Moisture Meter Facts and Myths

Moisture Meter Facts and Myths

Moisture meterOur continuing discussions on various aspects of the marine survey and some of the logistics involved in getting it done provides us with a perfect lead in for this a discussion on moisture meters. It’s been a while since we discussed these little guys and since moisture readings can be one of the more confusing of the items noted on a survey report let’s see if we can dispel some of the myths bandied about surrounding these infernal little devises. I say infernal with a bit of humor thrown in because in all reality as a surveyor I have to admit that I have come to rely on the data that they present, but only when in the hands of an experienced operator.

First of all let’s take a look at where the moisture meter originated and how it happened to wind up in the hands of marine surveyors and fiberglass repair professionals.          The moisture meter was originally developed by the lumber industry to assist in the scaling and grading of wood. Early versions were all of the analogue type and each had 2 sharp pins extending from the end of the meter’s housing which the operator pressed into the wood and the reading was displayed by the needle on the meter. About 20 or so years ago the meters lost the sensor pins which were replaced by a sensor pad on the body of the meter which was simply  held against the subject matter and the display produced a reading. This improvement allowed the meter to be used on various materials such as drywall, stucco and yes fiberglass. It wasn’t long before any marine surveyor serious about their craft had one of these guys in their tool kit. By the way the pin type meters are still in use by the lumber industry. Since no formal training or instruction was provided on how to interpret the information produced by the meter (remember they were mainly for use on lumber) many different approaches to the meters usage and data interpretation surfaced and became commonplace. Luckily since then most experienced surveyors have become proficient in their use but there remain many myths and confusions that still surround the use of these devises.

The first comment that I would like to make is that incorrect usage of the moisture meter has probably been responsible for more unnecessary repair and bottom jobs to fiberglass boats that all other diagnostic methods combined.

Secondly the moisture meter does not actually measure the moisture content of the substance. In actuality it measures the electrical conductivity of the material in question.

The theory is that since water is a conductor of electricity, the more moisture contained in a substance the higher the reading will be. This reading is then displayed on the meter, usually as a percentage.

This brings me to my next comment. Moisture readings should NEVER, NEVER be interpreted as, or reported as a percentage. My answer is always “as a percentage of what?” Here’s why. All fiberglass resins all have some level of moisture in their core makeup, some more and some less. Unless the surveyor was present on the day that the boat’s hull was popped out of the mold and if he was able to take moisture readings at that time, put the information on file for 15 years or so or until the next time the hull’s moisture levels were measured there is no way that percentages have any bearing on the resulting information. I still come across survey reports that report moisture levels as a percentage.  Add to that the fact that a boat hull’s make up is actually a combination of resins, gel coat (which is actually a thickened, pigmented resin) spun glass re-enforcement (of various configurations) and possibly a core material (balsawood, closed cell foam or plywood). Then add a few coats of anti-fouling paint and we have enough to seriously confuse any self-respecting moisture meter. This where the experience factor of the operator comes into play. The moisture meter is in reality a very simple devise to use. You place the sensor pad on the substance in question and read the display. That’s the easy part. Trying to understand and interpret what the meter is telling us is where the difficulty sets in.

The next question that arises is how deep into the substance can the meter actually read? Moisture meter manufacturers make claims and I don’t want to say that they are false but it appears that any meters depth of accuracy, again will depend largely on the substance being measured.

Does anybody notice a pattern developing here? The point that I’m trying to make is that there are usually more variables in the use of a moisture meter than there are absolutes and interpretation of the readings is the real key. I have taken moisture readings on hundreds of boats over the years have to admit that I still do not have it all figured out but I have learned enough over the years to know when to question the readings and investigate further by other methods. I see moisture meters being offered for sale to boat owners at retail outlets and when I’m questioned as to whether they are a good investment for any boat owner my answer is usually no. In most cases what happens is that inexperienced meter operators are easily confused by any or all of the issues listed here and they wind up calling someone such as myself to re-examine and make recommendations.

Taking moisture readings in ambient air temperatures below freezing is also a bad idea and since I have mentioned this previously many times in this column I won’t go into it here.

One thing that the moisture meter does do very well is to prove the positive, this is if a substance is dry the meter will show it easily. Its when the readings are elevated that the confusion sets in.

So I think that you can see that while the moisture meter is in reality, is a simple devise to use there’s a lot more to it and accurate interpretation of the data is the real key.
Reprinted From “The Seaworthy Surveyor” Ontario Sailor Magazine

Original Article By David Sandford AMS® 

FRP / Plywood Deck Repair on a Rosborough 28

Our club race committee boat is a FRP Rosborough 28 which I believe was initially used for lobster fishing in Nova Scotia up until about 1990 when we converted it for use by our club. Over time the aft deck sole which is comprised of plywood sheeting with a fiberglass laminate outer layer has deteriorated due to moisture intrusion from the elements and as a result has weakened considerably to the point where we deemed it unsafe and a repair was necessary.

To that end after the boat was hauled for winter storage last fall we began by shrink wraping the entire boat leaving enough head room to allow for an adequate working space above the aft deck. We also installed a hindged plywood door for easy access. This past week myself and a couple of  other members, Mark Backman  and Bart Bies began the repair and re-construction of the deck sole.

