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Construction - Basic


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Robinson Coupling

Splicing Bottles #1

Splicing Bottles AS#5

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Side Deploy #1

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Mk3 Staging Mechanism

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Construction - Launchers

Gardena Launcher

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Launch Abort Valve

Quick Launcher

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Drop Away Boosters

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Dark Shadow Deployment


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How Much Water?

Flying Higher

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Building a Launcher

Using Scuba Tanks


Video Taping Tips

MD-80 clone

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Servo Timer II




V1.3, V1.3.1, V1.3.2


Deploy Timer 1.1

Project Builds

The Shadow

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Flight Log Updates

#230 - Tajfun 2 L2

#229 - Mac Uni AON

#228 - Tajfun 2 Elec.

#227 - Zip Line

#226 - DIY Barometer

#225 - Air Pressure Exp.

#224 - Tajfun 2

#221 - Horizon Deploy

#215 - Deployable Boom

#205 - Tall Tripod

#204 - Horizon Deploy

#203 - Thunda 2

#202 - Horizon Launcher

#201 - Flour Rockets

#197 - Dark Shadow II

#196 - Coming Soon

#195 - 3D Printed Rocket

#194 - TP Roll Drop

#193 - Coming Soon

#192 - Stager Tests

#191 - Horizon

#190 - Polaron G3

#189 - Casual Flights

#188 - Skittles Part #2

#187 - Skittles Part #1

#186 - Level 1 HPR

#185 - Liquids in Zero-G

#184 - More Axion G6

#183 - Axion G6

#182 - Casual Flights

#181 - Acoustic Apogee 2

#180 - Light Shadow

#179 - Stratologger

#178 - Acoustic Apogee 1

#177 - Reefing Chutes

#176 - 10 Years

#175 - NSWRA Events

#174 - Mullaley Launch

#173 - Oobleck Rocket

#172 - Coming Soon

#171 - Measuring Altitude

#170 - How Much Water?

#169 - Windy

#168 - Casual Flights 2

#167 - Casual Flights

#166 - Dark Shadow II

#165 - Liquid Density 2

#164 - Liquid Density 1

#163 - Channel 7 News

#162 - Axion and Polaron

#161 - Fog and Boom

#1 to #160 (Updates)



Each flight log entry usually represents a launch or test day, and describes the events that took place.
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Day 133 - LaRF, Projects Update

Date: 30th March, 14th April, 27th April, 18th May 2013
Doonside, Sydney Observatory, Macquarie University, NSW, Australia
 Sunny, light winds < 10km/h early, 25C
Team Members at Event:
 GK, PK, Paul K, and John K.

It has been quite a while since the last update, mostly because we took a break from a couple of launches while we build more water rockets and attended club events. But there has been plenty of work in the background.

We spent some time in the past few weeks re-stocking our rocket component supplies including nosecone repairs, making up new splices and testing them, making a number of nozzles, parachutes, fairings etc. This allows us to quickly assemble a number of rockets when needed.

Locating Lost Rockets with LaRF

At the last NSWRA launch we tested a simple low power laser device for locating lost rockets in the tall grass. The LaRF (Laser Rocket Finder) proved very successful with 4 out of 4 rockets located at up to 850 feet from the launch pad. All were found quickly and within a couple of meters of where they were expected. We even found one within 2 minutes after a lawn dart at the previous launch. The rocket was black and green and half of it was buried. There had been about 5 people looking for it for over half an hour with no luck.

LaRF Prototype

LaRF Prototype setup to find rockets

Recovered rocket.

The design is based around a laser line generator used for aligning tiles or pictures in the home. The one we used is a Stanley Intellisensor Pro that is also a stud finder but we are only using the laser for this application. The light source is a red class II laser of less than 0.16mW. The beam spread is approximately 45 degrees from the source so the further you get from it the laser intensity is greatly reduced. The beam is approximately 4mm wide.

Laser Safety

Now it is never a good idea to look directly into a laser and so we did a number of calculations to work out what the beam intensity is at a certain distance, and to make sure it was safe to use. Because of the wide spread of the beam the intensity is quite low at the distance at which we are using it. Here are some good references on laser safety:



Doing range and beam divergence tests
Context photo

Beam divergence tests
With telephoto

To further reduce the laser intensity we used a polarizer rotated relative to the polarised laser beam. The polarising sheet came from 3D glasses that you get when you go to the movies. These use circular polarisers. The light from the laser is also polarised and hence only one polarising sheet was needed to attenuate the beam based on how much the polarizer was turned. You could use a couple of these to even further attenuate the beam.

3D glasses were used for the polarizer

Bracket for mounting the LaRF
On a tripod

Here is the polarizer which can be
rotated to adjust the attenuation.

Laser source mounted on the bracket

Left: Normal beam, Right: Attenuated
Screen distance from LaRF: 1m

Top view

Finding rockets

Finding rockets is simple. You just watch where the rocket lands and then aim the laser in the direction. The laser is far too weak to see in daylight and so you have to sight along the top of the laser at the landing location. The unit we have has sight marks which makes it very easy. You then turn on the laser and start walking towards the rocket. You occasionally look back over your shoulder to see if you are on track. If you can't see the beam you need to walk perpendicular to the beam until you see it again. This keeps you on the correct line of sight. It was amazing to see just how far you drift from the line when just walking in an open field when you think you are heading in the correct direction. As you walk down the line you just look for the rocket. It turns your 2 dimensional search problem into a 1 dimensional search problem.

It's essentially the equivalent of someone standing at the launch site and directing you through a walkie-talkie "left a bit... right a bit".

