Schräge Sparren

Schräge Sparren -->  Oblique rafters, Slanted Rafters, Skewed Rafters, Canted Rafters, Prow Rafters
Schräger Giebelsparren --> Oblique Gable Rafter

Rafter Plumb to Earth and Offset from Plate Line

Manfred Euchner
Handbuch der Schiftungen

Austragen von schrägen sparren -->Discharge of slanted rafters
Das fertige Modell aus verschiedenen Richtungen  --> The finished model from different directions
Holz senkrecht --> wood vertical
überhöhung --> cant - elevation
abgratung --> burring
Abgratungslinie--> deburring line
Betrachtung -- > viewing
Traufe -- > gutter --> eaves
Schwelle -->sill
Abschnitt --> section
Sparrenquerschnitt -- > rafter cross section
Grundsätzliches --> Basics
Grundriß --> Floor Plan, layout, outline, plan
Fuß --> foot
Gratsparren Grundverschiebung --> Hip rafter basic shift

Sparren einen einfachen Hexenschnitt


Rafters with simple witches section

Abgratungslinie--> deburring line

Sloping rafter edge bevel angle

Krallenspitze -- Jack Rafter Claw Tip Angle

Manfred Euchner
Handbuch der Schiftungen

Ermittlung der Klaue bei schifter
Determination of the claw at Schifter
Determination of the claw at Jack Rafter
Krallenspitze -- > Claw Tip

The math for the jack rafter claw tip. 

R5  = Hip Rafter Diamond Post Angle

R5 = arctan (tan Hip Rafter Slope Angle x cos adjacent plan angle)

Common Rafter Slope Angle - R5 = Claw Tip Angle

R5 = arctan(tan 27.50055 x cos 51.34019) = 18.01470

Claw Tip angle = 39.80557 - 18.01470 = 21.79100

R5 = arctan(tan 27.50055 x cos 38.65981) = 22.121943
Claw Tip angle = 33.69007 - 22.121943 = 11.568126

The plan angles are the opposite for valley rafter plan angles. Here we have a 8:12 & 10:12 hip roof  with the 8:12 plan angle at 51.34019° and the 10:12 plan angle at 38.65981°

In this drawing of the valley rafter you can see the plan angles are reversed. 

Klauenschifter -- the claw

Klauenschifter  --> the claw on the schifter( jack rafter) --> Jack Rafter Seat at Hip Rafter


Manfred Euchner --> Briallint
Handbuch der Schiftungen --> Everyone should buy this book.

German PDF file with the Klauenschifter calculations for saw blade bevel angles

Backenschmiege - Back Bevel

Reading thru the book Handbuch der Schiftungen by Manfred Euchner , I came across this method to  find the jack rafter side cut angle  in plan view. It's one of those drawings where you say, well of course of it works. Just never seen it drawn this way. It would also give you the roof sheathing angle.

German PDF file with back bevel saw blade angle (Maschinen winkel)

Schiftungen.

The consideration of the chapter .. Dachau averaging "given the numerous samples of composite roofs teaches us that the latter BEZW are formed almost exclusively by the intersection of gable roofs. Can be broken down into those. A simple gable roof, including understanding the shape of the roof, in which only two inclined to each other, intersecting planes form the roof in a straight line, like a lying, triangular prism, namely a right prism if the building floor plan rectangular, a truncated prism when it is trapezoidal in shape., the forming the bases of the prisms vertical levels, the gable of the roof or the building. become but the latter is replaced by planes which are inclined like the surfaces of gable roof to the horizontal plan level, ie with the latter an acute angle, so that the roof appears as a gable-less and in all drops out, the hipped, and the triangular faces, in which now the previously limited by vertical planes prism formed cut is glad Walme when the horizontal lying sides of the same with those of the saddle roof surfaces lying in a horizontal plane Krüppelwalme when the said sides in different horizontal planes.

