Scratching my head about a hole in the hull

[dalepo]

Yesterday I had a non-functioning depth sounder.

Today I have a non-functioning depth sounder and a hole in the hull.

Here's the story. I bought a simple Hawkeye depth sounder for my 22' fiberglass sailboat (a 1984 Spindrift). I tested the transducer by holding it in the water over the side and it worked fine. When I tried positioning it in the hull, I failed to get a reading, even with use of bag of water and vaseline methods laid out in the manual.

Researching further, I learned that transducers only work with solid fiberglass hulls, and that my failure to get a reading suggested that my hull is cored, not solid. Someone on the forum suggested cutting out a square of the inner layer + core and filling it with epoxy to seat the transducer.

In an attempt to probe the hull to determine the thickness of the inner layer, I managed to put a thin drill bit all the way through. The good news is that I now know the hull is exactly 1/4" thick. The bad news is that it now has a hole in it.

Q1: Is the best fix for the hole simply to cover a small screw with 5200 and screw it in, or is there a better way?

Q2: Is the 1/4" thickness consistent with the cored hull hypothesis? And if so, is the idea of somehow scooping out the inner layer to seat the transducer still a viable one, or would it be too likely to compromise structural integrity?

[chris95040]

Originally Posted by dalepo

Yesterday I had a non-functioning depth sounder.



Today I have a non-functioning depth sounder and a hole in the hull.



Here's the story. I bought a simple Hawkeye depth sounder for my 22' fiberglass sailboat (a 1984 Spindrift). I tested the transducer by holding it in the water over the side and it worked fine. When I tried positioning it in the hull, I failed to get a reading, even with use of bag of water and vaseline methods laid out in the manual.



Researching further, I learned that transducers only work with solid fiberglass hulls, and that my failure to get a reading suggested that my hull is cored, not solid. Someone on the forum suggested cutting out a square of the inner layer + core and filling it with epoxy to seat the transducer.



In an attempt to probe the hull to determine the thickness of the inner layer, I managed to put a thin drill bit all the way through. The good news is that I now know the hull is exactly 1/4" thick. The bad news is that it now has a hole in it.



Q1: Is the best fix for the hole simply to cover a small screw with 5200 and screw it in, or is there a better way?



Q2: Is the 1/4" thickness consistent with the cored hull hypothesis? And if so, is the idea of somehow scooping out the inner layer to seat the transducer still a viable one, or would it be too likely to compromise structural integrity?

No, a 1/4" thick hull is solid fiberglass.

Some transducers can work through the hull material, some cannot and are meant to be mounted through a hole in the hull. What model of transducer do you have?

I guess if I accidentally drilled a small diameter hole in my hull below the waterline, after spending some time pondering if boating was the right hobby for me, i'd countersink both sides, tape the bottom shut, and plug it with thickened epoxy using a toothpick to make sure I filled the cavity. The countersinking on each side would add bond area and make it so my plug was mechanically held in place even if the bond to the hull failed for some bizarre reason.

It would be a neater fix and wouldn't be much more work than the 5200 and screw. And wouldnt require cracking open a tube of 5200.

Oh, wait a second, your boat is in the water? [emoji23]

[tkeithlu]

QUOTE: " after spending some time pondering if boating was the right hobby for me"

While I think that Chris95040 has a good design for the repair, I must take issue with the jab at you for making a minor mistake, totally irrelevant to whether you have chosen the right hobby. You are pursuing a boat problem and came to the forum for some help. Good for you and good luck with it.

If you use 3M 5200 to repair the hole, simply freeze the rest of the tube. I'm using a two year old tube at present - just give it 15 minutes to thaw each time you need some.

[GordMay]

HawkEye® Installation and Operation Manuals
➥ https://support.norcrossmarine.com/h...ration-Manuals

[Jammer]

Originally Posted by chris95040

I guess if I accidentally drilled a small diameter hole in my hull below the waterline, after spending some time pondering if boating was the right hobby for me [....] Oh, wait a second, your boat is in the water?

You must be one of those people who has never made a mistake.

[Jammer]

Originally Posted by dalepo

Q1: Is the best fix for the hole simply to cover a small screw with 5200 and screw it in, or is there a better way?

There are lots of ways to fix something like that.


For a permanent repair without removing the boat from the water, I would put some waterproof tape on the hole from the outside, clean, dewater, sand, and dry the repair from the inside, sanding with 80 or 120 grit in an area about 2" diameter, and apply epoxy thickened with colloidal silica. It sounds like a big deal but it's really not. I don't think I would trust a small screw with 5200 by itself in 1/4 fiberglass. Even if sealed, I would sand the area around it and epoxy over the whole thing.

