I have come up with a quick and easy to fix those occasional but unavoidable gouges, dings etc. on your faom board planes. I was flying an Old Speedster in the local high school gymnasium for my first flight after a 15 year break. I was not used to rudder control and ended up using my old habits with left (aileron) and up elevetor. That resulted in too much up and sort of a hammer head stall. I did not have enough room to recover resulting in a hard nose landing. The propeller broke. One of the skwewers broke out in the front and the skewewer that holds the back of the swappable core in place pushed about 1/2' through the foam. I used the gift card idea to reestablish the skewer holes in both parts and was left with the tears that were made. I was able to get the paper roughly back in place but it still looked bad. That is when I came up with this idea.
First make sure everything is flat or indented, no bumps. I used a pie serving spatula heated with a heat gun to "iron" the area. Then just take a piece of paper off of a scrap of foam and cut if in a rectangle slightly larger than the defect. I like to nip the corners off at a 45 degree angle which helps the patch blend in. Ideally the patch should be smaller than a piece of clear packing tape. Cut a piece of tape about 1" longer than the patch. Carefully position the patch in the center of the tape. Then apply the assembled patch over the damaged area pressing down and rubbing especially at the edges of the paper patch. I just used my thumb nail.
There is actually a raggedy diagonal tear in the foam board running down and to the left from the skewer.
The tape also helps the edges of the new hole from getting tattered.
(The next thing I did was to add ailerons to the Old Speedster. Hopefully that will be the real "fix". No more unplanned hammer heads!)