Moisture Meters - Use and Abuse Of

[Ships_Cat]

Occasionally there is a post with questions or claims about moisture meters, their use and the meanings of the readings.

The August/September edition of Professional Boatbuilder Magazine has an article in it on their use which some may be interested in. If so, an electronic copy of the magazine can be found at http://www.proboat.com/.

Click on the magazine page cover then navigate to page 46.

John

 

[Bergman]

Thanks for this

An interesting article.

I have always had a deep suspicion of these machines and more specifically the way that some people use them.

I had a survey on my last boat where the surveyor used a Tramex meter.

He checked along the skeg and pronounced that it was full of water.

He also checked the keel which he also said had areas of high moisture.

Strangely when checking the "water" in the skeg it was confined exactly to the length and width of the prop shaft, and in the keel followed the shape of the metal structure of the drop keel. In both cases the "moisture" content dropped from very high to very low instantly -in a fraction of an inch.

On that basis he was recommending £4-5k spend on osmosis treatment.

I think what I am saying is that more significant than the meter is the ability of the man using it, and perhaps the integrity too.

 

[boatmike]

Excellent practical article.
The thing that I believe most people should see is the relative absorption rates of Vinylester and Polyester resins shown on the graph. The lab tests show high water content of Poly which most series production boats are made from. It is therefore EXPECTED that a boat that has been in the water for say 2 seasons will have a high reading when lifted out. This is NOT an indication of a problem requiring repair. Leave alone for as long as possible and check again. In other words Guys.... if it aint broke don't mend it and if a surveyor tells you a boat has a high moisture content ask. "How long has it been in the water for?" and "How long ashore?" Also be very wary of any boat with foam core beneath the waterline.

 

[fireball]

Our surveyor wouldn't tell us what the moisture reading was - he said it was meaningless as it depended how long the boat had been out of the water (about 1/4hr!) - but would say that it was as expected and he was happy that it was a dry boat .... very helpful surveyor quite happy to answer my stupid questions .... !!

 

[Guest]

Misuse / abuse of a very useful tool is widespread. Sadly true.

Later post about "Metal-detecting" yes it does happen and surveyor should have been more careful.
Second wet or unsound bulkheads can lead to false readings .... eg : A boat I surveyed in Southampton. Had high readings in specific lines and areas. When I find these - I run the meter along horiz. / vert. to see if has a pattern. The Tramex is excellent for this.
I then asked the owner if he had ever had a water problem inside .... answer Yes - the boat had been left open one year and serious rain ingress had occurred. I could actually detect the level the water reached .. and he confirmed such.

Yes .... care is to exercised with any tool - this one can lead to some expensive bills if not used well.

I hope though that instances like this shouldn't deter buyers / owners from having surveys done ... not all surveyors are cr*p ....

 

[AndersGu]

Excellent article!

 

[simon_sluggett]

[ QUOTE ]
I then asked the owner if he had ever had a water problem inside .... answer Yes - the boat had been left open one year and serious rain ingress had occurred. I could actually detect the level the water reached .. and he confirmed such.



[/ QUOTE ]

Is it wise to paint the inside of a boat (for cosmetic reasons) if it is bare and unpigmented GRP? Does this trap the moisture under the paint, or would it protect it from water in bilges etc.

 

[Guest]

Reading again it gives slight error ...

the boat was left open on mooring for some days ... one year. He then had bulkheads take up water .....

The readings I had gave perfect schematic of his internal bulkheads ... where the hull to bulkhead joints were having trouble drying out.

Onto painting internal GRP - I personally think it is preferred for 2 reasons ......

a) Often bare grp has awful hand scarring fibres and matt catching the unwary ..... cleaning off and painting reduces this.

b) If done well when internal is dry and before bilges have water in ... it can stop internal moisture take up. Take note that most water inside a boat comes from Fresh-water sources ... so is less dense and can invade laminate easier than saltwater ...