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The Ultimate Custom Snowboard
Mechanics of Composite Materials
MEAM 474/674
Spring 2000 Project


Group Members

Eno Yliniemi
Jeremy Aaby
Justin Strike
Luke Ellenbaum


 Internet Research
Material Selection
Design
Fabrication
Testing and Results
Lessons
Learned

 

Internet Research
The search for snowboard design and construction began on the Internet. Several company sites were found searching for "snowboard".  Typical board construction was found at sites like Arbor, Prior, Built,  and Coiler snowboards.  These manufacturers described each layer of their boards from the sintered base to the urethane topcoat.  Ideas for board lay-up were generated using these proven designs.

After conducting our Internet search, our group decided to use a solid wood core with carbon and glass fiber.  Inserts were also purchased.  These were to be placed in the wood core before lay-up.  It was decided that the wood core was not to be full length.  This was confirmed by web sites that had not used a full length wood core in the manufacture of their boards.  This would also enable more tolerable lay-up.  The edges were also considered and part of the initial design.  We chose to use a Sintered P-tex base for the bottom finish.  We did decide to neglect dampening foils, tip and tail protectors, and top-coat in the initial planning and design (see Material Selection for more information).

Below is the construction of an Arbor Snowboards board (“Woodie”), this image was one of many that showed the construction of a typical board.

1- Protective Coating
2- Wood top-Sheet Material
3- Triax Fiberglass
4- Full Length Wood Core
5- Insert Retention Sheets (not Shown)
6- Triax Fiberglass
7- Rubber Dampening Foil
8- Rockwell 48 Hardened Steel Edges
9- Aluminum Tip and Tail Protectors
10- P-tex Base


Material Selection

The group decided to use a solid wood core with carbon and glass fiber.  Inserts were also purchased.  These were to be placed in the wood core before lay-up.  It was decided that the wood core was not to be full length.  This was confirmed by web sites that had not used a full length wood core in the manufacture of their boards.  This would also enable more tolerable lay-up.  The edges were also considered and part of the initial design.  We chose to use a Sintered P-tex base for the bottom finish.  We did decide to neglect dampening foils, tip and tail protectors, and top-coat in the initial planning and design.

The following is a list of materials used:

  • E-glass plain weave fabric
  • Carbon plain weave fabric
  • Birch wood core
  • Steel binding inserts
  • Fiber Glast epoxy resin with 2-hour curing agent
  • Micro-balloons
  • Polyethylene base
    • Design

    Lay-Up Schematic

    Glass was chosen to be the primary fiber for the board because of its cost and flexural properties.  One layer of glass was oriented at +/-45 to compensate for torsional loading.  One layer of 0/90 carbon was used to increase stiffness and strength.  A polyethylene (p-tex) base was applied to improve board performance, allowing for wax application.  We used three fiber layers on the underside of the board due to the increased amount of loading we believe would be present in that location.

    Free Body Diagrams

    There were three types of primary loading concerning the design of the snowboard.  All of which were bending types of loading.  Assumed to be the most common was the four-point bend.  The weight of the rider would be distributed between two points of contact and the reaction points were assumed to be out side of those resulting in the free body diagram below (Figure 1).

    Figure 1.  Four-point bend loads

    Other types of loading considered for design were the three-point bend (Figure 2) and the off centered three-point bend (Figure 3).


    Figure 2. Three-point bend loads


    Figure 3.  Off-centered three-point bend loads
     


    Fabrication
    The following images show the steps taken when fabricating our board.  First a mold was created out of plaster of paris.  Then the birch core was shaped and holes were drilled for the metal binding inserts.  Next, the laminate was assembled using the layup scheme shown above and placed in the plaster mold.  After curing the excess was trimmed off using a ban saw.  Then the p-tex base was applied in strips and heated until coalesensce.  Finally, the base was sanded until smooth and the bindings were attached.


    Snowboard placed in plaster to create mold


       Finished Mold            Sanding Wood Core

    Close Up of Core While Sanding


    Laying up the Laminate


    Snowboard in mold after edges were trimmed


    P-Tex applied in strips to bottom of board

    Ironing P-tex until coalescence


    Sanding P-Tex base after ironing

    Our Group with the Finished Snowboard
    L-R:  Eno Yliniemi, Jeremy Aaby, Justin Strike, and Luke Ellenbaum


    Testing and Results
    Four-point bend tests were conducted to determine the flexural strength of the laminate.  We also wanted to see how the laminate performed in comparison to a wood core alone, so we tested a wood sample and a laminate sample. The following pictures show the samples during and after testing.  The wood sample failed in brittle fracture, whereas the laminate did not fracture upon failure.


    Wood Sample at Maximum Deflection


    Wood Sample Failure


    Composite Laminate Failure


    The bottom side of the laminate after testing (notice delamination)


    The top side of the laminate after testing (notice matrix cracking)
     

    Results

    The load and deflection curve is shown below.  Notice that the laminate was able to carry a much higher load and deflected more than the wood.  The next figure shows the stress vs. strain curves for the wood and the laminate.  The wood has a higher modulus of elasticity than the laminate, explaining the brittle fracture.  The laminate had a higher flexural strength and strain to failure than the wood.  Because snowboarding requires high flexural strength and strain rates, we found that the use of composite laminate for snowboards is appropriate.


    Lessons Learned
  • Sandwich composites are ideal for providing the properties required for good performance in a snowboard (namely light weight and flexural strength).
  • Given the correct starting materials and appropriate equipment, an adequate snowboard can be produced by hand lay up, though some quality may be compromised.
  • Countersinking the binding T-nuts in the bottom of the core would provide a smooth bottom with no bumps to create resin rich deposits where cracks and delamination from the core might occur.
  • A mold with no lip around the edge would be a better alternative than the edged plaster mold used.  A flat mold with the tail and nose contours on the ends only would produce the lay-up.  The shape of the board could then be cut from this sandwich laminate.  The excess material removal process would be simpler than it was with the laminate resulting from the edged mold.
  • A liquid resin for the base coat (polyethylene) would be ideal.  The only materials we were able to acquire were repair strips, which had to be ironed to coalesce.  A liquid resin to poor on or a continuous polyethylene sheet would provide a much smoother uniform base for waxing.
  • Resin infusion rather than hand lay-up could increase the fiber volume fraction of the board.  A uniform distribution of resin could be obtained while using less epoxy.  The vacuum would also provide a uniform compression of the laminate to improve its strength.
  • The overall appearance of the board could be improved through the use of a polyester gel-coat on the top surface.



    •  
     Internet Research
    Material Selection
    Design
    Fabrication
    Testing and Results
    Lessons
    Learned