Not a dumb question. At the turn of the century (1900), Bee Keepers like Danzenbaker and Quinby experimented with “closed frames” in which there is no gap as you speak of. Some argued that having no gaps between frames allowed the bees to retain their heat more for better wintering. However most were concerned that closed frames would end up squishing too many bees and the frames would end up getting propolized together. Uncapping a closed frame design would seem more difficult too.
The current end bar frames design (Hoffman style) avoids the problems of the squishing bees, uncapping, and propolis while providing an easy way to space your frames properly (by sliding them together).
A triangle design might work but it seems like the frames might be a bit wobbly in the box. I’m making some homemade foundationless frames this winter to play with this summer. I’m simply cutting all pieces to the same width for the top, bottom, left, and right and then gluing on little spacer boards on the end bars to make them into pseudo Hoffman end bars. Those little glued on boards give me the spacing between frames I want. It’s probably a dumb idea for me to make frames myself, but I like to try a little of everything at least once. I’m logging how much time it takes just for fun!
Discussion on closed vs open frames Google books, circa 1907http://books.google.com/books?id=6QlDAAAAYAAJ&dq=facts%20about%20bees&pg=PA7#v=onepage&q&f=false