Is a hull moisture reading necessary ?

[richardoren]

My surveyor says YES - especially since the boat has been sitting year round in warm waters.

From reading David Pascoe's articles I thought that the older (1968) solid fiberglass hulls on Hatts were safe from osmosis, or at least osmosis in its terminal form found in cored hulls.

I don't care didly about cosmetic blisters, as long as they don't endanger the structure or impermeability of the boat.

Should I pay extra yard fees for drying out the boat for a week prior to survey, or is it superfluous on a vintage Hatt?

Thx

Richard

 

[Genesis]

Worth nothing on a solid hull.

On the decks and hullsides a percussion test will tell you what you want to know, along with a careful inspection.

Moisture meters measure conductivity, which is not conclusive in solid or even cored laminates. Good for an indication but if it comes up wet you need to take a core - good luck getting a seller to let you do that.

 

[bostonhatteras]

pay extra for the yard to dry the boat out for a week prior to survey! that must be some pretty good snake oil they apply to dry it. your boat is what 38 years old, I don't think its going to delaminate now after going strong for this long. I agree that a percussion test/sounding the hull is all that is required. the decks with balsa coring are another matter, and the experience the surveyor has with the instrument and interpreting the reading has probably more importance than an unqualified numerical number/reading anyday. ask why that reading means what it does.

 

[thoward]

David Pascoe has an article on them. From my understanding, it is not worth a whole lot.

 

[Capt.Erich]

A week will not do a thing to "dry out" a hull. This process takes a lot of time, labor, and money. The typical process involves stripping the hull to bare fiberglass, doing moisture reading over the entire hull and mapping the wet spots. Depending on the severity of delamination, the wet spots may be ground down and allowed to dry for weeks or even months. Those spots are monitored and eventually filled and faired and the hull covered in epoxy or other barrier coating. I've seen this done on several boats only to end up with bisters a couple of years later.

For a 40 year old hull of solid fiberglass... a major waste of time and money. Just my opinion.

 

[Pascal]

when i had my boat surveyed, i discussed this with the surveyor. he said he brought his moisture meter and was ready to use it on the wet hull if i insisted to but warned that the results would be meaningless. he recommened sounding the hull instead.

made sense to me... seems like moisture meters can be a useful tool under certain circumstances but no more than that

 

[REBrueckner]

I did a little surveying some years ago and used a moisture meter. The above posts are all appropriate. Even six months on shore may not dry out a hull..they will all appear saturated when hauled....it's a waste of time....But it could be useful for deck coring and moisture checking there. A rubber mallet for tapping underwater hull parts is a reasonable way to go.

I watched a surveyor tap a sister ship to my 1972 48 YF a few years ago at haulout...he got a little concerned about a different sound around the aft struts....I told him likely the glass was beefed up there and maybe a plate was in the glass as Hatt reinforced a lot of stuff....he moved on and was not concerned....He may have spent 10 minutes or so tapping underside of hull,maximum....

Most older Hatts are wet but with the hull thickness likely they'll still be wet 50 years from now and still going strong....

 

[REBrueckner]

Oh, I forgot to mention....osmosis is reportedly greater in fresh rather than salt water...which is not commonly known...It may have been Pascoe's site that pointed that out under his blisters paper..wherever I got it it was a relaible source...

And moisture readings around the roof where the flybridge is screwed to the top can be of value..many Hattas are also wet up there..it migrates to the aft corners of the roof and is often detectable there as well. Mine was wet when I bought it, so I drilled two 1/8" holes outboat where it would drain outside my bridgedeck softcover...they oozed for several months and I haven't worried since. I just did not want freeze/thawing to continue with lost of moisture during the winter season. I found some loose roog fastenings and rebedded them in fresh caulk..maybe that was a leak source, maybe there were others.
A source of water inside flybridges are snap fastenings..lift a dot type...I used to have life preservers get wet in soaking rain...took me a long time to find the lift a dot screws fasteners were dripping in storms....bedded them in a tiny amount of caulk,.,,dry ever since....When installing canvass fasteners in fiberglass, ALWAYS be them in a tiny glop of caulk...

 

[richardoren]

Thanks Guys!

THANKS GUYS!

This will simplify life and make the survey scheduling a lot easier.

Cheers,

Richard

 

[Boss Lady]

look at this thread http://www.samsmarine.com/forums/showthread.php?t=4909&highlight=moisture+meter
Fiberglass resin is waterproof. You can get capillary wicking along exposed fibers that will penetrate into the resin in an extremely localized area, this is what can cause blisters.

Cored laminates can get water intrusion along seams and screw holes, but you cannot measure that through the fiberglass, you would have to grind away the glass and measure the moisture content of the wood.

Anyone attempting to tell you that you need to "dry" out fiberglass should be viewed as suspect in either their knowledge of physics or their business practices. Run the other way!

here is another thread http://www.samsmarine.com/forums/showthread.php?t=4254&highlight=moisture+meter

 

[garyd]

We used a moisture guage on my boat some time during the process. The only moisture was under the exhaust tubes. I thought that the integrity of the hull in that area had been breached.

However, when we removed the wedges just under the exhaust ports we found the moisture, the wedges that Hatt put on were made out of plywood and glassed onto the hull bottom. They were soaked. Once removed no more moisture tah dah.

garyd

 

[Boatsb]

I have a 40 year old boat and cant imagine the moisture meter not showing some level as the boat has been in the water and has some ( very little ) water in the bilge.

