Gone Skiing

Have you got snow? Get yourself ready for some action in the ‘white stuff’ with our tricycle snow skis suitable for medium size electric or I/C powered sports models

The idea of producing snow skis for models is not new, in fact many modellers have produced their own skis in the past and have flown very successfully with them. The skis shown here are constructed from all wood, and successfully flown on many occasions – when the weather was right.

The plan for the skis has been designed to fit a single A4 page so that it can be included here, and also downloaded from the Traplet (RCMW) web site at no charge to avoid cutting up your favourite magazine. This magazine can also be taken to a High Street photocopy shop and copied, but be aware that a charge for this service may be made. Note that it is not necessary to reproduce the plan at the same size. It can be enlarged or made smaller.

All dimensions needed to cut out the skis are shown on the plan and the construction is really quite simple. This tricycle undercarriage ski set is easy to fit and very effective. All you need to do is remove the wheels and insert the axle into the hole in the axle block and refit the retaining collets and clip on the suspension springs. As simple as that. So why not get yourself ready for some snow fun now?


Description
The materials used for this are quite simple. The skis are constructed from 3.5 mm or 4 mm plywood with either alloy U-shaped undercarriage axle support brackets, or axle supports blocks made from laminated ply or MDF wood, or solid shaped hardwood block. These are secured with either bolts in the case of metal brackets, or PVA glue and countersunk wood screws for the wood block support. Most standard manufacturer’s undercarriage units should be suitable and should fit quite easily. There is nothing complicated about the construction - just a little steaming required for bending the wood at the front of the ski around a pattern from solid block or a template. Even gentle persuasion will suffice. The outlines for the two curves (front nose leg and main undercarriage) is shown on the plan.

The plan shows two different size skis: The smaller of the two is the front ski and is made to the size shown on the plan. The longer main ski pair are both 17” (43 cm) long, but shown reduced in length on the plan.

Construction
For each of the two main skis first cut the two 4 mm (3/16”) thick plywood ski parts to length and width from the plan template (that’s one for each ski). Then take one of the two ski parts and bend the front of this ply piece to the required shape shown by using either my method, or by using your own preferred bending method:

Wearing heat-proof gloves, I first boiled the kettle and held the front end of the ski over the steam. This forced the steam into the bend area and softened the wood sufficiently to start a bend in the right position. While the wood was still damp I placed the front of the ski in a bowl of water and allowed it to soak more. After a few minutes I wiped off the excess water and placed the ski on the flat worktop with a spice container under the front of the ski, trapped against the wall. By applying pressure in the bend area the wood took up the required curve easily.

This was done individually to allow an easy bend - but make sure they match. If the wood is damp enough it shouldn’t spring back. When the bend is sufficient just set the skis aside and allow to dry thoroughly overnight. Repeat this for the front ski – if required.

When dry, shape and finish the edges of the ski with a razor plane then finally sand to shape the rear end by rounding off the corners to finish.

The axle support is a laminated block of MDF or solid hardwood cut to the shape on the plan. Round off the edges for smoothness. Mark and drill an axle hole in each support of the size required to suit your axle. This hole can be drilled slightly oversize and a short piece of brass tube inserted as a liner for the axle to prevent unnecessary wear to the wood if you wish to go this far.

Add the wooden block for the undercarriage axles by drilling pilot holes in the ski and block, and countersinking the underside of the ski deep enough to take the screw head and some wood filler, and make sure the finish is smooth. For metal (or Dural aluminium brackets) simply drill two holes for each and secure with a countersunk bolt from the underside, and nyloc nut.

Finally give the surfaces a good painted coat of wood protection (International Yacht varnish is a good all-round weather protector) and a coat of paint can be applied later with a couple of coats of clear varnish to harden the paint finish.

Finally, I added small expansion springs to the front and rear of the blocks and attached to the axle to keep the ski aligned in flight and act as springing for rough terrain and assist with taxiing on the snow or ice. It is not there as airframe suspension! This can be replaced by slack control-line wires or fishing line attached at the front and rear of the ski and to the fuselage to prevent tipping, or omitted completely - the choice is yours.

Flying Tips
For softer snow it is advisable to flatten the runway surface area first as it does have an element of grip when not compacted. Soft powder snow does also act as a good braking area and will stop a model very quickly - in a cloud of white powder! For harder compact snow and ice the skis will serve you well.

Flying with skis is no different than with wheels, but do not allow the skis to dig in on landing. Have fun!

Grateful Thanks
I would to express my sincere thanks to Brian Cheadle from Deep River, Ontario, Canada for the photos of his fellow Algonquin Aeromodellers Club members who gathered on New Year’s Day 2007 for their annual snow Fly In at their flying site in Pembroke,Ontario.. It certainly looks like they had some real fun with a varied selection of models!

Click here to download : Gone Skiing full Article pdf

Click here to download : Ski Template pdf