clamp onto the gunwale/transom with an arm to raise and lower the transducer.
Has anyone used these, and if so, where would be the best place to mount one on a Tomcat?

If we just attach a couple of starboard transom savers for traditional mounting, is there an ideal position on the profile for mounting in an area of least turbulence/greatest water contact?
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jkidd



Joined: 23 Oct 2006
Posts: 1609
City/Region: Northern, Utah
State or Province: UT
C-Dory Year: 2007
C-Dory Model: 22 Cruiser
Vessel Name: Voyager
Photos: Voyager (JK)
PostPosted: Sun Aug 19, 2018 9:20 am    Post subject: Reply with quote

They don't recommend between the motors or in front of the props including the swing when your in a turn. You shouldn't mount them behind a strake or behind something that will cause a turbulent. So it can be challenge to find a good spot. I'd say some where close to the trim tabs on a piece of Starboard. As far adjustable it should work as long as your going slow I wouldn't do it at plane. Maybe someone has some pictures of the stearn of a Tomcat not sure how much room there is on the back of one. Might have put some on each side.
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thataway



Joined: 02 Nov 2003
Posts: 20778
City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
PostPosted: Sun Aug 19, 2018 1:28 pm    Post subject: Reply with quote

You want the transducers on the outboard side of the prop which rotates away from that area: the area of least turbulence. I have standard transducers on the Starboard hull of my Caracal Cat, and the Tom Cat when I owned it. Both hold the bottom well at speed. Properly set up (that is with the counter rotating prop on the Starboard side--the reverse of what is done with the standard monohull), either hull will work.

The Panoptic 21 is another story. Basically these have to see "Forward"--and were primarily designed for putting on trolling motors, so you could have the transducer on the front of the boat. The "beam" can then be rotated in the direction of your casting.

The installation manual of the 21 TM (Transom Mount) states:

Quote:
Poor transducer location may result in poor transducer performance or impact the handling of the boat.

The transducer should not be mounted in a location where it might be jarred when launching, hauling, or storing.

The transducer should not be mounted behind strakes, struts, fittings, water intake or discharge ports, in-hull transducers, or anything that creates air bubbles or causes the water to become turbulent. Turbulent water may interfere with the sonar beam.

The transducer must be mounted with the transducer face submerged and facing forward. The transducer shape requires a larger surface area to be submerged than a typical transom-mounted transducer. The large submerged surface area creates drag that can impact the boat's handling and top speed, ranging from a negligible drag to unacceptable drag. You may need to adjust your boat's trim tabs if the transducer is not mounted in the center of the transom. For optimal results, the transducer should be mounted as close to the center line as possible.

When operating at speeds greater than 12.9 km/hr (8 mph), the performance of the transducer is limited, the bottom return is diminished, and the depth information and alarm may not provide warnings for potential shallow depth areas.

The transducer has an effective forward range of between five and eight times the depth of the water. For example, in 3 m (10 ft.) of water, the effective forward range is between 15 and 24 m (between 50 and 80 ft.). Water conditions and bottom conditions affect the actual range.


The reality is that you are not going to "see" items such as semi submerged logs, or items on the surface. Wind chop and waves may impact the images.

The unit is limited to a multiple of the depth of the water, so in 4 feet of water, it may be 20 to 32 feet--the Tom Cat from transom to forward waterline is about 22 feet!

There is a valid reason that, although forward looking sonars have been available for the commercial and high end recreational market for a long time, but they are retractable into the hull transducers which extended a significant distance down into the water. (Westmar and Furuno were the primary units)

Using a transducer bracket which slides up and down on the transom is a great idea--but....there is a problem--the outboard bracket goes across the entire transom. One could work around that, but I wonder how satisfactory this will be? You would have to either have a remote mechanism for lowering and retrieving the bracket/Transom mount, or manually go all of the way to the motor bracket. The physics may be a problem also. The slide up and down bracket usually is on a conventional transom, where the lower part of the mount is only a few inches at the most from the lower edge of the transom. In the Tom Cat, it will be secured 20" to 25" from the outboard bracket and there will be turbulence of the bracket body, and cat hull in front of it--I suspect it may not work well.

Side scan may also be limited with a cat, unless you use two transducers--I would suggest that unless you are a die hard fisherman, that you not use this feature. The down scan should work fine.

