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Since our founding in 2003, we've become the largest, most sophisticated and ground breaking group supporting you, the serious water rocket flyer! Whether you are a beginner or an expert, the WRA2 has something for everyone.

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.

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New Competition Class

This forum is for non-members to ask questions about our competitions. Please check our FAQ page before you ask.
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Re: New Competition Class

Postby SaskAlex » Wed Oct 21, 2009 12:30 am

If it was 200 psi even a good bike pump would suffice. Mine will do that. It's awesome when all you have to take to your launch site is a bike pump.


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Re: New Competition Class

Postby The Sky Dart » Wed Oct 21, 2009 8:18 pm

SaskAlex wrote:If it was 200 psi even a good bike pump would suffice. Mine will do that. It's awesome when all you have to take to your launch site is a bike pump.


Are you sure you are not mistaken? 200 psi from a bike pump? A track pump I have suppose to produce 160 psi, but I struggle to get over 160.


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Re: New Competition Class

Postby RaZias » Thu Oct 22, 2009 12:51 pm

The Sky Dart wrote:
SaskAlex wrote:If it was 200 psi even a good bike pump would suffice. Mine will do that. It's awesome when all you have to take to your launch site is a bike pump.


Are you sure you are not mistaken? 200 psi from a bike pump? A track pump I have suppose to produce 160 psi, but I struggle to get over 160.


There are bikes pumps at 240 psi.


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Re: New Competition Class

Postby The Sky Dart » Thu Oct 22, 2009 4:51 pm

RaZias wrote:
The Sky Dart wrote:
SaskAlex wrote:If it was 200 psi even a good bike pump would suffice. Mine will do that. It's awesome when all you have to take to your launch site is a bike pump.


Are you sure you are not mistaken? 200 psi from a bike pump? A track pump I have suppose to produce 160 psi, but I struggle to get over 160.


There are bikes pumps at 240 psi.


I haven't seen any, but if so, 250 psi limit should not be an issue.


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Re: New Competition Class

Postby SaskAlex » Thu Oct 22, 2009 6:38 pm

Well, just because a pump is rated to, or has a gauge up to, 240 psi, doesn't mean it's likely you will be able to get that. The gauge on my pump goes up to 260 psi. I can get 180 fairly easily, and about 210 if I put all my weight into it. I weigh about 170 lbs.

Now, those car pumps are really cheap. Probably a lot cheaper than any bike pump capable of 200 psi. So I don't know if it would really help get more competitors by making the limit 200. It would just be nicer for me :wink: . I still stay either limit would probably be fine. Some will be happier with one, some the other.


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Re: New Competition Class

Postby WRA2 » Tue Nov 03, 2009 4:45 pm

Here is the second draft of the new WRA2 Altitude Challenge. Comments welcome.

I. WRA2 Altitude Challenge General Design Parameters

1. Rocket must use Water as its primary reaction mass.
2. Rocket mass cannot exceed 1,500 grams. This is the total dry weight of all flying components in a flight ready condition including the pressure vessel, fins, nosecone, payload bay, camera, altimeter, flight computer, deployment system, batteries, and nozzle.(no reaction mass)
3. Water Rocket must use compressed ambient atmospheric air at no more then 200 PSI (13.79 Bar) as its energy. Other gasses have much higher compression ratios and there needs to be a baseline so the record is fair to all. (see section II for special rules regarding bottled air).
4. Pressure Vessel and Fuselage of Rocket must be constructed from lightweight nonmetallic materials.
5. Rocket must be launched from a stationary position on a fixed launcher. (Slingshots,trebuchets, catapults, cannons, and all other forms of launcher boost assist are forbidden). Launch tubes are allowed as long as the internal pressure of the rocket is the only supply of energy.
6. Rocket must be completely scratch-built using materials which are not manufactured for model rocket parts. (with the exception of the Camera and Altimeter) Raiding hobby shops for nosecones, or fins, or any other pre-manufactured items is prohibited. (manufactured items that are not designed for rocketry such as wind up toys are allowed)
7. Rocket must carry onboard a commercially produced altimeter to document the maximum altitude of the flight. Ground based and/or timing based altitude measurements are too error prone and are unacceptable.
8. Flight must be recorded by ground-based video to validate flight duration and recovery. It is required proof the flight actually happened. (if using bottled air is used then the 10 minute max pressure hold must be shown).
9. Entire flight including apogee must be photographed by an onboard video camera.If using a peak altimeter then the ground video will also show the display of the altimeter as the rocket is recovered following each flight.
10. Record Altitude is calculated as the average of the two highest flights the rocket achieves within a 2-hour period (note: If using a peak altitude altimeter the average will be for 3 flights in 3 hours). This prevents dumb luck, the “perfect storm” scenario or false readings from giving a false record. Results must be repeatable!

This criteria was inspired by high profile competitions such as the Ansari X-Prize.
11. The same rocket must be used for all averaged flights. The only portions of the rocket which can be replaced are expendable or consumable items. (batteries, tape, deployment chemicals, water, etc..) The same rocket must be used for all attempts. Items which are damaged in any record attempt must be repaired and reused. Any competing rocket must be sturdy enough to survive multiple launches and the recovery system must be robust enough to prevent damage. “Expendable” rockets are disallowed from competing.

