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Air cannon for launching bait into surf

A place to ask general spud cannon related questions.
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Re: Air cannon for launching bait into surf

Unread postAuthor: jackssmirkingrevenge » Tue Dec 24, 2013 12:10 pm

If you're willing to make the effort, a spring loaded ball valve can give you good flow and fast opening with some measure of consistency.



Here's one way of doing it: http://www.sentex.net/~mwandel/cannon/air_gun.html

A modified sprinkler valve is an easier off-the-shelf way of achieving similar performance though.
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Re: Air cannon for launching bait into surf

Unread postAuthor: Skeeter 115 » Tue Dec 24, 2013 1:57 pm

Yea, dont use a line on it. I think it will be close enough for a test. After the shot, you may have some suggestions on what you would do to make a cannon to launch out 500' or so.
What are you going to use for a projectile ?
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Re: Air cannon for launching bait into surf

Unread postAuthor: PeteS » Tue Dec 24, 2013 2:13 pm

Skeeter 115 wrote:What are you going to use for a projectile ?

Ice cylinders, freezing them now.
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Re: Air cannon for launching bait into surf

Unread postAuthor: Skeeter 115 » Tue Dec 24, 2013 2:20 pm

Cool (punn intended again).
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Re: Air cannon for launching bait into surf

Unread postAuthor: Skeeter 115 » Tue Dec 24, 2013 6:46 pm

Jackssmirkingrevenge, Nice, A spring loaded ball valve, could work. As far as air dump speed for a 1.5 barrel, what valve would you use ?
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Re: Air cannon for launching bait into surf

Unread postAuthor: Ragnarok » Tue Dec 24, 2013 8:17 pm

To be quite honest, a modified sprinkler valve is probably less effort to do right than a spring loaded ball valve and likely more effective. Yes, ball valves have very high flow when fully open, but even spring loaded, they usually take longer to open than the projectile will be in the barrel for.

A sprinkler valve will have an opening time around 5 milliseconds once modified; and while its maximum flow might only be a third of the flow of a ball valve, it achieves that while the projectile is barrel-side of the muzzle.

Opening time is a very important characteristic for a launcher valve; while it has its diminishing returns (an improvement from 0.1 ms to 0 ms might be infinite, but will be practically irrelevant to performance), ball valves generally stay on the wrong side of that unless you belt 'em wit' t'ammer. </lancashire accent>
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Re: Air cannon for launching bait into surf

Unread postAuthor: Lockednloaded » Tue Dec 24, 2013 8:18 pm

How often does it need to fire? It seems to me that a burst disk setup for a fixed launcher firing a heavy projectile would be ideal and very easy to make.
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Re: Air cannon for launching bait into surf

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Re: Air cannon for launching bait into surf

Unread postAuthor: PeteS » Wed Dec 25, 2013 6:00 am

Lockednloaded wrote:How often does it need to fire? It seems to me that a burst disk setup for a fixed launcher firing a heavy projectile would be ideal and very easy to make.

I agree that would be easy and could work well. It doesn't get any simpler, just two sections of pipe separated by a union. If filled from an air tank or compressor it could just be pumped until the disk blew out. You could do that with a bike pump too but it would requite legs or some other support to hold and aim the cannon while you pump.

On the ball valve setup, one thing is that especially if you use threaded parts, you can easily convert it to a sprinkler valve later if you want.

BTW, I should have test results from the ice shots in my cannon a little later today.

Update:
I tried it and the results may need further clarification but:
1. The projectiles wound up being heavier than planned, closer to 10 ounces
2. It kicked like a mule with that heavy projectile and 80 psi.
3. With the short barrel it went about 300'.

This is my first experience with such heavy projectiles so I may be wrong, but I suspect that with a 6-8 ounce projectile and a much longer barrel you would be getting into the range you mentioned.

I have a piece of PVC that is a little longer, but not as long as I would suggest. So I don't have a way to test the 5' or longer barrel that I'd suggest using. That said I will check what I have and maybe try another shot if I find a long enough piece of 1.5" pvc laying around.

BTW, it would be pretty easy for you to build a prototype. All that it would really require is a pressure rated 10' length of pvc, a pvc cap, some primer and glue, and either a ball valve or a union to use with a burst disk (or both). Make it all with 1.5" pvc stuff and just cut the 10' length where you need to to get whatever chamber to barrel ratio you want. You could throw the whole thing together in 20 minutes and then let it dry overnight. If you add threaded fittings you can easily try different valves including the already mention burst disk and ball valves as well as a sprinkler valve. Glue and all it will probably be less than $20.

