skin is not hurt( or burnt ) but I melted the foam under the skin, about 5 inch's or so behind the spar. I have used this expanding foam before on a smashed front corner, sprayed it into a small hole i drilled into the outside edge and presto new corner,get a hot iron roll it around to get the right shape strong too. I was going to fix the dented ones up and use for spares, even made wing joiners for them but never glued them in. Make me an offer, they are my spare's, i'll just have to keep her higher.