Any advice on how to repair?

Ouch that's going to need a significant amount of material cut out to check the blank by the look of it. Does it extend right through to the bottom? Definitely fixable just a matter of cutting all the damage away and re building, others will know more about it than me, you will get the right advice on here .Howd it happen was it a mast hit?, it looks like its been dropped on something. Definitely all layers need re building though.

Get it to a pro board repairer, it will be repaired safely, will sail properly and you never know it's had major damage.

Here is what I would do considering location. So semi- laparoscopic surgery.
1. I would squeeze cracked parts back nicely. Don't chip graphics
2. Then cut out a small piece of the rail marked in green (keep that piece).
3. Then take/dig out substantial amount of the foam core under that crack (maybe half a foot around) that crack.
4. Then you can prep strips of carbon/glass cloth and glue on the top and bottom (you working 100% inside the board) covering the crack and inject the crack a bit with epoxy before. It will likely soak anyways. Basically you rebuild carbon shell from inside. Put as many layers are you need. Can look sloppy too (after all it's all inside.)
5. Then pore in polyurethane 3-4 density foam. Sand to accept the rail piece you cut and glue it on adding few layers of glass around.

The poly foam is closed cell plus it's just nose area. Pretty simple fix with minimal damage to the graphics. Spray paint the rail blue and you can hardly find the board was even fixed.

Cheers

Remove the bare minimum required to get the pieces aligned.
Inject with white Gorilla glue. Cover with tape to drive it inside. Dry minimum 2 days.
Then sand 2cm either side of the crack no deeper than the ABS foam.
Glass with 1 layer 150g carbon, then 2 layer 120g s-glass.
Fair and paint.

Don't pull out pieces of the core or inject epoxy.

Whatever you do, don't just squirt polyurethane into the core. As a rule polyurethane melts polystyrene.
If you propose to squirt foam in there test it against some EPS first to be sure.

^^Quite the opposite. Polyurethane foams and glues don't dissolve styro.

However, Aussie folks DON'T listen to yanks about Gorilla Glue. There are quite a few types made by Gorilla, and only one is OK. One of them is about the worst thing you could ever stick in a board.
You need the honey coloured one that's almost odourless - in Australia its available. I use Tarzan's Grip Mega Bond, same thing.
The advantage to that is it sets by using moisture- so any dampness in the core will make it set faster and a bit harder.

I would not use leto's method as its very hard to work inside out, and all just to preserve graphics. Nah do it the normal way. You need to remove the hi density foam layer, fill the stryro crack with foaming polyurethane glue (as above), fair, replace hi density foam with a nice bevel (scarf joint) and glass over.

If you have never done board repairs before, this is NOT the one to start with. This is the kinda one to tackle after a few nose jobs and maybe a 4" sized one on flat deck. That foam layer will be a compound curve for a start.

Get a pro repair, or hammer it level with care, fill it all with UV cure resin to seal and put up with it ugly

Select to expand quote

GasHazard said..
Whatever you do, don't just squirt polyurethane into the core. As a rule polyurethane melts polystyrene.
If you propose to squirt foam in there test it against some EPS first to be sure.

As Mark Says, polyurethane is fine, it's polyester that melts styrene

Show us underneath.

I would do what others have described.
In brief:
1. Snap it back level
2. Clean up loose fibers
3. Drill along the crack a few holes
4. Inject polyurethane glue
5. Trim excess and sand area
6. Apply several layers of glass and/or carbon

It's not an area of stumping nor affects integrity of the board. The most important is to keep it dry.

Anyway, that's how I repaired mine and kept repairing until I learned proper forwards :D !

Or learned to not buy Starboard....

Mark,

Perhaps its different stuff here but I've used both the white and the honey colored Gorilla glue, the white stuff was significantly better. Cured more flexible, denser and sanded much better.

I've stuck together some pretty messed up boards with it and I'm going to use it on my next foil box install rather than thickened epoxy (which I'm not convinced attaches well to the core).

I like Manuel7 approach. Similar to what I suggested but for this fix and location I would work from inside. Nothing is going to melt using polyurethane foam. Very safe. Gorilla glue is a no. Even if the glue doesn't melt anything you need flex in that area and Gorilla glue dries pretty stiff and dense.

My advice here

www.seabreeze.com.au/forums/Windsurfing/Foiling/Foil-board-Repair-Job-The-new-nose-you-all-need?page=1#18