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While many conventional woodworking techniques apply to this modern marine composite, there are key differences to keep in mind before making the first cut.
Photo, Mike Longman
If you own a boat built in the last few decades, chances are it’s got King Starboard on it somewhere. And that’s no coincidence. Thanks to its ease of use and nearly limitless lifespan, King Starboard has become a go-to marine building material and an ideal choice for fabricating many things, from doors to dashes.
Launched in 1988, King Starboard is a high-density polyethylene composite board that requires no maintenance and is impervious to everything from UV rays to harsh chemicals (think high-tech marine plastic). Unlike wood and other traditional boatbuilding materials, it never rots or delaminates, and it never needs to be sealed. And the bonus: It’s extremely easy for the average boater to cut, finish, and install using basic woodworking tools and techniques.
You can purchase King Starboard material in thicknesses from ¼ to 1½ inches, in sheets sized 54 by 96 inches (1½-inch material is available only in 48- by 96-inch sheets). While initially offered only in white with a matte finish, many other options now exist, including multiple colors, densities, and finishes. Partial pieces are often available at marine supply stores. If you need a complex shape, companies like Boat Outfitters in Central Florida offer CNC cutting services to fabricate precise parts based on your supplied templates or dimensions.
For DIY boaters, King Starboard makes it possible to construct a variety of boat upgrades at home, such as cutting boards, tackle stations, hatches, and swim platforms to name a few. But while it cuts and handles much like wood, King Starboard has some idiosyncrasies that make it quite different in some regards. Like any building material, you must take these traits into consideration to ensure your DIY masterpiece comes out the way you envision. So before you break out the T square and saw, keep these eight tips in mind when working with this unique and versatile marine staple.
1. Starboard expands and contracts with temperature variation.
This material expands and contracts at a rate of 1/32 inch per linear foot for a 40 F temperature range. For example, a 96-inch piece of material cut in a 60 F shop would expand by ¼ inch when its temperature rises to 100 degrees. While this may not seem like much, and it likely won’t affect many projects, it’s important to know when working on something with small tolerances, like a door within a metal frame.
2. To mark cuts, use a pen instead of a pencil.
Mark cut lines with water-based markers or pens, or even a china marker, as most household cleaners will remove the markings. Pencil is one of the few things that can stain King Starboard. 3. Most adhesives don’t work. King Starboard rejects most standard adhesives (including paints), so mechanical bonds are recommended wherever possible. If you must use an adhesive, consider these specialized products: Chem-Set 6105 Polyolefin Bonder, Lord 7542-AB, or 3M’s Scotch-Weld DP-8005. Many marine caulks will work for sealing gaps, but their adhesive properties will be greatly diminished. Another option for joining material is heat welding with a plastic hot air welder and polymer welding rods, but this requires some trial and error.
3. Most adhesives don’t work.
King Starboard rejects most standard adhesives (including paints), so mechanical bonds are recommended wherever possible. If you must use an adhesive, consider these specialized products: Chem-Set 6105 Polyolefin Bonder, Lord 7542-AB, or 3M’s Scotch-Weld DP-8005. Many marine caulks will work for sealing gaps, but their adhesive properties will be greatly diminished. Another option for joining material is heat welding with a plastic hot air welder and polymer welding rods, but this requires some trial and error.
4. It’s not load-bearing and can bend when improperly supported.
Despite its many benefits, King Starboard is more flexible than marine plywood and other composite coring materials. For this reason, it’s not recommended for structural uses like stringers, bulkheads, or large hatches that may be walked on. Thicker material flexes less, and supporting beams can be installed longitudinally beneath large spans to increase rigidity. But you may consider alternative materials for applications that will receive heavy foot traffic if proper bracing isn’t possible. When cutting large pieces, adequately support the material to avoid bowing that can pinch saw blades and produce inaccurate cuts.
5. It can melt.
Starboard softens at temperatures above 180 F, making it unsuitable for high-heat applications, such as inside engine rooms. This also makes it important to keep it away from heat sources in the shop, such as portable table heaters. Built-up heat from a slow-moving or dull saw blade can also cause the material to heat up and melt back on itself, so be sure to keep a moderately fast feed rate when cutting. The manufacturer recommends making straight cuts with a 50- to 70-tooth carbide blade. More specific tool and feed rate recommendations can be found on King Starboard’s website.
