...in the words of A.M. Robb, there was an "upper limit, in the region of 300 feet, on the length of the wooden ship; beyond such a length the deformation due to the differing distributions of weight and buoyancy became excessive, with consequent difficulty in maintaining the hull watertight." Pollard and Robertson concur, emphasizing that "a wooden ship had great stresses as a structure. The absolute limit of its length was 300 feet, and it was liable to 'hogging' and 'sagging'." This is the major reason why the naval industry turned to iron and steel in the 1850s. The largest wooden ships ever built were the six-masted schooners, nine of which were launched between 1900 and 1909. These ships were so long that they required diagonal iron strapping for support; they "snaked," or visibly undulated, as they passed through the waves, they leaked so badly that they had to be pumped constantly, and they were only used on short coastal hauls because they were unsafe in deep water.
John J. Rockwell, the designer of the first of this class, confessed that "six masters were not practical. They were too long for wood construction." Yet the ark was over 100 feet longer than the longest six-master, the 329 foot U.S.S. Wyoming, and it had to endure the most severe conditions ever encountered while trasporting the most critically important cargo ever hauled...
So it should be clear by now why... people somehow see a "problem" in building of the ark.
Resource: National Center for Science Education (ncseweb.org), The Impossible Voyage of Noah's Ark, by Robert Moore