Rusted front wing repairs

A bit of as different blog post for a change - I need some help with diagnosing what's really going on with my front wings, and patches of rust in the same place on both sides of the car that has completely rotted through.

This area was corroded when I got the van, so I welded it up as with so many other areas. Water kept coming through the weld from the inside though, and I couldn't work out where it was coming from. It instantly started rusting again and the paint blistering with water from the inside. This is the condition on the right hand side now:

I set about fixing it the other day, and pulling the rusty metal away, found this (on the left hand side):

It's hard to see, but there is some fibrous type of material in behind the metal. It runs horizontally along and then goes down the rear edge of the wing. It's as though it's some sort of support structure for the wing. It explains the source of the water coming from behind. I guess it absorbs water and later gives it back out. Any ideas what it is, and what's best to do about it? I could go about getting the whole wing off, but don't want to unless absolutely necessary - I could easily weld a patch over this area and make it look presentable enough, but would need to get rid of the resin stuff that's been soaking up water.


8 April 2014 Update:

A bit further investigation including speaking at work to a couple of blokes who started their careers working on CF's at the factory, and no further forward. Decided to take the plunge and open up the holes a big bigger to investigate. This is a better picture of the resin.

I pulled the resin off, and this is what's left:

Turns out it's some sort of sealer for spacing the wing away from the metal work underneath. It only runs around this upper corner as that's where the metal structure underneath goes - further forward there's a void behind. Clearly the sealer was absorbing water and causing my problems. Should be an easy job now to weld back up and make it good. This is the sealer that came out:

I'll post some pics up when i've done the welding.