By George Nichols
Various examples of the finished
These skis are made from formica, which can be picked up at a local cabinet shop or one of larger lumber chain stores (Home Depot, etc)
1) From a piece of 3/4" pine or soft fir rip a slab 1/4" to 3/8" depending on sizes of ski and plane. Cut to length needed. Use a piece of steel wire to form the curve on the bottom of keel. Use a band saw or scroll saw to cut the curve. Cut the axel blocks from the same piece of wood incase one slab is thicker than the other, a finish carpenter I am not .
You might have noticed that I do not have a sharp up turned tip. I use a flexible stick and start at the heel of the keel, near the top, and when I get to the axel, I am down to the bottom of the keel and no bend in the stick from the axel to the toe of the keel. I bend the stick to mark the curve.
The axel block can be installed now or after the ski has been epoxied. It may be easier before the face of the ski is attached, since it could be in the way if you want to shape the block or drill the axel hole after its epoxied to the keel.
2) This view shows the method of attaching the keel to the ski face and the reason for finding centerline.
3) This view shows how the axel block is reinforced with fomica scraps and a hole for the axel is drilled, approximately the dia. of the wheel axel you normally use. The formica is tough and does not wear, and should outlast the ski.
4) This view shows the torsion bar attachment on dural landing gear. Drill a hole in the dural gear clos to the axel, shape 1/16" steel wire with a loop to fit a bolt through, use a lock washer to help keep it tight here.
The wire can go either forward od behind the axel. The larger the plane, the shorter the wire before making a 90 deg bend. On .20 sized planes 4"to 5", on larger planes 3"to 4". The shorter the wire the stiffer the ski will move up and down.
Drill a slightly larger hole in the keel to allow it to slide without binding. I have not used a wheel collar as the wire does not come out.
5) This view shows the attachment for wire gear. Tension is governed by wraps around the axel and a length of wire tail in both directions down the length of the ski and up the landing gear towards the fuselage. Adjust incidence by forcing the ski up or down slightly past the point you want it. It only take a time or 2 to get the right position.
6) This shows Bill Petersons way of adjusting for incidence and the springs for holding skis level with some movement to float over bumps
7) This view shows that a loop around the landing gear above the axel will secure the torsion wire and hold it in place.
8) This shows the nose ski for my Kadet Sr. The Formica is so slick it would not turn. We ripped a slot from the rear of the ski up into the keel and a piece of Formica was epoxied into it vertically to form a rib. No more steering problems.
9) This is the tail ski assembly for a tail dragger. Warning! this was installed on my .20 sized Cub and it shifted the CG back to far. I found this out when I stalled it at about 25' up on an approach, which is why I fly an .20 Airchild now, it did make a world of difference in taxiing though.
I hope you have as much fun building these as I did. You will find that the snow conditions will change the requirements for the skis. Light fluffy powdery snow will require a larger ski. You can get by with smaller skis both width and lengthwise with hard packed or frozen snow. I make mine a bit over sized to meet requirements for all conditions.
I do not find but slight trim change difference, if any, from using wheels.
I seem to stay on top of the snow, and this shallow curve may be why I don't notice any major trim changes.
If you have have all your building done and skis you can get a lot of cold weather flying done! Good way to get that all weather flying patch.
Best wishes -Salmonfly
Questions or comments? - George Nichols firstname.lastname@example.org