6. You can sand the edges but not the surface.
It’s OK to sand the raw edges to remove scratches, but don’t sand the top surface as it will permanently mar the molded-in matte finish and make future cleaning difficult. To clean up and soften hard edges, sanding works well, but using a router with a carbide round-over bit produces clean, smooth edges for professional-looking results.
Some Common Uses Of King Starboard
| Tackle drawers | Cup holders |
| Cutting board/rigging stations | Electronics mounts |
| Tool holders | Doors |
| Leader spool holders | Dashes |
| Hatch covers | Upholstery backing |
| Swim platforms | Transducer mounting pads |
| Tables | Backing board for deck hardware |
Get ideas and inspiration for your next project, more tips and tricks, and premade King Starboard components at Boat Outfitters. Follow all manufacturer instructions, recommendations, and good practices for each of these uses as well as others.
6. You can sand the edges but not the surface.
It’s OK to sand the raw edges to remove scratches, but don’t sand the top surface as it will permanently mar the molded-in matte finish and make future cleaning difficult. To clean up and soften hard edges, sanding works well, but using a router with a carbide round-over bit produces clean, smooth edges for professional-looking results.
7. Always drill pilot holes when using screws.
This material doesn’t compress like wood, so you must drill pilot holes close to the diameter of the screw shank you intend to use. If the application will be subject to large temperature variations (in the sun or freezing temperatures), drill oversize holes to prevent warping as the material expands and contracts. When using screws or thru-bolts, countersink them for a cleaner look, as the heads will not sink into the surface like many woods. For the ultimate finish, precut plugs will completely conceal the fasteners.
8. Cutting it makes a mess.
Cutting and drilling King Starboard creates stringy plastic shavings that are harder to disperse and dispose of than wood sawdust. In addition to environmental concerns, they can clog tool exhausts, cutting tables, and bits. To help mitigate the mess, use large drop cloths or cardboard sheets in your work area to capture shavings, or have a helper use a shop vac to capture them as they’re produced.
Alternative Marine Boards To Consider
While King Plastics introduced high-density polyethylene composite board to the marine market nearly three decades ago, comparable materials are now produced by several other plastics manufacturers. That said, the Starboard name has become the “Kleenex” of marine HPDE lumber, meaning, regardless of who makes it, there’s a good chance it will still be referred to as Starboard around the docks.
Here’s a look at a few products that are similar in composition, as well as some other composite boards with some differing characteristics that are also suited for marine use. Note that this list focuses on marine plastics and doesn’t include structural boatbuilding composites designed to be laminated with fiberglass like Coosa and Divinycell. Whichever material you choose for your project, carefully examine their specifications to make sure it will safely perform in your desired application.
- Seaboard With a composition similar to Starboard, Seaboard is another HPDE UV-stabilized marine composite sheet. An obvious difference is a slightly modified surface texture, but most other traits are comparable. Seaboard’s material offering is more limited than King Starboard’s, with fewer densities, colors, and finishes available.
- Marine HPDE Sheets Sold under the names of Marine Board, Boat Board, HPDE Marine Sheet, as well as others, these products also share many of the same properties of King Starboard, but this isn’t guaranteed. Especially with the influx of foreign-made goods, ensure the HPDE sheet material you choose will perform well in the marine environment, particularly in the presence of UV radiation. Before choosing one of these materials, take a good look at their material data sheets to make sure they’ll meet your needs.
- Expanded PVC Board Another popular marine plastic is expanded PVC board, a sheet material that uses a foaming agent to increase its thickness while reducing density. This makes it significantly lighter than HPDE but also less strong. Benefits include the ability to be glued, painted, and easily thermoformed, while drawbacks are decreased rigidity, a propensity to dent or scratch, and edge soiling due to its porous structure. Expanded PVC is commonly used as an upholstery backing, but other uses on boats exist, including trim and interior paneling.
- G10 Board G10 is a bit different than the materials listed above, as it’s not an extruded plastic, but it shares some common uses and characteristics. Made from layers of woven fiberglass impregnated with epoxy resin, G10 board is very strong for its weight, resistant to saltwater and UV light, and can be glued or painted. However, its rigidity makes it tougher to cut and drill, and its unfinished fiberglass appearance makes it less suitable for use where cosmetics are important. Because of its strength, G10 is often used as a backing material for hardware, seacocks, and rigging.