How big was the ark (in modern terms)? How many species could it have contained? How many were there to be contained? BIB502-1-12

I’m really interested in responding to this discussion question as by learning more about the construction of the ark I will be better able to defend my belief that the Bible is the inspired word of God. In this teaching, CM brought out again the cartoon most of us saw in Sunday School of the little ark with animals hanging out on the deck.
When God said to build an ark, Noah built an ark, spending more than a century building it. The amount of gopher wood required is mind boggling. And building a huge boat when there had not been rain before, a very great act of faith.
I like the often repeated jokes that the Titanic was built by experts and the Ark by amateurs. The Titanic was billed as “the ship that not even God could sink,” you think?
Noah may have been an amateur; however, he built the ark using God’s dimensions. Genesis 6:15-16, “And this is the fashion which thou shalt make it of: The length of the ark shall be three hundred cubits, the breadth of it fifty cubits, and the height of it thirty cubits. A window shalt thou make to the ark, and in a cubit shalt thou finish it above; and the door of the ark shalt thou set in the side thereof; with lower, second, and third stories shalt thou make it.”
Using the smaller value of a Cubit being 18 inches the ark would be 450 ft. in length, 75 ft. in width and 45 ft. in height. This would be about 522 railroad cars and hold 125, 000 sheep. It is estimated that there are about 18, 000 species and most are smaller than sheep. Even with two each of the unclean and seven each of the clean animals, there would be more than enough room for all with room left over for food and Noah and his family.
The ratio of the width to height of the ark plus the displacement assured the ark of righting itself in a rough sea. God also instructed Noah to pitch the ark within and without. Pitch can be translated to mean atonement and or to cover. Given that the ark was pitched on both sides, it will likely be discovered as God has a reason for his requirements.
A few years ago the movie 2012 was released and I watched it on a huge screen and surround sound. The special effects were awesome with the hero staying just ahead of the destruction caused by horrific earthquakes. A small remnant of the billions of people inhabiting planet Earth was saved by boarding not spaceships but arks. In my opinion the majority of the people spared were more representative of Ham and his linage rather than the righteous Noah. Of course the movie was anything but a biblical, however, I found that the use vehicles to sustain life were arks to be very interesting.

Added 7/26/12
It's an interesting concept and I agree with you that "the Ark is a type of salvation through Jesus Christ." The Ark was a barge rather than a powered vehicle that could be steered through the waters. Surviving the flood and its aftermath would require that its design and capacity be correct. Having God as the master designer, one could rest in the peace of knowing that all would be well. Just as Noah (rest) could rest in the Ark, we can rest on the assurance of Jesus of justification through faith.