AHOY! Cardboard Boat for Racing

Have you ever thought of doing something many think couldn’t or shouldn’t be done? Of course you have, that is why you are here on Instructables.com!

I was proposed with the following challenge:

Build a vessel OUT OF CARDBOARD capable of supporting at least one person to follow a 200 yard race course for two rounds. No this is not a model! This is an actual passenger carrying vessel!

The rules include:

• Corrugated cardboard ONLY! The use of wood, metal, plastic, foam, or fiberglass is strictly prohibited. No wax coated or pre-treated cardboard is allowed.
• Only bare, raw, brown, fibrous cardboard. Various tapes, adhesives and other accessories are allowed, but will be covered in greater detail later.
• You cannot just wrap the entire craft in layers of duct tape!
• All members of the boat are required to wear personal flotation devices. You know, for if or when your ship sinks.

This is how I and my crew did it. It is by no means the only way, but more documentation of our creation and some suggestions. We decided on a pirate theme. We chose to decorate the ship to loosely resemble a pirate ship.

(The challenge was an actual sanctioned event, but doing it solely for the pleasure of the personal challenge is a fantastic reason also!)

Structure:

• Large sheets of cardboard – Old appliance boxes work great! Ask local stores for their old boxes. (Since ours was for an actual sanctioned event, we had 8 foot by 4 foot sheets available.)
• Duct tape – (good for tight seals on edges, but hard to paint)
• Masking tape – (good for going over edges and easy to paint, but not real water tight)
• Sturdy waterproof glue – I found carpenter’s wood glue works best. It comes in large bottles, dries quickly, holds tight, and is waterproof!

Decoration:

• Latex house paint can decorate but also is a great sealant (oil based is not allowed in most sanctioned events because it can leave oil in the water) Look for cheap or returns!
• Cardboard tubes like wrapping paper tubes

Tools:

• A sharp blade to cut cardboard
• A straight edge
• Clamps
• Sandbags – Optional, but are good to hold the hull bottom together while gluing.
• String - Optional
• Oars or paddles to propel the vessel
• Our imagination!

I do NOT recommend using anything like Thompson Water seal. While it sounds ideal, it is not. It works on decks and driveways by soaking into the surface. It will soak into cardboard and make it very wet and weak. Keep the sealing to the latex paint.

There are many things to consider for the boat:

• Will there be a theme? Titanic, pirate ship, battleship, canoe/kayak, dragon, banana? (Yes, banana!)
• Larger boats are faster for straight-aways, but are a beast to have to turn around corners. Smaller are more agile, but will hold fewer rowers.
• How many passengers do we plan to carry? 1, 2, 5, 10?
• One of the things to consider about our craft was the total weight of our craft and crew. This makes sense, right? Heavier could sink.

“But, JokerDAS, how do I know how big to make it so it won’t sink?”

Stand back! I am going to lay down some science!

1. 60 pounds (or 28 kg) of mass displaces about 1 cubic foot of water.
2. Add up the weight of all the crew.
3. Divide by 60.
4. This provides the number of cubic feet that a boat will displace or sink into the water. That may not make much sense yet, but wait, there’s more to it than that.

Take this example:

We have a four man crew. Our total crew weight was 900 lbs. Divide that by 60 and we get 15 cubic feet of water displacement.

That means we could have a boat that is 5 foot long, 3 feet wide and 1 feet tall making a volume of 15 cubic feet (5 X 3 X 1=15) and still theoretically stay afloat. I say theoretically because the water level is to the top edge. That does not even take into account the boat will also have mass.

BUT make the sides of the boat too tall to accommodate the displacement, and we may not be able to reach the water with our oars!

We finally decided on the measurements. The rectangular hull of our boat was 8 foot long, 3 feet wide and 15 inches tall. It had another 2 feet of bow after that.

Plan ahead before you make your first cut!

We had a plan, we had our materials, we had our dream!

Now it is time to make our craft! (We did not have decent pictures of this process, but I created a scale model out of cardboard.)

1. First we laid out a large sheet of cardboard.
2. Then we measured out and drew the bottom of the boat (8 foot by 3 foot), also called the hull. Leave a couple extra feet at both ends to use later for the structure.
3. Since the hull plan was larger than the individual sheets of cardboard, we attached another sheet with duct tape. We made sure the entire seam was covered.
4. With the sharp blade, we scored the cardboard along the lines drawn. This was done by cutting only halfway through the thickness of the sheet of cardboard, leaving the other side whole. This will be one less seam to seal later.
5. Flip over the sheet.
6. Bend the sides up.
7. Tape the raw cut to cover the edge. This made a large U-shape.
8. We used some string to hold the sides upright so they do not lean back downward.

Now there is something that reassembles a boat. But the sides were still quite floppy. More structure had to be added to hold the sides in place. We essentially created cardboard 2 X 6’s.

