Lost and found
Ellen and Kathy get messy with rubber in the lost at sea video extra.
Lost at sea diaries
Better latex than ever
How do you make a life-jacket out of kapok, rubber and the chemical process of vulcanisation? Find out more about rubber and vulcanisation.
Free magazine
Jonathan Hare's diary about the challenge for the Lost at Sea programme, part of the fifth BBC/OU TV series Rough Science, based in Zanzibar
I make up a vibration switch so that the LEDs only get the power in bursts if the apparatus is moving (which it will do out on the open sea). This consisted of a metal spring surrounding, but not touching, a central wire. When there is movement the spring wobbles and makes contact briefly with the central wire. This was wired into the circuit so that the sea water battery’s charge-up the capacitors constantly and on movement this power is supplied briefly, by the vibration switch to the LEDs.
"I realised that my sea water battery idea had a design problem"
I realised that my sea water battery idea had a design problem. Simply dipping the apparatus into the sea won’t work because the sea water itself is a good conductor. If you dip the apparatus into the sea each cell will fill with water which is what we want, however each cell will also be short circuited by the conducting sea water, which is not what we want to happen. The way to get over this was to put some sponge into each cell. On immersion this soaks up water and keeps the cells wet even when the apparatus is pulled out of the sea, whatever the angle.
I tried this out in the sea and it worked!!
Finally put all the gear together onto a pole so that when Kate is in the water she can hold the lights above the water or fix the contraption to the life-jacket.
Day 3
Spend the day perfecting the final design and spending some time helping Ellen and Kathy seal up the rubber coated bags. This was a long job. Also help Mike make a detonator for the rockets out of a lighter. This idea works well but the lighter fails after a few tries. Have to go for an electronic ignition system with a hand drill battery, cables and thin wire.
We wait till it is dark and Kate goes out on the sea somewhere. The rocket / flare is launched and we follow the heading to see if we can find Kate in the water. Eventually after some time we can hear her but can’t see a thing then we see some little lights flashing ….
Kate looked very comfortable in the water in our Rough Science life-jacket.
< previous Page 2 of 2
Content last updated: 26/01/2005