The lines in which the saddle roof surfaces intersect Walmflächen glad ridges, and the intersection with the ridge of the roof is called attack point.In the horizontal projection of the ridges bisect the angle of the building plan, if the roof pitch on all sides assumed to be equal, and therefore we obtain for roofs with the same roof pitch the projections of the ridges and at the same time the attack points by bisecting the angle of the floor plan.The position of the points is not attack without affecting the distribution of the binder of the saddle roof. Of the main bundles of the same one is usually two on the same so that it faces with their the Walme, vertical sides are under this points found on this page, the hip rafters and indirectly the remaining timbers that form the hipped, a prop. The hip rafters are such that the amount drawn on the upper bounding surface of Gratsparrens center line with the ridge line, of which we have the projection in Gruudriss, coincide, ie that, conversely, a to outline level in the projection of the ridge built vertical plane of the hip rafter length of halved. Those parts of the roof areas, for which the ridges form the upper boundary formed by rafters, probably as the other rafters of the gable roof begin at the foot of the same (at the eaves), but not reach up to the ridge, but are au blunt the hip rafters Creating, they are all of different lengths and hot as distinguished from the rafters of the gable roof Schiftsparren or shifter. Similar considerations can also hire for such parts of roof surfaces for forming the timber rafters which. Absorbed from the ridge to a Throat rich (Kehlschifter), which is known to arise if the building floor plan has a re-entrant angle. The spatial valley line as well as the ridge line forming the median line of the upper surface of a bar, which is called a collar beam.

Traditional Roof Framing Geometry Layout Techniques 1

The traditional roof framing geometry used by the French and Germans carpenters of the past , represents the timber in three-dimensional visualizations( Stereotomy). This allows the carpenter to layout complex cuts from 2 dimensional plans that represent the true shape of the rafter or timber framing joint.

There are no English translations of the traditional roof framing geometry used by the French and Germans and this is best illustrated in the French book Traité Théorique et Pratique de Charpente, by Louis Mazerolle in 1866. The techniques used by Louis Mazerolle are vague and need a lot of research to follow his techniques and the written words in his book are hard to translate from French to English. The books I've boughten on Traditional Layout  have helped me to understand some of the techniques used by Louis Mazerolle, even though their written in French or German.

This article will explain what I believe, to be the basics of understanding the traditional layout methods. These 12 basic techniques must be completely understood to produce drawings that represent the true shape of  the timber on 2 dimensional plans.

Traditional Layout Basics 

1. Hip Rafter Offset -->Hip Rafter Shift --> Gratsparren Grundverschiebung
2. Hip Rafter Dihedral Angle for Hip Rafter Backing Angle --> Diederwinkel
3. Rafter Block Rotated Plumb To Roof Surface
4. Rafter Block Rotated Perpendicular to Hip Rafter Run Line
5. Rotating the Roof Surface From The Ground Line
6. Hip Rafter Internal Edge On Roof Surface
7. Jack Rafter Bevel Angles
8. Jack Rafter Miter Angles
9. Hip Rafter Level Line
10. Hip Rafter Backing Depth
11. Lip Angle Line (barbe line, beard line)
12. Lip Length Line-> Claw line-->Klaue 

1: Hip Rafter Offset

See my article on Hip Rafter Offset for examples of drawing the hip rafter offset. The hip rafter offset will align the edges of the hip rafter with the two roof planes on each side of the hip rafter. Each and every drawing should start with the hip rafter offset lines to establish the planning points of the hip rafter. 

2: Hip Rafter Dihedral Angle for Hip Rafter Backing Angle

The dihedral angle triangle establishes the hip rafter backing angles and it is used to draw out the rafter blocks rotated plumb to the roof surface and the rafter block that is drawn perpendicular to the hip rafter run line that establishes the dimension used to draw the hip rafter internal edge on the real roof surface that in turn establishes the jack rafter miter angles.

3: Rafter Block Rotated Plumb To Roof Surface

This rafter block is titled at the slope of the hip rafter backing angle in plan view. It is used to draw the 3 lines that represent the rafter being rotated into the roof surface.

4: Rafter Block Rotated Perpendicular to Hip Rafter Run Line

There different ways to establish the internal edge of the hip rafter on the roof surface, but I think this is the easiest way to remember and to establish this line. 

