This research proposal was written for the Union College Mechanical engineering department at the start of my project on Bamboo skis. It provides a comprehensive summary on the project.

1. Bamboo: A More Sustainable Alternative To Existing Downhill Ski Core
Materials
Sarah Subik
Union College
Mechanical Engineering Department
Professor Joel Lefever
March 20, 2019

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Abstract:
The product evolution of downhill skis is over 5000 years long, however, the most recent
era in the ski industry has focused on material engineering to fine tune desired high performance
characteristics such as flexibility and control. ​The materials in downhill skis are sports grade
materials carefully selected for their characteristics. ​One current research area in the industry is
finding an alternative material to the traditional wood or composite cores which are expensive
and unsustainable. A comparison will be done between bamboo and traditionally used maple
hardwood to analyze whether bamboo has the properties to compete with existing material
options. Mechanical properties in connection to performance, economics, and environmental
impact were established relating to the materials’ availabilities and manufacturing processes. A
cheaper and more sustainable ski would lower the upfront cost of skiing to consumers, creating a
larger market and allowing more people to enjoy the sport.
Introduction:
The ski industry is an environment where styles change by the season and customers pay
thousands to get the cutting edge advantage touted by each new design built with high grade
materials. The skis used today are very different from the snowshoe-like design made of animal
bones that were used 5000 years ago [1]. This rudimentary design was created in Scandinavia
and Russia for transportation during hunting, and eventually the military, long before the ski
design was altered for recreational use. Metals were added to the edges of skis in the 1920’s for
greater control at high speeds, making the sport safer. In 1950, the first commercial aluminum
core ski became available offering a stronger and more precise material in ski construction.
Later, in 1960, the first fiberglass ski was marketed, replacing most of both aluminum and
wooden ski construction with its lightweight properties [1]. A trend in ski engineering is making
the material as light as possible while still retaining the necessary mechanical properties for
performance.
In skis, as with most high performance sports, the major goal is to create a design that
will have both balance and control sustained throughout dynamic motions and high impacts. For
downhill skis this stability is obtained by using a material that will dampen the vibrations that
occur at high speeds. However, it is also important for the skier to be able to ‘feel’ the terrain and
have a ski that will be responsive creating a fine balance in material dampening. This balance
between ​feel and eliminating vibrations, is based on the energy dissipation properties of the
material​. ​The second major property in ski materials is the flexibility axially in comparison to a
high torsional strength. This combination allows the ski to handle loads at multiple points of
intersection while having strength when up on edge in turns. The life of a ski is affected by the
fatigue of materials after seasons of high impact, making materials with high durability and yield
strength necessary for longevity. Getting into specific needs of skis only lengthens the design
requirements. Women’s skis must be lighter, shorter, and softer in order to reduce the energy

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needed to flex them. Similarly children's skis are made on a smaller scale with extreme flex for
forgiveness and easy maneuverability [2].
The extreme design requirements in downhill skis are satisfied through layering
processes such as the use of a rubber layer to absorb vibration in metal skis. In this layering
process the core is placed in the center and surrounded with other materials to complement its
properties. The core’s flexibility, strength, weight, and availability are all carefully considered
when selecting the material. Unfortunately, these demanding properties are best achieved by high
grade composite materials or numerous layers of material resulting in skis being expensive. This
makes them inaccessible to consumers who may just be getting into skiing or don't go often
enough to justify the price. Bamboo is a relatively new core option making an appearance in the
downhill ski market with the potential to fix this exact problem.
Wood has been used in skis, following the use of bones, because although it seems
simple compared to the composites used today it offers good strength and flexibility.
Unfortunately, it has poor torsional strength due to the fibrous nature of woods and absorbs
moisture because it is sensitive to humidity. However, when combined with the right materials
the cellular structure of wood offer low density with strong properties allowing it to still be used
today. One of the most desired woods in skis today is maple which unfortunately is not cheap or
highly sustainable. However, bamboo is a strong grass that offers many interesting properties
and grows fast enough to be considered sustainable. ​In the past, improvements to equipment,
particularly those necessary for safety and performance, have had major effects on the sport’s
expansion as more people consider it a viable option.​ Bamboo as a material in skis would create
a ski with good properties at a price more approachable for new skiers or skiiers needing other
options.
Research
Bamboo has a lower embodied energy than existing options due to lower handling costs
and fast growing rates (13-30m in 2-4 months) making it considered sustainable [3]. Additionally
it is biodegradable and can grow in diverse climates making it highly available. This availability
makes it a cheaper material. Beyond mechanical properties the grass offers a smooth and clean
looking aesthetic when it can be left exposed on the ski. Although bamboo is a strong material
option it can be difficult to sell as the existing designs are not well backed with field research and
many people are hesitant to invest in a bamboo ski until they are well reviewed. Beyond this,
many companies have not yet figured out how to engineer the ski out of 100% bamboo, currently
many incorporate other materials such as Titanium making the cost close to the same as non
bamboo skis [4]. Companies who have tried to make sustainable skis with 100% bamboo are
typically smaller companies that can not make as much profit, keeping the price of bamboo skis
still high.
Additionally as a relatively new material emerging into ski manufacturing, it gets
neglected as a material because of little research done on its strength and moisture in relation to

