This page was printed from https://marinefabricatormag.com

Foam: The what, when and where

May 1st, 2017 / By: / Interior, Shop Techniques

A comfortable custom exterior seating design for one client’s site-specific alcove.
A comfortable custom exterior seating design for one client’s
site-specific alcove.

Cushion foam is an important component of any marine seating project. From cockpit cushions with hull angles to bosun’s chairs and boat mattresses, choosing the best solution for cushion foam is a bit of a science. The task can feel daunting given the complexity of choices in foam types, materials, densities and compression factors, but choosing correctly is crucial to a project’s success.

Foam types

Foam is essentially a group of air bubbles trapped inside a solid matrix.

Open-cell foam is characterized as a soft material. The surfaces of the bubbles (the cells) are broken and interconnected so that air moves easily through all the spaces of the material when the foam is squeezed or compressed.

Open-cell foam is ideal for cushioning, padding and backing for furniture when you are looking for a balance of comfort and support. It is also useful for occasional bedding products and is generally available at an affordable price in standard sizes and heights as well as cylinders and wedges. Polyurethane foam (polyfoam), memory foam and latex foam are the three most common types of open-cell foam.

The original blue and pink polyfoam layers of this exterior cushion acted like a sponge absorbing water. These were replaced with fast-draining Dryfast foam.
The original blue and pink polyfoam layers of this exterior cushion acted like a sponge absorbing water. These were replaced with fast-draining Dryfast foam.

Closed-cell foam is generally much denser and firmer than open-cell foam. Its air bubbles are completely sealed (closed) off from those around it. These materials typically have higher compressive strength, because the air does not dissipate when the foam is squeezed or pressed.

Closed-cell foam is often used in flotation equipment and marine products, because it does not soak up water. It is also resistant to solvents, petroleum products and has antimicrobial properties to prevent the growth of mold and mildew. I have rarely used it for seating cushions, because it is not comfortable to sit on. However, I recently noticed that West Marine utilizes closed-cell foam in their bosun seats for support. We recently supplied an expedition vessel with 4-inch x 96-inch laminated layers of closed-cell foam. The sheets had to wrap over the length of 96-inch carbon fiber poles for protection.

Factor in comfort

When choosing foam for your cushion project, you generally need a balance of comfort, support and durability that is appropriate for your application. I recommend you have different foam samples on hand so your customers can evaluate their preferences during “sit tests.” This is especially valuable when working on custom projects.

Support: The thickness of the foam will affect its ability to support weight. Consider the weight of the person being supported. A larger person (more than 250 pounds) will need firmer foam.

Site measurement check (height and depth) for a cushion back wedge in Dryfast foam.
Site measurement check (height and depth) for a cushion back wedge in Dryfast foam.

Comfort: The softer the foam, the more comfortable it will be. Adding a Dacron®/fiberfill wrap topper is an excellent way to add a bit of comfort while still having a good supportive foam. The fiberfill also helps in “filling out” the sides and edges of a firm foam inside of the cushion covers. Since fiberfill compresses easily, cut your foam to size without compensating for the fiberfill; otherwise, you’ll end up with a boat cushion that has a baggy appearance.

Durability: Higher density foams have a much higher resistance to collapsing or bottoming out than lower density, inexpensive foams. Applications in which a cushion is used onboard a vessel should lean toward a higher density. Seating that is used only occasionally could use a lower density foam.

Additional considerations

Cost will obviously be an important factor in your choice. The price for upholstery foam is based on sheets of a specific size and weight as well as density. Some vendors will offer custom cutting and pricing for upholstery foam if you do not need the large pieces they normally sell. Expect the price to be slightly higher per square foot than if you bought it in larger sheets and then cut it yourself. Upholstery foam can range from $12 a sheet (sold in 24- by 24- by 2-inch sections) to more than $126 a sheet (sold in 6- by 24- by 84-inch sections).

Dryfast foam is available in soft #30, medium #50 and firm #70 densities. It can be cut into numerous shapes and sizes.
Dryfast foam is available in soft #30, medium #50 and firm #70 densities. It can be cut into numerous shapes and sizes.

Dryfast foam allows water to flow through it rapidly, making it ideal for exterior boat cushions as it does not retain water.Dryfast foam allows water to flow through it rapidly, making it ideal for exterior boat cushions as it does not retain water.

You will find out rather quickly that foam is available in various thicknesses. Also, some states have flammability laws that may lock you into using foam rated as fire resistant. Check with local and national suppliers for these requirements as well as samples, sizes, custom cutting options and pricing.

Ultimately, the “perfect” cushion foam for a given project depends on the primary use of the piece you are fabricating. Understanding an application’s requirements and your customers’ expectations is the best way to determine the ideal foam choice among the wide variety of options available.

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

New pilot roll bar cylinders incorporate a #70 Dryfast foam core with a 1/2-inch EVA closed-cell foam for added firmness.
New pilot roll bar cylinders incorporate a #70 Dryfast foam core with a 1/2-inch EVA closed-cell foam for added firmness.

