This is my kit built Craft Air .40 size Firebird, approximate circa late 1980’s. This is a pattern qualified plane by IMAC.
I use it year round and fits very well as my snow plane. Using a simple OS .46 LA it is easy to start in cold weather, reliable and the size/weight of the plane is perfect for snow skis.
The recommended formula for the skis length/width is to achieve 14.5 sq. in per pound of plane total weight. The 2 combined gives me up to a 5 lb. plane. You’ll notice that I prefer not to use a tail ski since the tail floats very well on the snow. These skis were cut 3” x 12” and multiple kerf cuts where the bend starts. This makes forming the tip much easier.
After removed, apply CA to the kerf cuts to help retain the curve in the tip.
A backbone of 1/8 ply is also installed to help retain the shape and act as an anchor point for the robber bands.
In this case I drilled and tapped the landing gear to attach the rubber bands or safety string to but a notch filed on the sides and zip tie can achieve the same results. It is IMPORTANT that the landing gear hole in the attaching block be that same height as when the wheels are on to maintain the same angle of attack. My plane is a tail dragger but tricycle gear skis can be made also for the front landing gear as shown
All said and done, you can easily order skis, but if you want the total JOY of that seldom and occasional winter snow flight, enjoy modeling and love to do it yourself, I recommend these.
Chet Blake