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The combination of water, compressed air, and a plastic soda bottle serves as a great source of propulsion for a backyard rocket (assuming you have a big back yard).  Typical versions of these rockets involve taping or gluing on the nose cone and fins which can be challenging to keep attached and often end up fairly crooked and wobbly.  Why not try a different approach where you build a rocket frame around the soda bottle and don't rely on direct attachment to the bottle?

I made this at TechShop   www.techshop.ws

Step 1: Materials & Equipment

Vector drawing software (I used CorelDraw)
Laser cutter (my TechShop has a Trotec Speedy 300)
1.25 liter soda bottle
Cardboard box (taller than your rocket, 16" in this case)
Hot glue gun

This instructable assumes some basic familiarity with CorelDraw and a laser cutter.






Step 2: Measure Bottle for Key Dimensions

First you need to understand the dimensions of your plastic bottle.  A set of large calipers makes this much easier, but a ruler will work just fine with some patience.  If you have to err one way or the other, tend towards the larger side as the bottle will expand some when pressurized and you don't want the frame to be pushed or bowed out.

I converted these measurements into a series of reference rectangles.  The height of each rectangle matches the key vertical dimensions in the hand drawn diagram.  I added a rectangle to the top where the nose cone will go.  I also added a rectangle to the side of the bottom where the fin will go.  I decided that I wanted the long part of the frame (that runs most of the length of the bottle) to be 0.5" wide, and that became the basis for the width of the other rectangles.  If you squint you can see that these rectangles represent a very coarse outline for one side of the rocket.

Step 3: Design Vertical Side Pieces

Now you can use the various intersections of the reference rectangles to start adding curves.  For most of the curves I used the simple 3-Point Curve tool.  For the nose cone the shape wasn't looking quite right, so I used the B-Spline tool which lets you add more control points to the curve.  This led to a smoother transition from the long vertical section into the nose cone, as well as into the tip of the nose cone.

Once you have the desired shape, use the Virtual Segment Delete tool to remove the unnecessary reference lines.  If you haven't already, change all of the lines into red lines with a hairline width to indicate that these are cut lines and not engraving lines.  The final step is to add a slot at the top and bottom areas where the support discs will go.  This is where the vertical and horizontal pieces will interlock to hold the assembly together.  I measured my cardboard and it was 0.15" thick so I made my slots 0.16" wide so that there wouldn't be too tight of a fit.

Step 4: Design Top Support

The top horizontal piece consists of a round disc with four slots to interlock with the four vertical side pieces.  Referring back to the design of the sides, you can see that this disc intersects after the shoulder of the nose cone (where it is already narrowing).  The radius of the nose cone at that point is about 2", so you should create a disc that is a little smaller to make sure it doesn't protrude after assembly (due to tolerances).  This disc is 3.8" in diameter, and you should add two perpendicular rectangles to represent the slots.  These should be 0.16" wide to allow the 0.15" thick cardboard sides to slip in reasonably.  I also obtained the measurement for where the slot starts on the sides from the other design file.  To make it easier to draw I added a reference rectangle centered on the circle.  This makes it easy to use the Virtual Segment Delete tool to remove all of the extra line segments. 

Step 5: Design Bottom Support

The design of the bottom support ring starts out similarly to the top disc, but with a hole in the middle through which the neck of the bottle will pass.  I decided that I didn't want a complete ring at the bottom for two reasons.  It adds aerodynamic drag, and it looks a little funny.  So I added three reference rectangles that let me uniformly scoop out a section of the ring between each set of fins.  The scoop is created with the 3-Point Curve tool and the appropriate nodes and intersections on the reference rectangles.  Finally use the Virtual Segment Delete tool to get rid of all of the unnecessary line segments.

Step 6: Play With the Laser

Off to the laser for some very fast cutting (cardboard doesn't take much to cut).  Here I set the laser to 100% power and 1% speed.  It turns out that was a little slower than I would have liked and left some smoky residue on the back side of the pieces.  Had I not run out of cardboard I would have tried a faster setting for a nicer finish.