Polyethylene foam is very rigid, yet it has excellent buoyancy and is typically used in flotation equipment and other nautical products.

EVA foam (ethylene-vinyl acetate) is a UV-resistant closed-cell foam that is very firm, yet has a soft rubbery feel.

FloTex foam is not UV resistant, yet it is often used for boat and yoga mats as it has a squishy texture.

Neoprene foam is a flexible, form-fitting and durable sponge rubber that provides good thermal and moisture insulation. It resists ozone, sunlight, oxidation and many petroleum derivatives and chemicals.

Finished pilot roll bar cylinders with Silvertex™ Vinyl covers.
Finished pilot roll bar cylinders with Silvertex™ Vinyl covers.

Additional closed-cell foams include: crosslinked polyethylene, polystyrene, gym rubber, polypropylene and Volara.

Memory foam quickly molds to pressure.
Memory foam quickly molds to pressure.

Polyurethane foam (polyfoam) is the lowest quality of foam and will often not return to its original form.

High density foam is sold primarily for mattresses, average sofa and chair cushions, interior boat cushions and camping pads. Some vendors offer high density foam (also called high resilient foam) which is used in expensive seating, including yachting and boating, because it is very buoyant
and resilient.

Memory foam is also known as miracle foam, wonder foam or viscoelastic foam. It has additional chemicals that increase its viscosity and density. It is often used as extra padding atop a mattress as it is soft, comfortable and compacts rapidly as it conforms to a shape. Developed for space shuttle seating, it is used for mattresses and is the most unique foam currently on the market.

Latex rubber foam is a non-allergenic foam. It was the first type of foam on the market and the longest lasting. It is used in top-of-the-line products including mattresses and cushions. It is of a better quality than high density foam.

Rebond foam excels in situations where other foams do not hold up to demanding daily use. It is highly resilient and stands up to high impact usage. Ironically, we are currently replacing rebond foam on pilot cylinder roll bar cushions because they absorb water, which seeps out from the seams and gets the crew wet. We utilized an extra-firm #70 Dryfast foam core layered with a ½-inch closed-cell EVA foam topper.

Dryfast foam allows water to flow through it rapidly, making it ideal for exterior boat cushions as it does not retain water.
Dryfast foam allows water to flow through it rapidly, making it ideal for exterior boat cushions as it does not retain water.

Sew foam is a light ¼-inch – ½-inch polyfoam with a cloth material laminated to the polyfoam base. This foam is great for creating a fuller, more cushioned look and feel, particularly under quilted upholstery in boats and car seats.

Shredded foam can be used in throw pillows, cushions, patio furniture, cushion backs and many other applications. It is available in regular shredded foam and shredded memory foam.

Dryfast foam is also known as outdoor foam, marine foam and open-cell foam.

This foam is highly recommended for outdoor use where moisture and water is prevalent and especially in marine cushion applications, because it does not absorb moisture like conventional foams. Here in the tropics it is widely used for boat cushions, boat mattresses and patio furniture. Whenever possible, cushions with Dryfast foam should incorporate a mesh material underneath to allow for water drainage.

The large, open cells of Dryfast foam provide a degree of airflow not present in other foams, allowing the foam to dry quickly, even after complete saturation. I recently became aware that the Dryfast foam formula is antimicrobial and helps suppress microorganism growth common in damp areas. Because of the antimicrobial formula and air circulation, Dryfast foam could also be used in home products like bedding for those with health concerns.

Density and firmness are two important measurements of foam quality. Knowing these factors will help you select the right foam for your application.

Different foam manufacturers may use different numbering or rating systems. In the common four-digit system, the first two digits specify the density of the foam and the second two digits specify the compression (firmness) of the foam. Firmness is measured in terms of ILD (Indention Load Deflection), also sometimes referred to as IFD (Indention Force Deflection).

Density technically means taking a solid chunk of 12- by 12- by 12-inch foam and weighing it in pounds. The denser the foam, the more resilient and durable it will be.

Upholstery foam is rated in density by a 2-digit number ranging from 18 to 35 with a decimal point between the 2 numbers. A #18 foam would be 1.8 foam. Here are some usage guidelines:

  • 1.8 (extra soft, used as back cushions)
  • 2.4 (comfortable soft, firmer back cushions)
  • 2.7 (soft, soft seat but firm back cushions)
  • 2.8 (medium soft, medium soft seat)
  • 2.7 (medium, medium seat)
  • 1.9 (medium firm)
  • 2.8 (firm, typically a 2-inch thick dining room chair)
  • 3.2 (extra firm)

Compression (firmness) is an ILD/IFD value represented by how many pounds it takes to compress the foam by 25 percent. A higher number means firmer foam and a lower number means softer foam.

Leave a Reply

Your email address will not be published. Required fields are marked *

Comments are moderated and will show up after being approved.