Perminant Transom Transducer Mounting with Adhesive?

[minuteman62-64]

I've read a bunch of threads about transducer mounting. The concept of trial mounting with something like 4200, to determine correct position, seems like a good idea. I'm wondering about the feasibility of perminently mounting the transducer with 4200.

Aluminum hull, transducer to be transom mounted, strictly salt water use. I know I can drill holes thru the transom and adequately seal them when mounting the transducer, but I just don't want to put any more holes back there.

I'm thinking of mounting the transducer bracket to an aluminum plate (to get some surface adhesion area) and then using 4200 to perminantly (at least until I need to remove it) attach it. Any one done this? Thoughts?

 

[Lyle29464]

Re: Perminant Transom Transducer Mounting with Adhesive?

How about 4200 a 3X6 of starboard to the hull. Then you can move the transducer around till you get it right?

 

[emoney]

Re: Perminant Transom Transducer Mounting with Adhesive?

I tried that once and didn't have much luck. My plan involved a square block of Teak, but I never got good adhesion. If you can find something that will stick, no reason why it won't work. I was trying glass too.

 

[minuteman62-64]

Re: Perminant Transom Transducer Mounting with Adhesive?

Here's where I'm going. First two photos show mounting plate cut from a sheet of 1/8 inch thick 5052 aluminum. It is about 2" X 3". The studs are #10 SS machine screws, spaced to fit the transducer bracket, counter sunk into the back of the plate and secured with JB weld (I used my Dremel Tool to cut some groves in the head of the screws and the counter sunk portion of the plate to help prevent the screws from turning when I mount the transducer bracket).

Third photo shows the mounting plate secured to the transom (on the right) with 3M 4000 UV (the blue stuff is painters tape used to hold the plate in position). On the left is a piece of 1" X 1" aluminum angle attached to the transom with 4000 - this will be used as a test piece to determine how tough the adhesive will fasten to the transom.

More to follow.

 

[minuteman62-64]

Re: Perminant Transom Transducer Mounting with Adhesive?

Here's my not-so-scientific test of the scrap piece of aluminum bonded to the transom. It's a 1" long section of 1" X 1" aluminum angle (1 sq. inch for you tech. types). Only prep was to wipe the angle section and the area of the transom where it was to be joined with a paper towel. Tested after about three days of curing.

First, I pulled on the angle with a pair of vice grips. I pulled till the boat and trailer began to roll up a very slight grade. Seems like tensle strength won't be an issue.

Next tried to approximate the loading that would occur on the transducer bracket mounting plate. Hooked a bucket over the vice grip handle, 7" out from the angle, and began to fill it with water (first photo). It failed with a bucket plus water weight of 16.4 lbs. (by my bathroom scale). That's about 9.6 ft.-lbs. of torque on the angle. Second photo shows neither the bond on the transom nor the bond on the aluminum angle failed. The failure mode was the 3M material parting.

I could dig out my old text books and refresh my memory on peel stress calcs. - but I'm satisfied that the 3M 4000 UV provides a pretty good bond for the 6 square inches of my transducer bracket mount (at least for testing the transducer mounting location).

 

[minuteman62-64]

Re: Perminant Transom Transducer Mounting with Adhesive?

Here's the completed assembly. Application area lightly sanded and cleaned w/acetone. Two runs so far - fishfinder seems to work OK w/transducer in this location (I have no basis for comparison) and no signs of adhesion failure.

I took to heart the concerns of the transducer coming free and "slingshoting" into the cockpit. You can't see it, but the cable is zip tied to a through bolt at the top of the transom.

The two bolts to the left of the new mounting are from the 1980's "wide body" transducer that was on the boat when purchased. From everything I've read, using those bolts to secure my bracket would have put the new transducer in a poor location w/regard to prop/hull interference. So, in deference to the 50 percent of you guys that believe in hull anodes, I used one bolt to mount an aluminum anode. If I have any problems down the road with the adhesive transducer mount I'll use the other bolt to secure a new, wider bracket to the hull in kind of a "side saddle" arrangement.

So far mission accomplished. Transducer and anode mounted without additional holes in transom (as you can see there are plenty of holes there now).