moisture meters
 

I put this in general discussion but didn't get much responce. Can someone give me some advice about purchasing and using moisture meters to check for moisture in balsa core? I'm thinking it would have to be a pinless type. Wouldn't the pin type give bad readings due to the balsa being in seperate little blocks with no continuous surface? Thanks.

To the top once for all the people that are only here on weekdays from work.

I don't put much faith in moisture meter measurements on a fiberglass boat. They may be fine for measuring the moisture content in lumber, but they can't reliably measure moisture within or through fiberglass. IR thermography or even a spot radiometer can sometimes aid in locating a saturated core but I haven't found any nondestructive test that works with 100% reliability all the time in every situation. I have wanted to try ultrasonic testing, but have not had the opportunity.

As I've already started the repair I have no problem removing the glass to get to the balsa. Trying to get some idea just how much moisture is in it and how far it extends. Thanks

Sorry, I misunderstood.

Moisture Meter
 

As a marine surveyor I use the GRP-33 moisture meter on every boat I survey. The moisture meter is only a indicator of a possible wet condition that should be followed up with sounding the area with a phenolic hammer. Many times the moisture meters will show false readings of high moisture due to voids or type of materials used in the lay-up procedure. Improper bedding of thru-hulls and improper or not sealing of the core material before installing thru-hulls are common sources of water-intrusion into the hull. A hole saw to obtain a core sample tells the real story after a moisture meter and phenolic hammer determine area to drill. (marine surveyors do not use hole saws...only recommend further investigation) Maintaining a dry bilge is very important since in my opinion nothing good ever comes from water in the bilge. The moisture meter is a good tool if you understand its capabilities and limitations.

Ok thanks. After the obviously rotten balsa has been removed how do you know how much moisture is acceptable in the surrounding area? Does all balsa that is even damp need to be removed? How do you know when to stop?

Moisture Meter
 

The first thing you need to determine is where the water intrusion started. Thru-hull, trim tab screws, etc. The moisture meter will read highest near this area. As you work out from this water intrusion starting point the moisture meter should start to read lower if the lay-up infusion of resin process was done properly. Mark the hull with a marker and note the readings as you work outward from the source of water intrusion into the balsa core. I do not go by numbers/percentages on the moisture meter. Whatever the meter reads in a proven dry hull core area is what you are looking for. Take a core sample at this area. There is controversy regarding wet balsa core and I have heard manufacturers say that the damp balsa core does not affect the structural integrity of the hull. I personally don't buy that. Regards, Steve

Thanks for the help. If anyone else has any advice, feel free.