In addition to a straight bar, rolling layer or semicircular arch, one can also close the opening in the façade with a segmental arch.
Motivation phase
Drawing a segment arc.
In the video below you can see how one draws a segment arc.
Permission to use the video from youtube: youtube.com/watch?v=Y7MzqJZWp8
Information phase
Installation of a segmental arch.
* A segmental arch also needs support.
* To brick a segmental arch you use a mold, wich may be removed when the mortar has hardened.
* Build the mold with two fiberboards along both sides, close the top with flexible sheet material.
The width of the mold corresponds to the width of a brick.
Use a nail and string as compasses to mark out the circle and a jigsaw to cut out the mold.
You should underpin the mold with lathing, secure the mold firmly in place and adjust it perfectly.
> Marking off a segment arc:
* In the picture below see the different steps to make the support:
1: The distance
2: straightness
3: porring point
4: apex or crown
5: Arrow, porring or sting.
6: Onset.
7: Birth.
8: Outer arch line.
9: Inner arch line.
Own course & wikipedia.
Information phase
Calculation segment arch.
1: Method 1:
* Given: birth line or centerline AB
* Construction: divide the line AB into equal parts. One thus obtains the poring point E
* Construct the arc AB with E as center and EA or EB as radius.
Photo: own course
Information phase
Calculation segment arch.
* Method 2:
>Method 2, span and height given:
Given: birth line AB
The height CD
Construction: on the line AB, draw a perpendicular bisector
Transfer the known arrow CD
To draw the perpendicular bisector on the lines AD and DB
Where the perpendicular bisects is the porring point E
Using E as the center and EA or EB as the radius, construct the segment arc.
