After 30 years of saltwater use, the intricately curved anodized-aluminum trim along the cap of the open transom of my outboard-powered 21-foot center-console fishing boat was falling apart. Corrosion had eaten away at the metal, and its once-lustrous finish was now crusty and riddled with ragged holes.
I wanted to buy new trim from the factory, but production of the model had long ceased, and no replacement trim was available. Commissioning a custom piece of trim from a fabricator proved a bit too expensive for my budget.
Making my own seemed like the way to go. I started with 1-inch aluminum 90-degree angle stock for the straight run across the outboard edge of the transom where the liner meets the hull. On each end of the straight run, however, the transom curves upward to meet the rail cap. Bending the aluminum stock proved too difficult for me, so I turned to another material—1-inch PVC 90-degree angle stock—to adjoin and bookend the aluminum trim. The PVC is 3/16-inch thick, which is drillable and holds fasteners well, and the light-gray color complements my boat and blends well with the aluminum angle stock. It is available in up to 6-foot lengths for $21.08 each from grainger.com.
PVC angle stock is rigid and chemical-resistant but becomes malleable with the application of mild heat, and so it can conform nicely to inside and outside bends. It returns to a rigid state once it cools. Here are the steps I followed to shape one curving piece of trim, a process that needs to be repeated in a mirror image on the opposite side.
Skill Level: 2.5 of 5
Finish Time: Approx. 3-4 hours per each curved piece of trim
Tools and Supplies
- PVC 90-degree 1-inch angle stock ($21.08/6-foot length; grainger.com)
- 2-foot-long piece of two-by-six hardwood lumber
- Jig saw or coping saw
- Scrap cardboard and masking tape
- Pencil or marker
- Heavy-duty scissors and razor cutter
- Assorted vises and clamps
- Heat-resistant gloves
- Heat gun
- Miter box and fine-tooth back saw
- Bastard file
- Power drill and bit set
- No. 10 Phillips 3/4-inch-long truss-head self-tapping screws
- Phillips screwdriver
- Marine sealant
- Shop rags (to wipe away excess sealant)
Create a Template
If you have not done so already, remove the old trim. If it comes off without bending or breaking, you can use the old trim as the template to build a jig as outlined in the next step. If the old trim is not usable for this purpose, securely tape a piece of cardboard against the outside of the transom, then with a pencil or marker, carefully trace along the curve of the transom. Then remove the cardboard and cut carefully with pair of scissors or a razor cutter with a fresh blade along the line you traced. This piece of cardboard will serve as your template for building a jig to shape an inside curve in the PVC stock.
Build a Jig
I used a piece of two-by-six hardwood lumber about 2 feet in length to build the jig. Using the template, trace the radius of the curve so that it carries from the top edge of the wood to merge with the end of the piece of lumber. Next, use a jig saw or coping saw to cut carefully along the line that you drew, ensuring that the cut is as perpendicular as possible to the broad side of the board, thus creating a flat surface on the narrow edge for clamping and bending the PVC 90-degree angle stock. If not, you might have to sand the narrow edge of lumber to obtain a flat and level surface after the cut.
Tip: Depending on the radius of the curve you need to create, you can use a two-by-four (for a smaller radius than in this project) or a two-by-ten (for a larger radius) to build the jig.
Heat and Bend
Lock the jig into a vice with the broad side vertical and the curved portion on top and hanging over the edge of your work surface to allow the heated PVC to bend around the end of the board. Clamp one side of the PVC angle stock to the top of the jig so that the other side of stock is oriented upward (to accommodate the inside curve). Gently and slowly warm the PVC in the area of the bend with a heat gun. Keep moving the heat gun to avoid overheating or crinkling of the plastic. As it softens, guide the stock carefully around the radius of the curve until you have created the desired bend.
Tip: A pair of heat-resistant gloves allows you to shape the curve of the heated plastic without suffering any burns to your hands.
Fit and Trim
Let the angle stock completely cool with the clamps in place until the PVC angle stock becomes rigid again. Then unclamp it from the jig, and test-fit it to the transom edges to ensure that the newly curved piece follows the bend and fits flush on all surfaces. Assuming a good fit, also note where you need to trim the PVC stock on each end, marking both with a piece of masking tape. Cut the angle stock to fit with a miter box and a fine-tooth back saw. Leave at least 1/8 to 1/16 inch of extra length on each end. This will allow you to file down the last little bit of material for the tightest fit possible.
Read Next: How to Apply Clear Coat to a Fiberglass Boat
Drill and Secure
Refit the piece of trim in place—recheck your cuts to make sure everything fits well and flush. Then mark the best location for the mounting screws. Avoid screwing into the apex of the curving portion of the trim or along the vertical leg of the angle stock. Instead, secure it along the straight horizontal portions of the PVC. Drill pilot holes with a No. 21 bit through the trim and into the transom cap, and use stainless-steel 3/4-inch-long No.10 Phillips truss-head self-tapping screws. Bed the surfaces and pilot holes with marine sealant. Don’t overtighten the screws so as to prevent cracking the plastic.
Tip: Before attaching the replacement trim, fill in and seal the old screw holes from the original trim. In this case, I filled in the old holes with Marine Tex.
