Mormon fiction loses to scientific fact and principles. The design of the ark has been shown to be one (if not the most) stable ships that could have been designed, tested in the same manner as other ships.
The Jaredite 'barges' fail that test every time, they keep sinking.
Nonsense. Neither the Bible nor the Book of Mormon provides a "design" for Noah's ark or the Jaredite barges.
The Bible tells us the overall dimensions of the ark: 300 by 50 by 30 "cubits." (Presumably, a cubit is about 18 inches, but we cannot even be sure of that.) It tells us the vessel had several stories, a door, a window (!), a covering of some sort (Genesis 8:13), and interior rooms. It was sealed inside and out with pitch.
Beyond that, we know very little about the ark. What was the shape of the hull? Dd it have a lean or a bluff bow? What was its draft? Did it have a keel? How was it framed, braced, and planked? What is "gopher wood"? What kinds of tools were used to construct the vessel? How many animals were taken aboard? How much food and water were stored aboard? How was ventilation provided?
Such questions can be multiplied indefinitely. Although attempts have been made to address these issues, at this point all we have is conjecture. Unless and until we find the ark itself—or God provides more information— we cannot know much for certain about Noah's ark.
Our knowledge of the Jaredite barges is similarly incomplete. The Book of Mormon does not provide enough information for us to reconstruct the barges. We are told that they were the "length of a tree"; they were "light upon the water"; they were "tight like unto a dish"; and that their ends were "peaked." Each barge had a single door and two openings in the top and bottom, at least one of which could be stoppered in some way. Although the text refers to steering the barges (Ether 2:19), there is no information about how this was done.
We are told that about 22 persons embarked on eight barges; but we do not know how many or what kinds of animals were taken aboard. Indeed, many of the same questions that might be asked about Noah's ark might also be asked about the Jaredite barges.
Unless and until we find remains of the barges—or God provides more information— we cannot know much for certain about them.
I believe in the Jaredite barges for much the same reason as I believe in Noah's ark: I accept both the Bible and the Book of Mormon as the word of God.