2011 London Dormer

Tony McGartland sent me the 2011 London Dormer file several months ago asking me if I give the geometric construction lines of the sloping ridge dormer a go.  All of the WorldSkills Carpentry competitions have two things in common. A polygonal ground plan and a sloping ridge dormer. The polygonal ground plan isn't all that hard to construct, but the sloping ridge dormer is a tough one to get a handle on. Mainly the jack rafter perpendicular to the roof surface and skewed from the plate line.


Here I developed the ground plan, profile and elevation to develop the valley sleeper.


This drawing shows the relationship of the valley sleeper bevel to the ridge line. This drawing is just a reference drawing. It has nothing to do with the dormer. I needed to make sure the valley sleeper bevel was the same geometric construction with any type of ground plan.


I placed the valley sleeper material over the develop drawing and scribed the lines to construct the 3D model of the valley sleeper.


Next, I did the same thing for the sloping ridge and the front gable rafter.



 I couldn't reverse engineer the jack rafter perpendicular to the roof surface, so I decided to see if I could come up with any theories using a dormer with a ridge that is not sloping. 

Here's the ground plan.  

3D perspective of the dormer with a level ridge.





Here I developed the roof surface ignoring the valley sleeper. Using the standard folding roof surface development and developing the  jack rafter on the roof surface developed the correct miter and bevel angles at the ridge.


In the next post I'll develop the dormer with a sloping ridge. 







Komentar

Posting Komentar

Postingan populer dari blog ini

Layover Valley Rafter Basics

Gambar
Before I get into the Hexenschnitt for the Layover Valley Rafter I needed to review the basic geometry that defines the layover valley rafter. I needed to make sure I could draw the layover valley rafter correctly in plan view (ground plan). Here's one method of a basic drawing using the layover valley rafter backing triangle to position the layover valley rafter material on the roof surface that defines the  layover valley rafter in plan view. The  layover valley rafter top bevel is easily defined by extending the  layover valley rafter backing triangle to the top of the  layover valley rafter. The other  layover valley rafter line in plan view is defined by the bottom edge of the  layover valley rafter material sitting on the  layover valley rafter backing triangle. (Roof Surface). The  layover valley rafter plan view lines at the intersection of the two roofs. I tried this method for drawing the  layover valley rafter, but this method seems to be slow of a process for determinin
Baca selengkapnya

Hip Rafter Edge Bevel and Backing Angle

Gambar
In complex roof framing there are 7 main roof framing angles. Hip Rafter Backing Angle Valley Sleeper Bevel Angle Plain Titl (DP) Main Plan Angle Adjacent Plan Angle  Main Profile Rafter Slope Angle Adjacent Profile Rafter Slope Angle In this article I will discuss the hip rafter backing angle and the valley sleeper bevel angle. These two angles determine the miter angle and and saw blade bevel angles for jack rafters and purlin rafters that are plumb to the earth and for jack rafters and purlin rafters that are skewed from the eave line. A thorough knowledge of these two angles is critical in complex roof framing using geometry or trigonometry. The hip rafter edge bevel was avoided in the 12th century on some roof structures by rotating the hip rafter into the roof surface plane. However, by avoiding the hip rafter edge bevel, the carpenters-builders had to have a knowledge of the Valley Sleeper Bevel Angle. They didn't call it the Valley Sleeper Bevel Angle, but it's the same
Baca selengkapnya

Layover Valley Rafter Hexenschnitt #3

Gambar
In the book Das neue Buch vom alten Wissen der Schiftung The new book on the ancient knowledge Schiftung The new book on the ancient knowledge Roof Framing The new book on the ancient knowledge Roof Framing Geometry by Bernd Küppers I'm stuck on page 23. The geometry in the book, just doesn't return the correct miter angle for the Layover Valley Rafter Witches Cut (Hexenschnitt). I don't know if I'm drawing it incorrectly, or the BE (Bottom Edge Plane of the Layover Valley Rafter) should be drawn differently. Similar drawing at File: Kehlbohle mit Hexenschnitt.jpg There's 3 canted planes that define the Layover Valley Rafter Witches Cut Miter Angle. The main roof surface, the square tail fascia plane of the main roof and the the square tail fascia plane of the adjacent roof.  I think the problem with my geometric drawings is defining the intersection of the roof surface with the adjacent  square tail fascia plane.
Baca selengkapnya