Bending the Tips and Camber

Template and outline

Talbot made a template from 1/4-inch plywood so both skis come out the same: mark the length and the widths at tip, waist, and tail; draw the tip by hand; and trace the long side curves along a thin batten clamped at the ends and sprung to the waist width ¹. Trace the template onto each blank and saw the outline, keeping outside the line; Talbot found a jigsaw drifted and recommends a bandsaw ¹. Hansen’s class used a bandsaw too, though another class shaped skis with axe, plane, and drawknife ².

Leave the top flat for now: you’ll taper the thickness after bending, but the bending zone must be thinned first.

Thin the bend

Plasticized wood can be compressed 25 to 30 percent along the grain but stretched only 1 to 2 percent. When a bend would make the outer face more than about 3 percent longer than the inner, industry uses a metal strap on the outside to carry the tension ³.

The outer face grows by about thickness ÷ radius. A tip 3/8 inch thick bent around a 12-inch radius stretches about 3 percent, right at the limit; a 3/4-inch tip on the same curve would split. So:

• Plane the front 18 to 24 inches down to about 3/8 inch before bending, thinning gradually from the full thickness behind it. Talbot’s finished skis taper to 5/16 inch at tip and tail ¹.
• Make the curve gentle and long. Richardson’s ideal bend begins so gradually that you can’t say where it starts, and a thin bend is stronger in use than a thick one ⁴.
• If a tip still cracks, bend the next one with a thin steel strap clamped along its top face.

The arch under the foot is so slight, 3/4 inch over several feet, that it needs no thinning.

Build the mold

Talbot’s form is a long box of two 1x8 pine boards held 12 inches apart by cross braces, wide enough for both skis at once. He drew the tip curve a little steeper than he wanted, because the wood springs back after it comes out, and screwed the tip braces in place so they can be moved; one brace holds the tip down into the curve ¹. Hansen’s students adjusted their molds to set the camber under the foot at the same time as the tip ².

To set the camber, put a block about 3/4 inch thick under the foot of the ski and clamp tip and tail down. The ski comes out with a little less arch than the block once it springs back.

Soak or steam

The Wood Handbook’s times: steam or boil about 38 minutes per inch of thickness for wood at 20 to 25 percent moisture content, and about 75 minutes per inch for drier wood. Below 20 percent, heat alone isn’t enough and moisture must be added too ³; unless you know your blanks are wetter, use the longer figure.

Hansen’s class soaked the blanks in a hot-water bath on the wood stove ². A steam box works too: a closed plywood box or pipe long enough for the front third of the ski, fed with steam from a kettle or wallpaper steamer. Soaking the tips in water for a day beforehand adds some of that moisture.

Bend and set

Work fast once the wood is hot:

1. Pull one ski from the heat, set its foot on the camber block, and clamp the tail.
2. Press the tip down into the curve steadily, not in jerks, and lock it under the tip brace.
3. Clamp everything and do the second ski.
4. Leave them overnight. Hansen’s skis set overnight before release ²; longer is better if the wood is wet.

A bent piece keeps its shape once it has cooled and dried in the form. Later changes in moisture can relax the bend, which is one reason to seal the skis ³.

Try it

Bend a test strip first: a piece of your birch 3/8 inch thick and 2 feet long, steamed and bent around the tip curve. If it cracks on the outside, thin the skis more or use a strap; if it springs back a lot, steepen the curve in the mold.