Holes Again

[johngalt]

A new question for the group. I am replacing an old transducer that is going to leave me with 2 [two] 3/8" holes under the new Airmar fairing block . The question is-What do I need to do to these holes? Will the sealant applied to the new fairing block be enough, or do I need to glass in these holes ? I am grateful as always for the sage advise that I have received here. Thanks, Bruce

 

[bobk]

Will the holes be well covered by the fairing block such that an impact will not let water in?

I'd at a minimum coat the old holes with epoxy to seal the raw glass edge. Best job would be to grind and fill with glass epoxy and then re-fair. If the old holes are well protected, a reasonable compromise would be to coat the edges with epoxy and then fill the holes with an epoxy/glass fiber mix, then sand and finish the job.

By the way, what is Airmar?

Bob

 

[johngalt]

Hello Bob . Airmar is the brand of the transducer recommended by Garmin. The fairing block is a "high-performance" polymer block that is 3" wide at the max and about 10" long and tapers to a point on both ends and requires one 3/8" anti-rotation bolt in addition to the 2" hole required for the transducer itself. The 2 old holes will on the centerline of the new block about 1-1/2" in from the edge. Bruce

 

[Capt K]

Bruce, can you bed the new block and transducer in place then fill the old holes with West System (or equivalent) from the inside? If you can, you will be set pretty much forever!

K

 

[johngalt]

Hello Kevin, nice to hear from you. I can indeed do as you suggest . As a matter of fact, it almost seems as if you were reading my mind . Is this a reasonable idea? Will the resin alone do the trick? I would love to deal with the holes in this fashion. Bruce

 

[Genesis]

For a 3/8" hole yes, resin should be fine. You might want to lay a layer of cloth over the inside and outside, but that will require grinding to prep on both ends (as a scarf.)

I would mix structural filler with the epoxy to the texture of ketchup or perhaps a bit thicker and do it that way, then sand and fair once hard.

I filled a 1-1/4" hole left by an old transducer on Gigabite and went with the whole deal laying up a patch, scarfing both inside and out, laying cloth, etc, but a 1-1/4" hole is a LOT bigger area than a 3/8" one.

 

[johngalt]

Thanks for the info gents. I opted for pure resin to fill the holes. First I reamed the holes to get out any excess sealant from the previous bolts, then I took a tapered countersink bit to the inside and outside and made the holes kind of hourglass shaped. Then I put electrical tape over the holes in the hull and temporarily tightened the fairing in place. The I filled the holes with resin from the inside and let it cure. We shall see how it works when I remove the tape tomorrow and do the final install of the transducer. Thanks again, Bruce

 

[Maynard Rupp]

I have that Airmar block on our Hatteras. First, all depth transducers are made by "Airmar". If you have a depth sounder I will bet that you have an Airmar transducer. That plastic block has to be cut lengthwise at an angle. The angle is what it takes to make the transducer level with the earth when installed on your boat's angled bottom. I split ours on a table saw after clamping it to a block of wood. This is a tricky job, so be careful. After it is cut the upper half goes inside your hull and the other piece, (the one with the large recess for the actual transducer head), goes on the outside. Now when you install all this stuff, your hull is sandwiched in between the two pieces. The anti-rotation bolt is forward. The transducer's gland nut is the other clamping force on this package. So any small holes that remain within the confines of the block are in a serious sandwhich and with the 4200,(I never use 5200), they should never present a problem. I would still fill them somewhat before the install.

 

[REBrueckner]

There are new AIRMAR transducers that fit flush with the outer hull.....no fairing block required!!!!!....the transducer can be "pointed" down without a fairing block...saw one this weekend being installed...really cool

 

[Capt K]

There are new AIRMAR transducers that fit flush with the outer hull.....no fairing block required!!!!!....the transducer can be "pointed" down without a fairing block...saw one this weekend being installed...really cool

I have two of them on my boat, now.

K

 

[34Hatt]

O.K how do they account for the fact that bottoms have different angles to them?????

 

[Avenger]

The elements are tilted inside the transducer body. They're offered in 12 and 20 deg. The only downside is you need to put a fairly large hole in the hull. About 2 in. I think.

http://airmartechnology.com/airmar2005/ex20/RMProducts/ElectCat.asp?ProdID=37&Man=All&PageNo=500

 

[DeeRow]

The only downside is you need to put a fairly large hole in the hull. About 2 in. I think.

From the brochure linked from the page you referenced, "92.25 mm (3.75”) hole size"

They are big. You can get an ardor that nests two hole saws so that you can replace an existing transducer with the larger transducer.

Mark

 

[MikeP]

That's a pretty big hole...

I think I'd prefer the standard sensor/fairing block which just uses a 1" hole or thereabouts. Then again, the standard method requires two additional smaller holes around 5/16" for the fairing block bolts as well so I suppose it's less work to just put in the sensor. But still - that's a pretty big hole.

I realize that the engine seacocks are even bigger than that but they HAVE to be. I figure that small holes are better than big holes given a choice but it probably doesn't really matter.

 

[johngalt]

For what it's worth , the transducer I just installed with the fairing block required a two inch hole just for the shaft of the transducer itself. Of course it is a transducer that works with the sounding module that goes with my Garmin 4212 multifunction display. It gives depth , speed and h2o temp. Also the 4212 with the proper chip will give 3d bottom topography. I assume that that is the reason for the size. Bruce

 

[johngalt]

Also, the bottom angle on my 41c just happened to be 12 degrees at the mounting location I chose so the fairing-less one would have worked. But a 3.75" hole is kind of large. Bruce

 

[MikeP]

The Garmin-branded sensor (with associated fairing block) which came with my 3010C provides water temp, water speed, depth/bottom profile and fish finder and the sensor only required the 1" hole I mentioned for the transducer. Actually, as I recall, it was a 7/8" hole. Admittedly, the 3010c is ancient technology but you'd think newer tech would need a SMALLER transducer, not a bigger one.

 

[johngalt]

Mike, I agree that newer technology should bring about the need for smaller penetrations , but that is not the case for me. My 4212 did not come with a transducer as it was sold as a chart plotter. I got the depth sounding module for Christmas and that also came transducer free. I think that in some aspects the technology has changed;one can get a transducer that requires no penetration at all. They supposedly will shoot right through the hull , but I doubt the effectiveness on a boat like mine with a hull thickness in excess of 3/4" of solid glass. Bruce