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Part One: Fabricating knee-rise contour cushions

January 1st, 2020 / By: / Interior, Shop Techniques

By Terri Madden

Stylish, durable hi-lo/knee-rise contour cushions have become extremely popular. Translating a customer request for durable, comfortable and impressive contour cushions when you’re starting with a blank canvas can be quite challenging.

Stylish, durable hi-lo/knee-rise contour cushions have become extremely popular. Executing these successfully can elevate your company. However, a project with contour cushions has a high degree of difficulty and requires expertise in specific techniques that can easily consume more hours than estimated. It’s a delicate dance to fabricate seating that is not only functional, attractive and easy to maintain, but that can also withstand the marine environment. Depending on your expertise and perspective, taking on such a project can be a daunting challenge or a welcome opportunity. 

Here are the techniques we have developed at Sand Sea & Air Interiors to ensure that our hi-lo/knee-rise contour cushions meet our customers’ expectations while sticking to a timely and profitable deadline. 

Establish project requirements

There are many questions you need to answer prior to fabrication. These include:

  • How will the cushions be attached to the area? (Is the attachment point in fiberglass, wood, railings, etc.?)
  • How will the cushions be secured in place yet also easy to install and remove?
  • Which of the recommended materials best fit the customer’s design sense and budget? 
  • What considerations are required for access to coolers, the engine room, storage lockers, etc.?
  • When will the boat areas be accessible for patterning and installation?
  • Which foam densities and heights will best fit the space? (Use “sit tests” to establish this.)
  • How much will you charge to fabricate an actual size mock-up to review with the customer for final approval? (This sample will come in handy with future customers, so perhaps you can bill for half the time and cost incurred. We have mini mock-ups of several cushion styles as well as an illustration chart that provides a great visual aid for customers who may not be familiar with the many styles of custom cushions.)
  • How will the front face, corner and contour areas be fabricated? (Familiarize yourself with the various cushion shapes by making sketches, illustrations and prototypes of the options.)
  • Does your price quotation detail your cost for all materials and the time required for each step of your project? Have you summarized the time and materials that keeps cost of goods at 35 percent? 
  • Have you thoroughly reviewed every step needed for patterns, construction, final inspection and installation to ensure your time is accurately accounted for in your price quote? 

If you have done all of the above and used the construction tips mentioned in this article, you can feel proud that you have fabricated an award-worthy project that has met your customer’s expectations and your technical and business goals. 

Terri Madden owns Sand Sea & Air Interiors Inc. in San Juan, Puerto Rico.
www.sandseaair.com.


SIDEBAR: Contour cushion construction methods 

Type 1: A cushion composed of fabric and/or vinyl components with interior chambers (zippered sections) that separate the high and low areas of foam. (See Type 1 project example sidebar.)

Type 2: A cushion composed of fabric and/or vinyl components with interior foam chambers that are stapled in sections to a rigid base (marine plywood, PVC or StarBoard®) to hold one or more areas of foam within a cushion. 

Editor’s Note: Type 2 contour cushion construction will be covered in a future column.


SIDEBAR: Type 1 project example 

For an aft mezzanine seating project for a 37-foot 1987 Bertram, the customer selected a Sterling Silvertex® for the knee-rise and lumbar cushion areas, which complemented a Seagull Sailcloth Sunbrella® used for the seat and back cushions. Marine dryfast foam and polytetra fluoroethylene (PTFE) thread, as well as Velcoin® Fasteners, were installed to hold the cushions in place.

We did several sit tests and fabricated a physical sample to achieve the customer’s desired look; the sample incorporated a knee-rise cushion with a rollover contour that is typically used on a much larger vessel. 

Seat cushion final dimensions: 

23 inches long x 20 inches deep x 4 inches for the low area and 5 inches for the knee-rise

Foam specs:

  • Low seat: #50, 4-inch medium firm dryfast foam cut 23 x 15 inches
  • Knee-rise: #50, 5-inch medium firm dryfast foam cut 23 x 6 inches 

The design also needed the rollover to align with the fiberglass lip of the lid, which required opening to access the engine room. We accomplished this with an additional 2 x 3 x 23 inch piece of #50 foam that was attached to the lower edge of the forward area of the seat foam. 

Knee-rise topper: 

#50, 1-inch medium firm dryfast foam cut 23 x 15 inches and glued over the top and face of the 5-inch foam to produce the knee-rise contour to the top front and face cushion area. 

We cut a slight taper angle along the 23-inch length of both edges of the 1-inch foam to provide a smooth visual transition for the alignment of the hi-lo edges of the seat. 

To allow access to the engine room, the rollover needed to align with the fiberglass lip of the lid. This required additional foam that was attached to the lower edge of the forward area of the seat foam. 

To produce the knee-rise contour to the top front and face cushion area, we glued 1-inch foam over the top and face of the 5-inch foam. A slight taper along the length of both edges of the 1-inch foam provides a smooth visual transition for the hi-lo edges of the seat. 

Preparation tips:

Prepare the two foam sections first, as they will provide the foundation for your pattern pieces. Include notch indicators for joining panels accurately along both the length and width. 

Prepare cushion bottom and zipper bands similar to a standard cushion other than the top and hi-lo side bands.

Prepare the knee-rise area from your foam contour. Pattern and mark a vinyl top and side band. We mark the vinyl or fabric the same as our foam, taking into consideration the compression factor and seam size to produce a tight fit. 

SIDEBAR: Assembly for a cushion with an interior zipper pocket 

Cut a 5 x 22 inch piece of vinyl to prepare the interior zipper pocket that will hold the knee-rise foam in the forward chamber of your cushion and the low foam on the other side of the interior pocket.

Center and sew a 22-inch length of #5 zipper along the length of the vinyl.

Cut the 22-inch length of vinyl from end to end along the center of the zipper teeth. You now have two pieces that are 2½ x 22 inches.

Sew one length of the zipper/vinyl to the inside seam of the upper cushion panel along the knee-rise transition seam. 

Sew the other length of the zipper/vinyl to the mesh base. Align the zipper retention band so it is perpendicular to the upper and lower cushion panels. Sew the rollover panel to the seat panel.

Sew the sides and zipper bands and topstitch. 

Note: Interior zipper edges can be closed/sealed with slider(s) on teeth after the entire cushion is assembled and topstitched and after the knee-rise foam is in place. 

The interior zipper panel will be reduced to 4 inches when each side is sewn independently along the top transition seam and bottom mesh. The 4-inch interior zip band will give a snug fit between the hi-lo foam.