Here we go!
Measure up from the tail of the board 150mm/6 inches from the tail, mark the centerline if you have not already done so. The space between the holes of a Twin-Tip fin is 38.5mm/1.5 inches.
Make 2 pilot holes on the centerline using a fine 1mm drill. We’re going to drill right through the board with the pilot drill and then using a 5.5mm wood bit, drill halfway from the hull, then halfway from the deck – meeting in the center. The drill will not tear the wood & leaves it nice and clean.
If you choose to make your board using lightweight Paulownia or Red/White Cedar you will have to over drill the fin hole with an 8 to 10mm drill bit and then fill the hole by scotch taping one side of the hole and filling it with epoxy/silica mix or a suitable casting abs type resin, which is poured into place and left to cure. Once it has cured the hole centers are marked in a similar way and drilled as explained previously. This will be covered in a separate video based upon how to shape a Paulownia preformed blank and apply the glass fiber/hot-coat.