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Old 07-29-2012, 10:28 PM   #1
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Transducer Installation Advvice

At my next haul out (within a month), I will be installing a new Interphase Probe transducer. The transducer diameter is 1". I am going to remove an existing paddle wheel speed sensor (very old) which has a diameter of ~1 3/4". I have a new fairing block or may be able to use the existing fairing block. I am expecting to refill the hole with epoxy and re-drill the plug with a 1" hole. Here's my question - should I also put a glass mat layer inside or should the epoxy plug be sufficient (fairing block should provide good overlap over both the inside and outside of the hole)?

Any other suggestions appreciated.
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Old 07-29-2012, 10:50 PM   #2
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Is your hull cored or solid below the waterline? I know a lot of the 42s are cored. If it were me I'd be looking for a transducer with the same diameter stem even if it had a speed sensor, which are useless. I don't think I would trust just filling the hole and redrilling it smaller.
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Old 07-29-2012, 11:13 PM   #3
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The KK42 is cored.
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Old 07-30-2012, 09:50 AM   #4
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I filled some through hulls on my last boat " fiberglass" used wax paper over the hole with duct tape, Mixed Cabosil with resin and poured it into the through hull before it was full i shaped some lightweight glass cloth and ended up with 4 layers spreading out about 12 inches square," fairing block was removed" the on the bottom 2 layers , sand and resin untill smooth gell coated it and moved the Through hull 6 inches used a fiberglass block and it is still working for the new owner i just didn't feel comfy with all that extra space around something through the hull under water.
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Old 07-30-2012, 10:13 AM   #5
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Experts will tell you that simply plugging a hole in fiberglass produces a very weak repair because there is only secondary bonding.

If you go to west marine or another marine retailer, you will find some pretty good and relatively inexpensive books and DVDs on fiberglass repair. I have them at home and read and watch them from time to time.

As I recall, you're supposed to grind out the area to twelve times the thickness of the surface in a taper, then put several layers of fiberglass mat in to provide strength.

Don't take my word for it, read the books.
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Old 07-30-2012, 10:50 AM   #6
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Absolutely do not fill the hole with only epoxy. You will need to have the hole re-glassed properly and if you don't have the knowledge and skills to do this yourself, have the yard do it for you. You can't fix this offshore somewhere when, not if, it fails. Chuck
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Old 07-30-2012, 11:40 AM   #7
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Sorry i didn't further explain Capn Chuck, I assume that everyone who would attempt any repair would know about feather the edges and like i said my patches were 12x12 for a small through hull !
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Old 07-30-2012, 12:12 PM   #8
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Feathering the patch would be a must but I think with a cored hull it may not be that easy. It would definately require someone who knows what he's doing. I still think the best bet is to find a transducer with the correct size post to match the hole, even if you had to change the entire sounder you would be money and time ahead.

I had the same issue and opted to replace the fish finder with a newer one, it gave me an up to date sounder and was something I could do myself.
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Old 07-30-2012, 12:53 PM   #9
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Quote:
Originally Posted by GoldenDawn View Post
At my next haul out (within a month), I will be installing a new Interphase Probe transducer. The transducer diameter is 1". I am going to remove an existing paddle wheel speed sensor (very old) which has a diameter of ~1 3/4". I have a new fairing block or may be able to use the existing fairing block. I am expecting to refill the hole with epoxy and re-drill the plug with a 1" hole. Here's my question - should I also put a glass mat layer inside or should the epoxy plug be sufficient (fairing block should provide good overlap over both the inside and outside of the hole)?

Any other suggestions appreciated.
While not the prefered method...if the fairing block is made from a strong material that won't rot (like FRP) and there is good overlap and the whole shebang is epoxied together...on a cored hull where the previous hole is also filled with reinforced epoxy...I think you would be fine...

The key would be strong, non-rotting fairing blocks with sufficient overlap.

The argument is...anyone ever see a wood planked boat with butt blocks??...is so the same principle applies.
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Old 07-30-2012, 08:42 PM   #10
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GD. I have a removable paddle-wheel speed sensor - it slides into a plastic sleeve mounted in a faring block. If yours is similar, you might consider making an adaptor/bushing which would allow you to mount your new tranducer in the original sleeve. It could be machined from PVC pipe or fabricated in GRP and would have dimensions of roughly 1-3/4" o/d x 1" i/d.
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Old 07-30-2012, 11:38 PM   #11
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Thanks for the advIce guys. Will have a couple alternatives in mind and see what it looks like during the haul out. I have both the existing fairing blocks on the speed sensor (exactly as you describe Shoalwaters) and a new one I purchased with the transducer.

I got a berth going around northern Vancouver Island so will be offline for a week or so.
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