transducer attachment

Thanks for the helpful responses and the generous offer. I think I'm leaning toward giving the sliding mount a try.

Now, as I ponder my winter projects, I find my OCD symmetry affliction urging me to try mounting the transducer between my twin engines, right on the center line of the boat. (Isn't the thought of that visual balance just irresistible?)

OTOH, the sounder has worked great with the transducer where it's been for 7 years, on the starboard side of the transom, and my neurotic attachment to the "If-it-ain't-broke . . ." principle gives me the heebie-jeebies when I contemplate changing anything.

Has anyone with twin engines on a C-Dory or Venture hull tried center mounting their transducer? Dare I do it?
 
I can't speak to twins (although yes, the symmetry is very appealing!), but I did notice - when I went to mount my transducer - that the instructions recommended to put it on the starboard side of the prop if you can. I guess the effects of the prop make the port side the "bad" semi-circle. So I suppose it's possible that you would get that effect from the starboard engine with the transducer in the center (?).

Will be interesting to hear if other twins folks have good luck with it in the center.
 
To mount my transducer - I used Starboard with 5200, 3 years ago, no screws, 3 months a year in a slip/in the water, 20 below zero in the winter and it's tight as can be. Like Dr. Bob advised, I cut groves in the back of the starboard using a table saw. Then I put a layer of 5200 on the grooved starboard like laying tile, I let the 5200 dry. Then I roughed up the dried 5200 with sand paper and applied another layer of 5200 and applied the starboard to the boat. I clamped it for 24 hours. Works great.

Kevin
 
Sunbeam":18k0y35g said:
I can't speak to twins (although yes, the symmetry is very appealing!), but I did notice - when I went to mount my transducer - that the instructions recommended to put it on the starboard side of the prop if you can. I guess the effects of the prop make the port side the "bad" semi-circle. So I suppose it's possible that you would get that effect from the starboard engine with the transducer in the center (?).

Will be interesting to hear if other twins folks have good luck with it in the center.
Click to expand...

I'll probably stick with the starboard side placement. I've also heard or read of this prop-created disturbance issue. I guess the normal right hand spin of a prop messes more with the water relatively near the surface on the up (left) side than it does on the down (right) side as you face the front of the boat. Makes some sort of intuitive sense to me, but I don't know how significant the effect is, or how much it varies with boat and engine size and hull shape. Maybe in the center, between two engines rotating in the same direction there's some kind of net cancelling effect? Where's a good hydraulic engineer when you need one?

(Aside: Sometimes my symmetry disorder makes me dream of counter-rotating props on my little twin engines. Even when I tell myself that would be a ridiculous, unnecessary and expensive complication requiring more spare props, and even though I know the engines are not going to be symmetrical internally, still . . 8) . . - Good thing there not available.)
 
Yes, the reason that it is recommended to put the transducer on the stb side is because of the down stroke of the blades on the right side of the prop, and less turbulence on that side. In the center, especially with counter rotating props, would be the worse place for the transducer.
 
breausaw":2hjymlad said:
I was going to do the exact same thing to my boat but opted for an in-hull transducer, it has worked great!
Click to expand...

Which transducer did you go with and where did you put it? There is a current thread in the Electronic forum about these, Maybe you can share some details there?



As for the center mounted transducer with twins.. I have mine set up that way. It works ok there (they are both right rotating). I have the stock garmin transducer, maybe a larger transducer would be a problem there.
 
Well, two discoveries from the Furuno site's AIRMAR manuals for installing transducers:

1. Regarding placement of a transducer:

Boat Types
•
Single drive
—Mount a minimum of 15cm (6") beyond the swing radius of the propeller (see Figure 1).
•
Twin drive
—Mount between the drives a minimum of 15cm (6") beyond the swing radius of the propeller.
•
Trim tabs
—Mount inside the trim tab, space permitting.


2. Regarding a sliding mount that can lift the transducer out of the water between uses:

CAUTION:
CHIRP transducer—Always operate the transducer in water. Operating in air will allow the transducer to overheat resulting in failure



First, regarding the placement - I'm pretty happy with the starboard side placement I'm using now, and I don't know how optimal this recommendation may be for twin engines mounted as closely together as they are on a C-Dory or Venture.

Second, regarding a sliding mount - the caution against out-of-water operation is only academic as far as I'm concerned. The warning apparently applies only to CHIRP technology transducers - I guess you really don't want to forget to lower a CHIRP transducer into the water before you turn the sounder on. As far as I know, AIRMAR makes only one transom mount CHIRP transducer (TM 265). I'm looking at either a 258 or 260.

I doubt these discoveries will influence my decisions, but thought others might find the information useful or interesting.
 
Any of the transducers will heat up some when run out of water. The higher the power, the more it will heat up, and more danger of damage to the transducer, but most of the lower power units most likely will not be damaged. The CHIRP runs a number of frequencies--and has to have more heat dissipation.

"Airmar’s B265LH, for instance, includes eight ceramics: A large one, nearly three inches in diameter, handles the high frequency range while a cluster of seven one-inch ceramics handles the lower frequencies.

