How to Make a Keystone Cushion for a V-Berth

Item # X-HT-200642

Create a comfortable double bed in your v-berth by adding a keystone filler cushion. This small, irregularly shaped cushion may look tricky to make, but we’re going to break down the steps for you to make it easy to pattern and sew. If you need to make all new cushions for your v-berth, check out our "How to Make V-Berth Cushions" post (#200620XHT).

A keystone cushion for a boat's v-berth

The keystone cushion we made for our Islander37 sailboat is a trapezoid shape, which is pretty common, but yours might be a different shape depending on your boat’s v-berth configuration. Our keystone cushion sits in its own tray with trim board between it and the main v-berth cushion. If you have a similar setup, you’ll want to add extra width to the top of your foam so the filler cushion will be flush with the main cushions. To do this, measure the width of the filler board and add that width to the top of the foam width measurement. The end result will be a cushion with an angled edge.

The key to making a great fitting keystone cushion is careful patterning and attention to detail. In the video, we break down the patterning steps slowly with calculations so you can get the best fit possible for your filler cushion. When patterning your fabric, be sure to take into consideration any designs on the fabric. You’ll see we were careful to match up the stripes on the fabric with the existing v-berth cushions for a cleaner look.

The keystone cushion in place in the v-berth

In this video you will learn how to make a pattern for your filler cushion, cut the foam to size, pattern the top and bottom plates, add a zipper, and sew your cushion.

Video Chapters:

  • Patterning — 0:21 min.
  • Cutting Foam — 1:19 min.
  • Patterning Top & Bottom Plate — 4:57 min.
  • Cutting & Sewing Boxing — 7:49 min.
  • Creating Zipper Plaque — 12:52 min.
  • Sewing Boxing to Plates — 18:35 min.
  • Inserting Foam — 20:41 min.
  • Materials List — 22:15 min.

Materials List:

  • Marine Upholstery Fabric (we used Sunbrella® Upholstery Fabric)
  • Dura-Skrim® Patterning Material #122463
  • Marine Interior Foam (we used 4" Dry Fast Foam #184M2454)
  • Cushion Underlining Fabric #103934 (Optional)
  • V-69 Polyester Thread
  • YKK® #5 Coil Zipper #104387
  • YKK® #5 Coil Non-Locking Zipper Slider #104333

Tools List:

  • Sailrite® Blade Foam Cutter #121244
  • Sailrite® Edge Hotknife #103800
  • Deluxe Magnetic Sewing Guide #103597
  • Seam Ripper Deluxe #18104
  • Sewing machine
  • Marker
  • Tape measure
  • Yardstick
  • Scissors
  • Pencil

Do you have a filler cushion in your v-berth? Have you ever re-covered it? Share your tips and advice with us in the comments!