You will need to buy or scrounge a fill valve. I typically use the skinny presta valves from bicycle inner tubes. If you leave a 1" or so circle of rubber around the stem you can glue it into the cap with contact adhesive. Drill a hole in the end of the cap. Coat the inside of the cap with contact cement where the rubber will be, coat the rubber, and let dry 5 minutes. Stick the stem through from the inside, burnish the rubber so it sticks well, and put the retaining nut on the outside of the stem. Be sure to do that before gluing the cap on.

Another Update:
I found a barrel for another cannon that I adapted to this one. It will have a bit more dead space due to being adapted, but it is more than twice as long (probably 48" total). I will give it a try later.

And Yet Another Update:
OK, good news. I went out with the 48" pvc barrel and some ice slugs that were closer to 7 ounces. The result was about 600' of range with 80 psi and me just eyeballing the angle at about 45 degrees. The recoil was a good bit less with the longer heavier barrel and the lighter projectiles. It still had a pleasing kick though.

You could probably get better performance yet with a bit longer barrel. Also more pressure would help if needed, just be careful and don't over do it. I figure that 80 psi is fairly conservative, do be sure to use pressure rated pvc though.
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Re: Air cannon for launching bait into surf

Unread postAuthor: dart guy » Thu Jan 02, 2014 9:17 pm

You will need a shock leader and possibly a spring or elasic band. if you can get that to out perform a heavy duty cast from a 11 foot spinning or casting rod with reasonable weights like 4-7 oz sinkers i will be extra impressed but look back some people have built some good cannons that may fit that.
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Re: Air cannon for launching bait into surf

Unread postAuthor: Skeeter 115 » Thu Jan 02, 2014 10:23 pm

If I go with a 54" barrel, what ratio would I use to push an 8oz slug out that much barrel ?
Still working on cannon design and volume of chamber.
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Re: Air cannon for launching bait into surf

Unread postAuthor: PeteS » Fri Jan 03, 2014 6:22 am

Not sure what size is optimum, but on the one I tested for you with the barrel I tried the test with I think the C:B ratio was something around 0.8:1. Some folks use quite a bit bigger chambers. A little bigger wouldn't hurt, but I would probably stay under 2:1 to avoid having to pump up too big of a chamber. So, I think something in the 1:1 to 2:1 range would be good.
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Re: Air cannon for launching bait into surf

Unread postAuthor: Gun Freak » Fri Jan 03, 2014 7:48 pm

Keep in mind the constant resistance of the fishing line will cause the ammo to go a lot less far than just a sinker alone. Here's an idea, why not just load the sinker into the barrel and have the leader and bait dangling out of the barrel?
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Re: Air cannon for launching bait into surf

Unread postAuthor: Skeeter 115 » Sat Jan 04, 2014 8:48 am

The shock will yank the hook out of the bait.
PeteS, Did you use the cannon in your post above with a 48" 1.5" barrel ? And you used a 0.8:1 ratio with a 7oz plug and got 600' ?
Is your sprinkler valve modified on the inside for more volume ?
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Re: Air cannon for launching bait into surf

Unread postAuthor: PeteS » Sat Jan 04, 2014 11:15 am

Skeeter 115 wrote:PeteS, Did you use the cannon in your post above with a 48" 1.5" barrel ? And you used a 0.8:1 ratio with a 7oz plug and got 600' ?

Yes to all of that with the following caveats.

The barrel was 1-1/2" schedule 40 PVC and 48" long. The 0.8:1 C:B is at least close to what I used. I am unsure of the volume of the 2" elbows and there was a little dead space due to the fittings used to adapt the 1-1/2" barrel to the 1" valve, so it might be off a bit, but it is not off by a very significant amount. I feel confident that the reading is within +/- 0.05 (so between 0.75:1 and 0.85:1).

The ice slug was about 7 ounces. It started at 8 ounces but was molded for a slightly larger aluminum barrel so I shaved a bit off by rubbing it on the concrete out on the firing site and did not have a scale along to check. Again the weight is close to correct, but not exact.

Is your sprinkler valve modified on the inside for more volume ?


The solenoid was removed and a blow gun pilot installed. The vent hole and metal tube were plugged with epoxy. I could have just left the vent screw in place, but the little metal tube does need to be plugged. No other mods were done.

The following link shows the same 1" globe valve that I used and a similar mod. He used a ball valve as a safety and it looks like he cut off the metal tube before plugging it but otherwise it is essentially what I did to the valve.
http://thehalls-in-bfe.com/GGDT/library ... 1_mod.html
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