Thanks Bert.

Spoke with a couple of folks (owners and others) and the consensus was that this is not a high-load/shear area. The crack hasn't spread for quite some time, so I suspect there might have been some single event that might have formed the crack.

Based on Jake's thoughts (not the carbon stringer stuff... I'm an amateur), I ground down until there were no cracks/voids to see if there was anything really obvious causing this problem, and I couldn't find anything.

It did appear that there was no lateral reinforcement of the core material.. just the two laminated sides. Maybe a very thin glass layer in this axis..

So I grabbed some epoxy and glass weave and laid up about 3 successive layers to build up that area (extended about 2 inches top and bottom of cracked area). Slapped a bit of gelcoat on top (slightly off color which may help identify repaired area in case something else happens down the road).

Hope to get it in the water this weekend (fx ESE 12-15kt) to see if (1) the repaired area is stronger than surrounding area which may cause more cracks (2) how the gelcoat holds after being applied to 24 hr cured/sanded epoxy (120 grit) and (3) if anything else pops up.

I did NOT use the microlight (dangit) which would have helped ease the sanding frustration!

The other frustrating part was trying to keep the glass weave together when cutting such thin strips..

next project: remove & fair daggarboard. Might have to rebed mast base plate screws