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force capacity [3]. There is also the factor of durability in relation to species and age, there are
over 1000 species of bamboo to choose from each with different properties to offer [5]. The
treatment of the bamboo also produces another realm of properties. Bamboo will mature in three
to four years. If cured and left untreated, the material will last ten to fifteen years on average [3]
Maple hardwood is harvested from the sugar maple tree which can take over a hundred
years to fully mature, resulting in a dense wood but also lower availability. This length of
growing time in conjunction with the long time necessary to season the wood make maple an
expensive wood in comparison to other options. For its expensive cost and low availability
maple offer unique properties in comparison to many other woods. Maple hardwood is stronger,
stiffer, harder and denser than not only other species of maple but also most other lumber.
Although, maple is a dense wood it is easy to work with [6]. Maple not only offers good strength
and hardness but it has high resistance to abrasion and wear while still allowing good steam
bending properties [7].
Proposal:
Based on known mechanical properties bamboo offers great strength and pop to the ski,
better than any wood can. However, bamboo is known to split easily requiring a lot of glue
which adds weight to the ski. Additionally, most bamboo skis today are laminate mixtures or
layered with composites which make creating a testable prototype complicated [8]. Similarly,
while maple offers the best density and durability of currently used woods for main core
materials, it is commonly layered with composites to compensate for its poor elasticity and
forgiveness [8]. Building a ski from scratch is a complex process and due to the proprietary
nature of ski companies it is difficult to know where to start. Alternatively, buying a maple and
bamboo ski to fully test for each property, and be able to account for the added effects or
composites and laminates, is too expensive of an option.
Considering the existing budget, the prototypes will instead only consist of three layers; a
base, a core, and a top sheet. Sheets or maple around 19mm will be bought to later be shaped and
sanded down to around 12mm for the ski. Mature bamboo around four years old and completely
dried wil be bought with about a 100mm diameter to be spliced into strips. Each prototype will
be built to be around 0.5m length and 0.072m width, tapering will be done proportionally
creating a wasit in the middle of the ski. A base layer of ptex (​Ultra High Molecular Weight
polyethylene UHMW) will be glued on the bottom of the core to simulate the base layers while a
top layer could be simulated with 3mm of fiberglass. All layers and fibers will be glued together
with a basic waterproof glue.
Once the prototypes are assembled they will be put through a series of experiments to test
properties relative to ski performance such as flex, torsion, and energy dissipation. The strength
of the skis will be tested using a tensile tester. The flex test will be performed using a specialized
set up on the tensile tester machine to simulate a three point bending test. Torsion will be tested
by applying both an up and a down force simultaneously (see Figure 1).

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Figure 1:Torsion Test with an upward force applied in forward underside and downward force
applied to upper farside
Data will be collected electronically in each process and then analyzed in comparison to both
each other and the properties of existing skis. The data in combination with known knowledge of
the materials and ski manufacturing will be used be used to determine how bamboo compares to
maple and whether it’s viable. Below a table has been formulated to outline the project to
completion.
Week Objective
March 18 Planning
March 25 break
April 1 Construct
April 8 experiments
April 15 analyze data
April 22 interpret data
April 29 presentation
May 6 Steinmetz
May 13 paper outline
May 20 paper draft
May 27 paper revision
June 3 paper done
June 10

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References
1. M. Michelson, “An Abbreviated History of Modern Ski Technology,” ​REI Co-op
Journal​, 12-Nov-2018. [Online]. Available:
https://www.rei.com/blog/snowsports/an-abbreviated-history-of-modern-ski-technology.
[Accessed: 21-Mar-2019].
2. “How to Choose Downhill Skis | REI Expert Advice,” ​REI​. [Online]. Available:
https://www.rei.com/learn/expert-advice/downhill-skis.html. [Accessed: 21-Mar-2019].
3. D. Awalluddin, M. Ariffin, M. Hanim Osman, M. Warid Hussin, M. A. Ismail , H.-S.
Lee, and N. H. Abdul Shukor Lim, “Mechanical properties of different bamboo species,”
MATEC Web of Conferences​, vol. 138, Dec. 2017.
4. “Ski technologies for effortless rides down the slopes,” ​Innovation Origins​, 07-Dec-2018.
[Online]. Available:
https://innovationorigins.com/ski-technologies-for-effortless-rides-down-the-slopes/.
[Accessed: 21-Mar-2019].
5. “Bamboo plant,” ​ScienceDaily​. [Online]. Available:
https://www.sciencedaily.com/terms/bamboo.htm. [Accessed: 21-Mar-2019].
6. “Hard Maple,” ​The Wood Database​. [Online]. Available:
https://www.wood-database.com/hard-maple/. [Accessed: 22-Mar-2019].
7. “Hard Maple,” ​American Hardwood Information Center​. [Online]. Available:
http://www.hardwoodinfo.com/specifying-professionals/species-guide/species-guide-h-z/
hard-maple/. [Accessed: 22-Mar-2019].
8. P. Magazine, “Understanding the Wood Core in Your Skis,” ​POWDER Magazine​,
12-July-2017. [Online]. Available:
https://www.powder.com/gear-locker/theres-a-tree-in-my-ski/. [Accessed: 22-Mar-2019].