By Larry Walton When Robert Lipskoch was drawing the plans for his house, his kids wanted a curved slide from the second to the first floor. Although the slide did not remain in the plans, a dra- matic dual curved staircase emerged as the center- piece of the house plan. Robert laminated the curved stringers in place using 16-in. wide strips of thin plywood and finished both sides with oak veneer. He constructed the treads of steel frames and plywood panels between the stringers, which means the stringers also func- tioned as knee-walls that we fit with caps on top and bottom. He laminated the caps in place with 1/4-by- 3/4-in. oak strips. The balusters, which support the handrails, were designed to penetrate the stringer caps, which meant the handrails needed to match the curve and climb of the stringers. This would be achieved by glu- ing and clamping the handrail components together directly on top of the stringers.
TWISTED MYSTERY I can't explain the trigonometry involved, but the combination of stair rake (ascending at an angle) and curving around a plan-view radius results in a continuous twist in the rail from bottom to top. The right rail in our dual stair case curves clockwise as it goes up while the rail itself twists counter-clockwise so the top of the rail remains at the top at any point along the stair case.