Q2: Is the 1/4" thickness consistent with the cored hull hypothesis? And if so, is the idea of somehow scooping out the inner layer to seat the transducer still a viable one, or would it be too likely to compromise structural integrity?

Usually, core materials are at least 1/4" thick, so a cored hull or panel will be somewhat thicker than that. The feel of the drill bit and appearance of the shavings while drilling would tell you more -- if the drill moved consistently through the material and the shavings were uniform, you are in solid fiberglass. If the drill had a decided "step" movement as you drilled, or you had wood shavings mixed in with the fiberglass shavings, there was core.


I have a Hawkeye depth sounder in my 14' aluminum boat, and used K-Y jelly while positioning it (less contamination to clean up than with vaseline). The use of K-Y for this purpose was a source of great amusement to younger members of the extended family. I still need to glue it in place more permanently.



Having used the Hawkeye, while it does work it is more easily fooled by difficult bottoms and will lose its lock in deep water more quickly than other transducers I have used. I don't believe it produces much output power. While it is attractive because of its small size and low price, there may be better alternatives.

[cal40john]

Originally Posted by dalepo

Yesterday I had a non-functioning depth sounder.

Today I have a non-functioning depth sounder and a hole in the hull.

Here's the story. I bought a simple Hawkeye depth sounder for my 22' fiberglass sailboat (a 1984 Spindrift). I tested the transducer by holding it in the water over the side and it worked fine. When I tried positioning it in the hull, I failed to get a reading, even with use of bag of water and vaseline methods laid out in the manual.

Researching further, I learned that transducers only work with solid fiberglass hulls, and that my failure to get a reading suggested that my hull is cored, not solid. Someone on the forum suggested cutting out a square of the inner layer + core and filling it with epoxy to seat the transducer.

In an attempt to probe the hull to determine the thickness of the inner layer, I managed to put a thin drill bit all the way through. The good news is that I now know the hull is exactly 1/4" thick. The bad news is that it now has a hole in it.

Q1: Is the best fix for the hole simply to cover a small screw with 5200 and screw it in, or is there a better way?

Q2: Is the 1/4" thickness consistent with the cored hull hypothesis? And if so, is the idea of somehow scooping out the inner layer to seat the transducer still a viable one, or would it be too likely to compromise structural integrity?

The reason for the bag of water is to find where in your boat the transducer will work. Did you try just one place or several?

[ggray]

Originally Posted by Jammer

I have a Hawkeye depth sounder in my 14' aluminum boat,

Wow, I didn't think it would work at all! Interesting.

[chris95040]

I dunno fellas, if you can't crack a joke about someone drilling a hole in their boat, what's the internet even for? [emoji23] i mean come on. The fact that we are all capable of such things is exactly what makes it hilarious. (I gave them pretty lengthy advice on the repair, obviously *not* discouraging their boating hobby.)

[Strait Shooter]

I thought it was pretty funny too, but I'm pretty sure you shouldn't use that as a yardstick or anything.

[boatpoker]

Sounds to me like the boat is not in the water.

Even a high quality transducer designed for shoot-thru will not function
if the boat is not in the water.

[dalepo]

Thanks to all for the helpful responses. A few points to follow up:

- Yes, I tested the transducer when the boat was in the water

- No, the boat was not in the water when I drilled the hole in the hull

- I've confirmed with the boat's designer Chris's surmise that the hull is solid glass. (I probably should have thought of that sooner.)

- The transducer in question is pictured below. I'm under the impression this is the kind that's supposed to be able to take depth readings by shooting through the hull. Have I got this wrong?

- Having intended my story as an occasion for self-deprecating humor, as so many boat-related stories are, I was amused by the suggestion that I reconsider my choice of hobbies, and have duly done so, with--predictably-- no change in the outcome.

Sounds like the next steps are to epoxy the hole, launch the boat, and try more locations for the K-Y lubed transponder, ideally in that order.

[jeanathon]

Are there holes for mounting a bracket? The shape suggests it is a transom mount transducer.

[Jammer]

So, maybe you know this, but in your photo, it's oriented the wrong way. The part shaped like a clothes iron has to be down, that is, in contact with the hull.

[Franziska]

Originally Posted by tkeithlu

QUOTE: " after spending some time pondering if boating was the right hobby for me"

While I think that Chris95040 has a good design for the repair, I must take issue with the jab at you for making a minor mistake, totally irrelevant to whether you have chosen the right hobby. You are pursuing a boat problem and came to the forum for some help. Good for you and good luck with it.

If you use 3M 5200 to repair the hole, simply freeze the rest of the tube. I'm using a two year old tube at present - just give it 15 minutes to thaw each time you need some.

Wow the freezing idea is great. Are you sure it does not affect the product?
Does that work with Sikaflex as well?