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rabidsheeep

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Well, HA! i laugh at my dad saying rockets arent helping me in school...

apparently the science olympiad team has to build a bottle rocket *ears perked up* for the national competition or something...

immediatly i start thinking of that huge bottle rocket that was on the LDRS discovery show...

well apparently science olympiads focus on going backwards in technology because it has to be an air powered 1 liter bottle of soda...

no problem though...

the rules are strict so basically everyones is gonna end up lookin the same... nosecone, fins, pumped fulla air

now i know how to pump the things and blah blah

the thing is that the contest is about how long the rocket can stay in the air

so of course it shoots 40 somewhat feet (we did it in camp once) and then falls and crashes...

except for the fact that i had an idea... stick a parachute on it (and maybe tie a string to an rc car and drive it around like a kit but thats "too cool")

now i have an idea how to do this but im thinkin the best way to do it would be to spring load it...

how in the hell do i go about doing this i have no idea (this is where you all flock to rescue me)

it cant use any explosives/pyrotechnics or anything slightly fun related :p

also what is the lightest material i could use for a chute? im thinking of getting my mom to get me a big sheet of mylar (moreso for my use :D ) but i dunno whats the lightest thing you could get...

and if ya got any ideas throw em out...

P.S.-- if i do good my teacher might forget about a few of those failing grades :D
 

sandman

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How about a simple mechanical timer...consistancy with the timer might be hard.

Or have a pressure bladder connected to the bottle with a small vent hole that releases a spring loaded chute when the bottles pressure drops!

Keep it simple, just a few moving parts.

sandman
 

rabidsheeep

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my idea was just to have it sliglty secured on and fall off... ill try a bunch of ideas
 

sandman

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a "mechanism" would be more "scientific"!

More points!!!:D

Build it into a body tube nose cone section at the top!

sandman
 

wwattles

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Would an intentional drag-separation work? Make a nose cone (bottle's gonna need some aerodynamics anyway) that has enough weight to it that when the boosting stops, the cone keeps going to deploy a chute? Adds stability (noseweight) too!

WW
 

edwardw

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Is this a 2L water rocket or just air powered. I have built a TON of water rockets and have my own custom made launcher. My record for altitude is around 750 feet and almost 250 yards when going for distance.


For the fins and to make life a lot easier make a 'fin can'. Take a 2L bottle and cut a band out of the middle that is 8" long. You should now have what looks like a 2L bottle with no top or bottom. Make sure the cuts are straight and then heat up a pan (one not used for cooking) on the stove to medium heat. Then touch one end of the modified bottle to it and it will curl. One second or so should be enough. This gives the bottle a lot of rigidity. Now you can glue your fins onto this section and just slip them on and off the other 2L bottles and it is a lot easier. When I flew these at meets I have at least 5 fin cans sitting around.

Also, these things don't like flying straight at all. We finally spiraled our fins and it was a huge improvement. A typical fin was about 4" tall, 2" wide at the base and a right triangle. When we put them on the fin can we slide the ring around a bottle so that it wouldn't lose shape during gluing. We offset the top of the fin maybe .1" from the bottom and the spin was more than enough to get it stable.

We also used hot glue and foam fins (you know the kind of foam for crafts, it comes in 10 colors and is self adhesive) We stuck two sheets together since they were adhesive (usually two colors for cool effect) and then cut and glued our fins to the fin can with hot glue. Then we did the fillets with hot glue. We never had a fin shear and if it landed hard the fins are foam and don't get hurt.

DON'T glue anything with any type of glue to the main bottle that hold air! It will weaken it a lot. That is why I used a fin can that slides on because then the bottle isn't weakened. When I used them at 100 PSI the bottle would stretch in circumference by about 1/4" of an inch - that's a lot and you can see it too!

I tried without success to get a drag separation to work. I probably did 100 launches and never had good results with it. I finally decided I needed something more reliable and easy.

A good method to separate them involves cutting and turning another bottle upside down on a 2L bottle to make a 'nose cone' Then you pack your chute and attach it with tape to both the nose cone and the booster. Next, I took a film canister and hot glued it upside down inside at the top (where the bottle necks down) Next I made a paste of thin white glue and a lot of baking soda. I cast this into small pellets about the diameter of a quarter and 1/2 tall. Once they were done I put a pellet inside the canister and tack hot glued it to the bottom. I then took another film canister and heated it in warm water. Once warm I took and pushed it around another canister so I could fit the two together. This is the assembly.

