Category Archives: 3D Printed Boat

“The Boat”, as it is fondly referred to by the team, is another project within Washington Open Object Fabricators. This boat was made entirely out of recycled HDPE milk jugs, and was raced in the Seattle SeaFair Milk Carton Boat Derby.

Milk Carton Derby Day

Today was the day of the race for the WOOF 3D printed boat. (There is a story in the Seattle Times.) In the end, stuff happened, and the boat ended up being a simple small boat, similar to the previous year’s boat. The bottom was made out of a pressed board of milk jug HDPE, with more HDPE printed on top This can be seen in figure 1, on top of a piece of plywood, which is on top of the printer bed. You can also see from figure 1 that the boat had a couple leakage points. These had to be manually filled in with an “HDPE gun” made by one of the team members. This was basically a print head not attached to a printer.


Figure 1. The boat in Big Red, WOOF’s large 3D printer.


The Seafair Milk Carton Derby created a special category for us: 3D printed boats. Since we were the only contestants with a 3D printed boat, we raced last year’s boat against this year’s boat (figure 2).

One thing I learned from working on this project is that HDPE is actually pretty tricky to work with. It shrinks by 2% when it cools, which adds up fast on a large object like a boat. For example, the warp in the walls of this years boat that you can see in figure 2 was caused by this shrinkage. (Last year’s boat had the same problem, but to a lesser extent since the walls were thicker.)



Figure 2. Last year’s boat on the left, and this year’s boat on the right.


In the end, the new boat got a crack in the bottom, and kind of sank just before the finish line. We still won our race though, since the old boat made it safely across the finish line, and we were the only people in our category. 🙂

I learned a lot working on the boat team, but probably the most important are: a) how to work with HDPE, and b) never let milk jugs sit around for more than a week before washing them.



Figure 3. Boat team lead Matt, and club president Brandon racing the two boats.


Update on Quinn’s Printer, and Boat Design

Last week I got a lot more work done on Quinn’s printer. The X and Y axises are now up and stable, and the extruder is partly done (Fig. 2).


Figure 1. Where I started from on Quinn’s Grawmet.


Figure 2. Quinn’s Grawmet after a day’s work.

Yesterday I also made some headway on a seat design for the WOOF boat. The actual body of the boat was designed by another WOOF member, Dana (Fig. 4). I’ve been collaborating with him on both the seat design (Fig. 5) as well as some of the overall design. He has taken both physics and statics (which I have not as of yet) and so was able to give me a lot of helpful technical feedback.

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Figure 4. Boat Design by Dana H.

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Figure 5. Seat design in progress (only half shown) by me.

Collecting Milk Jugs

Planning is underway for WOOF’s Seafair Milk Carton Derby entry this summer. For those who don’t know, Seafair is an annual summer festival we have here in Seattle, and the Milk Carton Derby is an event where people race boats made out of milk cartons. These tend to be very elaborate rafts, sometimes quite large and creative, and often held together with duct tape. Since WOOF is a 3D printing club however, ours entry will be a bit different.

WOOF entered a 3D printed boat (made from recycled milk jugs, of course) for the first time the Milk Carton Derby last year. We made a tiny boat that managed to come in second. More on that can be seen here:

This year we plan to build a much bigger boat, and get in a test print or two. This means we will need a LOT of HDPE plastic milk jugs. Printing will be done on Big Red, a giant fused deposition printer made from a plasma cutter, but more on that later. (In the meantime, there is a cool article on Big Red here: Anyway, based on the number of milk jugs used last year, it’s estimated we may need around 1000. Since I am on the Boat Team at WOOF, this past week I have started to collect and horde milk jugs.

First I managed to get a couple from my friend, Ransom, and today I tried going to a couple Starbucks in town. This proved to be quite fruitful. The Starbucks people seemed happy to hand over the contents of their trash cans, which were mostly milk jugs.


After today, I now have almost a full trash bag full. I feel quite productive.