Update:
for 22 years old, i think i may have one of the WORST memories of anyone. My father had already explained to me how it’s done a few years ago. a “learn and forget moment.” Thanks for the info tho guys.
theres plenty on it in here. Its how I learned to do it. Its just a hole drilled through to the fin box and filled with resin, then drilled out to 1/4 inch.
I can show you how not to do it…
make sure you put the tape down good, or you get to run around trying to figure out how to keep the resin off your room floor…
it’s okay, allan…it cleaned up nice.
drill a pilot hole from the back of the box through to the deck. then, come back and drill a larger hole from the deck back through to the box. tape off the deck side (better than allan did), and then flip it over and fill your hole with resin (usually pigmented white). after it’s cured, remove the tape, and then drill a smaller hole right through the middle of your resin-filled hole (so that there’s still a barrier of resin all the way around it between the foam. take some rope, tie a knot in one end so it can’t pull through the hole, and then pull the non-knotted loop end through the box to the deck. and you’re done. simple. clean. unobtrusive. never bother with ugly leash plugs ever again.
I agree its the cleanest leash attachment if you have a center box. Plenty strong too, whichis good for longboards.
For your exact numbers: drill from the box side first with a very small bit - less than 1/8". Then go back down from the deck side with a 3/8", which is the same size as the opening in the box. I then tape inside the box and back up the tape with a piece of wood cut to 3/8" thick and wrapped in wax paper. Its a very tight fit and if I get any leaking, its inside the box where it’ll be invisible, and not out on the deck of the board. Flip the board back to deck up, and mix epoxy & white pigment. Fill the hole - again, working from the top you can see when you’re flush. Even 5-minute epoxy from the hardware store takes pigment well & comes out plenty strong.
Next day (you want it to be well-cured) drill back out to 1/4". I do this very carefully - like 1/16", 1/18", 3/16", 1/4". Knot the rope & pull it up through the box. Comes out super clean.
I pretty much do it the same way as described above but I do get a little carried away. After drilling the 1/4" hole, I would flair out the deck side with the cone shaped Dremel tool bit. I also cap the deck hole with 3" diameter circle shaped 6 or 4 oz. glass (on the sanding coat). I gloss coat over and drill out the capped hole, sand and polish. This might be a little over kill but it is super strong. I also cap my center fin boxes too prior to glossing. I guess this comes from sailboard construction influences taught to me by Charlie Wong who ran the Naish factory.
Aloha,
D