It was a book about a group of kids becoming adults following the main character who is weaker then the others but has a very creative mind and a knack for inventing. I believe it takes place in a very Norse setting.
A few random things I remember is he designed the boat they use on the adventure. There is a one handed badass guy who the inventor makes a prosthetic for who joins them in there journey. There is a hidden compartment on the ship only known of due to its planks going the wrong direction.
Any help would be appreciated.
by classymonkey03