GRP. A fabrication tecnhique 3
Sheets of GRP are normally joined up with the 'good' surfaces (facing the table when laid up) outboard and the rough surface is used for the jointing layup. To avoid resin running onto the good surfaces, that may be finished surfaces, lay a strip of masking tape along the join.
The surfaces that are to be laid up onto MUST be cut back to 'Grey' with all cured surfaces (Glossy) cut away. This ensures a good bond when resin is laid "Wet on Dry". (Work "Wet on Wet" if possible) 40 or 60 grit "production paper" is normally used for this