Maker Raft Race - August 5th 2017

Discussion
31

Thanks to @Esther_Gladstone, @Damian, @tobyspark, @lewisss , @Edd and @joeatkin2 for contributions to raft discussions. This is a wiki, so please feel free to edit and add your conclusions!

  • What we did:

  • Raided the snug for possible materials

  • Scribbled, sketched and discussed

  • Spent half an hour climbing in and out of wheelie bins

  • Googled/youtubed various ideas

  • Our three current proposals:

  1. Wheelie bin
    • Wheelie bin, usual way up, equipped with outriggers and a rear fin. 2 people stand inside, one paddles on each side
    • PRO: Fairly simple construction, easy to transport (it has wheels!), comedy value, potential to use existing bin in fetching Makerspace red
    • CON: Poor hydro-dynamic qualities, large draft, quite likely to capsize, possibly a bit cosy
  2. Bottles/tubing
    • Acquire large number of (say) 2 litre plastic bottles with caps, add vinegar and baking soda and quickly seal (higher pressure = more rigidity), lash together in some sort of framework, put a platform on top. 2 people rowing. Alternatively, replace bottles with large plastic drainage tubes/ducting, etc.
    • PRO: Small draft, tried and tested idea, some potential materials identified in the snug
    • CON: Where to get all the bottles in time?, Many small components = bigger risk of falliing apart
  3. Bath tubs
    • Two second hand fibreglass bath tubs, seal up plug and overflow holes, lash together, as many people as can fit paddle furiously
    • PRO: comedy value, bathtub is (very) roughly boat shaped
    • CON: need to find bathtubs and get rid of them afterwards

  • Key considerations:

    • Are we trying to build serious raft, or comedy vessel?
    • What materials are needed, and how to acquire cheaply and quickly?
    • Who is able to give what time to the project?

  • Definite to-do points:

    • Make paddles (suggest short armed with T-grip, for double handed use)
    • Find 2 metre pole, and attach some sort of flag…

  • Buoyancy calculations…

    • 1 litre of water displaced by air = 1 kg mass that can be supported
    • 2/3 submersion of craft suggested as likely to ensure buoyancy and minimise capsizing risk
    • 12 stone = c.75kg. So assume 2 people, plus 50kg of raft = c.200kg total weight
    • Therefore, target of 300 litres of water displacement… maybe less for lighter materials and crew

  • Other points to mention:

    • Mark has 4 x 25 Litre plastic jerry cans he is happy to lend
    • 1 wooden door, and a number of planks in the snug thought to be fair game (TBC)
    • Several lengths of pare plastic piping in the rafters thought to be fair game (TBC)

CONCLUSION:

  • Tom thinks option 2 is the best, suggest using door from snug (possibly covered in fake turf), attach 2 jerry cans to the underside at each end, fill gap between with as many plastic bottles as can be found, attach plank at 90 degrees at each end to form outrigger (attach more plastic bottles). Minimal prep, structure could be flatpacked for transit and reassembled with a few hand tools. attach bottles with a lot of gaffer tape? Maybe an @ members to collect bottles in a couple of clearly labelled bags in the space, and then build structure in a couple of evenings the week of the race.
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