humidity in fiberglass??

Hi to all,
i recently bought a joubert- nivelt 1981 quarter ton, the boat remained 2 years in water and as we took it out of water we had seen in some area (near waterline and under bow) some diffuse small (5-6 mm) blisters in thin gel coat , some have transparent fluid, other are dry , i know i have to mesure humidity in fiberglass to chose the appropriate job, but we are in a far isle in south italy withouth appropriate machine to evaluate the umidity of fiberglass.
Is there any way to have an approssimate idea of water in fiberglass without appropiate instruments or to be sure the hull is dry to use epoxy on it ?
thanks to anyone should give suggestion
Fair wind
Jelfiser

 

No. Either use a moisture meter or cut a coupon and weigh it before and after drying it in an oven. Moisture meters require a fair amount of experience to interpret the readings. It may be cheaper to pay someone for the service. Blisters and clear liquid are not necessarily water only. They can be excess hardener left in the resin or other chemicals.

 

thank you, the problem is that there they don't have a moisture meters and i cannot pay no one for that , seems to me so expensive buing one , or cut a cupon on a small boat ...

 

A moisture meter like the CT33 is US$133.00
http://www.odyssey.on.ca/~electrophysics/o_usa.htm

 

Thank you very much, gonzo...
i'm just evaluating to buy from US, here in italy boats, epoxy and moisture meters are much more expensive !!!
those i've seen in italy were about 450 euro (US $540.00)

best regards
Francesco

 

a very simple way to see if moisture level is at an acceptable level is to take some clear plastic ~30cmsq.,,and tape all edges to surface,,apply a little heat for a few hours...if condensation shows on the bag surface,you are not ready for recoating!

 

Great ... that's what i was looking for!!! thanks very much

 

...oh,yeh,,I can varify this method--a surveyor once doublechecked my assessment with moisture-meter.
......a good way to accelerate removal of moisture is with more plastic,tape,and a vacuum pump.You can use a vacuumpump from air-conditioning service-the difference between these and purpose built pumps is the extended run-time and the existance of a fan in the purpose built pump,,,so you can either pay 4x the $$ for a purpose-built pump,,or attach a computer fan or two onto a airtech's service unit!!

 

I've never seen that, can you explain me better ?
Do you suggest to cover the entire hull with osmosis and creating vacuum? for how long time? do you think that a fridge pump is also ok? they often use it for laminating fiberglass ....

 

...1-yes.vacuum bag the full underwater area.
2--until it passes the moisture test...count days rather than weeks!
3--I've heard people use fridge pumps,etc,,,but the pump I use is a nice portable unit that is supplied to air-conditioning technicians for evacuation of very large systems.

Another difference that a purpose-built vacuum pump sometimes has is a primary/secondary vacuum,where it can remove a large volume of air,,then a more powerful aspect kicks in for the actual -work-.You can replicate the 'primary' action with a simple shop vac to remove the larger volume.

some tips.....A suggestion I'd make is to use recommended bagging film rather than going cheap with (porous) poly film,,use proper bagging adhesive,,,and have a # of separate sections so you don't go totally mad if you're trying to find a leak--it's good to make careful choices where to simplify!--some would say ANY of these simple choices could be a mistake.

Before bagging,,or when doing a conventional air-dry of a hull,,,it's VERY helpful to do occaisonal wash-downs with TSP and water.It seems somewhat counter-intuitive to actually be applying moisture,but the TSP cleanses the chemical residues and vastly accelerates the overall process.

.....remember to have a collection chamber to collect fluids before they are drawn into the pump!!!--this will also give a clear demonstration of volume of fluid collected.

...Of course all the information above INCLUDING the initial moisture test assumes you've fully stripped the area down to bare fiberglass(?!),,,if not,you MAY get desired results but definetly a lot slower...

 

yea, ive yet take away gelcoat ... i think next month i'm going to work with that... thank yot very much !!!