Whatever floats your boat!

Posted by on June 2, 2011

Alternatively entitled, “1001 Uses for Old Taekwondo Boards, Use #1”

Our son, like every other child in his Taekwondo class (so I hear), has an under-bed full of these boards. The sheer joy derived from breaking them evidently grants the boards immunity from ever being discarded. This leaves us with a lot of boards which, incidentally, float.

Materials for Propeller Raft:

  • Lightweight wood, such as balsa wood, or if you happen to be so lucky, board-breaking boards from Martial Arts class.
  • Straightedge, such as a ruler. We used the edge of an envelope. ‘Cuz we’re flexible like that.
  • Propeller – ours came from the Party store, and is the type you’d find for 5/$1.00 at the dollar store.
  • Rubber bands
  • Glue
  • Screw Eye/ Eye bolt
  • Pocket knife, exacto knife… something sharp but non-lethal.
  • Straw

Cutting a groove for the propeller in both sides of the wood (we used the straight edge to make, well, a straight edge for the groove):


After Experiment #1 (aka Friction, or, Will the propeller shaft move more smoothly inside the wooden groove, or inside a straw? Straw, totally.), gluing a straw into the wooden groove:


Missing steps include (and not necessarily in this order):

  • Insert a screw eye into the end of one of the wood bits. If you look closely, you can see the screw eye underneath the straw in the above picture.
  • Loop a rubber band through the screw eye.
  • Glue, and when the glue completely fails to hold, rubber band the two bits of wood together such that the straw cannot come loose.
  • Insert propeller shaft into straw


Here, Andrew puts the rubber band around the propeller blade:


Twists, and then lets go:


And to the tub, where we try for experiment #2 (or, Which will go faster, the raft with a truck, or without a truck?), and find out that Murphy’s Law ALWAYS applies to experiments (it was very difficult for Boo to wind the propeller and balance the truck at the same time). Lucky kid, I didn’t learn that lesson till grad school.


2 Responses to Whatever floats your boat!

  1. Linda

    THANK YOU! Don’t stop posting these! My 8-yr-old son will be making the pinhole head camera for a science project. AWESOME!

  2. Sarah

    I love it! Granted, no broken boards here, but I think I know a place with some balsa wood. This will be great at our park this weekend– where there is a ‘lake’. And an art fair. Where we will go once we’ve become prunes.

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