I designed and built molds and boats and did my research into the issues with fiberglass and the absorbtion of water into the fibers. A heavily built boat like the hatts that were properly rolled out will have minimal voids for the water to accumulate. If its in a warm climate there is no expansion from freezing and thawing so the saturation ( I estimate less than a gallon in a 50 foot hull) should be considered a non issue.

Pounding ( Sounding ) the hull is the best way to check for voids and delamination and should be the preferred method by most surveyors. My Surveyor spenta good 15 minutes on a 41 foot hull and found nothing but solid glass. Thank you Hatteras. way to build a boat back then.

 

[exsailor]

Had experience with a bottom paint years ago that sent the meter into a frenzy. Called paint manufacturer and confirmed that it would do that. Recent 53 survey was the old fashion way ... bang, bang, bang all over the hull.
ByronS

 

[Boss Lady]

a moisture meter reads electrical resistance. Take a number 2 lead pencil and draw a heavy line on a piece of paper, then place the probes on the line and tell me how much moisture it is reading. Bottom paint is laden with copper, an excellent conductor. Salt residue combined with humidity will give a reading on a moisture meter, even on the skin of fiberglass, paint, or plastic. It is nothing more than a vert sensitive ohm meter, set up for the general resistance found in most common wood. Even a different species will throw off the accuracy. It is Voo Doo, and is just a way to legally rip off amateur wood workers, and now it is finding its' way into being mis-used in other areas.

Water in deck coring is not even a problem generally, wood rot is the enemy. Water in cores used for hull sides and God forbid below the water line, is a problem because of the hydraulic hammer effect that will cause delamination. Rot would be the secondary problem.

Do some research and become knowledgeable on this before you buy a boat. There are plenty of self annointed experts that will tell you what they know, most of which is not based upon sound science or physics. The meter is a prop to make them appear knowledgeable.

The hammer test will tell you the current condition of the hull and decking.

Go to this link for a reality check on the real methods of checking a hull.
www.flirthermography.com/media/2005-001 Allinson.pdf
In this test using a capacitance moisture meter and a resistance moisture probe, the surveyor shows how the meter goes off scale when testing the balsa core using the resistance probes, well, this is no surprise since salt water conductivity will do that to a highly sensitive scaled meter. The surveyor is ignorant of how the meter is affected by the salt water intrusion. The use of thermography is a novel approach to quantifying a problem. This all boils down to how much money do you want to spend to detect the obvious? This is a Sea Ray with a cored hull.

Solid fiberglass devoid of air pockets cannot absorb a detectable amount of moisture that can be measured short of using extremely expensive testing methods and equipment.

The major issue is detecting existing delamination. Cored hulls require detecting of water intrusion that leads to early hull failure. Cored hulls are a different story.

 

[bobk]

I've got to jump into this discussion with a different view based on 50 years of boating and 40 years in plastics research including some research on the cause and cure of blisters. There are one or two good easy to read technical articles on the causes of blisters that you can locate on the internet. If I recall, the authors were researchers from MIT but I don't have the references handy.

First, there is more than one type of moisture meter. The one with two probes referred to in one of the posts is for wood. I believe it measures conductivity and does not work on fiberglass. The one I use for fiberglass is a capacitance meter. It shows relative moisure in the laminate, but will also respond to embedded metals or near-by screws etc., so it requires a bit of experience to interpret 'moisture' readings. I've seen surveyors who don't want to use moisture meters, or play down some wet areas that the meter locates. That could be dangerous to your wallet.

What can you learn from a moisture meter scan of a solid hull? Lots in my opinion so long as you do not use the type of paint that produces a wet response. For example, I had a trawler with a deep keel. When it was 4-5 years old, I went over it with a moisture meter and found a wet spot on the keel that had no blisters and sounded fine to a tapping hammer. I ground back a bit of gel coat and water started to trickle from a few pinpoint holes. The laminate was very thick at that location, but wasn't wet out correctly and bilge water was escaping. Problem found and fixed.

I wasn't so lucky when surveying the 48MY we just bought. I was running around trying to watch the surveyor instead of using my own meter. The surveyor tapped the bottom and used a meter over a lot of it and even compared areas above and below the waterline at two foot intervals. HOWEVER, neither of us ran a meter along the hull by the aft rub/spray rails. A few months later we had leaks on the leading edge of these that was probably caused by improper placement of lifting straps. The plywood stiffeners behind the rails were wet and that was easily dectectable with the meter after the fact. That was an $11000 problem that might have been negotiated before purchase.

Never trust tapping alone when surveying topsides. You can miss leaks into the core that have not yet rotted the core and sound fine. You can often use the moisture meter to locate a problem in an early stage and correct it easily before it requires serious $urgery. I can tell you where the vulnerable places are on 48MY's because I used my own meter in doing presurveys before making an offer and found most of the breed had water in the same places.

A moisture meter is only a three hundred dollar investment and in my view ought to be in everyone's tool box both for regular check-ups and maintenance as well as when looking at prospective boats to buy.

Bob

 

[Boss Lady]

Bob, I agree with you that in the right hands a capacitance meter can be a useful tool. You also have to know when the meter is lying to you. Paint, wiring, screws, and other materials can cause a false reading. The biggest problem I see with the over reliance of using the Voo Doo meter, is very few people can use it properly in context with surveying a yacht. I have seen problems declared where none exist and problems missed. The average person can get taken advantage of because these guys use the props very effectively and trust them. I say that you are better off if you become knowledgeable like you have. You relied upon a surveryor and got burned, I am sure that your inner voice was talking to you, while the survey was going on. This is exactly why I guess I am a bit alarmist about the whole moisture meter issue.

Chris