Yeah don't worry. It's just that school started again so I'll wait for the next vacation to continue working on it

Cool thanks.... Gotta love google
BTW, I now know the right dosage for my chamber, and then I duct tape my end cap for security. It now shoots every time and the potato blows up on target 350 feet away

If you do, it would be a very good idea to install a chamber fan as well to aid in venting the chamber.

How do you install a chamber fan?

Yeah i'll do that. I think I'll still use the coke bottle cap to insert the fuel with a syringe 'cause the hole is smaller than the end cap so less fuel will be lost.

OK thanks you guys. I have tested with less fuel and the potato has launched about every first spark. It already goes really far with the cap flying off. I did however try duct taping it to see if that would hold it in place... For now it works, but I'm afraid it won't last long....
Here's a picture ...

no it isn't threaded, so it can easily be removed by the blast, and it FLIES and makes the combustion a LOT louder... i use duct tape for now to hold it in place for now until i buy a new endcap.
Or, should I glue the end cap permanently and drill a hole for the top of a coke bottle and use that to ...

Well the space is really small, about 3mm maximum. I'll try spraying less next time. However, I need to change the end cap, because the one I have screws on easily, it's a lock kind (screw to the right once and it will go click). I will get a better one this afternoon and see whether it will fly off ...

If I make the spark gap bigger it doesn't spark... Is that normal because it is a small sparker or is it just me?

How can I use a seringe???

HI, I just made a combustion type spud gun with a piece of 80mm PVC (combustion chamber) and a long piece of 32 mm PVC(barrel). I use a piezoelectric sparker to which I attached 2 wires that go into the combustion chamber. I use deodorant as a propellant.
First I put the potato in, then I put the ...