Village Science

Boat Design


A 6, 15
B 3
C 3
D 1, 2, 3


F = MA

Surface area

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 purpose:

  • Planing boats
  • Displacement boats

Planing 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 step”.


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 uncomfortable ride.

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.

High sides:

  • 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 difficult.

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 outboard motor.

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.


Gradual turns of a displacement boat cut the water


Blunt bow plows water

Displacement Boats

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 wife’s 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 motor.

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 it’s 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.

Traditional Craft

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 flowing water.

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.



sidesBoat 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 sanded.

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 isn’t a problem, a considerable amount of money can be saved by using paint that doesn’t 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 it’s 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 plywood.

Both plywood and lumber boats are easily destroyed when run in the ice.


Aluminum is an excellent material for boats. It doesn’t rust or rot. It is light and doesn’t 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 can’t 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.

skin boat

Skin boats

Although no longer common in many parts of Alaska, skinboats are still the whaler’s choice in Barrow and the Arctic. Skins are very strong and flexible. They don’t 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 aren’t practical for village people, but they do fit in airplanes and can be inflated at remote locations. Many can be driven by outboard motors.

Even less mention will be made of the hideously noisy airboats that plague some of Alaska’s rivers.



  1. Look at the different boats in the village. Identify the planing boats and displacement boats. Some fishing boats are a compromise between the two.
  2. 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?
  3. Ask a local boat builder what happens if the transom doesn’t have enough angle.
  4. What are the different materials used in boat construction in your village?
  5. 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?
  6. Talk with a local boat builder about boat design. Does he agree or disagree with some of the thoughts in the above text?
  7. 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?
  8. Ask the oldtimers about shooting out of a canoe. What precautions must be taken?
  9. Try poling a planing boat upstream in swift water. Paddle or pole a canoe in the same place. Compare the effort.
  10. 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?
  11. 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.
  12. Carve a displacement or planing boat from soap or cottonwood bark.
  13. Ask oldtimers how they hauled big loads long ago. How is that different from today?
  14. Draw an upriver boat. Draw a downriver boat. Which do you prefer?
  15. 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?
  16. 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.
  17. 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 isn’t 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.
  18. 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? Why?
Student Response

Student Response

  1. What are the two different kinds of boats?
  2. Which of these two kinds of boats is better for carrying a big load with a small motor?
  3. Which of these two kinds of boats is better for running around with a light load?
  4. What is the most important thing to remember in designing a displacement boat?
  5. A planing boat is better when it is wizxxde or slim?
  6. Which planing boat will get on step faster, one with a flat bottom or one with a V bottom?
  7. Which planing boat will give a smoother ride in rough water, one with a flat bottom or one with a V bottom?
  8. Which is better for your location? Why?
  9. What are the advantages of high sides on a boat? What are the disadvantages?
  10. What is the force called that slows a boat with a rough bottom? How is this remedied with a wooden boat?
  11. There are four common materials used in boat construction. List them and one advantage and disadvantage of each.


  1. One boat travels 20 miles upstream in a swift river where the average current is 10 mph. The boat’s 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?
  2. 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?

Questions or comments?
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