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Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL
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jkidd



Joined: 23 Oct 2006
Posts: 1609
City/Region: Northern, Utah
State or Province: UT
C-Dory Year: 2007
C-Dory Model: 22 Cruiser
Vessel Name: Voyager
Photos: Voyager (JK)
PostPosted: Sun Aug 19, 2018 4:38 pm    Post subject: Reply with quote

Looks like you can buy a Min Kota transom bracket for $45 and a replacement shaft for $50 then mount the PS 21 with the trolling mount. Then you will be able to raise and lower the transducer and aim it as well.
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JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Sun Aug 19, 2018 5:22 pm    Post subject: Reply with quote

jkidd wrote:
Looks like you can buy a Min Kota transom bracket for $45 and a replacement shaft for $50 then mount the PS 21 with the trolling mount. Then you will be able to raise and lower the transducer and aim it as well.

After Dr. Bob's post I removed the PS 21 from the dealer quote, and figured I'd fabricate something for the PS 31 like what you described as a future upgrade.
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jkidd



Joined: 23 Oct 2006
Posts: 1609
City/Region: Northern, Utah
State or Province: UT
C-Dory Year: 2007
C-Dory Model: 22 Cruiser
Vessel Name: Voyager
Photos: Voyager (JK)
PostPosted: Sun Aug 19, 2018 5:43 pm    Post subject: Reply with quote

Sounds good I think I would look at the LVS 32 instead of the PS 31 when your ready.
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thataway



Joined: 02 Nov 2003
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City/Region: Pensacola
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C-Dory Model: 25 Cruiser
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Photos: Thataway
PostPosted: Sun Aug 19, 2018 7:46 pm    Post subject: Reply with quote

Certainly a great idea to use the transom mount and trolling motor shaft--but if you are going to that extreme, why not put it in the front of the boat? Granted you have to have a mount--but securing it along side the anchor roller would be a possibility---maybe a little easier to walk back and go onto the outboard platform--vs reaching out from the foredeck hatch to lower it. But forward you will have a much better "view"--without any hull or turbulence artifact....

How practical is all of this? I never had a problem with a dozen trips to Lake Powell. Never had a problem in the shoal water around Pensacola and the entire Florida coast, including with sailboats and trawlers. Touched once in Alaska with the 6' draft of the Cal 46 and also a "spire" off the coast of Turkey (uncharted) where I did hang up for a few minutes with 7' draft of the 62 foot ketch. I did do damage to the skeg of an outboard on a RIB in AK, but I was traveling at 25 knots at the time--and didn't have a chart or chart plotter--dumb mistake on my part. These are the "Groundings" in over 65 years and over 250,000 miles...

A friend of mine has a 56' Carver, and backed into to a dock in Decatur, , Alabama and there was a "strut" of some type between the fingers about 40"' down. He did over $20,000 damage to props and shafts (650 HP each engine, which were at an idle speed.) The marina did not know that the brace or strut was there. Would have an item like the Panoptic helped? Well, yes it might have, if he had it pointing backward--but he would have to have two units--one aft of the props & rudders, pointed aft, and one forward of the shafts pointed forward--plus he would have to be able to retract them when at speed!

I think they are great for fishing--and some boats for collision avoidance under ideal conditions--but I still wonder if they are ready for prime time for the C Dory?
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JMacLeod



Joined: 26 Jun 2018
Posts: 173
City/Region: Stuart
State or Province: FL
C-Dory Year: 2018
C-Dory Model: 255 Tomcat
Vessel Name: C-Shalom
Photos: JMacLeod
PostPosted: Sun Aug 19, 2018 11:20 pm    Post subject: Reply with quote

thataway wrote:
--but I still wonder if they are ready for prime time for the C Dory?

Maybe it's from growing up in a "Disney" family, but everytime I read your advice I hear Jiminy Cricket's voice.

Ready for primetime? Practical? Keep us from running around? Probably not.
Coolest new tech on the boat under $1500 for the captain to play with? Maybe.
If it helps the admiral catch a fish? That would probably tip the scales in it's favor.

Either way, final judgement on it's merits has been postponed to sometime in the distant future after the pending AC, genny, solar, davit, rack, handrail, lighting, entertainment, storage, and interior design projects are complete.
Most likely after the next gen of tech comes out rendering the current comparisons obsolete. Rolling Eyes
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