These pictures of cracked end caps are examples of the worst case I have seen. They show years of neglect and ineffective amateur repairs.
The first picture shows several hair line cracks that could be cured with 3M 5200. I might enlarge the cracks with a Dremel tool before filling them. The takeaway is that they are large enough and numerous enough to allow water into the pine wood that the cap covers. That wood is structural. It holds the window. Also water will find it's way to the floor and you will never know it until it too late.
Curious about this picture is that the cap is a dingy brown. The 5200 is white like the AL next to the cap. Why is the cap brown? Has there already been substantial water damage that has discolored the cap?
Same rig, drivers side. It looks like someone tried to patch the crack with some sort of tape. I would guarantee the wood behind the cap is rotted. Note the WA tag - Hurricane Ridge is a super wet area of the state.
I would say this rig needs the cap replaced, if caps are still available. Once removed rebuilding the wood frame would be possible. Joining new wood to the existing remnants with West System epoxy. Inside surgery might also be required.
If an new cap can not be obtained, I would cut away the damaged area of the cap leaving the edges for a mold and rebuild with West System epoxy and FG mat. Gflex with a filler added may be the ticket. [West 105 would certainly be the best choice, but would be rather expensive for such a small project]
Puzzling to me is that a crack on the cap seems to extend to the AL skin. It extends all the way to the stripes. Could part of the AL have been patched with FG?
This is a rig to walk away from.
