I have two Nacra 5.7's, side by side. The hull on my first boat will flex slightly when you put your knee into it, any location. Not a lot, no creaking/cracking noise - just a little "give." The second, no flex at all. I always assumed a little flex was normal, now I'm not too sure. Could this be a foam core/no foam core type issue? If it's normal, which is better? The more flexible hull seems lighter, though I can't really tell for sure. I believe one is a"85, the other "87 can't recall which is which.
Thanks
Chris
My 81 5.2 oilcans like crazy, my 86 5.7 is solid. The 5.2 is glass only, 5.7 is foam laminate. Im not sure if they made the 5.7 as a glass only boat, but if they did it would have been in 85 the first year. The main reasons the switched to foam sandwich was increases stiffness and reduced weight. A lot of give isnt a huge deal in the glass only boats especially on the side of the hulls. If they crackle then you may have to eventually open them up and add a layer of fabric and resin. Otherwise i wouldnt worry about it.
I have an '84 N5.7. It is solid glass. The decks are stiff, but the side will oil can, more in some places than others. It is most noticeable when you walk on the inside of the hull, during righting. OF course it is stiffer near the internal bulkheads.