How to Build a Sand Rail

When building your sand rail, think "catamaran," not "truck."

The sand rail -- aka "dune buggy" -- isn't a car. It isn't a truck, and it sure isn't a fancy-pants VW Bug. In terms of function, the dedicated sand rail works more like a side-by-side snowmobile or racing powerboat than it does anything else. This unique conglomeration of tubes and motor is a study in simplicity, designed to skim over sand like a powerboat over water. Building a sand rail is as difficult and time consuming as you want it to be, and the approach you choose will depend on that all-important ratio of time to skill and money.

Things You'll Need

• Sand rail design
• Engine and other components
• Tube bender, mechanic's tools

Instructions

1. Apply Isky's Law of Inverse Proportions. Often credited to racing and hot-rodding legend Ed Iskendarian, this combination in-joke/maxim states that time, money and skill relate in inverse proportions. The more money you have, the less time and skill you need; the more skill you have, the less money and time; the more time you have, the less skill and money required. Take a realistic assessment of these three factors before proceeding, since they'll determine everything you do from beginning to end.

2. Look at your operating conditions. Sand rails are incredibly versatile off-road devices: fast, simple and lightweight, the sand rail concept doesn't need much modification to work as a rock buggy, roadster or dedicated dune navigation device. But if you want a road-legal buggy or do-it-all off-roader, build one of those.

3. Work forward from the ideal of a racing powerboat. A racing powerboat is actually a trimaran; it has two thin outriggers on the side that actually ride in the water, and a very shallow-draft center hull to allow the boat to float and control airflow under the boat. There are three basic concepts you'll want to import from the powerboat: light weight for skimming across the "water," rear weight bias to go up on a plane and rear steering. Yeah, that's right: rear steering.

4. Select an engine and powertrain. Any good hot rod is built around the engine and the tires, so you'll want to start here. While the lightweight and air-cooled VW four-cylinder is the traditional choice, you might want to go with something a bit more powerful and modern. Almost any modern front-wheel-drive, four-cylinder will put out twice the power of a VW, and these days you can buy a complete, running donor car for less than the cost of a good VW transmission.

5. Select your tires. The more powerful engine may be a bit heavier, but you can offset that weight by using wider rear tires. The engine's greater horsepower will keep those wider tires spinning, and the tires will provide the traction to keep your rail up on a plane. Just like a bigger prop allows a boat to use a more powerful engine, your more powerful and modern engine will allow you to get away with wider rear tires. Plan for the tallest, skinniest, lowest-profile tires possible for the front. The front wheels are essentially a "rudder" that stabilizes and directs the front of the car, so side area of the wheel is a lot more important than the tires themselves.

6. Engineer your steering system. This is where things get a bit complicated. Yes, you could just run a conventional steering box to turn the front wheels, but that doesn't make any sense in this application since the idea is to keep the front tires up and out of the sand as much as possible. Instead of relying solely on your front-steering rudders, utilize the power steering mechanism and suspension from your donor car to turn the rear wheels. You can connect the steering rack to a "tiller" lever -- where the hand brake would be -- via a cable-and-pulley system.

7. Build your chassis. This is where Isky's Law comes in; if you've got a doctorate in TIG welding and engineering, and nothing but time, then build a chassis to your specification. If you've got money but don't have the requisite skill or time, have a race-car fabrication shop build a chassis for you. If you've got a lot of money and no time, then just buy a pre-fabricated chassis and bolt the parts on yourself. A wide, short wheelbase will make your car more nimble but slower and less stable at high speed. A long, narrow chassis is better for high speeds but more prone to roll over while cornering.

8. Install a full sheet-metal "belly pan" that spans all the way from the front bumper of your chassis, under the engine and around the rear bumper. This is your rail's "center hull," and its purpose is two-fold. First, it keeps your tube chassis from digging into the sand, helping the rail skim over its surface. Second, it helps to keep sand out of your mechanical bits and eyes. Counter to popular practice, you'd do best to completely wrap the chassis, suspension, engine and transmission with some kind of lightweight skin. Even canvas is better than nothing, but thin-gauge aluminum would look better.

Tips & Warnings

• If possible, have a removable subframe and drop the motor out the bottom, this makes design, removal, and installation so much easier as well as not having to remove everything on the top to get the motor out.

References

• Chassis Engineering; Herb Adams
• The Off-Road 4-Wheel Drive Book; Jack Jackson

Resources

• Read this Article in Spanish
• Read this Article in Spanish