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There is really very little sewing required for this project. If the cushion is larger than one fabric width, there will be seams joining segments. And all cushions will require vertical seams to close the squares at the corners. If there is a platform, that is it! If a fabric bottom is utilized, there will be a bit more work -- zipper will be sewn into the bottom plate and then that plate will be sewn to the top plate with its attached facing.

Connecting Segmented Panels

Red Seam Allowances

The calculator rendition will display a red border along edges of each panel segment to indicate seam overlap. These red areas will be as wide as the scale width of the edge allowance input. To join two segments, first apply 1/4 inch basting tape (Sailrite part #129) to the top surface of a segment right on the edge of the fabric where a red line is on the rendition. Keep the tape right along the edge of the fabric. Peel the paper backing away from the tape, revealing the adhesive underneath. Then place an appropriate segment on top of this first one -- the "top" surfaces of the fabric should be face to face. Match them carefully along the edge marked in red.

A Magnetic Sewing Guide is Helpful

Then run the matched panels through a sewing machine with a straight stitch inside the two edges exactly the width of the edge allowance. A magnetic sewing guide will help keep this stitch straight and accurate, but a strip of masking tape on the machine can also work in this capacity.

When the two panels are opened (as though they were butterfly wings) the seam allowance will be underneath. Fold the basted seam allowance over on one side or the other and press it in place with a warm iron (set the iron temperature appropriately for the fabric).

Creating the Corner Angles

If there are squares cut into each corner of the top plate and facing panel, l/4 inch basting tape (Sailrite part #129) applied to the fabric's top surface on one edge of the square can be used to secure the square corners prior to applying a straight stitch just the edge allowance from the matched edges. Make sure all the corners are folded to the top side of the fabric so that the seam allowances will be hidden when the cover is inverted. Also be careful to reverse at the end and the beginning of each stitch to lock everything in place.

If the corners of the top plate are cut on a diagonal as suggested in the last chapter, it will be a little easier to keep everything lined up (there will be more scrap fabric outside the edge allowance seam). As a result, many find that they can skip the application of basting tape. Do be careful to keep the row of stitches at right angles to the matched bottom edges of top plate and facing fabric. It is even worth going to the trouble to mark the seam line on the fabric with a carpenter's square.

We like to keep the first quarter to half inch of the corner seams unsewn to better fit the bottom plate in place -- that makes corner basting easier.

Zipper Installation

If this cushion has a platform, skip to "Completing a Platform Cushion" below. Otherwise, we assume here that a material unlikely to ravel is used for the bottom plate (we normally use "cushion underlining material" Sailrite part #s774, 768, 772 and 103934). This greatly simplifies the installation of a zipper. Start with a closed zipper without a slider and roughtly the length of the cushion. Run 1/4 inch basting tape along the outer edges. Peal the paper backing off the tape and baste the zipper in place lengthwise down the center of the bottom plate on what will be the inside surface. Run two rows of straight stitches along each tape side -- the stitches should be just inside the basting tape to ensure that the tape will not gum up the slider.

Slider Pull Tab Down

Work the zipper slider on from either end. Be careful to install it so the pull tab is up against the fabric of the backing plate. Then sew across each end of the zipper to lock the slider in place. If the machine balks at sewing over zipper teeth, simply whip round the zipper teeth at both ends by hand with needle and thread.

Slit the bottom plate from one closing stitch to another right down the center of the zipper tape. The slit can be started with a utility knife and then finished with a pair of shears.

Completing a Cushion with Bottom Plate

Matching Center Marks

Find the center of all the edges to be sewn and place marks on the face up side in the edge allowance. Start the final assembly by placing the bottom plate face up on the floor or on a table. Run 1/4 inch basting tape all round its edges. Peal the paper backing off one side at a time and smooth the appropriate facing edge (with the top plate face down) in place starting from the center marks and working to the ends. Each side can be sewn after basting or the sewing can be put off until all the basting is done. Each stitch line should be just the edge allowance inside the two basted panels. As before, a magnetic sewing guide can be very useful here.

Completing a Platform Cushion

Platform Cushions are finished with the foam in place over the top of the backing board. Turn the top plate with its sewn facing right side out. Carefully push each corner out to the seam line. Then pull the cover down over the foam with the board underneath and staple it in place on the back of the board. We like to start in the center on each side and work gradually to the corners. That is it! The platform cushion is complete -- no need to go on to the next chapter.

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