II. Bottled Air Rules

1. Only bottled atmospheric air is allowed. No exotic gasses, cryogenics or combustibles.
2. Tanks must be certified. (copies of tank certifications will be provided and filling station receipt).
3. All local laws must be complied with for handling pressurized tanks as well as any certifications that the operator may need will also be provided upon a record submission.
4. To prevent "stomp rockets" the rocket must remain pressurized to full launch pressure for a period of no less then ten (10) minuets. (The ground view camera will show both the tank and rocket on the launcher during this 10 minute period).
5. Bottled air pressure source must be located at the minimum safe distance of 50 Feet (15 meters) from the launcher (this allows the bottle air pressure source to be safely controlled in the event of an emergency).

III. Safety Rules

1. All WRA2 Water Rocket Safety Rules must be followed.
2. All launched parts of rocket which travel over 6 meters (20 feet) in altitude must have a recovery system which limits their descent rate at time of touchdown at ground level to a maximum velocity of 10 meters/second (33 feet per second) This includes all pieces which separate or are shed off in flight. Fast falling rockets, boosters, debris, or rocket parts can be very dangerous. Recovery system malfunctions for any part will disallow any record flights.

IV. Pressure Vessel Rules


1. Pressure vessel must be entirely fabricated by the rocket builder.
2. Pressure Vessel cannot be constructed using any portion of an existing high pressure enclosure. (i.e. no Paintball tanks, CO2 tanks, SCUBA tanks, Propane Tanks, etc.). The object is to engineer and build your rocket yourself.
3. Pressure Vessel and all external parts of the rocket may not be fabricated from metal. (see the WRA2 water rocket safety rules).

V. Reaction Mass Rules

1. Reaction Mass must be primarily ordinary tap water.
2. Thrust must come from expelling reaction mass, not from air discharge. That would be considered an Air Cannon projectile.
3. Water Reaction Mass must fill a minimum of 20% of the volume of the Pressure Vessel. Token amounts of water added in an attempt to qualify an air cannon projectile as a water rocket are not allowed.

VI. Filing a Record Claim

1. All record claims must be filed to the WRA2 Contest Submissions for public review.
2. Items required:
· Onboard video for both flights
· Ground videos for both flights (including altimeter display upon recovery if using a peak altitude altimeter)
· Raw altimeter data for both flights (if using a logging altimeter)
· Time and date for each flight
· If using bottled air: copies of the tank and operator certifications


Optional Items:
· Design drawings
· Detailed still photos
· Simulator data

3. Maximum file size 20MB per file


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Re: New Competition Class

Postby The Sky Dart » Tue Nov 03, 2009 5:35 pm

200 psi - I'd prefer 250psi at least, but it's up to the forum. How about a poll?

7. Rocket must carry onboard a commercially produced altimeter....

What exactly constitutes "commercially produced" and why DIY altimeters are not allowed? There are only two or three companies in the world manufacturing such things and these altimeters are not exactly cheap. Not in the UK at least. Since peak altimeters are allowed it becomes possible for a team to assemble a simple but equally reliable altimeter. As soon as the altimeter detailed description and schematics are provided as a part of the record claim, such altimeters should be allowed.

11. The same rocket must be used for all averaged flights. The only portions of the rocket which can be replaced are expendable or consumable items. (batteries, tape, deployment chemicals, water, etc..)


"deployment chemicals" - What does it mean?

2. Items required:
· Onboard video for both flights
· Ground videos for both flights (including altimeter display upon recovery if using a peak altitude altimeter)
· Raw altimeter data for both flights (if using a logging altimeter)


Should it be "each" not "both"?

I suggest to add "including manometer display prior the launch" or something like that.


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Re: New Competition Class

Postby WRA2 » Tue Nov 03, 2009 7:32 pm

The Sky Dart wrote:200 psi - I'd prefer 250psi at least, but it's up to the forum. How about a poll?.


200 would put it in the range of more people. That is still more then an unmodified bottle could hold so it would still challenge people to build a strong enough and light enough rocket. Come to think about it, the rule should also state that less then 200 is also allowed (someone might want to forgo the reinforcement to save weight).

The Sky Dart wrote:What exactly constitutes "commercially produced" and why DIY altimeters are not allowed? There are only two or three companies in the world manufacturing such things and these altimeters are not exactly cheap. Not in the UK at least. Since peak altimeters are allowed it becomes possible for a team to assemble a simple but equally reliable altimeter. As soon as the altimeter detailed description and schematics are provided as a part of the record claim, such altimeters should be allowed.


Keeping it to commercially produced means that we do not have to certify every altimeter prior to competition (commercially produced altimeters will come from the factory calibrated). The other reason is that with a home brew altimeter the designer could program it to "read generously" (if you have the equipment and know how to design and build the altimeter then it would be easy to reprogram it). Sticking with commercial altimeters makes this more difficult. Maybe we need to put up a list of recommended altimeters (suggestions everyone) We can compile a list and publish it on the WRA2 site.



The Sky Dart wrote:"deployment chemicals" - What does it mean?


