I own a Necky Chatham 16 that has a small divit/indentation on the bottom that measures about 12x12. I simply cannot get the hull to go back to its shape. I have tried letting it sit out in the sun and even filled the cockpit with water. This has been on the boat since I bought it new and causes the boat to want to drift left. After a day of paddling it gets a bit annoying.
repairing “dents” in poly boats
You might want to try a heat gun/hair dryer on the hull… but not direct heat. I’ve had success in removing “indentations” in poly boats by applying heat (with a heat gun) to a damp towel placed over the intended area of repair. Keep the heat moving over the damp towel to soften the hull - and apply pressure from inside the hull if necessary. Good luck!
dent
If you use a heat gun BE VERY CAREFUL!
hair dryer
Id use a hair dryer and heat the area around the “wow” (about 20X20). Then lay the boat on a flat surface and use some type of weight or sandbag on the deformed area. It should come out.
hull divits
replace and step on it lightly a few times. Should grow back on its own.