Walk On Water

USD Engineering Competition

Competition Information

Last Saturday in February

USD Pool

9 a.m. to 1 p.m.

Get Ready to have Fun in applying science and engineering

Basic Task

• Design a pair of shoes to allow a person to walk a winding course across a pool in the fastest time possible

Basic Rules

• The shoes must be mirror images of each other

• No propellers or motors are allowed

• No paddles• Maximum 8 foot long

More Rules

• Shoes may NOT be tied together

• There may be no attachment above the knee

• The pilot must be able to easily escape (drowning is a poor choice)

Teams

• A team may have from 2 to 4 people

• One shoe pilot

• One team captain

Team Captain

• Someone responsible, able to coordinate work times and organize the team

• Responsible for getting the paperwork turned in on time

• Responsible for keeping track of costs

Shoe Pilot

• Able to swim

• Light with strong legs

• Competitive nature

• Willing to get wet

• Runner is often a good choice

Design Hints

Think before building Measure twice,

Cut Once

Basic Calculations

• 1 kg of water is 1 liter of volume

• 1 liter is 1000 cubic centimeters

• Each shoe should hold at LEAST 60% of the pilot’s mass

Shoe Design

• Things that float are good, things that sink are bad

• Plan on 20 to 30 cm of width

• Plan on 200 to 250 cm of length

• Calculate the thickness

Example - Pilot is 160 pounds

• 160 pounds is about 80 kg

• Figure roughly 2 pounds per Kilogram

• 30 pounds of shoes (15 pounds each)

• 15 kg of shoe material

• Total Mass to be floated: 95 Kg

Example Shoe Calculation

• Total mass to hold - 95 kg

• Call it 100 kg to be safe (this is called “Being Safe”

• Each shoe must hold 50 kg

Each Shoe Holds 50 Kg

• 50 Kg is 50 liters

• 50 liters times 1000 finds cubic centimeters

• 50000 cubic centimeters

Volume to hold: 50000 cm3

• Shoes will be 30 cm wide

• Shoes will be 200 cm long

• Solve for the needed thickness

• 50000 cm3 / (30 cm x 200 cm)

• Thickness needed = 8.3 cm

How to Make Shoes MOVE

Drag is your Friend,

Drag is your Enemy

Moving Forward but NOT back

• As little drag as possible is desired to move the shoes forward

• As much drag as possible is desired to stop from moving backwards

• FLAPS are needed

Flaps

• Fixed - Always the same shape

• Vertical - flaps move back and forth

• Horizontal - flaps move up and down

• Wheeled - flaps are attached to a paddle wheel structure

Fixed Flaps

• Fast and easy to make and attach

• Do not work well - little net forward motion

Vertical Flaps

• Act as a keel as well as a flap

• Work fast, independent of gravity

• Hard to transport and easy to damage

• Complicated to make and install

• Needs lots of material and hinges

• Time consuming to make

Vertical Flaps

Horizontal Flaps

• Fast and easy to make and transport

• The more flaps, the faster the response time

• Might be attached with duct or cloth tape

• Do not use wood or light floating material

• May have to weight the ends for a faster response time

Little Horizontal Flaps

Big Horizontal Flaps

Paddle Wheel

• Seen ONCE - worked well

• More engineering of parts necessary

• System needed to prevent from turning backwards

Attaching the Pilot

• Find an old pair of sandals or tennis shoes

• Tennis shoes are less likely to cause blisters

• Bolt, screw or tape them in the center of the shoes from front to back and from side to side.

• Make sure the feet can be easily pulled from the shoes

Practicing

• Put the shoes in the water - make sure they float

• Put the pilot (force may be necessary) into the shoes

• ‘Spot’ the pilot in case of a fall, no body part hits the concrete side of the pool

Pilot Practice

• Hold the pilot and make sure the shoes do not sink

• Allow the pilot to balance and not fall, yelling at the pilot generally does not help

• Throwing things at the pilot definitely does not help

More Practice Suggestions

• The pilot should walk around and not fall down (laughing at the pilot is not encouraged YET)

• When the pilot falls in, then laugh

• Figure out what went wrong and fix it

• Waiting until race day is a BAD idea to first put the shoes into practice

Now Laugh at the Pilot

Legs and Muscles

• If the pilot does not have strong legs, the legs will be sore at the end of the day

• If the pilot has strong legs, the legs will be sore at the end of the day

• Each person in the group should get onto the shoes at least ONCE and experience the thrill of water shoes walking.

Viking Longshoes1998 Grand Champions

Preparing the Team

On Your Mark

Off and Striding

Near the Finish Line

The Winners

The Winning PilotRobert Lobbia ‘98

Denise Cosio ‘98 Robert Lobbia ‘98 Morgan Teachworth ‘98

Jessi McDonald ‘99

Viking LongshoesFirst LJHS Champion

1996

Dr. Smooth1997 Winner

Floating WombatsWinners 1999

Little Point Walkers2000 Winner

Little Point Walker 22001 Winners

Get Started as soon as possible

Design first then build

Have Fun!