Expensive Moisture Meter vs. Cheap one and comparing - SailNet Community
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post #1 of 11 Old 05-02-2019 Thread Starter
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Expensive Moisture Meter vs. Cheap one and comparing

Hi All -

Sent this message to Maine Sail but wondering what y'all think too.

Maine Sail has an old article plus lots of discussion about the CT-33 moisture meter. We have two spots where the barrier coat delaminated from the hull and we have raw fiberglass (after sanding). I'm debating spending the money on a good moisture meter, or getting something like the Ryobi and shooting like 20 spots on the hull to see what it reads, and then shooting the two wet spots and comparing (and then putting tarps over the areas with a dehumidifier to try to dry them out and shooting them again). Any thoughts on these two processes? I also can't shoot from inside the hull to these two spots as there are multiple layers of floor and bilge. On the plus side, the boat was out of the water for the Winter (however, we hadn't sanded these spots down to fiberglass before the Winter). Just trying to figure out the best way to see when the spots are dry enough to epoxy and barrier coat again.. but still be able to get my boat in the water in the next 30 days. Would appreciate any thoughts!

s/v "Pelican" Passport 40 #076- Finished Cruising - for the moment -
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post #2 of 11 Old 05-02-2019
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Re: Expensive Moisture Meter vs. Cheap one and comparing

I have the Ryobi pinless meter and must say it works pretty well. I use it to do routine checks of my deck. Friend used it to check the cored hull of his J30 before he put it up for sale. His readings with my Ryobi were very close to what the surveyor got with his expensive meter.
The Ryobis were not available for some time I but note that they are available again at Home Depot.

Note that moisture meter readings are relative, so its difficult to compare readings from one meter to another. But once you have some readings on known dry and wet situations, the Ryobi does the job.

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Re: Expensive Moisture Meter vs. Cheap one and comparing

I'm confused. Do you have a wooden cored hull that you think is wet? If not, I would expect poor surface prep or application was the cause of barrier coat failure, not moisture.


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post #4 of 11 Old 05-03-2019 Thread Starter
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Re: Expensive Moisture Meter vs. Cheap one and comparing

It's a Passport 40... fiberglass through and through. We're not sure what caused the barrier coat failure but are talking to Interlux. With regards to moisture.. BECAUSE of the barrier coat failure we're seeing moisture in the hull (we see water droplets forming after we sand) so we need a way of telling how much and when it's dry enough to epoxy over.

s/v "Pelican" Passport 40 #076- Finished Cruising - for the moment -
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Re: Expensive Moisture Meter vs. Cheap one and comparing

What happened to the gelcoat? Blisters everywhere, I would think, if you have that much moisture. The only way fiberglass can absorb water is if the resin was not properly cured. It's really dissolving resin, as fiberglass simply can't absorb water. Thought Passport would have done a better job.


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Re: Expensive Moisture Meter vs. Cheap one and comparing

It's good to know that the Ryobi pinless meter is available again. I sold mine and wished I had it back. I'll go order one soon. Get it while you can.

Most stud finders work on the same capacitance principle, and can often be good enough to trace a moisture gradient to its source. So you may already have an acceptable tool in your workbench. (My stud finder bit the dust, which is why I'll probably get the Ryobi while it's available.)

No matter what meter you use, any meter is only as good as the person using it. There are MANY sources of false positives with capacitance measurement. If you really want to know, it may be best to hire someone who knows what they are doing.

