Gelcoat or epoxy?
 

2000 36' skater the underneath or rails are starting to separate. What I mean is the gelcoat? Is flaking off and showing the fiberglass. I bought some epoxy repair putty applied it and it ones right off after I time out. What is the proper material to repair these areas putting a two part epoxy down sanding and then a finish coats doesn't work. Do I need a professional o do this type repair? Help please