Step 7: Assemble and Hot Glue

Since all of the pieces are appropriately slotted, they go together quickly and hold themselves roughly in place.  Assemble them around the bottle (which is about to become a permanent part of this rocket).  Using the hot glue gun, apply a bead of glue to all of the seams that you can reasonably reach.  If you want a less permanent solution, and perhaps an easier way to make repairs, you could tape all of the joints.  Hot gluing is faster and I plan to just cut out another cardboard frame as necessary.

BE VERY CAREFUL NOT TO HIT THE BOTTLE WITH THE HOT GLUE OR THE GUN ITSELF!!!!

The heat will weaken the bottle (even if it does not put an actual hole in the bottle) which can lead to a frightening rupture on the launch pad.



Step 8: Go Launch Your Rocket!

The basic rocket is now ready for launch!  Building a launcher is outside the scope of this instructable, but there are lots of online references for that.  For even better performance you can improve the rocket with an actual aerodynamic nose cone.  The simple way to do this is wrap the nose cone area with tape (making the three dimensional nose cone shape).  If you want to get fancy you can first fill the cavities with expanding foam, shape them with a knife, then wrap the nose cone.  As a final note many school physics classes have rocket building challenges often involving adding a raw egg payload that has to survive the flight.  This same design can be adapted to a detachable nose cone with an area to hold an egg capsule and a parachute, but I'll leave that up to the students to experiment with. :-)
<p>am i the only person on this site who not only doesnt have a laser cutter but also never knew ANYONE had one?</p>
<p>Nope. The kids in college these days don't know how good they have it!</p>
<p>heyyy grilll, you thiccc af ;0 6969</p>
<p>What would you want to cut a laser for?</p><p>:-)</p>
<p>To get nice more precise measurements take a full unopened bottle of soda and bounce it on floor it will get all expanded as gas tries to come out. If you are using non carbonated beverage bottle put water baking soda.(bicarb) and a spot of vinegar in bottle and shake (after capping). After measures are taken, chill soda (gas goes back in faster), and release pressure slowly on the water/vinegar/bicarb bottle outside maybe, You can freeze it first which will be helpful.</p><p>Alternatively you could fill with water and freeze, but this can lead to uneven expansion.</p>
<p>Do NOT use a non carbonated beverage bottle for this type of thing. They usually are not strong enough.</p>
<p>That is very true, but there are some water bottles that have thick plastic for looks and can handle higher pressures than those cheap arrowhead bottles.</p>
<p>heyyyy grilll, u thicc</p>
You bring up a good point.<br>I did not know there was a difference in the plastic/thickness of them, other than new water bottles are extremely thin. So are Iced lemonade bottles a different plastic and thickness, or just water bottles. Iced tea bottles are usually PET as they handle heat better, I never looked at a soda bottle though. Iced tea is bottled at a high temperature so the plastic must be able t take it.<br><br>thanks
<p>cool</p>
<p>hello friend</p>
<p>hey babe ;)</p>
<p>niggerrrssniggerrrssniggerrrssniggerrrssniggerrrssniggerrrssniggerrrssniggerrrssniggerrrssniggerrrss</p>
<p>cool</p>
<p>hello friend</p>
minimalistic! cool, i imaging sealing up the cap (pointy tip o the rocket) would significantly improve the streamline... since the crossed paper tip is not providing muchaerodynamic advantage, right?
<p>hello friend</p>
i totally agree to your point in the last step... but sealing it off is pretty easy! what about masking tape and seal it? light weight, fluid tight...
sorry if i sounded rude...all i am saying is i love to see you tape it and a vid of test launch! hehe
<p>I will build this rocket for schoooooool!!!!!!!!!!!!!!!!</p>
<p>hello friend!</p>
What about recovery?
Hey great design. IVe been hot glueing to the bottle and always hated seeing the weakened plastic. I've not had a bottle blow up nut I'm always worried it might. I want to copy your design them cover the exterior in plastic.
