Osmosis Moisture Meter

[thinwater]

“Off the scale” from the surveyor is not overly helpful....

In fact, if they were in more than a few isolated spots, perhaps where there is an imbeded plate, this sounds like proof that he has not calibrated his meter. Remember that the moisture content cannot be 100%. Balsa really can't get higher than about 70% and solid glass MUCH lower. There is still laminate in there!

 

[Birdseye]

Thinking of DIY treatment of an osmosis riddled hull. The surveyor mentioned he used a Tramex Skipper meter to measure the moisture content of the hull and the readings were “off the scale”. I know of another meter a Sovereign make which is used by surveyors too. as the hull dries out, I’d like to take regular hull moisture readings myself to monitor the drop until it stops dropping at which point I understand it won’t drop further and I can consider the hull is as dry as it ever will be.

But, the Tramex Skipper costs a whopping £370 or so and I wondered if there were other meters I could use. I see Chinese meters for measuring the moisture in wood or concrete costing £20 or so, would they do the job? I’m not looking for accuate readings, I’m only interested in watching a drop in relative readings taken over several days. Anyone able to give advice?

Think carefully before getting a meter. I have a Tramex, bought some 15 years ago for a Prout cat which had the beginnings of osmosis. Tht said the cheap Chinese meter would do the job just as well because you arent interested in the actual number of the reading so much as how the wet area below the waterline compares with the dry grp of the topsides.
Trouble is you can end up with a sort of boat hypochondria, checking the hulkl every chance you get and worrying about slight changes in readings. I had this problem until one winter I checked everybody elses boat in the compound. Must have been more than 50 hulls and all but 2 gave a wet reading. I never mentioned the results to any other member since I didnt want to worry them but club bar chat showed only a couple of members aware they had a wet hull. If the conversation ever got to osmosis, the large majority were happily saying they had no problem.
Even after the Prout had been treated professionally, there were some readings that werent at topsides level.
So in short it depends on your temperament. If like me you are a worrier then dont buy one - ignorance is bliss.

 

[guardian]

Been there done that, an absolute waste of time and a ****ton of money..................................................................crack on!

 

[jwilson]

“Off the scale” from the surveyor is not overly helpful. If he’d given you numbers and written them on the corresponding areas of the hull, that would have at least given you a starting point. The Tramex is very good at finding moisture, be sure to think about where your heads, water tanks, stringers are make sure the bilges are dry before taking readings.

Tramex meters do go "off the scale" if faced with very damp GRP. The 0-100 scale is a hugely magnified part of a scale. 100% does not mean 100% water - it's probably more like 2 or 3%, and in any case as othesr have said no moisture meter actually is measuring water, but the electrical conductivity that water in a laminate creates.

As John Lilley says, picking a few non-cored nothing-behind-it areas of the topsides are good reference points: I those show say 20/100 on a Tramex, or whatever another meter shows, there is no point expecting lower on the bottom. Some GRP laminates contain conducting compounds as built, and will never show zero on a very sensitive meter.

If the cheap meters have more scales than the Tramex I'm tempted to get one - I have a Tramex but find it far too sensitive for some tracing damp jobs in a 200 year old house!