The first step was to remove the FRP laminate layers from the rotted plywood. To do this we utilized a curcular saw with the blade depth set at approxametly 3/16″ and cut through the laminate layers in the required areas.

FRP saw

Cutting through the FRP layer to separate it from the plywood

After the cuts were made the next step was to searate the FRP outer skin from the rotted plywood panels. For this we untilzed a variety of wrecking an bars and a hammer. Actually due to the deteriorated condition of the plywod that FRP skin came off rather easily. The rotted plywood was removed as well.

FRP removal from plywood

Removing the FRP from the plywood.

The plan is to re-used the existing FRP skin over the new plywood after a re-build of the structural components.

frp and plywood deck

After removal of the bad stuff and a thorough clean up this is what we had.

So far this represents about 5 hours of work and the next step will be a re-construct of the transverse sole suports.

More to come.



Marine Survey Inspections and Reports

We haven’t discussed marine surveys in a while so here goes. It’s late winter here in Canada and as we head into spring we ramp up into the busy season for us marine surveyors. I thought that a few posts on the processes of the marine survey inspection might be in order.

A Marine Survey is an objective report on the condition and value of a particular vessel paying close attention to the structure, installed systems, sails, rigging and motive power components. Survey reports are subject to the condition and accessibility of the vessel at the time of the survey. This is an important statement because the state of the vessel, as presented can affect the depth in which the surveyor can go to test and evaluate the vessel and its installed systems. For example a hull inspection cannot be performed without the vessel being hauled from the water. Electrical systems cannot be tested without charged batteries on board or available shore power.

When performing inspections test methods used by surveyors are usually of a non-destructive nature. What this means is that the vessel in question will not be disassembled by the surveyor for access to systems or components. If minor disassembly is required such as the removal of an electrical distribution panel the owner may be asked to sign a release absolving the surveyor of any issues that may occur as a result of his or her actions.

Hulls and decks are inspected visually for condition and structural soundness. In the case of fiberglass or wood construction moisture levels are verified and measured by percussive sounding and electronic detection.

Electrical and electronic systems are tested by powering up only when authorized, and providing power is available. If not visual inspections of all accessible wiring, fixtures and equipment are performed.

Plumbing systems are inspected for leaks and wear evaluations are based on visual inspections and reported life of the components.

Mechanical systems, engines gearboxes etc. are inspected for leaks, static functionality and overall general condition. If possible the engine may be started and certain dynamic run up tests will be performed.

Interior joinery is inspected for appearance, condition and structural soundness.

If the mast is stepped at the time of the inspection, rigging and spars are inspected from the deck only. For a thorough inspection arrangements should be made to de-step the mast. Sails should also be made available for a full inspection as well.

A pre purchase situation starts with all of the above and may also include a full engine and drive evaluation. Engine compression and oil pressure may be checked. On gasoline engines spark pugs may examined for telltale signs of problems such as oil consumption and internal component degradation.

At this point a sea trial will facilitate a running inspection of all spars, rigging, sails and loaded run up and tests of the all motive power components.

Survey reports should be subjective, concise, detailed and include pictures that not only indicate problem areas but also give a good general description of the vessel being surveyed. The report should deal with appearance and cosmetic issues only when they affect either vessel value or safety related issues. Current safety standards and regulations should be quoted where applicable. Although many vessels were manufactured before current standards were put into place and compliance may or may not required by law it is always good safety practice to ensure that any vessel is maintained as close to current standards as possible. Insurance providers may require compliance with certain current standards as well.

Reprinted From “The Seaworthy Surveyor” Ontario Sailor Magazine

Original Article By David Sandford AMS®


New EBook “A Guide to Sailboats and Their Systems”

I’ve just published my first EBook. “A Guide to Sailboats and Their Systems”

ebook guide to sailboatsEach year in my profession as a marine surveyor I get involved in a number of pleasure craft pre-purchase situations. Many of these involve first time boat buyers who, while they may have considerable sailing experience either with friends or chartering will often find themselves with little or no practical knowledge about the mechanical aspects of the boats that they wind up purchasing or how the onboard systems operate. As such I am often called upon to explain and demonstrate how these on board systems and devises operate.

That’s what this book is intended to do, provide both new and seasoned boat owners with some insight as to how various on board systems function and hopefully address some of the common questions that do arise. Whether it’s a safety related issue as to “Why is there a polarity indicator on my shore power panel?” or “What does the pressure gauge on my propane supply regulator do?” I’ve tried to answer them all and hopefully provide boat owners with some valuable insight as to how their on board systems function.

I’ve also included discussions on sail design and construction, an explanation of the different types of sailboat rig configurations and some good information on the basics of fiberglass hull and deck construction. There’s also a chapter on auxiliary power and the necessary systems that allow our on-board engines to function.

The intention here is to present a detailed overview to both rookie and seasoned sailors on how sailboats and their systems function.

So whether you are a new or seasoned sailor or are you just moving up to a larger more complex boat I hope that as a reader you find some interesting information here.

Available at all leading EBook retailers including

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