IMG 1096.JPG
FA info icon.svg Angle down icon.svg Project data
Authors Alex Watson
Status Deployed
Made Yes
Replicated No
Cost USD 112.44
Instance of Sundial
OKH Manifest Download

Background[edit | edit source]

Catherine Zane Middle School in Eureka, California, has partnered with the Engineering Design course at Cal Poly Humboldt in order to provide an opportunity for students to exercise their skills in sustainable engineering design. Our project team is called Division by Zero. Team members include Hannah Gidanian, Caitlin Gundert, Rick Thomas, and Alex Watson. The front of Zane Middle School features a large rectangle filled with bark mulch, 10 feet wide and over 100 feet long. This empty space receives a large amount of uninterrupted sun throughout the day. Zane wanted to improve this underutilized space and decided that a series of projects would be conducted by the Engineering Design class of Spring 2017.

Problem Statement and Criteria[edit | edit source]

Students at Zane Middle School currently do not have an interactive and tangible way to learn about the abstract idea of how the sun relates to the earth and the concept of time as a derivation of this relationship. There is a large, vacant section of the front of the school at Zane that has not been serving any purpose over the past several years. As a result, the bark mulch gets trampled across, leaving debris all over the pavement in front of the school.

Criteria Importance Constraints
Durability 10 Withstands abuse from students and elements while lasting at least 20 years
Safety 9 Must follow all safety regulations designated by the school.
Educational Value 8 Must be able to be used as a teaching tool for the teachers
Multiple Time Components 7.5 Can tell the month along with the time
Cost 6.5 Total budget of $400
Accuracy 6 Correct time and months
Interactivity 6 Gets the child engaged and interacting with the sundial
Aesthetics 5 Visually pleasing
Sustainability 4 Constructed of environmentally friendly materials
Precision 3 Recognizable time values

The Solution: Description of Final Project[edit | edit source]

A group of four Engineering Design students, by the team name of "Division by Zero" have partnered up with Trevor Hammonds and Kristopher Buihner at Zane Middle School in order to implement an interactive and aesthetically pleasing addition to the school front, directly in the center of the previously barren rectangle filled with bark mulch. The analemmatic sundial is stamped in a 9'x10' platform of cement on which middle school children serve as the gnomon. The student's shadow will tell the solar time. This sundial will serve to provide middle school students with an educational activity to emphasize the concept of solar time and the interaction between the sun and the earth in its orbital path.

Costs[edit | edit source]

Materials Quantity Cost Per Quantity $ Our Cost $
Table Cloth 1 17.99 17.99
Canvas 1 29.99 29.99
Dowels 2 0.69 1.38
Wood Letters 6 3.99 23.94
1x2 Furr Trim 1 30.99 30.99
1/4 in Plywood 1 Donated Donated
Wood Glue 1 4.99 4.99
Sand Paper 4 0.79 3.16
Total Cost $112.44

Prototyping[edit | edit source]

Many prototypes were made before placing the sundial in concrete. Prototyping on a canvas sheet proved effective.

Final Design of Analemmatic Sundial.

Calculations[edit | edit source]

Step Description Picture
1 First, find the dimensions of the space where the sundial will be placed. Then find the latitude and longitude of the location. After this is done, the ellipse of the sundial needs to be created. Use the length of the space available to find the major axis of the ellipse. The minor axis can be based on the average height of humans that will be using the sundial. To find the length of the minor axis, the length of a person's shadow at 12:00 needs to be calculated. The equation to do this is
Where: m= Minor axis
M= Major Axis
phi= latitude of location in degrees

After the minor and major axis are found, plug them into the ellipse equation:

Where the x and y are the xy coordinates.

Calculations were done with a latitude of 40.7892 Major Axis:9 ft Minor Axis:2 ft 11.25 in

Cad 2 cropped (2).png
2 Each number on the sundial is 15 degrees from the positive x-axis, and the XY values of the numbers for the time were found using the ellipse equation.

Radial units were then found by using sin(theta)=opposite/hypotenuse.

