SLED RX: EVERYTHING BUT THE WOOD

Your main material considerations in sled building are wood, plastic, metal and hardware.

I have talked about wood in past issues, so I will concentrate on the last three in this article. I am not going to talk about the different runner plastics here but rather focus on what is generally used for toboggan beds, handles, brushbows and gussets.

The most readily available plastic of this type is Tivar 1000 UHMW. The UHMW stands for ultra-high molecular weight. This dense plastic slides nicely and can be used on all applications for a sled. While usually white, UHMW comes in a variety of colors, including green, blue, yellow, black and red.

Most colored UHMW contains added solids that protect it from UV rays. If you can get your hands on only one type of plastic this is your best bet. A black plastic called HDPE, or high-density polyethylene, is also quite common and works well, though it is a bit softer and scratches easier. Most plastic comes in sheets from 1/8” to 1” and can be cut and routed with common woodworking blades and bits.

For a toboggan bed the ¼” thick works well and is usually cut 20” wide. You can shape any of these plastics into relatively tight bends by using a judicious application of heat to the area being bent and then clamping or bolting the piece into shape. Use a heat gun to warm the plastic, moving the heat point slowly making sure not to keep it in one point too long and causing any melting or burning. If the plastic is overheated it can become brittle and break very quickly so be careful when applying heat.

When the plastic is soft, bend it into the shape you want, preferably around a form that the plastic can be clamped. Wait until the plastic has cooled before removing from the clamps. In some cases, particularly for handles, top rails, and brushbows, you can bend the plastic into the shape needed and just fasten it in.Aluminum is a material that has become a major component in most sleds these days.

However, all aluminums are not created equally, and trying to use the wrong type for the application needed can be a recipe for failure. Often, it is where you purchase the material that can determine the type. Most hardware stores do not sell the type of aluminum you will need, and unless it is specifically marked with the alloy information, it should be avoided.

You are looking to use two main alloys in sled building, often referred to as ‘6000 series’ or ‘7000 series’ aluminum. These broad categories represent several alloys that are readily available and work well for sled building. Most of the 6000 series aluminum available is a specific alloy called 6061 and should have that number stamped on the material. This type of aluminum works great for brake brackets, toboggan angles, struts and x-braces.

For children’s or light duty sleds where a lot of braking force is not needed, you can use this type of aluminum for your brakebar. 7000 series aluminum is usually represented by an alloy marked 7075. This is one of the hardest aluminum alloys available and works well for brakebars, crosspieces and headboards. Most aluminum runners are an extruded 7000 series aluminum. Look for a local metals dealer and ask about their ‘drop’ pile because most aluminum comes in lengths ranging from 12’ to 25’.

Often businesses will have short pieces left over from special orders and you might be able find what you need. Most of the time you will find a good selection of alloy 6061 in a variety of sizes and shapes. Finding alloy 7075 may be difficult because it is more of a specialty item and it will depend on what alloys your local industries utilize. If you need to cut down the width of a piece aluminum and do not have access to a metal cut-off saw or power hacksaw, you can cut it on a table saw with a regular carbide blade. Be very careful and be sure to wear eye and face protection along with long sleeves and gloves because the aluminum dust is like small shrapnel.

General sizes for parts falls into various categories. Struts are made from ½” wide Schedule 40 aluminum pipe (alloy 6061 T6) with the ends flattened around a 3/8” UHMW plug. Brake brackets and other small pieces can be made from 1/8” thick 6061 aluminum angle, while for toboggan side angles 3/16” or ¼” thick 6061 aluminum angle works best. Brake bars are usually formed from ¼” by 1” 7075 aluminum flatbar and are bent around a curved form rather than in a sharp-angled bench vise. A short note on experimenting with alloy 6061 for use as runners.

Several people in the past have tried using square tubing for runners and have been less than successful in their efforts. The 6000 series alloys do not respond well to the continual flex in the runner and break usually right behind the rear stanchion. Efforts to control this failure by using expandable foam or UHMW inserts has not been successful.

For most sled applications with hex head bolts, the two main choices are either stainless steel or Grade 8 hardened. Each has an advantage: stainless bolts are hard and strong and will not corrode, but are a brittle hardness that can break when you are tightening them, especially if you are using powered tools in the process; Grade 8 hardened bolts are stronger than stainless but are not as brittle and they are susceptible to rust.

The problem many people face when trying to organize all the hardware needed for a sled is the lack of availability and consistency. Rarely will you find all the sizes needed, or some items may not be available in the material needed. It is pretty common to be able to get stainless steel bolts or machine screws and the corresponding washers and nuts. The same cannot be said for Grade 8 hardware. Hex head bolts in various sizes and threads are readily available, but screws, washers and nuts can be harder to come by. As you get into the specialty hardware needed, such as eyebolts, eyescrews or toggle nuts, you will generally find that these items are only available in softer material.

Usually, that is not a problem as long as you use the proper gauge of hardware for your purpose. On basket sleds use a minimum 3/16” eyebolt or screw for your tying points. I like to use T-nuts to fasten my bolts or eyes to my runners. This makes attachment easy and, done properly, does not compromise the runners integrity. T-nuts come in various lengths. For the best performance try to get the longest available – at least a ½” barrel length. When using T-nuts, or any other system for assembling your sled, remember to do all your drilling then give the runners a final coat of finish, making sure to get a generous amount into all of the holes. This will greatly reduce wood rot since bolt holes are natural pathways for moisture. A few final notes on hardware.

When you are planning your sled try to use a consistent bolt size to keep the amount of tools needed to repair a sled on the trail to a minimum. Try to use locking hex nuts with a nylon insert instead of regular hex nuts with a lock washer, and make sure that the threaded bolt end extends past the insert. If you run your bolts or machine screws up through the runner and have the nut on top be sure to cut off any exposed bolt length in excess of a ¼”. Since most bolts are available in ¼” increments with careful planning this should not be a problem.

When you are bolting through wood or plastic you should always try to use a washer to help distribute the pressure and prevent a bolt from pulling through the material. This might sound like a no-brainer, but I keep seeing $2000 sleds that are failing in places that could have been prevented by a 1 cent washer.

Hopefully, you have been starting to gather the materials needed to build your sled and have a firm plan in mind. In the next issue I will start showing you some shortcuts and techniques that will get you on the trail quicker. Until then, hope for snow. Happy Mushing!

David Klumb has been making dog sleds in Fairbanks, Alaska since 1980. David and his wife Joanne ran the 2006 Serum Run. For more information on Laughing Husky dog sleds, visit www.laughinghusky.com.

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