Tree Trouble?

Or – Alternative methods of getting aerials over tree tops

by Andy Gardner

Getting aerials across bush and scrub can be very time consuming and sometimes bad for your health, especially when you end up crashing through a gorse patch. While visiting Waianakarua for the equinox DXpedition, I arrived a day before Bryan and Mark, so during the day I got stuck into some aerial maintenance with Paul.

Paul uses a surfcaster and large lead weight to get a heavy fishing line across the tops of trees, then he pulls through the wire. Being on the receiving end when the weight comes sailing over the tree tops can be rather alarming. But it has to be done, as you need to know where the lead weight lands.

Later on in the week, I visited Dunedin for a day on business, so I brought back some “dry ice” to Waianak. Dry ice is frozen carbon dioxide. It’s very cold and great for freezing warts. When it warms up, it goes straight from a solid into a gas, and consequently takes up lots more room. This can be used to advantage. If you put a handful of dry ice in a 2 litre plastic soft drink container, add a cup of cold water, and screw the top back on, the carbon dioxide will rapidly transform into its gaseous state. The pressure inside the bottle builds up to a huge amount, and then the bottle explodes. Doing this in the open air causes a huge bang and results in a shredded plastic bottle, so be very careful and stand well clear! The ensuing release of high pressure carbon dioxide can be made use of. We did some preliminary experiments at Wainak using a chimney flue stuck in the ground. A bottle-bomb was dropped down the flue, then a bucket was placed upside-down over the top of the flue. After a few minutes, the bomb went off, and we managed to get the bucket to reach altitudes of well over 50 feet. Clearly, this had some potential applications in beverage aerial laying and needed to be examined further!

Unfortunately, while I was down at Waianak, a close friend at Riversdale died of cancer. He was an ex US Army Vietnam vet, and his Will stated that he was to be cremated and his ashes spread into the Pacific Ocean at the beach. It was his specific request that this be done by having good ol’ Andy launch a model rocket, which would climb high into the air, then explode, showering his ashes down into the water. After constructing the rocket, we found that it wouldn’t carry the entire load of ash, so some of it went via rocket, and the rest went via a container launched – you guessed it- using a carbon dioxide cannon. I found that a 2 metre length of steam pipe, blocked at one end, and big enough to fit a bottle bomb down, will launch another bottle which, if loaded with sand ballast, will travel over 100 metres before touching down. A nice simple, cheap method to accurately pull Beverage wires across canyons, bush, trees, etc.

Being in an experimental mood, I can also report success at getting a length of fishing line over the top of a group of mature pine trees (150 feet high?), using a model rocket launched on a slight angle. The first attempt failed, as the hot rocket engine melted through the fishing line shortly after take-off. The second, successful attempt saw a flame-proof wire leader being added at the rocket end. Further experiments will be reported later. Be careful if you try bottle bombs though – they can be dangerous!

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