Repair to hole in Laser hull
 

This Laser suffered a hole in the hull, just beneath the gunwale.  Not nice, but not too difficult to repair with a "blind backer."

After drilling four corner holes with a 6mm drill bit, Mr Dremel, with a grinding disc fitted, made short work of cutting away all damaged fibreglass.

"Here's one I made earlier..."  A single layer of chopped strand mat, glassed with polyester resin, cut out with scissors from a much larger piece.  This will be the blind backer, about the size and weight of a credit card.  You can also see the hole has been chamfered back along the surface with a sanding drum on Mr. Dremel.  This provides a greater area of adhesion for the fibreglass repair in a few minutes.  The blind backer must be placed inside the hull and glued to the inside to provide a surface to build upon.

Four small holes were drilled in the blind backer and two lengths of strong string passed through from behind.  Then the edges of the backer and the inside edges of the hole were smeared with "Five Minute" epoxy resin.  The backer was carefully angled inside the hole and the string pulled taut to hold the backer tightly in place while the epoxy cures.

This most excellent and ancient copper headed lump hammer provides sufficient weight to keep the backer tight in place as the epoxy cures.

After the epoxy has cured (30 minutes) the strings have been cut away and the area surrounding the wound has been masked with electrical tape ready for glass fibre.  The tape does not leave adhesive residue on the hull and glass fibre resin will not stick to the tape, an important time saver after the next step.  At the bottom, a sheet of acetate film has been hinged in place.

A quantity of polyester resin and fibreglass strands was mixed to the consistency of sauerkraut (sometimes called "kitty hair") and spread into the wound.  Then the sheet of acetate was overlaid, taped at the bottom, and a stiff plastic card was used to squeegee any excess material to the top, smoothing and consolidating the repair.  When the polyester has cured the acetate sheet will peel away and any excess will simply fall off of the red tape.

Time so far: 90 minutes.

Here the cured (three hours) fibreglass repair has been sanded to a level of 2mm below the surrounding hull area in order to allow space for new gelcoat.  Masking tape has been used which will be peeled away, carrying any excess, when the gelcoat is half cured.

I didn't get a chance to photograph the gelcoat application and finishing with wet and dry paper 400 grade then 800 grade then 1200 grade followed by rubbing compound to return the shine.  There is a very slight colour difference, but completely sealed and finished.  Total work repair time of three hours (excluding cure times).