Prototype Foot Strap Design Considerations for Surf Lifesaving Inflatable Rescue Boats: Technical Report #7 to Surf Life Saving New Zealand (SLSNZ)
Grobelny, M; Reay, S; Diewald, SN; Hume, P; Wilson, BD; Wooler, A; Merrett, R; Smith, V
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Background: Foot straps have been removed from IRBs due to concern they were causing lower limb fractures due to entrapment with rotation during landings. Purpose: To model possible positions and prototype designs for foot straps in IRBs. Methods: Strap measurements were taken from the SLSNZ boat in Raglan, then modelled with the alternatives to give an overview of possible placement for one person. Foot strap prototyping was conducted using 3D modeling with an initial EVA material design constructed. Results: A number of questions were identified that need to be researched to provide information for the design brief including: Can feet be parallel, or is it important for them to be staggered; Does the right foot do most of the work?; Which positions cause injuries?; Without a foot strap, how likely are the feet to bounce up away from the deck in big swell? Three foot strap concepts were modelled: Camlock adjustment; Quick release/pressure release clasp; Raised foam strap. A prototype EVA pad with strap was built. A moveable track with cam lock was conceived. Discussion: Foot placements needed to be adjustable for varying lower limb lengths. Foot straps need to be adjustable for varying foot sizes. Key priorities for design of the foot strap system include: Minimal fixtures; No hard/sharp edges; Keep boat deck flat without raising foot hold areas; Quick and easy to adjust; Strong enough to handle impacts and weight of crew; Positionable for shortest to tallest crew member; Ability to swap out strap to renew; Corrosion resistant. Review of all the project reports identified that ensuring three points of contact for the crew with the boat was important as a consideration for the phase II design project. Conclusions: Further testing is needed to assess foot placement as the current positions are not yet researched. Discussion on the pros and cons of the suggested foot strap prototypes is needed followed by construction and in‐the‐boat testing.