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Wadding ideas

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Wadding ideas

Unread postAuthor: SDdan » Tue Oct 27, 2009 10:34 pm

My Pumpkin cannon is ready. I picked out some pumpkins today and I need some wadding to make a nice tight seal. What are some ideas of materials that I can use?

I was thinking old t shirts or other cotton?

Thanks Dan
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Unread postAuthor: AngryChauncey » Tue Oct 27, 2009 10:40 pm

Depending on how much bigger your barrel is than your pumpkins, you could make a foam sabot. This would be the best option (providing that there is enough room for a sabot) because it can be designed so that it falls away from the projectile as it exits the barrel, rather than gets in the way. I guess if your shooting pumpkins, your cannon is pretty powerful so you could probably get away with using a t-shirt or something like that. Sabots are cool though. 8)
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Unread postAuthor: SDdan » Tue Oct 27, 2009 11:16 pm

What kind of foam do you use. Is it a barrel shaped flat piece or more like what I would use in blackpowder?

Thanks Dan
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Unread postAuthor: CS » Tue Oct 27, 2009 11:30 pm

They sell foam board at a lot of building supply stores. Largest I've seen is 2"x4'x8' (common as well though) $20 or so. If you need to stack a few pieces, just use wood glue to join them.

*****EDIT:*****
As Tech reveals below, foam will compress because of its cellular structure. But amid that I can say the DOW scoreboard I have is MUCH denser then any pool noodle. They are saying minimum compressive strength is 25 PSI, transitively no idea where that leaves you. Current status of this post: grain of salt. (Wait for more responses, you will get more direct responses. I've made sabots before, but can't go off much besides that.)
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Unread postAuthor: Technician1002 » Wed Oct 28, 2009 12:45 am

I vote against any type of closed cell flexible foam such as used in swim noodles. The reason is the foam size is dependant on the trapped gas bubbles. The first thing this stuff does under pressure (for example 2 atm or 15 PSI) is to change size. Having a sabot suddenly change to less than 1/2 it's original volume when you expected it to maintain its volume to block leakage will leave you with a useless sabot.

I learned this launching water bottles, rocks, golf balls, and such using pieces of swim noodle in a tennis ball barrel. A 6 inch long piece of swim noodle used as a golf ball sabot in a tennis ball barrel has no problems passing the golf ball in the barrel on a 100 PSI shot. It shrinks right down and goes right on past.

A moving blanket used to protect furniture works well. Don't ask how I know.. :D Rigid foam building board may survive the compression from pressure, but without testing I can't vouch for it.
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Unread postAuthor: psycix » Wed Oct 28, 2009 6:48 am

On small calibers I have found toilet paper to work fine. Maybe you could try a bunch of newspapers. Cloth rags should also work.
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Unread postAuthor: rcman50166 » Wed Oct 28, 2009 8:46 am

While I'm sure there are problems with perfect sealing, all the pumpkin cannons I saw used straw/hay to wad the pumpkins.
Image
You can see the straw/hay ends up in front of the projectile. The wadding is in the upper right of the photo. The pumpkin is in the middle there.
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Unread postAuthor: jeepkahn » Wed Oct 28, 2009 12:07 pm

If your shooting for fun, wadding is fine, PC rules state that competition shots are NOT allowed wad/sabot/etc... Punkin only...
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