It’s been a year and a day since the E9 cato that ruined what was supposed to be the second flight of my 3D Rocketry Lunar Eclipse Jr. Question is, did it ruin the rocket? I’ve had the bird sitting in the basement most of the past year waiting for me to figure out what to do with it. The rear end of the motor tube was charred and I’d discovered the thrust ring was too far forward, but I couldn’t tell the condition of the forward end of the motor mount, partly because of the baffle I put in the body tube.
Finally a while ago I decided there was no better option than to cut the fin can from the rest of the body to get a look at the damage. 
From the misplaced thrust ring forward the motor tube was, semi-literally, toast. But from the rear centering ring to the thrust ring it seemed in good shape and well attached to the fin tabs, and the forward centering ring was secure and in good condition. Last night I decided to go ahead with a bit of surgery that hopefully will return the rocket to action.
I used a sanding drum in my Dremel and some tweezers to remove as much damaged motor tube as I could, from the rear centering ring back and the thrust ring forward, and a little sanding wheel to remove the old fillets from the centering rings. Then I cut a couple of pieces of BT-50. This marked my first use of the Estes tube cutting guides I picked up a couple months ago. They worked.
The short piece I epoxied into the rear thrust ring, butted as well as I could against the remaining old tube. I used a spent E casing wrapped in a layer of wax paper to align it.
The long piece went in the other end of the fin can, epoxied to the fin tabs. I used more epoxy to make a fillet on the forward centering ring, and to install a coupler.
After that I cut a piece off a 24 mm spent casing to fill the space between the tongue of the motor hook and the thrust ring, and cut out a segment to let it get past the tongue.
I epoxied that in place. It’ll serve as the new thrust ring. Here I also put a fillet on the rear centering ring.
Finally (for now) I joined the fin can back onto the body tube. I used a piece of 3/16″ rod to line up the launch lugs. This was definitely a job for epoxy — given the need to adjust the alignment, I certainly didn’t want yellow glue grabbing and holding.
Now it just needs some refinishing. Any higher dimensional rocketeers that can see inside the motor mount from the zorth direction will be appalled but I think the local club members are confined to 3+1 noncompactified dimensions, so I should be safe. (Besides, it only looks ugly. I think it should work just fine.)
Great repair – clean and in line.