These are some shots looking down on my spark gap. This gap was made using 8 pieces of .75" copper pipe 2" long. These pieces of pipe were the bolted inside of a short length of 4" PVC pipe with brass screws. To set the spacing between each piece of pipe I used a hacksaw blade, which had a thickness of about .030". I have 7 segments available and it is quenched by the fan from a microwave oven.
Here are a couple side shots of the spark gap. I use a sherbet container with the bottom cut out as a plenum attached to the original mounting bracket for the fan from the microwave oven. That way the fan mounts very easily. The microwave oven bracket is screwed onto a piece of scrap plexiglas. It has quenched nicely all the way up to ~4kVA. The hardware used is 8-32 brass screws and nuts.