Or they could just go to the how to section or showcase to get ideas, since everything is there.
Seriosly, anyone who can't figure out how to build a spudgun and just want the plans to be handed to them shouldn't be building a spud gun to began with, especially since its pretty damn easy to make one.
I spent several hours researching how to make a potato cannon, and figured out my own design through my iginuity, and it doesn't seem fair to cater to the needs of new people to this hobby and this site (who would probably leave and contribute nothing after they got plans) when others had to learn through trial an error and use their MINDS to make their cannons.
I say just deal with the "give me plans" posts, they don't happen that often and i guarentee you even with a Plans Section new people will still post asking for plans on a specific gun which they couldn't find in the plans section (if they even bother to search). There really is no simple solution.
Offering no solution myself, i felt i'd suggest something. On the home page, have it so the first thing people see is big buttons for the how to and cannons showcase, with a note saying "specific plans are not offered on this site (so do not ask for plans), look in here for ideas on how to build your own."
It seems to me that no one really reads the rules (most new people at least), so the they don't realize they shouldn't ask for plans, maybe if it was on the front page in bold letters, it might curb the problem, or not who knows.
Stanford Class of 2012
"In the end our society will be defined not only by what we create, but what we refuse to destroy"- John Sawhill