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high power (ish) water rocket

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How will it work?

pretty well
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good
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it'll fart and fall over
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Total votes : 2
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high power (ish) water rocket

Unread postAuthor: FishBoy » Thu Oct 02, 2008 6:49 pm

This is my idea for a relatively high pressure water rocket that would be made as an out-performing alternative to the classic soda bottle rocket. This would be 1-2 feet of either 1" or 1/4" pvc with an endcap on one end and a female adaptor (for filling) and then a male adaptor with and encap with a male quick disconnect screwed in (fill/nozzle). The fins would be balsa, or in my case, fiberglass or fiberglass coated balsa (I might try Rag's idea of grinding the leading edge of fins to create spin)
Since I don't have a compressor, it will use a female quick disconnect with a schrader valve screwed in (not pictured).

edit- please excuse crappy microsoft paint skills
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This is it. (personal fill system not included)
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Last edited by FishBoy on Thu Oct 02, 2008 7:05 pm, edited 1 time in total.
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Unread postAuthor: Demon » Thu Oct 02, 2008 6:56 pm

Why dont you use air instead of water?

should work...(i mean your idea of using water)

you could also try to put a burst disk at the end of the thread part of the bottle and fill it with one mentos and coke, shake the bottle and LAUNCH!

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Unread postAuthor: FishBoy » Thu Oct 02, 2008 7:01 pm

I dont think you understand the concept of a water rocket. Water is used because it is easily obtainable and is much more dense than air (meaning it provides more thrust). Air is then compressed in the rocket with the water, and when the rocket is fired, the compressed air rapidly forces the water out of the nozzle, propelling the rocket. If I were to use air, like you suggested, the rocket would just hop and hiss a little, then fall over. Also, i understand your idea of a burst disk, but what you want in a rocket is a powerfull continous flow, not an explosion like burst.

edit:
also, the mentos and coke thing might work, but burst disks aren't as effective with water as they are with air. The rocket would work best if used as intended.
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Unread postAuthor: mark.f » Thu Oct 02, 2008 7:21 pm

I've always wanted to make a huge water rocket out of PVC.

A suggestion, why not add a test plug as a 'piston' in the pipe, that way it could be launched at any angle? You'd have to fill it from the top, though.
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Unread postAuthor: FishBoy » Thu Oct 02, 2008 7:31 pm

care to elaborate?
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Unread postAuthor: explsvcookie257 » Thu Oct 02, 2008 7:34 pm

Well plastic soda bottles can take about 150 they explode at like 200 I think I cant remember they did a test on mythbusters though. how would one out of pvc be better so why not make it out of aluminum even though its expensive you cant put it to much higher pressures and its light or just make it out of steel fittings. But if you make it i want to see it because I had the same idea why not make it like a cartridge shoot it almost straight up out of your spud cannon and it should burst while on its way out so it will be going super high and fast.
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Unread postAuthor: mark.f » Thu Oct 02, 2008 7:45 pm

FishBoy wrote:care to elaborate?
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Unread postAuthor: FishBoy » Fri Oct 03, 2008 5:20 am

ooo, i like it. However, most water rockets will still work at least sideways b/c of the venturi efffect, although the performance wouldn't be as good as a piston.
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Unread postAuthor: Demon » Fri Oct 03, 2008 6:51 am

You should make the rocket in copper pipe, its lightweight the sch40 pvc pipe...(and looks cooler)
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Unread postAuthor: jimmy101 » Fri Oct 03, 2008 12:27 pm

I don't see any real advantage of PVC or copper over a soda bottle.

The PVC pressure rating isn't all that much better than bottle and the PVC pipe + fittings will weigh many times more than the soda bottle. The higher pressure rating is going to be offset by a much smaller chamber and a much heavier rocket.

Using smallish diameter PVC (like 1") will allow pretty high pressures but the rocket will have to be very long to get significant volume. Using large diameter PVC and the max pressure drops off pretty quickly and the weight of the fittings goes up fast.

Metal will go to very high pressures but it is even heavier, especially when you add the necisary fittings.

BTW, most water rockets work fine even at pretty shallow launch angles. You just need the rocket elevated from horizontal enough so that there is water at the nozzle at launch. Once the rocket starts to move the water will shift so that it is pushed as far to the back of the rocket as possible. It is nearly impossible to vent air out of a water rocket without first ejecting all the water. You would have to launch the rocket basically horizontal or downwards for that to happen.

BTW2, I would stay away from balsa wood fins. They are too fragile and will break on the first bad landing. Google for paper or plastic rocket fin designs. I prefer fins made from plastic soda bottles. The plastic is essentially indestructable and the only problem you have is the fin breaking off the rocket body (which balsa will also do).

EDIT:
2" SCH 40 PVC, 0.68 lb/ft
2" SCH 40 Copper, 3.6 lb/ft
Copper is much heavier than PVC.
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