Ever wondered if your gingerbread house will still be standing by Christmas? Well, worry no more – a couple of UBC engineering students have analyzed the material’s structural strength in a series of “laboratory” tests.
As part of a second-year Integrated Engineering program, Mercedes Duifhuis and Sean Heisler explored how gingerbread stands up to pressure. Their 31-page report, Structural Analysis of Gingerbread, earned them an A+. And they got to eat the results.
“We’d made some gingerbread when we were studying a few months earlier,” says Duifhuis. “We pitched the prof on testing gingerbread as an architectural material and he went for it.”
Integrated Engineering is a multidisciplinary program with a strong focus on team-based engineering design. Other class proposals included an automatic washer/dryer for the ping-pong balls used to play beer-pong, a water-conserving barista sink and a hamster wheel speedometer.
“Allowing students to propose project ideas lets them branch off into their specific fields of interest,” says course co-instructor Leo Stocco of UBC’s Dept. of Electrical and Computer Engineering. For Duifhuis and Heisler that meant materials engineering with Heisler being particularly interested in test design and development.
“If students can apply their learning to something they care about, they will care about learning,” says Stocco.
Using a recipe found in the 1986 cookbook Sweet Dreams of Gingerbread by Jann Johnson, the duo made batches of dough that used fat as the test variable, adding either butter, margarine or shortening to determine which ingredient optimized structural strength. Their analysis is full of tables, diagrams and calculations and covers elements such as design, budget, and environmental impact, noting that “excess gingerbread . . . is biodegradable and very delicious with icing.”
The students considered testing an entire gingerbread house, but knew the icing that holds such edible edifices together would confound and confuse their findings.
“One of the surprises in doing this assignment was how a project as seemingly trivial as gingerbread can showcase so many engineering fundamentals,” says 20-year-old Heisler, who plans to pursue a career in project management. “Education isn’t just formulas – something fun can include important learning.”
The first challenge was standardizing the shape and thickness of the gingerbread pieces. After many frustrating attempts in their lab, a.k.a. Heisler’s kitchen, they created samples in a variety of shapes, including mini I- beams – tiny versions of the girders that resemble a capitalized letter I.
Once the material was ready, the students designed several tests. In addition to a density test, a tensile strength test looked at how the material performed under tension; a cantilever beam test measured bending strength; and a compression test evaluated gingerbread’s reaction to crushing forces.
The tensile test was the hardest to execute, they say. It involved clamping a piece of gingerbread at one end while the other was attached to a hanging weight. Formulae were used to determine the failure levels of stress and strain of the material. Numerous trials led Duifhuis to conclude, “Gingerbread is not very good in tension – it’s just not stretchy.”
The 19-year-old has always liked to build things. A finalist in a North American Lego construction contest while in Grade 6, she is contemplating a career in architecture.
The report describes the compression test as “subjecting the material to crushing forces until failure was induced.” The pair loaded all of Heisler’s textbooks in a stack about a metre high on a sample piece of gingerbread – until the cookie crumbled.
Of all the tests, the researchers deemed the cantilever beam test most important as “it directly corresponds to typical gingerbread applications.” In a three-point bending test, a gingerbread beam was suspended across a known span (between counters) and centrally loaded with a hanging weight. Dough made with margarine did best on this test.
So of the three fats, which is the best ingredient for architectural gingerbread?
The report states that samples made with butter, although the tastiest of the three according to the researchers, “exhibited a very ductile quality through compression.” In other words, too squishy. Beams made with margarine failed under compression, but were quite good in bending applications. Shortening was declared the best – but least scrumptious – fat for gingerbread construction.
Classmates consumed the construction materials in a post-presentation repast.
The report may be found at
More information on UBC’s Integrated Engineering program may be found at http://www.igen.ubc.ca/about/index.php.