Here's How

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  Step 1: Using coarse and then fine sandpaper on a cork block, shape hull by rounding front and streamlining the underside.
• Step 2: Cut a 45° angle at back of each sponson, to make a left and a right-hand sponson. Shape fronts to curve upwards into points.
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  Step 3: Glue, predrill and nail sponsons to hull sides so they are protruding from front by about 20mm and tops are flush.
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  Step 4: Cut tops of tails so they slope down by 8mm at front, and front edges so they slope back by 12mm at the top. Glue and nail tails to balloon block. Sand front edge of block so it is flush with front slope of tails. Shape front of wing to create an angle, then glue to tail tops. When dry, glue and nail to back end of hull (as shown).
• Step 5: Sand front edge of windshield to create an angle of about 45°. Glue and nail in place across the hull.
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  Step 6: Cut a vertical slit in centre of rear underside of hull, then cut a small plastic rudder from nail packaging. Test to fit, then remove.
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  Step 7: With boat upside down, use a succession of drill bits (3, 6, 9 and 12mm) to bore an angled hole through balloon block. When boat is upright, the hole should slope down towards back of boat.
• Step 8: Sand whole boat smooth. Paint with undercoat, then 2 coats of gloss enamel. Allow to dry. Add super-speedy stickers (optional).
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  Step 9: Cut plastic tube to length of hole. Feed neck of balloon through tube until opening is on other side. Push tube with balloon through hole of balloon block. Replace rudder and you’re ready to race. Place on water, blow up balloon, then let the boat go.