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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Easy fairing/shroud between 2 liters

Members post instructions to construct water rockets, launchers, deployment systems, staging mechanisms, splicing bottles, and payloads.
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uberpixel
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Easy fairing/shroud between 2 liters

Post by uberpixel » Sat Jul 26, 2014 12:42 pm

Not sure if anyone else has tried this, but I've found an easy (if not aerodynamically ideal) method to add a fairing/shroud to cover the tornado tube (or similar) coupler between 2-liters.

Unfortunately, the distance between the straight sides between two coupled 2-liter bottles is longer than the straight sided portion of a 2 liter (that you would use to harvest material to make a fairing). So to make a nice straight sided fairing, you will need to splice your 2-liters just to make the fairing - kind of a pain.

To simplify construction, I decided to use the straight portion of a 1-liter bottle since it's smaller diameter effectively shortens the amount of straight sided bottle required.

To make one, just find a straight sided 1-liter and carefully cut it down until it just barely fits snug once your coupler is fully tight. You need to be careful that you don't leave it too long or have irregular/rough edges or it will dent the 2 liter and may cause structural weakness in the 2-liter pressure vessel. I painted the inside of my fairings with spray paint to hide the couplers and add some flair...

Not sure how detrimental the hourglass effect is on the aerodynamics, but when properly fitted the fairing adds a lot of stiffness and integrity to the rocket which helps to keep it from kinking while handling on the ground.
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-uberpixel
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U.S. Water Rockets1
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Re: Easy fairing/shroud between 2 liters

Post by U.S. Water Rockets1 » Sat Jul 26, 2014 9:57 pm

uberpixel wrote:Not sure if anyone else has tried this, but I've found an easy (if not aerodynamically ideal) method to add a fairing/shroud to cover the tornado tube (or similar) coupler between 2-liters.

Unfortunately, the distance between the straight sides between two coupled 2-liter bottles is longer than the straight sided portion of a 2 liter (that you would use to harvest material to make a fairing). So to make a nice straight sided fairing, you will need to splice your 2-liters just to make the fairing - kind of a pain.

To simplify construction, I decided to use the straight portion of a 1-liter bottle since it's smaller diameter effectively shortens the amount of straight sided bottle required.

To make one, just find a straight sided 1-liter and carefully cut it down until it just barely fits snug once your coupler is fully tight. You need to be careful that you don't leave it too long or have irregular/rough edges or it will dent the 2 liter and may cause structural weakness in the 2-liter pressure vessel. I painted the inside of my fairings with spray paint to hide the couplers and add some flair...

Not sure how detrimental the hourglass effect is on the aerodynamics, but when properly fitted the fairing adds a lot of stiffness and integrity to the rocket which helps to keep it from kinking while handling on the ground.
140726_093629.jpg
140726_090958.jpg
140726_093621.jpg
140726_090915.jpg
140726_090931.jpg
-uberpixel
Nice suggestion!

This is actually a very effective design because the smaller diameter bottle contacts the tapered portion of the two pressure vessel bottles at a point where it adds stiffness. If you use a bottle of the same diameter as the pressure vessel bottles, it does add stiffness, but not as much because when the rocket flexes the larger bottle tends to slide over the other bottle exterior and the opposite side gets loose because the shroud bottle pulls away from it. This is a good way to stiffen a long rocket with a lot of mass on either side of the tornado tube. We've used this in the past just for stiffening, but also with a real sized fairing on the outside so that the narrow part doesn't cause drag.


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ptx
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Re: Easy fairing/shroud between 2 liters

Post by ptx » Mon Aug 11, 2014 1:19 pm

Nice idea this "double" fairing, I might try it at my next rockets.
Thx


ptx

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