DIY Seat Cushion for Sailboat Sternperch

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A sternperch is a bonus seating option on some sailboats. Also called a stern rail seat, this is a small perch nestled in the corners of the lower rail at the sailboat’s stern. It adds much-needed extra seating, but its hard surface isn’t the most comfortable to use. To solve this problem, we made custom cushions with marine-friendly vinyl fabric and foam. In this blog, we’ll show you how to make a small seat cushion to fit the shape of your sternperches. Let’s go!
Video Chapters:
  • Patterning Sternperch Seat & Cutting Foam – 0:42 min.
  • Cutting Top Plate – 2:29 min.
  • Cutting Bottom Plate & Adding Zipper – 3:18 min.
  • Cutting Boxing & Adding Piping – 9:16 min.
  • Sewing Boxing to Top Plate – 11:46 min.
  • Creating Hook & Loop Strips – 18:43 min.
  • Positioning H&L Strips on Bottom Plate – 21:28 min.
  • Sewing Bottom Plate to Upper Assembly – 23:43 min.
  • Using Silk Film to Help Insert Foam – 28:43 min.
  • Installing on Sternperch Seat – 31:37 min.
Materials List:
  • Sailrite® Patterning Material 60" – #126150
  • CushionRite® Dry Fast Antimicrobial Foam (Firm) – #124204
  • EverSoft™ Pebble Indoor/Outdoor Tan 54" Vinyl Fabric – #122212
  • Phifertex® Plus Vinyl Mesh Stucco 54" Fabric – #123811
  • Lenzip® #5 Black Continuous Molded Tooth Zipper Chain – #124253
  • Seamstick 1/4" Basting Tape for Canvas & Upholstery (36 yds.) – #122065
  • PremoBond® Tex 90 (V-92) Toast UV Bonded Polyester Thread 4 oz. (1,350 yds.) – #123958
  • Lenzip® #5 Black Style C Single Non-Locking Short Metal Zipper Pull (Molded Tooth Chain) – #124274
  • Morbern™ Seabrook Vinyl Welting/Piping Midnight – #120144
  • Sample of Morbern™ Seabrook Midnight 54" Vinyl Fabric – #105987
  • Tex 70 (V-69) Pacific Blue UV Bonded Polyester Thread 4 oz. (1,350 yds.) – #106030
  • Polyester Black Loop 1" – #105036
  • Polyester Black Hook 1" – #105032
  • Cushion Wrap Silk Film 54" – #103933
Tools List:
  • Sailrite® Blade Foam Saw V2 with Carrying Case (110V) – #121244
  • Tape Measure 120" – #102986
  • Scribe-All® Black Marking Pencil for Vinyl – #121977
  • Gingher® Scissors Right Hand Lightweight 8" – #101017
  • Sailrite® Ultrafeed® LSZ Walking Foot Sewing Machine (110V) – #311602
  • Sailrite® Ultrafeed® Industrial Sewing Table – #120934
  • Basic Thread Snips – #123222
  • Seam Ripper Deluxe – #18104
  • Sailrite® Clear Acrylic Ruler 6" x 24" – #102400
  • Cording Foot Set for Sailrite® Ultrafeed® LSZ (For Larger Welting) – #104854
  • Large Fabric/Leather Grip Clips – #126365
  • Suisei Magnetic Sewing Guide – #102983
  • Marker, Flathead Screwdriver, Shop Vac
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We found these sternperch seats on the Seaward 32RK sailboat we redid. We used the same EverSoft™ vinyl fabric, Morbern™ Seabrook piping and CushionRite® Dry Fast Foam to make the sternperch cushions that we used to make the sailboat cockpit cushions. That way, they perfectly blended with the cockpit, giving the whole area a relaxed, organized look. We recommend using coordinating fabrics throughout your boat to make the whole vessel feel cohesive.

Our cushion includes hook-and-loop straps that wrap around the seat supports to hold the cushion in place. Since this cushion is irregularly shaped, sewing straps on straight may be a bit of a challenge. Not to worry — the how-to video will give you all the instructions you need to make yours! Get tips on: 

  • Creating straps with enough length to wrap around tubing and other obstacles.
  • Setting straps on the fabric assembly so they match up on the finished cushion.
  • Sewing one end of each strap into the cushion cover while keeping the other end out of the way. 

If you’re new to upholstering for your boat, this stern seat cushion is the perfect project for you. It’s a great introduction to irregularly shaped cushions, sewing piping, using silk film with marine DIYs and more. Watch the video above to get started on the unique sailboat cushions you need to make your stern rail seats a comfortable choice on every voyage!

This tutorial is part of our Seaward 32RK Project Series. This sailboat is getting the full DIY treatment from bow to stern! Learn how to make a variety of custom boat seat cushions, a bimini with backstay slits, full-mesh sheet bags and more in this series. Click here to view all the projects we’ve completed for this total boat overhaul.

Materials List
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