GRP Tosher renovation

[bins73]

I’m spending the winter removing and repairing rotten wood on our 18’ Heard Tosher.
I’ve removed the rotten covering boards and coating - to reveal both skins of the hull. Should I fill the gap between them in order to reduce the risk of water ingress? If so, which compound would you suggest? I acknowledge it will need a proper clean first! Then I’m thinking a thick gloop of epoxy with microballoons to fill and seal the gap before fairing it and replacing the coaming then covering boards.

As always, very grateful to you all for the advice.

 

[DownWest]

I am slightly confused (not unusual..) But is that the the gap between the hull moulding and the turned up lip of the grp deck? If so, then, as you say. A good clean out and some thick epoxy gloop to fill it and clamp it up (a bit) before replacing the wood. I would be tempted to put a row of small ss machine screws and nuts along the joint..
Any pix of the whole boat?

 

[bins73]

I guess that’s what it is, the two skins. I’ve removed all of the rubbing strakes, coaming and covering boards - all of which were horribly rotten. It’s a question if where to stop - the stem post is similarly rotten, but is sandwiched between the hull and deck mouldings, and won’t be easy to replace without breaking the glass, which I really, really don’t want to do. The stern timbers, at the top of the gunwale, were also soaking and rotten, but were easy to remove and will have a new covering board.

I think I’ll use Douglas or WRC for replacement timber, rather than tropical hardwood - unless anyone suggests that is silly?

As you can tell, this is my first such project!

Photo of her last summer attached, doesn’t really show the dodgy wood!!