A 6, 15
D 1, 2, 3
F = MA
| Most Alaskans live or hunt on rivers. Boats are an inseparable
part of our lives.
There are basically two kinds of boats, each serving a specific
- Planing boats
- Displacement boats
Planing boats, once they get enough speed, skim on top of the
water. They go fast and are good for light loads.
Planing boats usually have a wide flat bottom, allowing the boat
enough surface area to get on top of the water. When a boat climbs
on top of the water we say it is planing or on
A V bottom is good for breaking waves, but provides less lift.
It planes to a limited extent.
Some planing boats have a V bow (front) to cut the waves, and
a flat bottom in the stern (back) for lift. This is a common compromise.
A V bow is helpful when the ice is running. The V bow parts the
ice, going to one side or the other of the ice pack. A flat bottom
boat constantly climbs onto the ice pack. The passengers have to
get out and push the boat off the ice.
Ocean, Downriver, or Big Lakes
People who travel in big bodies of water usually have boats with
a V bow because the wind causes big waves in open places. A flat
bow pounds on big waves, loosening rivets or nails, giving a very
Lake and downriver boats usually have much higher sides than upriver
boats where there are smaller waves. Downriver boats usually have
a high transom (back end) and use long shaft motors. These adaptations
keep the large waves out of the boat.
Upriver or on Smaller Lakes
People who boat in smaller lakes and narrower rivers prefer boats
that are flat on the bottom from front to back. This kind of planing
boat skims on top of the water, especially in shallow conditions.
Boats designed for small lakes and rivers usually have lower sides,
low transom and short shaft motors.
- Are often a hindrance to getting in and out of the boat.
- Add weight which is critical in shallow water.
- Cause the boat to blow around a lot in a side wind, making steering
Disadvantages of Planing Boats
The disadvantages of planing boats are significant.
They need a motor big enough to go fast enough to get on step.
If the load is too heavy, a planing boat is like a raft, slow very
hard to push. Big motors use more gas per hour and cost more to
buy and repair. On step, they are economical.
There is a sharp breaking point where a planing boat will either
be on step or plowing water trying to get on step. Sometimes fifty
pounds makes the difference between planing at thirty mph or plowing
at twelve mph.
We used to figure the gas consumption of a motor at full throttle
by dividing the horsepower by ten. A forty horsepower would use
four gallons an hour. A twenty horsepower used two gallons an hour.
Modern motors do better than that. Perhaps dividing the horsepower
by twelve would be a more accurate estimate of gallons per hour.
The new four-cycle outboards are even more efficient, perhaps dividing
horsepower by fifteen to get gas consumption per hour. Fuel prices
are so high now, fuel economy is an important aspect of buying an
Planing boats are terribly difficult to pole up shallow creeks.
The wide stern seems to drag all the water in the creek behind it.
There is a lake behind our village. In the creek to the lake, there
is a shallow section we call divorce country because
many husbands and wives get in big arguments trying to pole their
planing boats through there. Oldtimers easily poled their displacement
boats through to the lake.
turns of a displacement boat cut the water
bow plows water
A displacement boat has gentle, gradual lines that cut through
the water. It has a smooth shape to push the water out of the way
as gradually as possible. A sailboat is an excellent example. A
displacement boat cannot go as fast as a planing boat, but it can
carry a much bigger load with a small motor.
Oldtimers built and used displacement boats hauling hundreds of
pounds with three to five horsepower motors. Canoes, kayaks, and
umiaks are also displacement boats. Before motors arrived in Alaska,
people poled wooden boats up the river. Often they lined up, pulling
the displacement boats by ropes. They cleared the banks of brush
for long sections of river in order to do this. I have had to line
up several times to get home after breaking down.
My wifes family used to build displacement boats thirty-two
feet long, three and one-half feet wide with a very narrow stern.
They hauled all their winter fuel and food up a very swift river,
using only five to fifteen horsepower motors. They were slow but
hauled an enormous load.
