PVC bends and trouser tee

Start by multiplying the pipe's diameter by 3.4 to find the circumference. For a diameter of 120 mm this gives 120 × 3.4 = 376.8 mm. Round up to the nearest whole number, in this case 400 mm, which is used as the working dimension on the sheet.

Mark a line every 100 mm along the calculated circumference width so you get four equal fields. This forms the basis for the subsequent setting out of x and y coordinates.

The difference between x and y corresponds to the pipe diameter of 120 mm. Set, for example, x = 100 mm, which automatically gives y = 220 mm (100 + 120 = 220). Mark the two points and draw a cross line, and also mark where the lines cross the centre line.

Use the marked points and the height you found to draw the bend shape with a smooth, freehand curve. You can check the result by laying a 12-point shape over it to verify that the shape looks like a correct elbow.

Cut out two copies of the drawn model. One part — the lower one — is given tabs, while the other part is made without tabs. The two parts must be mirror images of each other, and the overlap must be positioned correctly so that the cladding sheds water.

Make a top piece in aluminium representing the throat of the bend, and fix it with tape so that the edge is flush with the side. Lay the flaps over it and check that the top edge of the bend lines up correctly with the horizontal piece. The end segment is laid on top last and follows the pipe precisely thanks to the piece underneath.

For the breeches tee, the segment-bend method is used, starting from an already fabricated tee. The part of the tee that meets at 90 degrees is used for the lower part of the legs, while the part that meets at 45 degrees is used for the upper joint. Remove half of each tee and push them together to form the profile of the legs.

The point length of the breeches tee's legs is calculated as the starting dimension (100 mm) plus the pipe's radius (60 mm for a 120 mm diameter), giving 160 mm. Mark 160 mm for the points on all three sides. For the top piece, use 100 mm plus half the radius (30 mm), i.e. 130 mm.

Draw both legs on the film. Remember that the two legs must be mirror images of each other. The upper part — which represents the 45-degree connection — must be drawn identically for both sides and used in two copies.

On the left leg, make tabs all the way up. The tabs in the 90-degree section are bent to 90 degrees, and the tabs in the 45-degree section are bent to 45 degrees. On the opposite side the tabs are removed, as they are matched by the tabs on the other part. The top part is fitted with no tabs at all.

Cut the sheet to the width: diameter × 3.4 + 50 mm overlap, i.e. 120 × 3.4 = 376.8 + 50 mm. Draw a centre line and mark 47.5 mm on each side of it (95 mm in total), as the centre line through the bend is 95 mm. Join the points with two parallel lines along the centre line.

Transfer the bevel from the trouser tee's 22.5-degree section onto a piece of cardboard, and cut it out. This cardboard is used as a template to draw the correct bevel on the middle segment.

Place the cardboard template against the sheet so the points hit the marked points, and draw along the edge. Then turn the cardboard template over and draw the bevel on the opposite side in the same way. Repeat the procedure for the second bevel, so the middle segment is fully marked out.

Cut out the middle segment. Provide the side facing upwards with flaps, which are to go in under the end segment. The middle segment can then be used as a template to draw the start segment, which is extended to the desired length and likewise provided with flaps.

Assemble the start, middle and end segments so that you get a finished 22.5-degree bend that ends up at 90 degrees overall (referred to as 1 whole and 2 halves). Check that all tabs are seated correctly and that the overlaps shed water.