Posted by Bengt Blomberg on February 11, 2002 at 17:22:50:
I am at the moment as occupied with rewriting my web sites in order to better present the new HotVac technique, that I have not had much time to check the Forum. HotVac provides a much easier and less costly
"osmosis" repair than the 12 year old and more primitive hyperabsorbtion technique used by OsmoCure which it will now replace.
Regarding moisture meters, the Sovereign penetrates a few mm only and is worthless for GRP. So far Tramex Skipper is the only one I have found which with a little experience can tell how deep in the laminate the hydrolysis has created damages where the water can enter and let the moisture meter indicate the size of the damages.
The GRP 33 I have not tested. What you need is a meter with three different sensitive ranges which can tell you about surface moisture like dew, moisture 1-8 mm deep and moisture down to 25 mm.
The first thing you can check is, that the sensor area is at least 600 square mm and that the distance between the centers of the two sensors is at least 40 mm. Otherwise it will never meassure deep enough.
However the moisture alone does not tell much about the hydrolysis state. It gives you a hint about where to drill a few test holes where you can check for acidity and delaminations only.
Many especially old hulls can hold moisture enough to drive the meter to full range without having any hydrolysis process at all and you can find hulls with severe damages filled with glycol and acid which does not show on the meter and practically no moisture. You can suspect such cases when the meter shows very uneven meassurements when passing along the hull even if they does not show any red other than when using the most sensitive range.
Always check that the pH in the laminate is not below 6. If it is you can be sure that the hydrolysis is active and must be stopped.
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