Because the beam is a vertical line you can travel up and down over rough terrain and still see the beam,

We did another trial run of the LaRF at the local oval and I had Paul drop a 20c coin in the grass about 150m (450 feet) from the LaRF. When he dropped it, he raised his arm and I pointed the LaRF in his direction. Paul then came back so I only had a rough idea how far it was. I walked down the beam and found the coin about 1m from the beam. This test was intended to see how well the sighting screen works ... works great.

Setting up tests with sighting screen

Here you can see the sight marks
used for aiming

The sight screen is removable for
easy transport.

Observer shift: approximately 20cm
Distance to LaRF: ~50m (telephoto used)
Distance to LaRF: ~150m
You can see that the sight screen is useful

A limitation of the LaRF is that the rocket must land within line-of-sight. If it lands behind trees then you won't be able to see the laser if the trees block your view of the LaRF. Also at distance while it was easy to see the beam it was difficult to see where to look for the beam. We have now added a black and white stripped sighting screen to make it easier to find the beam source from a distance. I think we'll be bringing it to all the launches from now on. It's more useful for small rockets rather than large rockets which are much easier to spot in the grass.

Quick Launcher Upgrades

We also took some time to improve a couple of little things on the quick launcher to make it even quicker to set up and re-configure. One of the main criteria was to make it completely tool-free to be able to adjust it and replace various components. These changes are designed to allows us to launch a variety of rockets easily during a launch event.

The upgrades included the following:

  • Swapping Gardena release heads. You can now hand tighten the retaining screw as you used to need a pair of pliers to tighten it enough to prevent leaks.
  • Changing nozzle offset from guide rail for different diameter rockets. You now only need to tighten two wing nuts. This used to need a screwdriver.
  • Changing the whole release head assembly. We can now swap from the Gardena system to the Shadow's high pressure launcher easily without tools.
  • Locking pin for guide rail has been replaced with simple latch. This makes it much easier to remove the guide rail and put it back onto the base. There is also no chance of losing the pin.
  • We simplified how the release head string clips onto the lever arm. This sometimes required a screw driver to loosen the release string.
  • We added a roller for the release string which makes the design more compact.

Large wingnut for hand tightening
release heads.

Wing nuts for adjusting launcher
offset from launch rail.

New roller for smoother operation

With the launcher we can now swap between the following:

  • 9mm release head for nozzle diameters of 10mm and less,
  • 16mm release head for 16mm nozzles (Maxiflow) with a 250mm launch tube suitable for single bottles,
  • 16mm release head for 16mm nozzles with an 1800mm launch tube,
  • 19mm high pressure release head with 1500mm launch tube.
  • 22mm Clark cable-tie release head with a 250mm launch tube suitable for full bore nozzles.

All these release heads can be adjusted relative to the guide rail for various diameter rockets. The only tool we now need is a hammer to pin the base to the ground, although we are considering making permanent mounting brackets at Doonside so we don't need to hammer the pegs in each time.

Latch for securing guide rail

Hook for connecting release string

Collection of release heads

Details of the launcher upgrade

Shadow Repairs

We bought a new roll of 84gsm fiberglass cloth so we could continue to roll more tubes and repair the Shadow. I've posted the progress of the repairs here on the Shadow Build Log with more photos. We wanted to get it finished before the Macquarie University Astronomy open night where NSWRA was having a stand again. We still need to do a pressure test before we attempt another launch. I think we will launch again at lower pressure first and then again step up the pressure for subsequent launches.

Getting ready to roll new tube

New tube glued in place

Shadow II repainted

Sydney Observatory

During the school holidays on the 14th April I took a day off from my regular work and went to the Sydney Observatory with my son Paul to help out with the NSWRA stand and demonstrations. We had beautiful weather and the club managed to get about 8 launches in and 4 static motor firings. The observatory staff estimated about 800 parents and children attended the observatory on the day. It was definitely a fun day. It was also great to meet Christy Berlatsky the Export Sales Manager for Hobbico, that owns Estes.

Firing an motor for the kids

Part of the stand shortly before opening.


George, Christy, David and John

Launching a paper rocket on an A motor

More photos:

Macquarie University Astronomy Open Night

On the 18th May we again attended the Macquarie University Astronomy open night where NSWRA had a stand and did a static motor firing. The event this year was held earlier than last year because the sun sets sooner so people can go look through telescopes earlier in the night. The sky was cloudless and so ideal for astronomy. There were a lot of people this year and all the club members were busy talking about rockets. Paul and John came with me this year and stayed the whole night. They both helped out and Paul did a great job helping Peter Berg from Berg's hobbies sell little paper rockets.

We brought our Shadow II and Polaron G2 again this year for show and tell. We didn't get home until about 10:30pm.

Paul and John helping out
during the evening

NSWRA display

Shadow II and Polaron G2

Some of the visitors

It was a very busy night

Firing a G motor

More photos:

NSWRA Launches

I also attended a couple of NSWRA launches in the last two months to take photos and just catch up on rocketry with club members. Paul also flew a couple of his rockets at one of the launches. Here are some photos from the two launches:

14th April 2013 -
I also made a few 3D photos:
27th April 2013 -

Flight Details

Launch Details
Rocket   Pod 2 (Paul's Praetor)
Motor   C6-0, C6-5
Altitude / Time   ? / ?
Notes   Good burn but angled into the wind. The second stage lit well and continued the pitched-over trajectory. Late deployment but good landing a long way from the pad,
Rocket   Pod 2 (Paul's Praetor)
Motor   C6-5
Altitude / Time   ? / ?
Notes   Good burn and good flight. Good landing right near the pad,



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