<p>Is there a video I can watch</p>
<p>that is cool</p>
<p>I must say, this is the nicest looking waterbottle rocket out there, and as out there as the people (grownups), who love making and using them!</p>
<p><br></p><p>methinks it is time to rekindle my love affair with water bottle rockets............ although after the last encounter (14 years ago!) that included a 20 litre water cooler bottle, a 12 volt tyre inflator, 10 litres of water, 5 small bottles of red food dye, and then standing there in awe watching the rocket rise on a bright red plume of water, but having totally forgot that gravity also had is part to play in this little escapade. .............. two wet and red coloured kids, two wet and red coloured dogs, and a wet and red coloured me was not exactly the best way to return home to greet my (long suffering) wife after her hard Saturday at work.</p>
<p>how many moths of community service did they give you?</p>
<p>I'm thinking the CorelDraw and laser cutter are like killing flies with a shotgun. I think this could just as easily be done with a compass, ruler, and Xacto knife.</p>
<p>err , yup. I like the coreldraw though , as you state it is overkill. But as a class project to learn to use the new toys of the trade not terrible. For the &quot;Back Yard&quot; Mad scientist Dad/Uncle/Mother, a large piece of graph paper and tools tou mention are easier. Use plastic coroplast signage for the cardboard, for nose cone just spiral tape or use shrinkabe saran wrap. </p><p>no matter how fancy a curmudgeon neighbor, (me) will complain anyway so if it goes 20 feet or 23 feet who will care. And the kid get their eyeballs ripped out no matter which way you make it!</p><p>be careful out there Lawyers take no prisoners, unless they can be bartered or sold for a good fee!</p>
<p>Like others making comment, I too have no laser, nor do I know anyone who owns one. I do however, own a couple of scroll saws, and a jig-saw. For the really under privileged, a set of hobby knives can be picked up from a lot of dollar stores. This looks like a great idea, although water and cardboard are not good friends. Plywood may be way too heavy, so it looks like cutting quite a few cardboard sets.</p>
<p>Another option to try is water resistant foam board. I don't have a laser either but expect to be hand cutting mine and making templates for group projects.</p>
<p>Good point, but do not use normal foam board. IT IS NOT WATER PROOF!!!!!!! I learned that the hard way after my rocket fins snapped in half</p>
<p>Nice design! Wouldn't the cardboard get wet and become all soggy?</p>
<p>Just take the bottle out in the sun, sit it on a piece of paper and draw the shadow! </p><p>Who needs all ths tech bling!</p>
<p>thats wat im talkin about </p>
<p>FOR REAL DUDE!</p>
<p>cooooooooool</p>
<p>where is ur tech shop with the lazor cutter.? at some school, where?<br></p>
<p>Cool ideas and techniques. But ...</p><p>The disk at the top is so aerodynamically wrong.</p>
<p>I also feel like the round top horizontal part is going to slow down the rocket as it seems to make it less aerodynamic. A video of the launching would be good to see</p>
<p>I agree with that.</p>
<p>You could have measured the circumference to get the Diameter of each section, if you didn't have a set of large Callipers.???</p><p>The idea of making the stabilising fins and frame self holding is good out of the box thinking &quot;thumbs up&quot; :)</p><p>Rachael </p>
<p>Why are you even worried about an exoskeleton for the bottle seems like it would just slow it down . Needs to be more aerodynamic . </p>
<p>nice instructible. Laser cutting way out of my wheelhouse. A thought, I think rocket would be stronger if cardboard grain ran north and south on the vertical pieces.</p>
<p>nifty</p>
Opps, my thing froze and the bottom portion did not load! Just read it. Haha sorry
I would imagine the flat piece near the nose just adds surface area? Maybe trying to wall the cone into the nose for something more aerodynamic.

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