I've posted a bunch of stuff comparing different options. In chronological order:

https://www.sailnet.com/forums/gear-...tml#post582990

https://www.sailnet.com/forums/gear-...tml#post723423

https://www.sailnet.com/forums/boat-...tml#post805660

https://www.sailnet.com/forums/gener...ml#post3017130

https://www.sailnet.com/forums/gener...ml#post3529522

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Re: Expensive Moisture Meter vs. Cheap one and comparing

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What happened to the gelcoat? Blisters everywhere, I would think, if you have that much moisture. The only way fiberglass can absorb water is if the resin was not properly cured. It's really dissolving resin, as fiberglass simply can't absorb water. Thought Passport would have done a better job.
Only two spots on the boat... for the past couple of years the ablative bottom paint has flaked off weirdly in these areas after repaint. This year we decided to do some exploring and sanded those two areas down to glass. You can basically stick your fingers on the epoxy/barrier coat around the sanded area and it just flakes off and there are signed of moisture. The rest of the hull is fine - just these two areas. I'm going to remove everything until it stops flaking off and adheres correctly, and then clean, epoxy x 2, barrier coat x 5, bottom paint x 3 these two areas. I just want to make sure I'm not sealing anything in with the first epoxy coat.

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Re: Expensive Moisture Meter vs. Cheap one and comparing

I hope you get it sorted out. I'm wondering if you really mean you've sanded down to glass or down to the gelcoat. Seems more likely you'd have moisture in the porous gelcoat or between the gelcoat and fiberglass. If you did sand an experimental area all the way to the fiberglass and picked at the surrounding areas, they would still be above the gelcoat.

It's not unheard of to have to peel the entire gelcoat (or whatever outer layer) and replace with vinylester. I'm not sure you can really dry out the poorly cured resin, if that's the problem. Had a friend need to recoat an old Taswell he owned, with vinylester. I'm surprised to think Passport has this problem, but I think they're built in the same yard as many other Taiwanese boats that had variable hull quality. You'd know better than I. What a pain. Hope you're out sailing again soon.


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Re: Expensive Moisture Meter vs. Cheap one and comparing

Interesting anecdote. Just went out to look at pics of the Passport 40, out of curiosity. One of the first I saw for sale touted a complete bottom job. One of their pics looked like it had refilled blisters along the entire length.


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Re: Expensive Moisture Meter vs. Cheap one and comparing

Quote:
Originally Posted by TakeFive View Post
It's good to know that the Ryobi pinless meter is available again. I sold mine and wished I had it back. I'll go order one soon. Get it while you can.

Most stud finders work on the same capacitance principle, and can often be good enough to trace a moisture gradient to its source. So you may already have an acceptable tool in your workbench. (My stud finder bit the dust, which is why I'll probably get the Ryobi while it's available.)

No matter what meter you use, any meter is only as good as the person using it. There are MANY sources of false positives with capacitance measurement. If you really want to know, it may be best to hire someone who knows what they are doing.

I've posted a bunch of stuff comparing different options. In chronological order:

https://www.sailnet.com/forums/gear-...tml#post582990

https://www.sailnet.com/forums/gear-...tml#post723423

https://www.sailnet.com/forums/boat-...tml#post805660

https://www.sailnet.com/forums/gener...ml#post3017130

https://www.sailnet.com/forums/gener...ml#post3529522
Well, I procrastinated too long and Home Depot no longer has the Ryobi pinless moisture meter. I even called their central number to see if they had any I could get. I had forgotten that my stud finder, which for the past 10 years did what I needed very nicely, had stopped working, so I finally went to buy a Ryobi and learned that it's gone. And I suspect that it's gone for good, since Ryobi sold their tools division to Kyocera and shortly afterwards Home Depot signed a deal to be exclusive dealer for some of the General Tools models. Usually when a retailer gets an exclusive like that it goes two ways, and they have to sell a certain quota to maintain their exclusivity (i.e., they are strongly discouraged from selling other brands). FWIW, one of the GT models that Home Depot and Lowes sells (MMD7NP) is the exact same one that I tested almost 10 years ago and found horrible reproducibility, even when testing the exact same block of wood.

I just placed a bid on a used Ryobi meter. I don't have any immediate need for it, but I want it in my tool bag and it will become almost impossible to get them. (Prices have already gone up to $70 for refurb units.) If you search around here, you will find a couple of surveyors who say the Ryobi gets readings that are just as reliable as the Electrophysics and other high $$$ gear that most surveyors use.

Rick S., Swarthmore, PA
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