The Initial Screen
The Initial Screen
These cushions are fabricated from a single piece of fabric. They can be sewn together very quickly. A bit more time is required to calculate and cut the fabric prior to sewing it. Fortunately, this calculator app streamlines that process! The calculator creates a scale rendering of the single panel of fabric needed to complete a project. The renditions are very accurate. If the following instructions are followed, a perfectly fitting cover will result.
Note the question marks in parentheses on the screen. A short description of the role of each input can be displayed by touching the accompanying question mark. This description can be retired by hitting the “exit” button.
Enter the following inch measurements: 22.5, 72.75, 3.5, 1, 54 — leave “orientation” at the default “Width” and hit “Calculate”. Decimal numbers must be used to dimension cushions with fractional measurements. Inches must rendered as decimal fractions and that can make initial data entry a little tedious. To convert 3/8 inch, for example, to a decimal divide the numerator by the denominator (which, in the case of 3/8, yields 0.375).
Trimming Fabric to Useable Width
Published fabric width figures are “nominal”. That is, the actual fabric will sometimes be wider than the published figure. Usually the edges of these fabrics will be rather ragged. It is intended that this extra material will be trimmed away or utilized as seam allowance. Having trimmed your fabric, measure its resulting width and enter that in the fabric width input field.
After Hitting the "Calculate" Button
The box labeled “Key Dimensions” displays all the measurements needed to build the cushion cover. These dimensions are applied visually in the rendition. In the case of our example, two lengths of fabric must be sewn together side-by-side to create the cushion cover. To join two length segments use what we at Sailrite call a "semi-flat-felled" seam (see the "Seaming Panels" video below -- what follows is a text version of the video). First apply 1/4 inch basting tape (Sailrite part #129) to the top surface of one segment right on the edge of the fabric. Then place the next segment squarely on top of the first face-to-face. Peel the paper backing away from the tape, revealing the adhesive underneath, and baste the panels together along their aligned edges.
A Magnetic Sewing Guide is Helpful
Then run the basted edges of the matched panels through a sewing machine with a straight stitch inside the two edges exactly the width of the edge allowance (1/2-inch). 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. Optionally, you can 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).
The key dimensions box will indicate the proper "Cut Size" as a simple width and length. These cushion covers are always rectangular so this is all that is needed initially. The calculator automatically builds in a 0.5 inch (12.7 mm) seam allowance when it is necessary. That allowance is in yellow on the rendition. The cutout dimensions include this.
In addition there is a reduction in the dimensions to insure a snug fit for the cover (thicker foam requires a bigger reduction to keep the fit snug.). The width dimension (on the fabric length here) is the twice the width of the finished cushion (22.5 * 2 = 45 inches) plus foam thickness at each end (3.5 * 2 = 7 inches) less 1/10ths of the thickness of the foam at each end (3.5 * 1/10 = .35 * 2 = .7 inches) plus the zipper seam allownce (.62 * 2 = 1.24 inches). The result is 45 + 7 - .7 + 1.24 = 52.54 inches. Note that the red "zipper allowance" in the rendition is also included in the overall cut size width.
Similarly, the length dimension (on the fabric width here) is the length of the finished cushion (72.75 inches) plus foam thickness at both ends divided by 2 -- just 1/2 of foam thickness since top and bottom are folded over on top of one another (3.5 * 2 / 2 = 3.5 inches) less 1/10ths of the thickness of the foam at each end (3.5 * 1/10 = .35) plus the two seam allownces (.5 * 2 = 1.00 inches). The result is 72.75 + 3.5 - .35 + 1.00 = 76.9 inches.
Mark the indicated rectangle on the backside of the fabric. Cut it with a hot knife if possible.
The Clear Plastic Ruler Makes Notches Easy
Then mark (again on the backside) the cutouts or "notches" at the four corners and the two center points. And cut them away with a hot knife. These cutouts will be used to create the thickness necesary for foam insertion. The corner notches are essentially squares that are half the thickness of the cushion less 1% of that thickness ((3.5 - .35) / 2 in the case of our example). The zipper hem is .12 more than the seam allowance so that must be added to the "length" of the corner cutouts on the zipper side corners. The center notches are the same "width" as the corner notches but twice the "length" ((3.5 - .35) / 2 in width and twice this in length).
With the fabric face down, fold a .62 inch hem onto the back side of the cover on the two edges marked in red on the rendition. This can be done accurately by marking a line on the fabric twice that depth and folding to it.
The Cover is Right Side Up -- The Zipper is Under the Two Hems -- Zipper Ends Should Match
Then with the fabric still face down, baste the “zipped together” zipper tape in place on one hem (this will be the back side of the cover) with the bulge in the zipper coil facing away and down or to the face surface of the cover cloth. Let the zipper overlap the length of the cover by one inch or so on both ends.
The folded outer edge of the fabric should be lined up under the center of the intact zipper teeth. Now fold the fabric back on both sides so the face surface is up. Baste the second hem in place over the exposed portion of the zipper tape so that the zipper teeth are covered.
Break the zipper apart (just peal it apart from one end or the other). Sew each half in place with a row of straight stitches.
Sewing this cushion cover is a two step operation:
1. First close the cover fabric blank --
With the cover face up, put basting tape on
two of the four sides designated with a yellow seam allowance in the rendition. These will be horizontal edges if the orientation is "length" and vertical if it is "width". Use this adhesive to baste together the fabric panel -- folding each yellow allowance over onto its mate (horizontal fold if "length" and vertical fold if "width" -- fold so the center notches are halved and the outer surfaces -- the "right sides" -- of the fabric face each other). Sew these yellow edges with a straight stitch 1/2-inch
inside the matched edges. Close the zipper by forcing the slider in place and running it all the way down the length of the zipper and off the end.
Slider Pull Tab Down
Then force the slider on again from either end so the pull tab is up against the fabric hem and run it half way down the length of the zipper. 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. The zipper will be closed with the slider in its center. Cut away excess zipper and reinforce the closure at each end of the zipper by sewing a piece of scrap fabric an inch or so square right over the closed zipper end.
A Corner "Flared" and the Fold at Zipper's End
2. Then flair out the four corners-- Use short strips of tape to baste opposing edges together carefully. And repeat the straight stitch 1/2-inch inside these matched edges. Note that the cover is "wrong-side-out" at this point -- the seam allowances will be inside the cover when it is turned "right-side-out". Carefully to reverse at the beginning and the end of each stitch to lock everything in place. Each flaired corner should measure on the stitch line about 1/2 inch less than the thickness of the foam or filler that will be inserted.
Open the zipper. Turn the cover right side out by passing it through the zipper opening. Push out the corners. Wrap the foam in silk film if it is likely to be exposed to water. If so you will be able to use a vacuum to compress the foam and easily slide it in place. If not some effort will be required to insert the foam, but be assured that it will fit!
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