We have about $50-$75 to sink into this project. I've been looking around, and I'm trying to figure out the best measurements to get all the ratios right. So here are my questions:
1) What's the best chamber diameter to use? 3"? Is it practical to use 4" chamber?
2) What's the best location for the sparker? I've read in the middle or in the end cap, but I'm not sure which is right.
3) If I want the gun to be 5ft long maximum, what should my chamber/barrel length be? 2ft chamber 3 ft barrel? Or 1.5ft chamber 3.5ft barrel?
I'm using aerosol for fuel. I'm planning on adding a chamber fan. Any tips/advice on that?
By the way I'm going to do interchangeable barrels so that I can take it apart to transport it (and so I can have different barrel sizes

Here are the plans I've been looking at so far:
http://potatocannon.nodice.org/cannonV2.html
What do you guys think? You'll know 100x more about this than me so tell me exactly what to do to make that spud fly as far as possible