Envisioning the Difference
Picture this in your mind: Pat the surface of water with your
hand. Gradually do this faster and faster. The faster you do this,
the more resistant the water seems. The slower you do this, the
less resistant the water seems.
A planing boat travels on the water so fast the water resists
downward motion, keeping the boat on the surface.
The displacement boat is designed to push the water out of the
way slowly so the water is less resistant. It cuts the water
If you put a big motor on a displacement boat, it will go somewhat
faster, but not as fast as you might think. At low speeds the resistance
of the water is minimal. If you have a displacement boat, you need
a small motor and a lot of patience.
The oldtimers had a lot of time, but not much money. Nowadays
we have more money, and limited time. If hard times come to Alaska
again, I will immediately switch to a displacement boat with a small
Actually, each family needs two boats, one planing boat to make
quick trips with light loads, and a displacement boat to haul loads,
fish, hunt, and go logging.
The Same Thing Said Another Way
As a planing boat travels quickly over the water, the momentum
of the water and its viscosity keeps the water from moving
out of the way quickly. The boat travels on top of the water. A
planing boat interacts with the water so suddenly the inertia of
the water gives the boat lift.
As a displacement boat travels through the water, the momentum
of the water will greatly resist the forward motion of the boat
unless the curves of the boat are gentle, allowing the water time
to move out of the way. A good displacement boat interacts with
the water gently, gradually and gracefully.
Canoes, kayaks, and umiaks are displacement boats. When the individual
is providing the power from his own arms, he can readily tell if
the boat is well designed or not.
Upriver canoes. If the bottom is perfectly straight, the canoe
will hold a straight course across a lake, but will be hard to turn
in a creek. Usually we put a little rocker in the bottom,
perhaps one inch in a fourteen- to sixteen-foot canoe.
Not enough rocker
Rocker just right
Too much rocker
If the canoe is too wide, it is hard to paddle or pole. However,
the more narrow it is, the tippier it is. Far upriver in swift current,
people preferred to pole the canoes with a small pole in each hand.
It is easier to pole against the solid bottom than to paddle against
A round bottom canoe is easier to paddle, but is very tippy. People
skilled in handling canoes preferred round bottom canoes, but the
rest of us are better off with flatter-bottom craft.
Years ago, people hunted from canoes. Many Native-built canoes
were very narrow. There are many funny stories about people shooting
a shotgun sideways out of a canoe. Shooting over the bow pushed
the canoe backward. Shooting sideways flipped the canoe over!
Poling boats were wide in the front and narrow in the back, allowing
the one poling to steer in any direction.
builders have to decide at what angle to lean the sides out. If
the sides are too straight, the boat is strong like angle iron,
but resists turning. When a load is added, the boat sinks down considerably.
If the sides lean out too much, the boat will turn easily, and
will haul a load well. The boat, in effect, gets wider and wider
as the load is applied. However, the boat will not have much strength
in waves. It will tend to bend and twist, breaking up in a few years
from the stress. The best angle is determined after the conditions
are identified and the length of the boat decided upon.
Both planing and displacement boats come in contact with the water.
The rougher the surface is, the greater the resistance is. The resistance
between the boat and the water is an example of friction. This friction
can cost many gallons of gas over a boating season. Any energy spent
in overcoming unnecessary friction is wasted energy.
There are several ways to reduce friction.
A wooden boat can be sanded and painted. Oldtimers used to dry
the boat and blowtorch the hair that develops on the
bottom and sides of a wooden boat. Aluminum boats can be lightly
Painting a boat, whether aluminum or wooden, reduces friction.
There are different types of paint. Marine paints are very expensive
because they contain copper compounds that prevent barnacles and
marine growth. In locations where this isnt a problem, a considerable
amount of money can be saved by using paint that doesnt contain
toxic copper compounds.
Now, village people use epoxy resin and fiberglass finishes over
wood. These provide protection for the wood, and greatly reduce
friction with the water. Years ago, spruce pitch and cotton caulking
were used as a sealant. It also smoothed out rough surfaces.
