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How to Make a Raft

(And Float Down a River on It)


My first river rafting adventure involved four friends. I sold the idea to them as an adventure-disaster, sure to get them wet and cold. We carried a hatchet, a saw, snacks, water, and scraps of rope - all in one small day pack.

We parked the car at a bridge and hiked upriver a few miles. We planned to build a raft, using dead trees and our scraps of rope. Then we would then hop on it and float back downstream to the car - which we more-or-less did. But that is another story - this is a how-to guide.

Making a Raft

An axe might help, but the easiest way to cut your trees will be with a saw. The toolbox-sized "short-cut" saws work better than longer ones, and are easier to carry. Otherwise, all you really need is 100 feet of rope or strong twine. This can be scraps. Alternately, you can buy whatever they have at the dollar store.

Once in the woods, scout for an area near the river that has a lot of dead trees. Apart from environmental concerns, live trees just don't float very well. Look for trees no more than ten or twelve inches in diameter, or you'll wear yourself out cutting them.

What kind of trees? If you have a choice, look for those with the lightest wood and those that are easiest to cut - try for both if you can. Dead and dry, maples are likely to weigh 45 pounds per cubic foot - meaning they won't give you much lift. They are also one of the more difficult woods to cut. White cedar, at 30 pounds per cubic foot is a better choice.

Cedar isn't really easy to cut either, however. My favorite is slightly dry-rotted poplar or cottonwood trees. Older specimens are like Styrofoam when you cut them, and probably weigh about 25 pounds per cubic foot. However, they will waterlog more quickly than other woods, so they are best for one-day trips.

Cut down the trees and then cut them into usable lengths. Shorter logs will mean more cuts. For this reason and for better maneuverability, build a longer, narrower raft. Aim for logs about ten to twelve feet in length.

How many? This depends on the weight of passengers and gear, and the wood. Water weighs 64 pounds per cubic foot, so when you subtract from that the weight of the wood you're using, you get your lifting capacity. For example, if the trees you are using weigh about 39 pounds per cubic foot, they will carry about 25 pounds per cubic foot (64 minus 39).

Suppose you have 600 pounds of people and gear, and your wood has a lifting capacity of 25 pounds per cubic foot. 24 cubic feet of wood will float you (600 divided by 25) - but try for double that or you'll be standing in the water as you "float." In other words, you are aiming for 48 cubic feet.

Time for math. The volume of a cylindrical object is pi times the radius squared, times the length. Pi is roughly 3.14, by the way, and there are 1728 cubic inches in a cubic foot. Suppose your logs are roughly 12-feet long and 8 inches in diameter. Radius 4 inches: Square that (4 x 4) and you get 16. Then multiply that by 3.14 and you have 50.24, which is multiplied by 144 inches of length for a total of 7,234 cubic inches. Divide this by 1728 and you get 4.19 cubic feet per log.

About 12 such logs will give you your 48 cubic feet of wood. Want an easier way? Get a bunch of logs together - a lot more than you think you'll need.

For best results, assemble the raft in the water - a lesson learned by hard experience. Cut five long skinny poles. Tie two to each log on top, at both ends, and tie one on top diagonally (important - another lesson learned the hard way). The other two will be the rafting poles you and your friend use to guide the raft.

Got a cooler? Set it in the middle as a seat, to keep any non-pilots out of the way - or use an old stump or log for this. Those of you "in control" (good luck) will have to remain standing for the duration of the trip, as you will learn from experience. That is how you make a raft and float down a river on it.

Note: Use the link here to read about
Steve's River Rafting Adventures.


The Ultralight Backpacking Site | How to Make a Raft