Welcome to the board, Neptune.

I tought about this subject some time ago, and apparently if they did not have such fourth funnel which easily adds 10's of tons of weight to the ship, the ship would probably be harder to sink, cost less at the price of public appearance.

The illustration could hardly depict the sheer size of Titanic without using some refference points from known objects like cars and comparable boats. However because it was so huge than any thing else of that time, the comparison method to show such sheer size was useless. So i think the reason for them to come up with a fourth funnel is for illustration purposes purely to market it easily in real and in poster.

<a href="http://www.titanic.com/modules/myalbum/photo.php?lid=71"><img border=0 src="http://www.titanic.com/uploads/thumbs/71.jpg"></a>

Click on the photo, and in the album again for enlargement

While the build quality was already higher than what it supposed to be, However when looked at the fact that the ship broke in half while sinking is mind juggling.

The luxury situation added alot of weight to the ship, Now adays, it is unthinkable that ships like QM2 and other luxury liners will add another funnel just for marketing , these ships now have luxury appearance with the foresight of responsible engineering and functionality for example by a very wide and high double level bridge with the total length full of windows from port to starboard.

<a href="http://www.titanic.com/modules/myalbum/photo.php?lid=267"><img border=0 src="http://www.titanic.com/uploads/thumbs/267.jpg"></a>

Click on the photo, and in the album again for enlargement