1. We cut 18 strips of cardboard about 40 inches long and 6 inches wide.
2. We glued 6 together and clamped them until they were dry.
3. We repeated this two more times until we had 3 “boards”.
4. The boards were notched about 2 inches from each end about 3 inches deep.
5. The sides of the hull slid into the notches.
6. One board was glued at about 15 inches from one end (the stern), the next about 4 feet from there and the last about 2 feet from the other end (the bow).

We had a nice U-shaped hall, but with the bow (the front) and the stern (the back) open, it didn’t look seaworthy. So we had to close off the ends.

1. To make the stern, we scored the underside and outside walls perpendicular to the 2 X 6 support brace.
2. We cut along the joint where the upright of the side meets the bottom to the score line.
3. Folding the bottom flap upward, we then wrapped the two side squares over. They should touch the 2 X 6 brace
4. We applied glue to the flaps.
5. With the masking tape we sealed all the open edges and scored edges. This boxed off the stern.

The bow was a little more complicated because we chose a slanting front for water dynamics and appearance.

1. Just like the stern, we scored the underside and the outsides at the mark perpendicular to the brace.
2. Again, we cut along the edge joint just like the stern.
3. This time we measured a triangular point from the bottom section of measured off hull.
4. We cut out the sides of the triangle shape.
5. We cut about 8 inches off the end of each side flap.
6. We then folded the sides flaps into the point.
7. We brought up the point so that it reached the top level of the sides.
8. Now we drew a line where the triangle meets the sides at this angle.
9. We scored this line from the outside. This formed two triangular shapes on the side flaps.
10. Now we folded the lower triangular flap underneath the large hull-bottom triangle. We glued and taped it to the bottom.
11. Excess was cut from the opposite side.
12. We repeated this for the other side flap.
13. Clamps were used to hold it all together while it dried.
14. Another triangle was measured and cut to cover the top opening of the bow.
15. All seams were taped and sealed.

Alright, our boat not only looks like a boat, but will hold up, but with only one layer of cardboard between the crew and the water, it would not last long. Time to add more layers.

1. Again, we started by laying out a large sheet of cardboard.
2. With mass quantities of glue, we glued another sheet right on top of it.
3. We set the hull on the center of the layered cardboard.
4. We traced around the hull.
5. Next we made three more 2 X 6 boards just like before, only longer than the length of the 4 X 8 foot sheets.
6. One was along the middle of the hull outline, the other two just inside the hull outline. All three were heavily glued down to the stacked sheets.
7. Use the sandbags to press the stack of hull bottoms together.
8. Set the hull was glued on top.
9. Flip the entire structure upside down and score along the hull edges to allow the sides and ends to bend up. Trim off extra parts to align with the bow point.
10. Return it right side up and heavily glue the side flaps of the large sheets to the sides of the hull. (Small sections of side flaps may need to be cut away to fit with the 2 X 6 cross beams.)
11. Clamp all the hull sides together.
12. Repeat with the bow and stern flaps.
13. Set aside to dry completely.
14. Finally go over every edge, seam and joint with glue and tape.

Since we opted on a pirate theme. We need our cog to resemble a pirate ship. This mean wooden looking sides, cannon ports, a main mast complete with crow’s nest, a chase gun, and of course the black flag with cross bones and happy face.

1. First we painted the entire structure (inside and out because water WILL splash inside) with beige latex house paint.
2. Then we painted the wood slats and nail heads all over the sides of the hull.
3. The cannon ports were made from more wrapping paper tubes cut to 5 inch length. The end was quartered and spread out. They were painted black.
4. We then cut 6 inch squares of cardboard, traced the tube in the center and cut out the trace. They were painted red and yellow.
5. The tubes were fed through the back of the squares.
6. The squares were glued to the broadside of the hull.
7. Cardboard anchors were cut out, painted black and glued to each front corner.
8. The mast was created using a few extra rolls of wrapping paper tubing taped together with masking tape. It was taped to the center 2 X 6 brace.
9. The Crows nest was made from just shaping some of the wrapping paper into a cone, painting and taping to the top of the mast.
10. String was used to tie the top of the mast to the bow and stern.
11. A chase gun was created by cutting a box and adding a cardboard mailer tube as the barrel. This was then glued to the top surface of the bow.

Our galley, the “Almost Perfikt” was complete. It was the day of the race.

I recommend having lots of extra cardboard boxes and tape on hand the day of the race.

After the first race, we took on lots of water. We had to make repairs using spare boxes and duct tape.

Soon, we were called for our second race.

We met Davy Jones' Locker! (We sank!)

Our clipper was scuttled! (The ship was a total loss.)

Our booty contained much pieces of eight! (We won a trophy and learned a lot!)

We are all now salty seadogs! (We are experienced and will rise again!)

There you have it: An Instructable on building a cardboard boat capable of carrying passengers for the purpose of racing.

This is by no means the ONLY way to build a box boat, but more a list of suggestions and observations made while we made our.

Try it yourself, landlubbers! Your imagination is your only anchor!

And as always, thanks for checking out my Instructable!