There are five common materials for boat building, each with its
advantages and disadvantages.
Lumber boats are inexpensive and strong, especially if the builder
has cut and seasoned his own lumber. They are repairable by the
builder too. Unfortunately, they require considerable maintenance
including painting and caulking. They often leak. They are heavy.
Knots occasionally fall out, leaving big holes. Eventually they
rot, even if they have been carefully maintained. Wooden boats have
been in Alaska since the whipsaw made lumber possible.
Plywood boats replaced lumber boats for a while before aluminum
boats arrived. Plywood has the same qualities of a lumber boat except
they tend to leak far less if properly caulked. Without modern glues
and caulking, plywood boats are not practical.
Some people build boats using AC plywood. While the glue is the
same as in marine plywood, the quality of the core of the plywood
is poor. Marine plywood is smooth on both sides and has a core made
of high quality wood. It is very expensive. When I build a boat
that is something of an experiment, I use AC plywood because it
is cheaper. My new design might not be worth the expense of better
material. When I am sure of the design, I use high quality marine
Both plywood and lumber boats are easily destroyed when run in
Aluminum is an excellent material for boats. It doesnt rust
or rot. It is light and doesnt absorb water or leak. It is
unharmed when run in ice, and is easy to drag over ice flows. Aluminum
boats can last a lifetime if handled carefully.
Unfortunately, with aluminum, the owner cant design his
own boat for his own purposes unless he has a custom boat made at
considerable expense. Aluminum is a bit noisy for hunting. This
is particularly noticeable with aluminum canoes. Aluminum is very
difficult or impossible for an owner to repair properly. Welding
aluminum has long been an obstacle for the common person. Some aluminum
boats have leaky rivets that plague the owner. Rocky beaches also
wear aluminum boats.
With hard use, aluminum boats crack in the transom, on the ribs,
and in the bow where the boat contacts the beach.
Fiberglass boats are fairly new to Alaska, at least where I am
from. Fiberglass is unharmed by running in the ice and slides well
over ice flows. It provides a low friction surface with the water.
Fiberglass is strong, and low maintenance, but does add considerable
weight to a boat. Fiberglass is easy to repair and is easy to apply
if the simple directions are followed. Fiberglass bonds well with
new lumber and plywood, but usually separates when applied to an
old painted boat, even if it is sanded well. Solid fiberglass boats
can be formed in any shape desired. Rocks are devastating to fiberglass.
All contact must be avoided.
There is one brand of fiberglass boat built in the Lower 48 that
can haul an awesome load. The low friction surface of fiberglass
combined with the wide bottom providing lift give this boat a very
respectable performance. Freight costs on fiberglass boats purchased
from Outside are high.
Although no longer common in many parts of Alaska, skinboats are
still the whalers choice in Barrow and the Arctic. Skins are
very strong and flexible. They dont get ice buildup in cold
temperatures and are repairable by the owner. Other than labor,
they are free. The disadvantages are:
- Animals, including your own dogs, want to eat your boat. To
store it out of the reach of animals often exposes the boat to
drying wind and sunlight.
- The skins require frequent oiling.
- The skins deteriorate within a few years.
- Skin boats are labor-intensive to build. However, this often
brings people of a village together.
Brief mention should be given to inflatable boats. They arent
practical for village people, but they do fit in airplanes and can
be inflated at remote locations. Many can be driven by outboard
Even less mention will be made of the hideously noisy airboats
that plague some of Alaskas rivers.
- Look at the different boats in the village. Identify the planing
boats and displacement boats. Some fishing boats are a compromise
between the two.
- What is the average length and width of the boats in your village?
What is the average height of the sides in the middle of the boat?
What is the average angle outward of the sides, in both the middle
and back? What is the average angle backward of the transom?
- Ask a local boat builder what happens if the transom doesnt
have enough angle.
- What are the different materials used in boat construction
in your village?
- How does the style of boat in your village compare with those
in the description in the above text? Are they downriver boats,
upriver boats, ocean boats, a combination, or something different?
