First water rocket construction log

[mazuzuri]

Hey

This is a small log i am making to detail my first attempt at a water rocket.
As i am new to making water rockets, not launching them as i have launched plenty,
the main idea behind it is to allow people to follow my progress, and hopefully give a few useful tips and pointers on how to improve my methods.

Today i started building my rocket and i have used most of the day assembling the core of the rocket, that is to say the main body.
The method used for assembling the bottles is taken from USWR's website, were i cut the end of the bottles and fitted them together.
Ekstra reinforcement comes from 2 windings of ducttape around each splice as well as around the middle of the 2 end bottles.

Entire main body
http://i58.tinypic.com/nbx284.jpg

Near the neck area of the bottles there is a fairly significant narrowing meant for better gripping when pouring.
During pressure testing of a single unmodified bottle this area expanded out a lot, but still held at almost 50% higher pressure than i am planning to launch these first baby steps with.
Needless to say i have decided to reinforce the areas to try and prevent expansion. To do this i took some fishing line and wound around, ontop of this i applied a coating of 2 part epoxy resin.

Grip reinforcement
http://i61.tinypic.com/2qs7ztf.jpg

This is about as far as i got on the first day of building, which is still around 8 hours dedicated work.
Before i continue building my rocket and adding fins, i will be pressure testing in a few days, once the splices have been allowed to fully set.
After confirming strength, or getting nice and wet, i will finish up the rocket and add the payload compartment, and nosecone.

While the rocket is setting i will begin constructing the launch ramp.
This will be a simple 20mm pvc pipe H frame launcher with a 50cm guiderod.
I would have chosen 22mm pipe for the guide rod, but only steel and copper pipe is delivered in that diameter.
The release mechanism will be a clark-cable tie releaser.

Last words for the first posting.
I currently have a stratologger altimeter ordered, might as well get something decent from the get go.
The rockets current dry weight is 170grams, my estimates put final assembled dry weight at between 3-400 grams.
Capacity 5.6 liters
10cm diameter, 85 cm length, this will be around 15-20 cm longer with payload compartment and nosecone, more or less.

If you managed to read this far cudos to you and thanks for the interest
Next update wil be when i have something of interest to report.
Until then mazuzuri signing out

[bugwubber]

Nice! Good luck on your build!

[mazuzuri]

Thanks, i just hope i made the splices good enough to hold. Otherwise im back to square 1 needing to empty another 5 2 liter bottles.

[Jamie5335]

Hello Mazuzuri,

I like the idea of the log, what glue are you using for the Spices- you are escalating quickly and I am looking forward to the videos!

Some pictures of the parachute release system would be great when finished! Reinforcing the bottle ends with the fishing wire sounds interesting, and I look forward to the results. I myself use fibreglass strapping tape with reinforcement of the bottle ends.

Jamie B

[mazuzuri]

Hello Mazuzuri,

I like the idea of the log, what glue are you using for the Spices- you are escalating quickly and I am looking forward to the videos!

Some pictures of the parachute release system would be great when finished! Reinforcing the bottle ends with the fishing wire sounds interesting, and I look forward to the results. I myself use fibreglass strapping tape with reinforcement of the bottle ends.

Jamie B

Thanks for the interest.
The glue that im using is locktite power epoxy, it's basically a 2 component epoxy resin/glue. If i havent made any mistake in mixing up some names then that should be able to glue onto PET.

What do you mean by escalating quickly? If you mean jumping straight to making a big rocket, then it is because i have "made" several single bottle rockets and launched them, so i decided that i would make a larger rocket from the bottles i had.
The reason i'm able to make this stuff in the time i am is because i am on holiday now.

The parachute release system at least on these first few rockets im planning on making will just be a loosely fitted nosecone that is knocked of once the rocket tips over at apogee. Maybe i will cannibalise the remains of my old r/c plane and make a manual release system.

I also considered using fiberglass strips, but it is a bit expensive for me to use in my learning stages.

I might as well also throw in the new update.
The launcher is almost finished, just need to drill a few holes in the locking sleve, and add 2 loops to the launch frame for the release cable.
The launcher is as mentioned a simple H-frame with a clark's cable tie release.
http://i58.tinypic.com/35kixox.jpg

Next update will be sometime next week once the glue has set and i can pressure/leak test my rocket and launch frame.

[U.S. Water Rockets1]

Just a word of caution:

If you put a lot of work into building a large rocket, you should put the extra effort into adding an active recovery system. There's a long history of passive systems failing, even the best ones failing 10% to 20% of the time. If you put a lot of work into a big rocket, it is a big loss if it crashes. The larger the rocket, the heavier it will be, so it will fall faster and hit with more momentum.

[mazuzuri]

That is one thing i am aware of, but thanks for mentioning it.

I recently found my old r/c plane from the attic and since it isn't in flying condition anymore ill probably take the controller and reciever and use it for a manually activated system.
Untill i am able to construct a recovery system that has been tested quite a few times with my remote activated system i will not be putting my stratologger altimeter onto the rocket, this is mainly since i can't get a stratologger without paying import taxes and such meaning i nearly pay 50-60% more than U.S. based people.

But this rocket is mainly a test rocket to see if the glue i decided to use will actually hold under pressure and to get a little practice with slip joint splices.
As such i won't take it to hard if it does come crashing down, since i will have gotten the most important thing out of it, which is experience.

[mazuzuri]

Update:

Just tried pressure testing my rocket, what a poor excuse of a pressure chamber it was.
The joints failed at a mere 30 psi. I havent got any video showing it, however it is painstakingly clear as to what failed.
The glue i am using apparently is a sneaky one, after a day of curing it was still slightly elastic so i thought it was okay to go.
In that regard i was wrong, after curing for 3 more days the glue had become solid and as such brittle.
This means i will be making single bottle rockets until i can procure a more suitable adhesive, to bad PL premium dosn't seem to be available in my country.

On a side note i have just pressure tested 2 different types of bottles, and i have to say i am a bit surprised.
the 2 bottles i tested are each half liter and roughly same shape, one however is almost 2.5 times thicker in the plastic.
the top is the thicker plastic.
http://i59.tinypic.com/295coiu.jpg

After pressure test at 160psi.
http://i57.tinypic.com/ifqsdk.jpg

As you can see the bottle with the thick plastic barely has any deformation after 10 min at 160 psi, the thinner normal bottle however shows a lot more deformations. not only did it swell emmidiatly, but afterwards the bottle has crumbled around the base.
In the morning i will do another pressure test with these bottles at 160psi and see how they hold up, my hunch is the thinner bottle might fail while the thicker should easily survive.