Friday, November 8, 2013

European Task Model #4

This European task model looked hard to develop at first, but using the draw down method  to develop the descriptive geometry for the timbers makes it fairly easy. Since both sides of the task model are mirror images of each other you only need to draw out the roof surface on one side of the task model and then make a mirrored copy of the rafters. 

3D drawing of the task model to check the rafters developed from the geometry.

Ground plan for the task model.

The internal edge of the hip rafter on the roof surface was developed from the dihedral angle triangle using the 2 different sizes of the rafters in the task model. 40x80cm for the jack rafter plumb to the earth and 40x40cm for the purlin rafter skewed from the plate line. 

Place the timber over the roof surface and draw the lines for the seat foot angle, jack rafter miter and bevel angles at the peak of the rafter and the claw lines. Remember, the top edge of the timber placed over the roof surface using the draw down method is the top of the rafter in the finished task model. If your using the folding roof surface, then the top of the timber placed over the folding roof surface drawing is the bottom edge of the finished task model.

Skewed purlin rafter placed on the roof surface to mark off the half lap joint in the jack rafter.

The claw tip of the jack rafter extended beyond the hip rafter, so I placed the jack rafter over the profile view to transfer lines to cut the claw tip. The entire jack rafter could have been developed from the profile view, but since we needed to draw out the roof surface for the skewed purlin rafter it was just as easy to mark the jack rafter timber on top of the roof surface.

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