Rebecca and her partner made great calculations, but fell a little short on building the boat itself. It imploded inwards in dramatic fashion about halfway across the pool.
I tried to give Rebecca and her partner tips about how to join the wood and how wood behaves, but it wasn’t enough in the end. When it came to building Cameron’s boat, I wanted to help them do something dramatically different that would not only get their boat across the water, but set it apart from other boats that would be christened that day.
The boys said that they got extra points for curves in the boat. 1/4″ pine will bent a little, but it snaps if the bend is too dramatic. I had the boys do some research on bending wood and we decided to try steam bending. This would allow us to get some dramatic curves without the wood breaking.We rummaged around in my shop and found some 4″ drainage pipe, a hose and some dust gates for the ends. We cut a hole in the drainage pipe for the hose and put the other end over a tea kettle to drive steam into the pipe. To keep the wood in the center of the pipe, we drilled holes in the pipe and ran dowels through the center of the pipe. It all becomes clear when you look at the photos.
To hold the wood in place while it dried after steaming, we built a form on a sheet of plywood by pounding nails a regular intervals along the curves we wanted to form. We had one form for the bow to stern shape and another form for the port to starboard shape. The plan was to use these shapes to create a strong frame for the boat and then steam and bend the rest of the wood and join it to the frame in place.
One of the keys to steam bending the wood was to elevate the end of the pipe furthest from the steam hose. This allowed the rising steam to reach the far end. Our first experiment bending wood was in a much shorter chamber and we found it took only a few minutes to soften the wood enough for it to bend pretty dramatically. However, in the 10′ long pipe, it took around 40 minutes before the wood was pliable enough for the dramatic U shaped curves of our boat.
The whole process was pretty tedious, but after breaking a few pieces and we finally got some of them soft enough to fit into the forms.We left them to dry for 24 hours and then took them out of the nail forms. This was pretty disappointing as the wood snapped back quite a bit. In all of my years woodworking, I’ve never done any steam bending. From what I’d read, I expected some snap back, just not to the degree we saw. It turns out that steam bending is fine to get the wood into the shape you want, but it requires that the wood be glued into a larger piece that holds it in that shape. It just doesn’t work for creating the initial shape of the boat.
I had limited experience with bent wood lamination, but knew that it was the strongest and most versatile way to achieve curves in wood. The problem is that you need material that is thin enough to bend without steaming and then you need to laminate each curved piece and let it dry. To try it, we cut a few pieces that were 1/4″ x 1/12″ (around 0.08″) and a foot or so long and glued three of them together in one of the curves in our nail form.
We were a little depressed, but it was time for plan B. This time it HAD to work because we were out of time. Whatever we did had to float and stay together.
The result was dramatic and wonderful. Now only did the wood hold it’s shape, but it was obviously MUCH stronger than the steam bent wood. Steaming wood tends to weaken the cell walls of the wood, reducing the strength. Lamination, on the other hand, makes the wood stronger. Wood tends to fail along natural weak spots in material. The shear strength is determined by the weakest point. By laminating three strips together, each strip supports the adjacent one. It is very unlikely that the weakest point in one strip is adjacent to the weakest point in another strip. That’s why skateboard decks, skis, snowboards, and other wooden pieces that require high strength are all laminated from thin strips.
The hard part is making the strips. We needed a bazillion strips that were 1/4″ x 1/12″ and eight to ten feet long. Cutting them on the table saw loses too much material to the kerf. You’d end up with 1/8″ of sawdust for every 1/12″ strip. Cutting them on the bandsaw is better, but since my bandsaw does straight lines pretty badly, it required that we cut them to around 1/6″ and then plane or sand them down the final size.
This was my job as I wanted the boys to keep their fingers. I have more experience with the power tools and have already enjoyed my fingers for 50 years. It was a long boring afternoon milling the strips. My recommendation for anyone contemplating using the lamination technique is to find a lumber yard that will mill them for you.
Once we had the strips, we started to glue together the strips that formed the ribs of the boat. There were four long ones for the prow to stern and nine short ones for the starboard to port (side to side) dimension.When the ribs were completed and dry (we left each rib in the form for around an hour before removing the clamps), we joined the long ribs to the short ones. Ideally, we would have notched the ribs to make a stronger joint, but the boys didn’t have either the skill or the time. Instead we simply glued the ribs together, one on top of the other and then ran a thin stip over it to make it stronger (see the picture).
Once the ribs were glued together, the rest of the board was built in place without forms. We laminated three strips along the top of the boat and planned to do something similar for the rest of the sides, front and back. However, Cameron came up with the idea of using a single thin strip and weaving it back and forth through the ribs like a basket. This enabled us to put the strips closer together without going over the weight limit.
Occasionally, one of the strips would break. It was a simple matter to repair it by gluing another short strip over the break.Once the wood frame was complete, it was time to paper the outside. This was probably the least fun part of the project. If you are good at wrapping presents, you’ll probably be good at papering the boat. Unfortunately, this does not include the boys or me. We should have gotten some help from Margie, Cam’s mom. In the end, we got it done, but it was a pain and took much longer than we anticipated. The only advise I can offer is that small pieces of paper glued together seemed to work better than huge pieces.
We made sure that there were at least two layers of paper in the area that would be below the waterline.
Like most boat projects, we didn’t start painting until late on the night before the boat was due. To get the glue on the paper and the paint to dry faster, we kept a fan with a heater behind it blowing on the boat. The boys put three coats of paint on the boat allowing about an hour between coats for it to dry.I believe it was Cameron that picked the pink paint. Blech! It’s pretty ugly. They nicknamed the boat the “Flying Pig” to commemorate the color.
We weighed the boat a number of times at different intervals to ensure we did not go over the weight. In the beginning, you weigh the strips and paper and guess how much the glue and paint will add. When the frame is partially complete you weight it and then, when it’s complete, you weigh the frame and paper together. We were always well within the weight. I think the final boat weighted around 3 1/2 pounds so we could have added a significant amount of material if we’d needed it.
My main concern for the boat now was the depth. I had encouraged to boys to make the draft more shallow leaving more material for strength and less for the boat’s size. We compromised at around 16″ deep, but I was still concerned that it was too deep for the pilot to paddle with their hands.Mrs. Zimmerman, Kyles English teacher had agreed to pilot the boat (more points for a teacher than one of the boys as pilot) and she is not a tall lady. When I saw her for the first time, I despaired. I had a vision of her sitting in the boat unable to reach the water with her arms.
As it turned out she was an experienced pilot. She brought a towel for the bottom of the boat so that she could kneel and long sleeves to protect her arms. She could only paddle on one side of the boat at a time, but she was able to reach the water. The asymmetrical paddling made it harder to go fast and navigate a straight line (she did a full 360 at the end of the pool), but she made it across the pool without event.The boats that made it were, for the most part, copies of one of the boats in the physics class that had succeeded in previous years. The boats that didn’t make it were generally just badly made. The boy’s boat was far and away the strongest. I think we could have carried twice the weight without incident.
If we had to build the boat again, we’d change the shape a bit, but the building technique was pretty sound. Their boat got full points in all categories and it’s destined for the ceiling of fame in the physics lab.
Nice job boys!