Courtesy Supersede Textured Supersede Marine Board provides a quickly installed, rot-resistant cockpit sole for this welded aluminum Thunder Jet model.
Manufactured sheet goods are essential to modern construction practices. Few residential or commercial structures built today are completed without a significant investment in plywood, OSB, MDF, sheetrock, melamine board, etc. While the compound curves and oblique angles that define boats make flat 4′ x 8′ (1.2m x 2.4m) panels a little less useful than they are in square-cornered terrestrial buildings, a refined menu of sheet good offerings have become indispensable to boatbuilders. Starting with plywood in the 1930s, sheet goods have served in myriad marine applications from structural members to hull, cabin, and deck sheathing, core material, and interior panels and components. Indeed, easing construction of hulls from plywood sheets informed a shift in boat design through the mid-20th century to embrace the cylindrical and conical curves coupled with hard chines that are all easily formed from developable surfaces.
Even as molded glass reinforced plastic (GRP) came to dominate recreational boatbuilding starting in the 1960s, quality marine-grade plywood remained essential to the industry. But as the quality of available plywood has diminished and the price has risen, many builders have been casting about for alternative sheet goods to build with. As the fleet ages, service yards—challenged by the need to replace plywood core and reinforcements in composite hulls and deck (especially in transoms) with rot-resistant structural material—have turned to fiberglass reinforced closed-cell foam alternatives like Koosa board, which has admirable material properties but a price that makes it impractical for many applications.
At IBEX 2024, Arizona-based Supersede introduced a new option for boatbuilders looking for plywood alternatives. According to company co-founder Sean Petterson, the genesis of the product was this question: “How do we replace plywood with something that’s a little more sustainable and make it a little better performing?”
Focusing on the sustainability first, the team looked to recycled plastics, of which there is an abundance in raw form. They chose polypropylene for availability, affordability, and its capacity to be extruded into uniform sheets of any length, which means custom lengths of 4′ wide material are available at the same price per square foot as stock 4′ x 8′ sheets. And “because it’s made out of recycled polypropylene, it’s going to be 100% waterproof,” Petterson said. The design and market goal was to create “a drop-in replacement for where you’re using marine ply today,” he said.
Courtesy Supersede In this pontoon boat deck built with Supersede extruded polypropylene, Marine Board is an easy replacement for structurally equivalent marine plywood.
During product development in 2023, the team talked to boat builders, repairers, and sales teams and were surprised at how much all players knew about the plywood and other sheet goods they were using. Petterson read the broad knowledge about the flexural modulus, fastener retention, water absorption rates, density, and impact strength as symptomatic of “an industry looking for solutions.”
To match weight and other material properties of marine plywood, the cross section of a sheet of supersede is a grid of extruded plastic with smooth surface sheets on top and bottom connected by pillars or web sections, like a series of closely spaced I-beams set at slight angles to enhance shear properties. So, each panel is shot through with roughly triangular void space that Petterson said can be sealed on the ends or on cutouts with banding machines or tape, especially if you plan to vacuum bag it as a core material in a composite structure like a deck or transom.
Courtesy Supersede The cross section of a sheet of supersede paneling reveals the open interior structure that keeps the panels lightweight.
He said the compression strength of Supersede is twice that of most marine plywood, and fastener retention is 1.7 times that of wood. He noted that metal screws winding through the extruded polypropylene tend to seal tightly with the material precluding water intrusion. But if water gets into some of the voids, he said there’s no structural penalty as there’s nothing to rot, and freeze-thaw cycles do not compromise panel integrity.
As for adhesion of coatings, carpet, decking materials, wood veneers, or composite laminates to the plastic, Petterson said there are measures that need to be taken to optimize it. Builders can specify corona treatment (a process Petterson describes as shooting the panel with a storm of tiny lightning bolts) of one or both faces of a panel. The result is a respectable dyne rating of about 50, which allows for good surface adhesion, according to Petterson.
Courtesy Supersede The cockpit support structure of a welded aluminum Thunder Jet awaits installation of the Supersede paneling that will complete the sole.
The other alternative that’s not possible with plywood is to leave Supersede panel uncoated. It is rot resistant and UV stable, so with a hot roller treatment that can texture the panel with a nonskid grit pattern or faux wood grain, the raw surface can serve as a deck or cockpit sole.
Petterson noted that the material is easy to work with, generating little dust, never splintering, and yielding fully recyclable production waste. “You take your offcuts, put them in a bin, then on the next truck on the way back here. We’ll weigh it and give you a discount on your next order,” Petterson said.
Product consistency is maintained through consistent lab testing of every batch of polypropylene material that comes in for production use. He noted that because sources of production waste vary, Supersede tests each batch for material properties and adjusts the content with their own amendment materials to get it into specification before generating the pellets for extruding the panels.
Currently the Marine Board is available in ½″ and ¾″ thicknesses, but Petterson said thinner options are in development.
Courtesy Supersede These Supersede samples illustrate the existing thickness and pigmentation options for the board. More are in development.
Following Supersede’s introduction to the marine market in 2024, Petterson said they are working with upward of 30 marine companies (mostly OEMs) and have distributors in North America, the Caribbean, and Europe.
Supersede, 21500 N. 8th Way, Suite 140, Phoenix, AZ 85024 USA, tel. +1-631-903-4965, [email protected]