- Talk with a local boat builder about boat design. Does he agree
or disagree with some of the thoughts in the above text?
- Look at a canoe if one is available. Are the turns and curves
gradual? Compare this with a planing boat. Which would you rather
paddle or pole upstream?
- Ask the oldtimers about shooting out of a canoe. What precautions
must be taken?
- Try poling a planing boat upstream in swift water. Paddle or
pole a canoe in the same place. Compare the effort.
- Compare the bottoms of the boats in your village. Feel them
if you can. How rough or smooth are they? If they are rough, how
did they get that way? How would you reduce the friction on each
one? Do boats in your area need paints with copper compounds to
prevent organic growth?
- Students should slap the surface of a small body of water with
their hand, a board, or paddle. Increase the speed with which
it is slapped. Notice that it seems to become solid
the faster it is slapped. How does this apply to a planing boat.
- Carve a displacement or planing boat from soap or cottonwood
- Ask oldtimers how they hauled big loads long ago. How is that
different from today?
- Draw an upriver boat. Draw a downriver boat. Which do you prefer?
- Ask oldtimers how they built canoes or kayaks. What are the
effects of changing width? Length? Did they put a rocker in the
bottom? How high were the sides? What were the problems they had
with materials? Today we weld and use synthetic caulking. How
did they fix leaks long ago?
- Ask around the village to find out the gas consumption of the
new four-cycle outboards. How many gallons per hour for each horsepower
rating? Divide the horsepower by the gallons to find the ratio.
Compare this with the gas consumption of newer two-cycle motors.
- Compare the difference in purchase price of a two-cycle and
a four-cycle outboard. The four-cycles are more expensive. What
is the price of gas in your community? Can you figure how many
gallons of gas a four-cycle would have to burn to pay for the
difference in purchase price? This isnt a simple problem.
You will probably have to do it as a class, but it is one everyone
must take into account when buying a motor.
- Ask in your village how much the boats cost. Compare the cost
of the different kinds of boats with each other. Ask people how
long each kind of boat lasts (plywood, fiberglass, aluminum, etc.).
In the long run, what is the cheapest kind of boat? Is it also
the most useful kind of boat? Do people still make their own boats?
- What are the two different kinds of boats?
- Which of these two kinds of boats is better for carrying a
big load with a small motor?
- Which of these two kinds of boats is better for running around
with a light load?
- What is the most important thing to remember in designing a
- A planing boat is better when it is wizxxde or slim?
- Which planing boat will get on step faster, one with a flat
bottom or one with a V bottom?
- Which planing boat will give a smoother ride in rough water,
one with a flat bottom or one with a V bottom?
- Which is better for your location? Why?
- What are the advantages of high sides on a boat? What are the
- What is the force called that slows a boat with a rough bottom?
How is this remedied with a wooden boat?
- There are four common materials used in boat construction.
List them and one advantage and disadvantage of each.
- One boat travels 20 miles upstream in a swift river where the
average current is 10 mph. The boats speed relative to the
water is 20 mph. The boat makes a round trip. Another identical
boat and motor travels 40 miles on a lake where there is no current.
There is no wind acting on either boat. Question: Do they both
make the trip in the same time, or is there a difference? If there
is a difference, why?
- Plywood costs $35 a sheet landed in the village. Screws to
build a boat are $4.50 a pound. Paint is $22.5 a gallon. The lumber
to build the ribs and other parts is $1.25 a board foot. Five
gallons of fiberglass resin flown into the village is $89. The
fiberglass cloth is $3.00 a linear foot. How much would it cost
to build a boat 24 long? The boat is 4 wide and will
take six sheets of plywood. It will require 4 pounds of screws
and three and a half gallons of paint (only available in gallons.)
Add 10% for incidental expenses like calking, glue, paint brushes
etc. An aluminum boat is $3,200 landed in the village. Which is
cheaper? Considering that an aluminum boat lasts twice as long,
which is cheaper?