Boat trailers use long support rails called bunks to cradle and transport boats. Traditionally made of wood, bunks are increasingly constructed from composite materials that offer benefits over wood. This article will examine the advantages of composite bunks, product options, and tips for choosing the right composite bunks for your boat and trailer.
Benefits of Composite Bunks
Composite bunks made from materials like fiberglass, carbon fiber, or HDPE offer significant advantages over wooden bunks:
- Longer lifespan – Composites resist rotting, cracking and insect damage better than wood.
- Reduced maintenance – No need to periodically replace cracked boards, re-stain, or re-carpet.
- Lighter weight – Composite bunks weigh less than wood, reducing trailer load.
- Consistent surface – Materials like fiberglass and plastic provide a uniform, smooth surface that protects boat hulls.
- Moisture resistance – Composites won’t absorb water and warp like wood.
- Easy to clean – Smooth bunks just need occasional washing versus carpeting upkeep.
- Stylish appearance – Glossy composites look attractive on trailers.
For boaters frustrated by constantly replacing damaged wood bunks, composites provide a durable low-maintenance alternative.
Types of Composite Bunks
There are several types of composite materials used to construct bunks:
- Made by layering fiberglass cloth and resin
- Custom molded or formed into standard lumber dimensions
- Provides very smooth finish that won’t damage boat hulls
- Naturally glossy appearance or can be gel coated any color
- Constructed from HDPE or similar durable plastics
- Extruded or formed into bunk boards and shapes
- UV-stabilized and impact resistant
- Recycled plastic options available
- Can be textured or grooved for traction
Carbon Fiber Bunks
- Made from woven carbon fiber sheets in epoxy resin
- Extremely strong yet lightweight
- Low friction surface protects delicate hulls
- High cost limits use to specialized applications
Composite Blend Bunks
- Mix of materials like fiberglass, plastic, foam and wood fibers
- Balances strength, weight and cost considerations
- Often made into core-filled boards like Wahoo bunks
There are multiple composite options to suit everything from small boat trailers to mega yacht transport.
Bunk Configuration and Shape Options
In addition to materials, consider the bunk configuration and shape needed for your boat:
Number of bunks – Two or three bunks are typical for most trailers. More widely spaced bunks provide better support.
Bunk width – Wider bunks spread load over more hull surface. Minimum 2″ wider than the boat keel.
Bunk length – Must fully support the boat’s length. Allow overhang for launch clearance.
Bunk shape – Flat, curved or V-shaped to match the hull. Custom shapes provide best support.
Bunk height – Set high enough for adequate road clearance. Adjustable bunks allow custom heights.
Bunk caps – Hard plastic caps on bunk ends provide smoother launch/retrieval and protect hull finishes.
Measure your boat and analyze its hull shape to select the ideal bunk design. Work with a marine trailer company for the best configuration.
Top Composite Bunk Brands
Popular manufacturers of composite boat bunks include:
- Offer fiberglass, HDPE, carpeted and bare composite bunks 
- Custom sizing and shapes available
- Bunk hardware like hinges, brackets and end caps
- Used by major boat and trailer brands
- Manufacture HDPE plastic bunk boards and kits 
- Custom extrusions for unique hull shapes
- Pre-drilled for easy DIY installation
- 25 year warranty against cracking, rotting
- Composite blend boards with wood core 
- Offer carpeted and bare boards
- Available in standard or custom dimensions
- Made in the USA
These and other brands offer a wide selection of composite bunks for DIY or professional installation.
Carpeted vs Bare Composite Bunks
Composite bunks are available either bare or with marine-grade carpet attached:
- Provide cushioning for boat hull
- Grip hull surface to prevent shifting
- Softer launch and retrieval
- Carpet reduces abrasion
Bare composite bunks
- Easier to clean and maintain
- Consistent smooth surface protects hull
- Won’t absorb water like carpet
- Visually appealing glossy finish
Consider ease of maintenance versus hull protection when choosing bare or carpeted composite bunks. Carpet can be added to bare bunks later if desired.
Tips for Selecting Composite Bunks
Follow these guidelines for choosing the best composite bunks:
- Carefully measure your boat’s dimensions and hull shape
- Consider number of bunks needed for proper support
- Factor in desired overhang for launch/retrieval clearance
- Match bunk width to the boat keel width or wider
- Determine necessary bunk height for road clearance
- Select composite material that fits budget and needs
- Choose bare or carpeted bunks based on preferences
- Look for UV protection if bunks are exposed to sunlight
- Consult with your trailer manufacturer for recommendations
Taking measurements and analyzing your boat’s design ensures you get composite bunks engineered for optimal support, protection and ease of launching.
Installing Composite Bunks
Composite bunk installation involves:
- Removing old bunks and preparing the trailer frame
- Mounting new composite bunks at the proper height and width for the boat
- Checking for level placement and adequate hull clearance
- Attaching carpet or non-skid pads if desired
- Testing the fit with the boat on the trailer and adjusting as needed
- Adding end caps for smooth launch/retrieval
For DIY installation, follow the manufacturer’s instructions. For extensive work, professional trailer technicians can complete the job.
Properly installed and maintained composite bunks will provide years of trouble-free boat support and protection during transport
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