CAD 1 Cropped (1).png
3 The place where a person stands (the scale of dates) is based on the Analemma, which is the path of the sun in the sky over the year. To find the distance for where to stand for each month using the equation:
Z is the distance from the origin
M is the horizontal radius of the ellipse
d is the declination for each month
theta is the latitude in degrees
Screenshot 2017-04-30-15-21-42-2.png
3 Each of the season lines which are plotted into the cement is based upon the shadow length at each hour of the day throughout the year. The shadow length was calculated by taking the tangent of the angle of elevation of the sun at each hour of the day on the equinoxes as well as the solstices. Using right triangle trigonometry, it was determined that the shadow length equates to the height of the pole (24") divided by the tangent of the mentioned angle.
Season Line Calculations.jpg

Construction[edit | edit source]


Cut out outlined Roman Numerals from 1/2" Plywood. Sand and round all of the sharp edges. Keep the numerals that are being used in one stamp together to ensure a similar size fit.


Cut out the square base of stamp from the same size plywood. Again, sand and round all edges.


Attach Roman Numerals to the base using 3/4" wood screws. Make sure to place roman numerals backward so that the impression of the stamp will be correct.

IMG 2716.JPG

Cut and attach 1" x 2" pieces of furring strips to make the frame for the standing locations. All measurements should be to the center of each piece of wood

IMG 2716.JPG

Glue two pieces of pre-made wood letters together to make them thicker.

IMG 2747.JPG

Cut and attach 1" x 2" pieces of furring strips to make the frame for the standing locations. All measurements should be to the center of each piece of wood

IMG 2750.JPG

Glue the letters of the abbreviated months onto a plywood base. Make sure to reverse the letters for the same reason as before

Cement pour.JPG

Create a form with plywood and fill five inches with base gravel. Fill the form with cement.

Smooth cement.JPG

After the concrete has been poured and smoothed out, allow the concrete to cure for 30 to 45 minutes. Begin laying out center string lines.

First stamp.JPG

Using the center previously marked by string lines, stamp the standing positions.

Month names.JPG

Stamp all abbreviated months in the center of the corresponding box.


Layout string lines for each roman numeral.


Stamp all of the numerals by lining them up where the corresponding strings cross.


Be sure to use consistent pressure while stamping to ensure the depth is the same.


Allow the concrete slab to cure for 24 to 48 hours.

How to Use it[edit | edit source]


To find the current solar time, stand in the box with the current and corresponding month. Depending on what date it is within the month, you may need to alter where you stand within the box. If it is early in the month, stand on the bottom line of the box; if it's the middle of the month, stand in the middle of the box, and if it's the end of the month, stand on the top line of the box.

IMG 2728.JPG

Face forward and stand up straight, then determine the time from the location of your shadow. Remember if daylight savings time is in effect, the sundial will appear to be an hour behind

IMG 2731.JPG

To determine the present season, place the gnomon on the marker at the bottom of the sundial. Notice the three seasonal lines and locate the tip of the gnomon shadow.


Measure the shadow length on two consecutive days at the same time. If the shadow length appears to be shrinking and falls between the equinox line and summer solstice line, the present season is Spring. If the length appears to be growing and is in the same location, it is Summer. If the shadow location is between the winter solstice and equinox line and appears to be growing, the present season is Fall, and if the shadow is shrinking, the season is Winter.

Maintenance[edit | edit source]

  • Rinse the imprint of the numbers with water to keep the sundial clean and the numbers visible.
  • Sundial season lines may need to be repainted depending on the rate of degradation.

Team Members[edit | edit source]

Instructional Video[edit | edit source]

FA info icon.svg Angle down icon.svg Page data
Keywords interactive concrete sundial, plywood, concrete
Authors Hannah Gidanian, Alex Watson, Richard Chase Thomas
License CC-BY-SA-3.0
Organizations Cal Poly Humboldt, Category:Zane Middle School, Category:Engr205 Introduction to Design
Language English (en)
Related 0 subpages, 7 pages link here
Impact 1,003 page views
Created April 7, 2017 by
Modified February 28, 2024 by Felipe Schenone
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