Damage done hitting a submerged log which has probably been in MortonBay for years as it was certainly water logged and just below the surface. No injuries except a few repairs required to board and new fin to be purchased.
Good for the weed now.
We can fix it with key hole surgery .The box is solid apart from bits chunked out the back. It's a deep Tuttle box and only damaged half way down. It's a carbon box ,so resin will stick. Almost no water got in. The box hole goes all the way to the deck and doesn't have recessed bolt holes and is a solid unit. The join between box and the bottom of the board is solid.
With a Dremel kind of grinder I removed all broken and loose bits . The rear corner radius part of the box are still there and are solid. I removed about 8 mm of foam behind the box and about the same down behind the good remaining section of the box, well within the PVC foam. Also undercut around the cleaned up split on the bottom.
Then made a PVC replica plug of the back of a fin.
The dummy fin head will be wedged in tight at the rear of the box. ( wrapped in plastic bag so resin doesn't stick to it ).
Using a super slow curing with almost no heat resin, (surfset flex ). It's tough and not brittle. Will be mixed with chopped glass fibres and milled glass. Then poke this mix down behind the green foam plug. Should be solid as an ox. Don't panic , the big chunk of resin won't get anywhere near hot enough to melt the EPS .Bog and paint the bottom. May need a layer of painted on resin inside the rear of the box and lightly filed for a perfect fin fit.
I am confident this will work unless there are other cracks in the box that I didn't see. If it doesn't work and leaks , out comes the box.
That's good, it's blown the back of the box out without damaging the rest of it. Advantage of deep tutlle the fin can go quite low without damaging the box.
Hole stuffed full of Surfset Flex resin with chopped glass and milled fibres and white tint for a touch of class.
Select to expand quoteAusMoz said..
Stronger and better than it was brand new!
Wow , easy shootin tex.
Could be a crack somewhere else and this fix is kaput.
Im at 75 % positivnesssss.
I was just thinking if you just wacked a fillet on that and glassed it in it would be a ok weed fin ,
nice job anyways 
Some spots around here have lots of mussel and oyster farms. Wonderful things, a massive plank of wood about 12feet long floating 6inches under the surface. You learn where they are pretty quick but sometimes the come loose and drift to new spots.
