SpudFiles

Tomorrow I am going to get the parts to make a cannon and I am wondering if these specs sound allright for good performance.

I'm thinking 3' of 2'' sch40 pvc, over under design using all 3/4'' and a 4-5 foot barrel of 3/4 inch for a barrel. By the way I am using a 3/4'' orbit watermaster for the valve, it leaks but I cant fix it. I'm open to suggestions because I dont know much, and thanks in advance for any help you guys have to give!

i would use a 1 water master the are much better than a 3/4 one.
it looks good for your first hope to see it soon.

Sad to say its not my first, I have just been dissapointed by piston guns not working but I just have 15 bucks sittin here and I wanted just a good average gun to have when I need to shoot stuff.

I have a gun I recently posted which is very simalar to what you are suggesting the only difference is that the valve is 1in and the barrel is 1in.I would go ahead and make it but definatly use a 1in valve it will increse performance significantly.I would recomemd a 1in or 1.25in barrel over a 3/4in one but that probably doesnt matter.

Well as far as barrels you could always make them interchangable by reducing them down to whatever size threads into the valve or whatnot. But like others said you would get much better performance with a 1" valve.

okay then I'll save my cash for a better valve and make a nice one thanks guys 8)

Edit: Actually I just thought about it and my 3/4 valve leaks so I need a better one anyway, and I got a videocamera with my christmas money so you can expect some damage videos!

how is the valve leaking? Is it fixable?

well Its leaking out of the barrel and I have tried multiple things to fix it. Im pretty sure the diaphragm isn't sealing correctly

Try cleaning it, there may be dust and sh|t on it. 8)