Here's an example of an EXTENDED TAIL PIECE using a "FAKE NECK" for a water rocket. It has a FULL BORE hole passageway all the way from the bottle neck, thru the couplings, pipe, and nozzle. So, is VERY FASTER than reduced nozzle rockets and those that use garden hose quick disconnects.
It has a design simular to a (sadly) discontinued toy called a "Super Soaker". It goes up very fast & very high!! This rocket is a performer!! It's one of my favorite. With the fins way behind the original neck of the bottle & the weight of the PVC pipe, it always wants to FLY STRAIGHT UP, even if you initally launched it from an angle, which is entertaining to watch.
This rocket does not come down like a "scud missle", it rather gently & slowly falls down SIDEWAYS and the fins make it spin like a windmill. With a little tweaking, this rocket might be able to come down like a glider plane.
I've used the thinner wall, and lighter, 1/2 inch PVC pipe. The pipe is rated at 315 psi, and is lighter than the more common Schedule 40. The fins are made of LEXAN and glued to the PVC pipe. The bottle can be unscrewed, because a bottle cap was used to make the initial connection. This tailpiece can be screwed onto just about any existing water rocket!!!! YEAH.
I call this the "PVC BOMBER". It's all PVC, with a 2" body. It's just an example of some of the possibilies. There is some 4 inch thinwall that might work better.
Why use a "FAKE BOTTLE NECK"? We ALREADY have Water Rocket Launchers that have been made to launch soda bottles. By faking a bottle neck, we can launch just about anything that can hold pressure & we can attach a bottle neck to. Also, faking a bottle neck allows us to explore new possibilities & invent new types of rockets.
See how the "FAKE NECK" is simular to the real thing?
An electrical reducer washer (1/2" x 3/4") is providing the "flange".
This is another "FAKE NECK" where I've added a garden washer to the tip. The washer has be grinded to a smaller outside diameter, to slip out of the launcher better.
THE TOP CONNECTOR
The top couplings, that connect to the bottle, is a combination of three parts:
(#1) The bottle cap was glued with JB Weld (epoxy) to
(#2) 1 inch 200 psi (thinwall) PVC pipe. The cap will slip PERFECTLY inside this pipe. The bottle cap has a 3/4 inch hole drilled thru the cap tip.
(#3) A 1/2" slip PVC coupler was JB Welded inside the 1" pipe. I now realize that I could have cut the 1/2" slip PVC coupler in half to reduce weight. The "cut" section would be positioned towards the bottle cap. There will be some gap filling require to make this connection, so try to center this connection as best you can.
Buy 1 inch PVC pipe, rated at 200 psi, it's a "thinwall" pipe. A bottle cap will slide perfectly inside pipe, so take a bottle cap with you to the store. (This pipe is handy for other projects I'll be telling you about in the near future.) Cut pipe of the length equal to the height of the cap, plus the (half) coupler, so about 1.25 inch. Set aside. Call this the "1 inch pipe fitting"
I like J B Weld, but some other epoxies might work IF they will stick to a (slippery plastic) bottle cap. I found J B Weld in the MEGA BIG TUBES at Wal Mart for cheap.
Mix up epoxy, apply to fill knurled ridges around circumference of bottle cap. (This will give it great added gripping power). A thin even coat is all for bottle cap, because any excess will be wiped off when pushed into 1 inch pipe fitting. Apply expoxy to inside surface of 1 inch pipe fitting. Press the cap into the 1 inch pipe fitting. Invert this subassembly.
Apply epoxy to inside surface of 1 inch pipe fitting, applying evenly and about .030 thick. Do same to coupler. Press coupler (cut end towards cap!) into 1 inch pipe fitting, AND CENTER a good as possible. The epoxy will need to fill a .030 gap between the two parts. Set aside until epoxy sets up hard.
Drill 3/4 inch hole ON CENTER thru cap. I accomplish ON CENTER with a "drill bushing" that temporarly fits inside the coupler.
Attach with normal PVC adhesives, your 1/2" pipe, with the fake bottle neck, to your new "bottle thread to 1/2 inch PVC" coupler.
HERE'S THE BEST CONFIGURATION I've come up with an improved version of the above Fake Bottle Neck. This uses a short peice (about 1/4" long) of 3/4 " copper coupling. This eliminated the work needed to truncate the PVC piece by grinding. This is far superior way of making a fake neck.
