Moisture meters.

[KINGFISHER 9]

Anyone used a moisture meter on glassfibre hulls? ... just pondering about spending £315 on a meter if I'm going to look at several boats to determine whether they're ok or riddled with the pox rather than pay a surveyor a lot of money to tell me the same thing. It would be a good way of sorting the wheat from the chaff before employing a surveyor to do a full survey on any that passed the soggy bottom test. Depending on the lay-up of the hull they need varying times out of the water before doing it. They can also be hired at £40 a time so I suppose you could do several in a short time but I'd probably be looking at several up and down the country over a longer period than they might be hired for. Anyone used one?

Tramex Skipper Plus looks like being the weapon of choice.

 

[forelle541]

I have a Protimeter and the readings are arbitrary. It's ok to check if your hull is drying and if it's wetter this year than last but there are just to many variables, time out of the water etc. a surveyor may get used to his meter but I think it's more of a judgment of the readings then cut and paste.

 

[VicS]

Couple of guides worth reading if you have not already done so

http://www.bluestarsurveys.co.uk/sovguide.pdf

http://www.passionforpaint.co.uk/downloads/skipperguide.pdf

 

[KINGFISHER 9]

Yes, thanks for that .... I had read the Tramex one but not the other. Is it a worthwhile exercise? ... I think so.

 

[johnlilley]

Moisture meter readings have a limited value & taken in isolation without any other visual and physical information could easily be completely useless. Physical existence of blistering overrides any moisture readings although not all blisters are "osmosis" but generally only experience can diagnose the type of blister present.
No one should ever make decisions on any invasive procedure to a hull merely on what a meter says in my opinion, hammer testing & visual examination must also accompany any diagnosis. High moisture readings should not condemn a boat.
The only exceptions I can immediately think of for the independent value of moisture readings is to ascertain the suitability of a hull for epoxy coating. There is no visual test that can confirm this. The other possible benefit of independent readings would be in the case of a hull that has been epoxy coated to ensure the work has been carried out to the required standard.
It is a sad truth that it is easy to disguise osmosis blistering by sanding the blisters flat & epoxy coating immediately after. Moisture readings may help discover this deception, but then one might be suspicious in the case of a boat for sale that has just been epoxy coated and never launched.

Cored decks can be a problem where moisture meter readings can help, but again, hammer testing should be employed along with the readings to give an overall accurate view.

If the boat is to be surveyed following a happy preliminary inspection then trust a good surveyor, meter readings incorrectly assessed can lead to walking away from a potentially good boat. Unfortunately there are still a number of surveyors that give too much credence to moisture readings without reference to other information.



John Lilley

 

[rotrax]

+1!

 

[jwilson]

Agree fully with John Lilley. As a broker I carry a Tramex meter, not because I want or pretend to be a surveyor but because I like to have some idea in advance of what a surveyor might say. If you do buy, hire or borrow one also take readings from the topsides (where unless the boat shows signs of having being totally underwater for a few years) you can more or less assume the GRP is more or less dry. If the topsides have fairly uniform readings of 40, readings of 50 underwater are of much less concern than they would be if the topsides read 0-5.

Tramex meters read to a fair depth, so if there is bilgewater inside, or a damp foam-vinyl lining, or a water tank against the hull, of course you will get high readings.

Moisture meters are not absolute, and you find 30 year old boats with very high readings yet no sign of 'osmosis' blisters. They do not actually detect moisture - but electrical conductivity - so some compounds in the GRP layup itself can cause false readings, without the material ever having touched water. A bone dry twenty year old glass top (slightly smoked glass) on a coffee table in my lounge always shows very high readings.

 

[richardh10]

I have a tramex moisture meter. If you want to borrow it you are more than welcome. Pm me and I can send it to you

Cheers

 

[KINGFISHER 9]

Good advice John ... I'm not an expert but I'm damned if I'm going to get 4 or 5 boats surveyed before deciding which one to buy! Maybe there's some other way of assessing a good or bad one ... all suggestions gratefully received!

Thanks for the offer Richard ... I'll let you know ... and, do you find it useful?

 

[Daydream believer]

You need to know how to understand how to use one. I have had 2, the first being a protimeter with probes for hammering into wood etc
The second with an electrical plate that has to be placed on the surface of the sample
The reading you get then has to be transferred to a correct reading by applying a correction factor from a table supplied with the meter
If you do not have a table with GRP on it you will never know the correct factor
In this case the best you can do is compare readings. Ie test the value of a known dry area & compare with a suspect area
But you have to know what level of moisture is actually acceptable

You also need to have a meter that has been properly tested & certified by an independant laboratory
I used to have mine done annually
So if you hire one you need the table with GRP listed & if poss the test cert. Some cheap meters do not read a low enough value starting at 12% plus so may not help

Not knowing your vocation & not trying to be disrespectful- but I suspect you would not have the experience to benefit fom one & would be wasting your money

 

[cagey]

Just a thought,
this kit is not measuring moisture only electrical resistance, why not use a multimeter that you can calibrate for very wet to dry. Realise its not the dogs but youre only separating wheat from chaffe. Have used this method in all my refurbs before calling in DPC people, surprising how it affects their survey and price, perhaps I'm just bee essing the bee sheeters but it works. Its only electrical continuity and I know s-d all about electrics.
Keith

 

[johnlilley]

Good advice John ... I'm not an expert but I'm damned if I'm going to get 4 or 5 boats surveyed before deciding which one to buy! Maybe there's some other way of assessing a good or bad one ... all suggestions gratefully received!

Thanks for the offer Richard ... I'll let you know ... and, do you find it useful?

If you have a look on my website & downloads sample surveys page you can get part of a free survey template for GRP. If you think it might be useful. just email me for the complete document completely FOC & no strings. I do not make the complete template available from the website because I need to have some control over who receives it as it is not for professional use as it took a long time to produce.


John Lilley

 

[KINGFISHER 9]

Interesting website ... I'll give it a good look through when I've got time! If I find a boat anywhere on the South coast I'll give you a call re survey.

 

[jwilson]

Just a thought,
this kit is not measuring moisture only electrical resistance, why not use a multimeter that you can calibrate for very wet to dry. Realise its not the dogs but youre only separating wheat from chaffe. Have used this method in all my refurbs before calling in DPC people, surprising how it affects their survey and price, perhaps I'm just bee essing the bee sheeters but it works. Its only electrical continuity and I know s-d all about electrics.
Keith

It's not actually just plain DC resistance you measure with a Tramex/Sovereign type meter, if it was they would be much cheaper. You might however be able sometimes to detect differences with just resistance, but you could also get very misleading results.