Interesting and thought-provoking comparison. For me, writing the novel, especially one as involved as EFAD would probably be harder than building the boat. The mechanics and stylistic elements of sailboats are pretty well documented and so you don't have to invent and design in a void. And you don't have to agonize over every weld and placement of every screw and bolt ... it would be readily apparent whether it was right or wrong in that moment.
For a novel, especially one as complex and as involved as EFAD, every word, every paragraph, the character development, the technical details, the psychological dynamics, the flow of the story, and the overall continuity ... all of it, has to be invented, and distilled from a lifetime of understanding and study. And the potential is there to hit a mental brickwall agonizing over every phrase and description to make it just right.
In other words, I think I could study for a year or so and then go build a sailboat, but I doubt that I could study for a year or so and completely invent a (complex, technically detailed) novel that is entertaining, interesting, and readable.
Of course if you build a sailboat wrong, you might die. If you write a novel 'wrong', no one will read it. I haven't seen your boat, but you obviously got the novel right. And since you were around to write the novel, the boat must be pretty solid as well.
(Sorry for hijacking the thread, but I am chatty this morning trying to warm back up from an early morning bike ride in 19 degree weather.)