This is a side view of the copper ringed fake bottle neck.
Here are the parts needed. From front left to right order, the left PCV part (cut from 1/2 inch PVC slip fitting coupler) is .740 inch long (this is the tip of the fake neck), next is a part (also cut from 1/2 inch PVC slip fitting coupler) that can vary in length because it's not cridical (this is part slide furthest on) in this case I've been using .300 inch for lenght), next is 3/4" copper coupler that is .250 long, next is 1/2 x 3/4 electrical reducer bushing (notice center portion is formed with a slight bump, put this bump UP because is will work better with most launchers). In the back of above photo is a 1/2 inch PCV thinwall pipe. The length of the pipe for my applications is 8 to 12 inchs, but it's very open for experimentation as to the length.
I weighed the three different 1/2 inch PVC pipe available. I used a 12 inch long sample.
(Sample #1) Schedule 80 = 3.33 ounces & rated at 850 psi (this is what I use in the launcher counduit)
(Sample #2) Schedule 40 = 2.63 ounces & rated at 600 psi
(Sample #3) Thinwall Pipe = 1.61 ounces & rated at 315 psi (this is what I used for these extended tailpieces)
THE EASY WAY
The above does look like a lot of work and a lot of parts to assemble. Yes, your right. Don't be discouraged, there is an EASIER SOLUTION for faking a neck. Why not cut a neck off a bottle and bond it to the PVC pipe? Yes, it works & MUCH easier. The reason for the above more complicated configuration is to see if a fake bottle neck could be made with very common components available at a common hardware store. The quest was achieved, now it's time to look at what's easier, faster, and cheaper, without loss of performance.
The solution was to use J B Weld and bond a cut off bottle neck to the bottom of the 1/2 thinwall PVC pipe, just below the fins. In fact, the whole extended 12 inch long extended tailpiece only weights 4 ounces, including the fins and top and bottom couplers!!!!
THE FINS
This is a top side view of one of the two LEXAN fin components that I glue to the 1/2 inch PVC
pipe. The "M" shape provides two fins for each piece. I've had very good luck using PL Door, Window, and Siding Adhesive, because it is a flexible polyurethane adhesive. OR better yet:
USE RUBBER BANDS
NOTE:Instead of gluing the "M" fins onto the extended neck, you might prefer using 2 each rubber bands to fasten. This will give you extra feature to adjust the center of gravity.
Curve the Tips for Spinning Rockets
Heather, my daughter, & I are ready to "launch into oblivion". I like to call these my "anti-gravity vortex rockets", because they always go UPWARD, regardless of the angle you shoot them. They really are a lot of fun.
INTERNAL LAUNCH TUBES
When using a BIGFOOT WATER ROCKET LAUNCHER SYSTEM, you can get more boost at launch, and more guidance, by adding an INTERNAL LAUNCH TUBE. Basically, you will insert (pressure fit only) a 1/4" PVC tube inside the riser, which is inside the trigger mechanism. The 1/4" PVC tube can be as long as the combined length of the inside of the rocket, plus the length of the tailpiece. With these rockets shown above, I was able to use a 25 inch long internal launch tube. That means the rockets loose very little power for the first 25 inches, which is a lot at initial blast off!!!! Also, the rockets are being AIMED and GUIDED in the intended direction for the first 25 inch also!!!!
The "internal launch tube". The bottom end of the 1/4 inch PVC interal launch tube is slotted in four places, and the outside diameter is grinded to a slight taper. Use schedule 80 PVC pipe!
The "loose garden washer". A common garden hose washer is the second and only other component in adding an internal launch tube. This washer is optional if you used the dimentions of the fake neck with the copper ring mentioned above. However, when using an internal launch tube, this washer will stay put on the launcher, and not disappear with each launch. I like to have this one only "loose garden washer", because I have good results, and perfect air tight seal.
Just drop the loose washer into the riser inside the trigger mechanism. Then push and twist the 1/4 inch launch tube into the riser. It's too easy to have this much fun.
Depending on how accurate you made the fake bottle necks, you may add and subtract garden hose washers to "shim" to get a seal to pressurize.
If you used the dimentions, I showed above, you can launch with, or without, the loose garden washer!!! Either way, you will get a perfect seal and full adjustments.
Here's the launcher with a 25 inch x 1/4 inch Schedule 80 PVC internal launch tube.
The "anti-gravity vortex" water rocket is ready for launch.
BLAST OFF