Rafter Block Rotated Perpendicular to the hip rafter run line. The 1.6105" dimension in this drawing  is used to draw the hip rafter internal edge on the roof surface. You can not draw out the jack rafter miter angle correctly without this dimension.

This next drawing shows the rafter block rotated on the other side of the hip rafter. The dimension used for the hip rafter internal edge on the roof surface is different for unequal pitched roofs.

5: Rotating the Roof Surface From The Ground Line

This should be a no brainer, but it's added here for clarity. The true shape of the rafter is developed from the roof surface.

6: Hip Rafter Internal Edge On Roof Surface

In this next drawing the hip rafter internal edge was drawn, on the roof surface, parallel to the hip rafter offset line using the dimension found from the rafter block rotated perpendicular to the hip rafter run line at the end of the dihedral angle triangle. The hip rafter internal edge establishes a line that determines the miter angle on the sides of the jack rafters.  

7:Jack Rafter Bevel Angles

The jack rafter bevel angle on the top and bottom of the jack rafter is always the same angle that is found on the roof surface drawing. You should always check these two angles to make sure your drawing the true shape of the jack rafter correctly.

8: Jack Rafter Miter Angles

The jack rafter miter angle on the side of the jack rafter is drawn using points 2&4 or 1&3. Points 3 and 4 are always on the hip rafter internal edge line.

9: Hip Rafter Level Line
The hip rafter level line is used to determine the backing depth on the side of an un-backed hip rafter.

10: Hip Rafter Backing Depth
The hip rafter level line and backing depth line is used to determine the placement of the plumb lines on an un-backed hip rafter.

11: Lip Angle Line
The lip angle line on the roof surface determines the points of intersection on jack rafters and purlins to draw out the lip cut angle on the jack rafters or purlins.

12: Lip Length Line

The lip line length determines the actual length of the lip cut on jack rafters and purlins.The lip line length line is determined by the point of intersection of the seat line in plan view and the seat line on the roof surface.

European Carpentry Competition 2012 Task

Here's my roof framing geometric development for the
European Carpentry Competition 2012 Task

Ground Plan
Profile
Roof Surface 1
Roof Surface 2
Roof Surface 3
Jack Rafter 1
Jack Rafter 2

While drawing the geometric development lines for this model, I realized I would have never even completed the geometric development in the 22 hours that the apprentice carpenters are allowed to draw and build the model. The European Carpentry Competition apprentices are amazing. 

Here's the task plans each apprentice carpenter had to draw and build their model. This presented problems to me right from the start. I've never used a 1:10 plan scale and the metric conversion was also a problem. My first mistake was with the dimensions that use 55 . I thought it meant 10 x 5.5 = 50.5 mm. It's suppose to be 55 mm, so I had to erase a lot of the lines and start over. All of the jack rafters are rotated into the roof surface plane. So I used the size of the jack rafters, 50mm x 70mm, to draw out the rotated section of the jack rafter, based on the hip rafter backing angle, to establish the 3 to 4 lines of the jack rafter in plan view and only to erase most of those lines for clarity or the lines not being drawn correctly.  

Here's the drawing of the jack rafter's section blocks that were drawn incorrectly.

Here's the drawing of the jack rafters in plan view without the section blocks that were drawn incorrectly. To make it even harder the jack rafter spacing is to the center of each jack rafter. That makes it hard to draw the jack rafters in plan view correctly. At least for me. I also, had to draw the elevation of the roof in plan view to establish where the plate line is placed.  

This next drawing is the profile view of the roof rafters to the right of the plan view and the rafter rotated to establish the rabattement roof surface lines. It also has the construction lines to establish the seat line of the rafters on the rabattement roof surface. 

Here's the drawing of the rabattement roof surface #1.

Here's the drawing of the rabattement roof surface #1 with Jack Rafter # 1, that is rotated into the roof surface.

Here's the drawing of the rabattement roof surface #1 with Jack Rafter # 2, that is rotated into the roof surface.

