How to Make a Raft
(And Float Down a River on It)
By Steve Gillman
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
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
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.