EPO split at seems

When I took off my rudder blades to refinish them (they are EPO 1s that had been left in the sun) I noticed that the head of the starboard blade was split. I thought I might inject epoxy+hardener+aerosil into the crack then clamp the two sides together. But I'm unsure how I might prep the internal surfaces? The crack is probably around half a millimeter wide at most so not very accommodating to prep work. By all I've read prepping seems an essential step of the process. Any suggestions?
Photos: https://imgur.com/a/0cI9mKQ

Its going to be tough to clean out that area, but I would make sure it’s dry. I would try to wedge a putty knife or similar into the crack to spread it apart and make sure the inside has dried out. Maybe also hit it with some compressed air to blow out any large debris. Then mask off the outside of the blade and pour/inject resin into the split. I would’t use microballoons because you want the resin to flow inside the blade. Then clamp the two halves together and let the resin cure.

sm

What did they fill the rudder blade with? Foam?

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ChuckC
H21SE- 408

EPO’s are (were) foam core. I don’t know the specific type of foam.

sm