Moisture content in hulls
A Sunday afternoon spent at home bimbling rather than sailing led me to wonder about moisture content in hulls.
I've not come across a recent Merlin that has put on weight that could be put down purely to moisture absorbtion. Back to the Future was reweighed after it's bow drop and refit and it had put on weight but it's pretty obvious where that had come from. I never thought to weigh the fittings before they were attached but the figures married up with what I expected.
Hi Chris, no reason to think so - she's almost completely stripped out now, and by next weekend I should have a completely bare hull and a bag of new fittings and string to put on her. It seemed like a perfect opportunity to weigh the hull and fittings separately as a before and after.
I don't know very much about the WODS, but it's pretty obvious that there is a lot more structure in them than the FRP CT hulls regardless of builder. They are also contructed in polyester resin which is heavier than the epoxy used in modern hulls.
Heaven Sent weighed 101kg at the champs with at least 3kg of correctors still in, 19 years old.
All good news - a testament to the build quality and materials - as Chris says, adding layer upon layer of grip and paint won't help. I guess 2% or 3% over 10years might not be far off, which is far less than I've absorbed over the last 10 years. Maybe I'm shaking the wrong tree here....
we reckon a repaint (just keying the exising material with 600 paper) sprayed 1lt of 2k + hardenener,gives 2 good coats coverage= 1kilo in weight, thats why we take off most of the existing material,a good 240 longboarding removes most of the old stuff,finish prep with 600 for a finih base = virtually no weight gain,.....as with most things,you get out what you put in....
Wearing a Marine surveyor's hat, the percentages that you see on moisture meters are pretty meaningless, most were designed for measuring damp in buildings. With a yacht hull, which is in most cases solid laminate, when looking for an osmotic condition, the moisture ingress is only likely to be into one or two layers of the outer laminate. Carbon and/or kevlar laminates might throw up spurious readings due to conductivity or just because kevlar can act as a wick. When considering a Merlin I guess that a moisture meter might identify whether there is water ingress between the laminate and the core, in which case it is likely to show locally extremely high readings. I would be extremely surprised if an FRP boat takes on any weight in its lifetime through natural causes. A non epoxied wooden boat ... that may be a different story