This is how it works. When you get ready to fly - you fill the canister you modified 1/2 full of warm vinegar and snap it on to the canister that is glued inside. The vinegar/baking soda pellet are not touching. Then you fit the nose cone on and make sure it is straight. At apogee when it tips over the baking soda/vinegar mix and produce a lot of gas - this will pop the nose cone off and then the chute will come out.

Once I had the system down I have had 100% success with this method.

Also other things I have learned is for optimal performance we used a golf ball as a weight. We would unscrew the top off the nose cone section and glue a golf ball there. That was the *perfect* weight for one 2L bottle, one fin can and a 2L bottle nose cone. And if you lawndard on cement, it bounces! In soft grass if you lawn dart you do have to dig the golf ball out though.

For a 2L bottle, between 1 and 1.25 litres of water was the right amount for our pressure - 100+ PSI. At lower pressures you need to reduce the amount of water.

Hope this helps!
 

teflonrocketry1

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rabidsheeep,

Good luck on your science project, sounds like a lot of fun. For ideas about parachutes and their release mechanisms in water rockets visit:

http://ourworld.compuserve.com/homepages/pagrosse/h2orrecindex.htm

Here are my water rocket book marks on the web:

http://www.geocities.com/wrgarage/

http://ourworld.compuserve.com/homepages/pagrosse/h2oRocketIndex.htm

http://homes.managesoft.com.au/~cjh/rockets/

You didn't hear this from me; add a little bit of soap to the water in the rocket it might fly higher.

Bruce S. Levison, NAR #69055
 

rabidsheeep

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we cant alter the volume of the rocket at all and can only pump 60 lbs per square inch in :(
 

powderburner

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That looks like lots of good advice, almost professional!

rabidsheep, if you want a light-weight parachute, try a shot at dry-cleaner-bag material. It is weak, and can be torn or stretched if you set out deliberately to do so, but it is plenty strong enough to make monster parachutes for this application. (cleaner bags were the preferred material for many years in NAR parachute duration contests)

Cut a 'chute as large as you can from a full-length cleaner bag. Because it will probably be about a 4 or 5 foot diameter, plan on using at least a dozen shroud lines (maybe as many as two dozen?). For shroud line material, use sewing thread (yes, it is strong enough, it will easily last through several deployments if you use large numbers). Tie knots in the parachute end (to make it more difficult to pull loose through the attachment) and tape it onto the edge of the plastic with a short tab of scotch tape.

If you can find a cleaner with colored plastic bags (black is excellent, but VERY rare) you can end up with the equivalent of a hot-air balloon after your canopy opens fully on a sunny day!
 

edwardw

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I never thought of a black parachute! That's a great idea!!! I will have to try that out in a couple weeks. I go on a mission trip for spring break to Arizona (sunny, hot :) ) and the kids love the water rockets...last year we left our prototype launcher with one of the Dads so he could make some for all the kids. Seems like the kids are getting really good at it too. I'm excited to see their progress.
 

OKTurbo

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Just to add....

If you're thinking of a reliable/cheap mechanical timer the Tomy timers work pretty good, but can be a pain to put together. Plus, you have to find the appropriate wind-up toy to sacrifice. (I have a box full of little wind up toys in the garage).

The rubber powered free flight model airplane guys use the Tomy Timers for (ironically) dethermalizing their planes. In your case, you want your rocket to stay up longer....the airplane guys want it to come down quicker.

A good alternative to the Tomy Timer is a Silly Putty timer. I'll try and get some pictures posted when I get my camera working.

Here's one way of doing it...
http://groups.msn.com/FreeFlightOnline/interestingstuff.msnw?action=ShowPhoto&PhotoID=62

http://www.mindspring.com/~thayer5/ffpages/tips/timer/timer.html

I've also used some called a "button" timer.
http://www.modelresearchlabs.com/badge_and_button.htm

On these type, basically you are pulling a rubber band over a lever...the lever is attached to a "viscous" timer that moves very slowly as the rubber band pulls on it. When the lever turns enough it will release the rubber band and "time is up"....you set up a mechanism to release the parachute.

Hope this helps,
John
 

rabidsheeep

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the chute for my tall bertha (it being red and black) is black and the red parachute went to the coke rocket...
 

arthur dent

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Originally posted by rabidsheeep
Well, HA! i laugh at my dad saying rockets arent helping me in school...


My daughter was asked to make a parachute for a science project.She made an x type parachute and went on to explain how it helps to cut down drift with out a major increase downward speed.......A+ :)
 
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