Hoverbug (1969)

Dick and Jenny Brewster hope to win a race for home-made Hoverbugs. They build their own Hoverbug but their rivals Charlie and Sidney bend the rules by enlisting professional help. The main trouble with the Brewster Hoverbug is that it keeps falling apart. until Dick and Jenny meet Mr Watts, a real inventor, who has developed an instant glue, Wattstick. But Wattstick proves to be only a temporary adhesive.