Introduction: Horizontal Sundial
There are many types of Sundials, but this one, I decided was the easiest to attempt using few tools and materials.
The main parts are;
The Gnomon- The vertical part of the Dial that casts a shadow to tell the time.
The Face plate- The area where the shadow is cast and thus shows the time.
The hour markers- Obviously, the parts of the dial that show the time at which the shadow lies.
They can be made out of almost any material as long as it remains rigid and weatherproof, and therefore I chose wood as it is easy to find and easy to work with.
Step 1: Tools and Materials
Tools & Materials
Wood of your choosing; I used a thin sheet of basswood for the gnomon and an square ply block from the dollar store crafts section.
Step 2: Planning the Build
There are 3 things that need to be done;
Build a Gnomon
Build the Face Plate
Putting it together
Step 3: Gnomon
This is probably the hardest part as it needs attention to detail and has to be planned and built before testing.
The sundial is dependant on your location. The gnomon has to be aligned with the slope side pointing to solar north and at an angle equal to the angle you are at to the equator, ie., your latitude.
Here in downtown Vancouver my latititude is 49 degrees North.
To find latitude i find that google maps is the easiest way to find it; right click on the area you want and click on "what's here".
With a protractor and a pencil, draw a line from one corner of the wood at the latitude degrees, and cut along this line.
You are left with a right angled triangle with your latitude as the other angle.
Next and finally for the gnomon, cut another line horizontally to this line but leave to peaks in the cut as in the picture.
These will be the inserts that hold it in place to the Face. I used the pocket knife to cut the small part between the peaks.
Step 4: Face Plate
The dimensions of the face plate are not so important. It is nice to have the gnomon take up at most half the length of the face; so if you use a circular face, the diameter should be between twice and 3 times the length of the gnomon.
One important part of this is to plan where the gnomon fits.
Draw a line so as to divide the face in half and one line perpendicular to that which lies close to the edge of the face.
Rest the gnomon along the line so that the latitude angle point is at the two intersecting lines.
Mark along this line where the two peaks in the gnomon meet touch it and cut into the wood. I used my pocket knife for this.
Later this will be secured.
Marking the time;
Firstly, without doubt, the line you drew to divide the face, also measures 12 o clock, or more specifically solar noon.
The time at where the sun is at its highest point and therefore the shortest shadows.
To mark the time on the dial, use the protractor again, and lining 90 degrees with noon, each hour on either side will be 15 degrees apart, so that 6am and 6pm will be both perpendicular to noon.
Draw lines from each hour point to the end of the gnomon line. These are the hour lines.
Step 5: Putting the Together
Pour some glue into the holes of the face and slot the gnomon into the holes once the glue has started to tack up a bit.
Make sure that the gnomon is exactly perpendicular to the face.
Wait for the glue to dry.
When the gnomon is dried in position, I mixed the glue with water and brushed the mix over the whole thing to give it a protective coating.
Step 6: Position Sundial
The sundial works by positioning it so that the gnomon points to solar north. This is slightly different to magnetic north;
To find solar north there are two way I prefer.
One; analogue watch; holding the watch parallel to the ground, direct the hour hand in the direction of the sun.
The 12 o clock position is straight ahead.
Now bisect the angle the 12 and hour and makes and draw an imaginary line.
For example, if it is 4 pm. hold the watch so that the hour hand at 4, points to the sun. therefore 2 on the watch points south.
And therefore opposite 2, 8 points north.
Just before noon, place a stick in the ground and mark the end of its shadow every few minutes.until a few minutes after noon.
The shortest point marked from the stick indicate solar noon. The line from the mark to the stick is the north/south line.
This is the line the gnomon runs along.
Find a place to postion the dial, and use one of these methods. The gnomon at solar noon will show barely should cast a shadow no wider than the thickness of the gnomon.
Step 7: Check the Time
Once everything is set up and complete, keep an eye out for the time. the shadow on each hour should line up with each hour line.
The only thing is, Daylight savings time doesnt work on sundials, so therefore during daylight savings it will be off by an hour and this will be needed to be accounted for.
In the picture it shows that its 11am.