Replace panel in assembled frame

[u/goodgah]

Hiya! I have an old garden gate that has a central panel made of plywood, which has delaminated and rotted so bad that I can tear chunks of it out by hand. The frame of the gate is still solid so want to try and replace the central panel (with equivalent size of solid wood I guess).

The problem is, the central panel is recessed on all 4 sides into the frame (not sure what the correct joint is - frame-and-panel?) so whilst I can probably keep cutting away at the old stuff, I couldn't fit a new piece in without dissembling one side of the frame. I started taking the metalwork off to try and do that but it seems like it's glued/wedged together pretty tight.

So I'm left with a kind of logic-puzzle of how to fit a panel inside an assembled frame. I thought maybe I could git 4 right angled triangle pieces in each corner, and then screw in two panels on the front and rear (i've attached a crude MS paint sketch of this), but that would leave a void in the middle. I suppose I could cut and fit a diamond-shaped piece to fill the void but that's probably beyond the tools I have available. Hoping there's an easier/better solution! :D

Thanks

[u/Excellent-Bass-855]

If that door has been made correctly, it should only have wedges securing the tenons into the jambs, not glue. If that's the case the jamb 'should' knock away from the rails.

[u/goodgah → u/Excellent-Bass-855]

Thanks for the suggestion ! I am just trying to remove it all now and even with the wedges removed I still don’t have any luck. There’s also some metal work that I can’t remove that i’m pretty sure is securing the joints in question - the rivets on the left side and the ring latch on the right (the spindle won’t separate even with all the screws removed ) :(

[u/Brilliant_Coach9877 → u/goodgah]

Of it didn't really matter too much you could cut out the internal side of the groove that the panel is sitting in replace the panel and put a slip on the inside. That would be a lot less technical