Wednesday 31 October 2018

Kite flying

We were down in Waterford over the Hallowe'en weekend with four generations present from the venerable 93 y.o Pat the Salt to three of his Great-grandchildren, incl. Gdau.I and Gdau.II. After an afternoon visiting while I stayed home to chop wood, carry water and tap out Blobs, the Gdaus returned, each with a plastic kite. The other had badged his mother to get him a kite, and she had announced that they would make one two three.  There are a number of places where you can find instructions and all you need is a sheet of plastic, some sticks, some string, and some scotch tape. Apparently, two of the kites had been airborne for longer than 3.5 seconds. That means that they were in the air for longer than Wilbur Wright on 14th December 1903, which therefore qualifies the kites as flyers.

Much later in the day, I dropped by Pat's to say goodbye to The Girl Who Invented Herself before she returned to Singapore. The kite-creative mother was there and I asked her how she made the decisions about proportions in her kite factory. She said that the instructions had been flexible:
  • the sticks could made from skewers taped together
  • the horizontal strut needed to be nearer the top of the vertical than halfway up
  • the stabilising ribbon needed to be about 6x the length of the vertical strut.
  • any plastic would do - she had bought a plastic table cloth
Apparently, the test-kite had flown but not too good: in a more-or-less uncontrollable clockwise spin. That is surely due to some asymmetry in the design: with more lift on the left-side of the kite. This is what brought me crashing to earth while paragliding. Small asymmetries in the lift can be damped by the stabilising tail-ribbon and some instructions advocate adding a steel washer to enhance this effect. Obviously, adding a brick to the end of the ribbon would counteract the lift entirely - on both sides: successful engineering is about compromise among competing requirements to achieve an optimal solution. Actually, in engineering as in evolution the optimum [best possible] isn't required; good enough will do. We discussed how the young chap could learn from that first attempt and make his mother incorporate design changes in Mark.II. 
  • using a tail that was only 3x as long as the kite but 2x wider
  • adding that washer
  • using longer sticks, not skewers, to even up the weigh
  • moving the cross-piece nearer the top . . . or nearer the midline
  • using more robust plastic - like a sheep-muesli feed sack and applying for sponsorship from Red Mills.
  • finding a lighter line to fly the kite from
Wilbur Wright came crashing to earth after his 3.5 seconds and it took him and his brother Orville 3 days to repair and modify their flying machine for their second attempt.  It takes a special sort of mind set to go for kite Mark.II, Mark.III . . . Mark.XXIX. Most of us flit off to the next bright thing or slump back exhausted on the sofa and switch on the TV for some slack-mouthed passive entertainment.

In teaching F&F microbiology or any lab-based classes, I frankly don't give-a-damn about the content; on my watch it's all about perfecting the process. In particular it's about testing the allowable variation that will have a good-enough outcome. Marjoram? - I think that's the French for butter. Happened two weeks ago in class: student-pair was tasked to make 500ml of VRB agar. Instructions on the bottle specified 28g/litre. This should mean adding 14g/500ml. Student-pair had been sleep-weighing and added 24g/500ml and asked what to do. This happens A Lot at The Institute because we baby the students: just follow the manual and don't take ownership of the science. Three options presented:
  • pour it down the sink and start again 
    • waste of €1 worth of ingredients
  • do some nifty calculations and dilute the over-egged agar to the required concentration
    • making more agar and pouring more plates [each costing 5c]
    • making more agar and throwing the surplus away
  • just using what they had made and seeing what happened
    • these 'strong' plates would be less wobbly
    • less time wasted piffling about over detail-schmetails
We went with the least troubling 3rd option. You have to be suspicious: why 28g ? Rather than 30g?  I'll bet a €5 note that it's because the original recipe used by microbiologists in the 19thC specified adding an ounce of powder, or even a generous spoonful to the mix. Over the years this allowable flexibility has become codifed and regulated and captured in SOPs [standard operating procedure] so they are idiot-proof. Idiots will find only 27g left in the bottle and decide they'll have to order another batch before they can carry out the experiment. STEMistas worthy of the name will use the 27g, maybe adding a jot less water and pouring 19 plates rather than 20.

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