Some competitors use chemical reactions (like mentos and diet Coke) to eject their parachute. Those are consumable items just like batteries.

The Sky Dart wrote:Should it be "each" not "both"?
I suggest to add "including manometer display prior the launch" or something like that.


You are correct it should say "each". I may list all of the items required for the ground video including the "launch pressure" displayed at the launch pad, the altimeter display, The launch and as much of the flight as you can (most rockets will fly out of range of the camera or land behind trees so losing sight with the ground camera will not disqualify a competitor provided that the onboard video is uninterrupted from launch pad to touchdown).

A couple of other items that need discussing are the primary reaction mass (There should be a clarification on what percentage should be ordinary water). Is 95% a good number (maybe some of you foam fliers could answer that) Would 95% work and still allow foam? Should there be a list of "banned substances" like liquid metals and other dangerous materials?

Should two stage rockets be allowed in this class?

We want to make this a fun class that people will join up to compete in without having to spend a lot on equipment
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Re: New Competition Class

Postby RaZias » Wed Jan 06, 2010 4:17 pm

This sounds good to me, by chance I bought a 230 psi bike pump and some fiberglass tape.


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Re: New Competition Class

Postby rockets-in-brighton » Wed Jan 06, 2010 4:41 pm

Just for clarification: could WRA2 confirm my interpretation of the rules on best flights within 2 hours (clause 10).

It reads to me as if you can fly as often as you like and choose any 2 hour period that brackets two good flights.

So if it takes me 25 minutes to prep and launch, I could get in 4 flights over 2 hours and choose the best two to average for my competition entry.

Theoretically I could keep going all day and choose the 2 hour period that gives me the highest average. Is that what is intended by the rule?


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Re: New Competition Class

Postby WRA2 » Wed Jan 06, 2010 5:35 pm

rockets-in-brighton wrote:Just for clarification: could WRA2 confirm my interpretation of the rules on best flights within 2 hours (clause 10).

It reads to me as if you can fly as often as you like and choose any 2 hour period that brackets two good flights.

So if it takes me 25 minutes to prep and launch, I could get in 4 flights over 2 hours and choose the best two to average for my competition entry.

Theoretically I could keep going all day and choose the 2 hour period that gives me the highest average. Is that what is intended by the rule?


That is correct, any two flights during any two consecutive hours. Theoretically you could fly all day and choose any two flights as long as they both occurred within the same 2 hour time window.

Say you flew 6 flights between 10am and noon and the flights that you made at 10:10 and 11:30 were the highest (and there were several in between). You could discard the flights in between and use those two highest. A flight outside of that 2 hour window would not count though so a flight at 2:30pm would not be able to be combined with the one from 10:10am.

Records must be repeatable and this is the best way to show it.


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Re: New Competition Class

Postby Tim Chen » Wed Jan 06, 2010 8:50 pm

What if I screw up a flight or something goes wrong?

For example, I launch at 10:00AM and the rocket goes well. Then I launch at 10:15 and the parachute fails. After effecting repairs I launch at 11:15 but my camera battery dies because I spent a long time fixing the rocket and left the camera on. I get a new battery and launch at 11:45 and everything goes well. That counts as 2 launches in 2 hours, right?


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Re: New Competition Class

Postby WRA2 » Wed Jan 06, 2010 9:31 pm

Tim Chen wrote:What if I screw up a flight or something goes wrong?

For example, I launch at 10:00AM and the rocket goes well. Then I launch at 10:15 and the parachute fails. After effecting repairs I launch at 11:15 but my camera battery dies because I spent a long time fixing the rocket and left the camera on. I get a new battery and launch at 11:45 and everything goes well. That counts as 2 launches in 2 hours, right?


That is correct Tim. Those two flights would count.


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Re: New Competition Class

Postby Tim Chen » Thu Jan 07, 2010 7:39 pm

WRA2 wrote:
Tim Chen wrote:What if I screw up a flight or something goes wrong?

For example, I launch at 10:00AM and the rocket goes well. Then I launch at 10:15 and the parachute fails. After effecting repairs I launch at 11:15 but my camera battery dies because I spent a long time fixing the rocket and left the camera on. I get a new battery and launch at 11:45 and everything goes well. That counts as 2 launches in 2 hours, right?


That is correct Tim. Those two flights would count.



That's what I thought. I remember someone talking about it in the past and just wanted to confirm. Thanks!


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Re: New Competition Class

Postby quique uy » Sat Jan 30, 2010 11:14 pm

about the altimeters
I is almost impossible to buy a commercial altimeter. but here in the Rio de la Plata has been developed Alfa Altimeter between Rockety Societies of Uruguay and Argentina that are being used for solid fuel rockets.
This certified by both Societies

can I use???

It is necessary on-board video??

about los altímetros
me es casi imposible comprar un altimetro comercial. pero aca en el Rio de la Plata se ha desarrollado el Altímetro Alfa entre las Sociedades Cohetera del Uruguay y Argentina que están usando para sus cohetes de combustible sólido.
Esta certificado por ambas sociedades

podría usarlo???

Es necesario el video de a bordo????

Un Abrazo


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