Never did see a way to establish the plumb cut on the ends of the jack rafters tails from the rabattement seat lines.

In this next drawing the theoretical hip rafter edge bevel line determines the Hip Rafter Backing line on the internal edge of the rabattement surface. That is developed from the Seat Line in Plan View and the Seat Line on Rabattement Roof Surface. If the Hip Rafter Backing line on the internal edge of the rabattement surface is not drawn correctly, you will never draw out the jack rafter bevel angles correctly.

The drawing area in the European Carpentry Competition 2012 is only about 8'x8', I  would need a drawing area of about 20' x 20' to draw this out on the drawing board using the rabattement method. So, I guess the drawdown method works better for the competitions.(coucher,  put-down or lay-down the roof surface)

All in all, I would have been disqualified from the European Carpentry Competition the first day.

Rafter Bevel Angles for WorldSkills Carpentry Competition

The American's don't send any apprentice carpenters to the WorldSkills Carpentry Competition, So I added a new android app on Google Play. 

SkillsUSA will only compete in those WorldSkills Competition contests for which it has a well-qualified competitor, a well-qualified technical expert, adequate industry support for advanced training and general operating costs of the SkillsUSA World Team contestant prior to the WorldSkills Competition.

In order to have an well-qualified competitor we need qualified technical experts as well.

The Canadian's send apprentice carpenters to the WorldSkills Carpentry Competition, so why can't SkillsUSA send a qualified competitor? Because we don't have any qualified technical experts.

This android app will not send a apprentice to the WorldSkills Carpentry Competition, but it's a step in the right direction for WorldSkills Carpentry Competition training.

See this list of Traditional Layout books for reference.
Traditional Roof Framing Geometry Layout out Books

Rafter Bevel Angles v 1.0
REQUIRES ANDROID:2.3.3 and up
https://play.google.com/store/apps/d...ls.bevelangles


Buy Rafter Bevel Angles for Android on Google Play

This android rafter calculator app is for the WorldSkills Carpentry Competition training. With this app the carpenter can verify their geometric layout method while using the traditional layout geometry. It has seat lip cut angles at the hip rafter for all of different types of rotated rafters as well as Hexenschnitt Gratsparren. Coupe de pied de noue, avec dévers inegaux.

All bevel angles are referenced from the traditional layout method used by the French and Germans carpenters. Use with the French Rabattement de Surface method (folding) or the German Flachenklappung method. Basiswissen Schiften or Charpente Les Traces. 

Jack Rafter Plumb To Earth Bevel Angles.
Jack Rafter Plumb To Earth Offset Bevel Angles.
Jack Rafter Plumb To Roof Surface Offset Bevel Angles.
Rafter Plumb To Earth Offset Bevel Angles.
Crossing Jack Rafters Plumb To Roof Surface Bevel Angles.
Saint Andre Cross Rafters Plumb To Roof Surface Bevel Angles.
Purlin Rafter Plumb To Roof Surface Bevel Angles
Witches Cut on Hip Rafter with Square Tail Rafters
Hip Rafter Edge Bevel Angles, Backing Angles
Devers De Pas for Jack Rafters Plumb To Roof Surface

WorldSkills Carpentry Competition

A challenging wood construction, mostly a roof timber model, shall be built for the Competition. The competitor shall independently solve the following tasks in the prescribed time of 22 working hours:

→  Elevation, development and assembly of a roof construction

→  Development of angle and valley rafters on polygonal, rectangular or square ground plans with even and uneven roof slopes

→  Construction of tower roofs including adjustment to the general roof construction

The following working techniques for the solution of a task could be possible:

→  Elevation of a roof construction in ground plan and profile

→  Developing a construction in which each piece of wood can be found in its true shape.

→  Determining all measurements, dimensions, lengths, cuts, angles and bevels required to perform the work.

→  Drawing and transferring of real lengths and cuts to the pieces of wood (scribing).

→  Processing the work pieces (assembly).

→  Mounting and fixing all wooden parts of the structure (erection).