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Old 23rd December 2020, 16:36
Mitchelkitman Mitchelkitman is online now
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Don't know you knowledge/experience, so apologise if you already know....
My prefered way is as follows:-
Using a powerfile, grind the area 10mm around each hole, almost through to the underside ie so only about 1mm thickness remains at the hole circumference but feathered to the edge of the area being worked on. Clean with acetone. Put a piece of selotape or parcel tape on the rear of the GRP (may need reinforcing with gaffer tape if a large hole. using glassfibre mat, cut pieces of the mat into the same shape as the area, starting off a little bigger than the hole, and increasing to be the size of the ground area (maybe 4 or 5 bits. ) Wet the smallest piece of mat with catalysed resin (do this on a piece of scrap card covered with parcel tape) and then put into position (can be messy to pick up - i use a small coffee wooden stirring stick), repeat with subsequent layers prodding to remove any air bubbles. You can add all layers at the same time (in fact it's preferable). Leave to set for a day and then rub down to a flat surface. DO NOT use P38 or similar filler, because it has no strength and will also shrink for many months, revealing the repair. For small holes (smaller than 8mm diameter) grind and clean as above,add selotape, but instead of using mat, just use 6mm chopped strands and resin pushed into the hole (beware air bubbles).
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