But there’s more to a CHIRP transducer than high-tech ceramics. It’s a simple fact of life that whenever you pass any kind of energy through anything it gets turned into heat, and a transducer is no different. One old problem that has been brought back to the surface by CHIRP is that the impedance of a transducer—its tendency to oppose the flow of electricity—varies depending on the frequency at which it’s operating. That’s important because if the impedance drops, more power flows through the transducer, making it more likely to overheat and more likely, in the long term, to degrade the piezoelectric characteristics of the ceramic."

Also the CHIRP transom mount cannot be installed as a in the hull mount as a standard transom transducer is.
 
When they recommend mounting the transducer in between twin drives, I wonder if that is because they presume you would not have room to mount to the side (because most twins are further apart?). Maybe the 22/25 don't have room either though - I don't know. Wonder if they would still recommend the center in a case where there was room to go to the starboard side of the starboard engine.

I had a problem with my (new) transducer on Powell. I'd be going along fine (high speed, low speed, rough water, smooth...) and all of a sudden I'd get the digital reading of 2.3' and a shallow water alarm (in all kinds of depths). Sometimes the fishfinder part of the reading would stay at the real reading, and sometimes they would both be at 2.3' Eventually it would fix itself but I could not figure out any consistent reason.

Finally I figured out that it would sometimes "fix" itself if I stopped, reversed relatively hard, then went forward again. But not always.

I had mounted it in the center of the up/down adjustment slots, so tried changing those. Down was no help; up seemed to help slightly. I had also mounted it just the amount they recommend outside the prop circle, but no more (because I was advised that the trim tabs affect it even more than the prop). However, since reversing and then going forward seems to fix it sometimes, I'm thinking of trying moving it further to starboard (away from prop; toward starboard trim tab). The problem occurs just as often at hull speed as on plane, and the depth sounder works great on plane (when it does work), so it doesn't seem to be the usual "lose signal when going fast" problem. I have not yet contacted Airmar.

I removed the core from the after sump, so I could mount a shoot-through-the-hull transducer there, but I like the water temp and speed from the transom mounted one.

Sunbeam

PS: Somewhat in the spirit of the thread: I considered using Weld Mounts to mount the Starboard backing board (I have used them in many other places on the boat), but in one of those "probably a horse apiece" decisions, went another way. I wasn't sure if adhering them to the gelcoat would be strong enough (dependent on the bond of small circles of gelcoat, ultimately), and though I considered removing circles of gelcoat for the WM's, decided not to (although as I said, it was sort of a horse apiece). Anyway, I ultimately removed the transom core from a largish area (behind the gelcoat/fiberglass surface, which only has a smallish hole in it), filled with thickened epoxy, and then drilled and tapped for flat-headed bronze machine screws (that run through the Starboard block). Then I tapped the block for the transducer screws.

PPS: Interesting about not running some transducers out of the water; I had wondered about that (but I just have the P66 triducer, not any kind of CHIRP one).
 
Sunbeam":l1h4pcd3 said:
Maybe the 22/25 don't have room either though - I don't know.
Click to expand...

There's room on the 25. I have twins and my transducer is mounted to the starboard side of my starboard engine, inside of the trim tab. I haven't had an issue with my transducer (currently an Airmar P66 triducer).

I mounted mine on starboard that is screwed in to epoxy-filled holes as well as 5200'd to the hull (dovetail grooves in the starboard).
 
I have wondered about a center mounting for the transducer too. I have twin 40's on a 22 and also trim tabs. My trim tabs are mounted almost to the outboard edge of the hull, right to where the downward curve for the reverse chin starts. The space between the inboard edge of the t-tab and the transducer is only a bout 3" and the space to the starboard outboard leg is only about 6". At cruising speed (15-20 knots) there are times when I loose bottom and in most cases (bottom being 100+ feet) it is not an issue. There are times that is not the case and I have wondered about placing the t-ducer in the center. Read the instruction (to starboard) so have not don anything with it yet. Probably due some modification to the t-tabs first.

I personally like the idea of having the t-ducer placed as a shoot through, and if mine goes out, that is probably the option I will pick. (See George's shoot through mount on KerriOn).

If I was mounting one on the transom, I would consider the center mount if you have the room, (6" space as suggested in the manual instruction"). If I was starting from scratch, I would have more space between the twins,, and have longer t-tabs, (instead of wider), and I think the center mount t-ducer would be perfect.

JMHO.

Harvey
SleepyC :moon

IMGP6699.thumb.jpg
 
After a couple of hours of testing, I can say the new mount works great. I get steady good readings at all speeds, right up to WOT. So far I've only run in very calm conditions. It is really nice to pull the transducer out of the water when I'm back at my berth, and that is the main reason I did this re-mount.

I do seem to have hit a sweet spot as far as location. I had no real complaints about the location of the original factory installation, although I am definitely getting better performance at higher speeds. The new location is slightly inboard of the old, but still just outside the recommended 6 inches from the prop radius. I wanted to move away from possible turbulence from the chine. I also dispensed with the wedge that the factory had used to compensate for the transom angle. I measured the transom angle at 16.5 degrees, which is just below where AirMar recommends that the wedge be used. The net result is that the trailing edge of the transducer is angled a degree or two down from the plane of the hull bottom. This may produce smoother and more consistent water flow over the face of the transducer.

Any way, so far so good. :thup
 
Back
Top