How to Upholster a Knee-Rise Seat Cushion With Curves
If you own a speedboat whose upholstery has seen better days, then this is the DIY series for you! We’re overhauling the entire interior of a used Malibu speedboat. Be sure to catch all the entire Speedboat Makeover Series to see the entire transformation. In today’s tutorial, we will be reupholstering a knee-rise cushion. This cushion style features a knee-rise, curves, boxing that wraps all the way around the cushion, and a backer board that the vinyl upholstery is stapled to. Let’s get into it!

We previously made a knee-rise cushion that is square in shape and has no curves (search #300464XHT for that tutorial). But we had a lot of requests from customers for a similar cushion style with curves and a backer board. We’re always on the lookout for tutorials that help our customers in their DIY work. So when the opportunity came to completely reupholster a speedboat with this exact cushion style, our DIY team jumped at the opportunity. We knew this was the exact DIY tutorial that our customers were asking for.
Knee-rise cushions have a fabric pull inside the cushion that separates the two different foams inside — the high-rise foam and the low-rise foam. This is what helps to create the firm front edge of the cushion, which is the distinguishing characteristic of knee-rise cushions. The original foam was compromised with some mold spots and had been flattened and compressed with time. We decided to replace the worn-out foam with new Sailrite® CushionRite™ foam. CushionRite™ is high-quality upholstery and seating foam suitable for all of your marine, outdoor and indoor cushion applications.
When it comes to vinyl boat upholstery, there are a lot of choices. Sailrite® stocks only the best, highest quality vinyl upholstery brands on the market. You won’t go wrong choosing from our selection of hundreds of vinyl upholstery fabrics. We chose EverSoft™ Indoor/Outdoor Vinyl Upholstery for our Speedboat Makeover Series. EverSoft is a four-way stretch vinyl. The fabric’s stretch properties make it easy to pull and staple the vinyl to a backer board, making it a great choice for this project. The textured pattern mimics the look of real leather for a high-end, luxurious style.

In this tutorial video you’ll learn some valuable DIY techniques that you’ll be able to use on other projects as well. Some of the things you’ll learn include:
- How to check foam for damage and evaluate if it can be reused.
- How to use patterning material to trace the cushion shape and add transfer marks.
- How to create and sew a fabric pull inside the cushion cover.
- How to sew the two halves of the top plate together with the fabric pull.
- And much more.
Are you ready to tackle this DIY boat cushion project? Press play on the video below to get started on this knee-rise cushion with curves tutorial.
Video Chapters:
- Intro — 0:00 min.
- Removing Old Fabric & Evaluating Foam — 3:49 min.
- Patterning & Cutting New Foam — 9:18 min.
- Creating & Sewing Fabric Pull — 13:09 min.
- Cutting Boxing to Size — 15:23 min.
- Sewing Two Halves Together — 19:00 min.
- Trimming Top Plate — 22:11 min.
- Sewing Boxing to Top Plate — 24:03 min.
- Stapling Fabric Pull to Backer Board — 32:21 min.
- Pulling Cover Over Foam & Stapling — 35:18 min.
- Materials & Tools List — 47:04 min.
Materials List:
- Dura-Skrim® Patterning Material 74" #103134
- Super 88 Spray Adhesive 13 oz. #123287
- CushionRite™ Standard Antimicrobial Foam (Medium) #124231
- Fabric Backed Sew Foam 58" #124306
- Headliner Adhesive 13 oz. #123288
- EverSoft™ Indoor/Outdoor Teak 54" Vinyl Fabric #122218
- EverSoft™ Indoor/Outdoor Black 54" Vinyl Fabric #122217
- Top Notch® 9 Silver Gray 60" Fabric #120450
- Polyester V-92 Thread from Sailrite
- Seamstick 1/4" Basting Tape for Canvas & Upholstery (36 yds.) #122065
- Polyester Carpet Binding Beige 1-1/4" #120236
- EverSoft™ Vinyl Welting / Piping Black #122597
- 21 Gauge 3/8" (10mm) Staples 10,000/Box (Stainless Steel) #8010SS
- Cushion Wrap Silk Film 54" #103933
Tools List:
- Staple Lifter #120037
- Gingher® Scissors Right Hand Lightweight 8" #101017
- Sailrite® Blade Foam Saw V2 with Carrying Case (110V) #121244
- Scribe-All® Black Marking Pencil for Vinyl #121977
- Tape Measure 120" #102986
- Clear Acrylic Ruler 6" x 24" #102400
- Deluxe 5-1/2" Magnetic Sewing Guide #103597
- Sailrite® Deluxe Fabricator® Sewing Machine Package (110V) #400600
- Cording Foot Set 1/4" for Fabricator® #400414
- Left Edge Guide Foot Set 4mm for Sailrite® Fabricator® #400111
- Sailrite® Short Nose Upholstery Staple Gun #121410
- Marker, Pliers, Tape Measure