Structural-Grade Fiberglass Composite Panel

Coosa Board Bluewater 26 is a structural-grade fiberglass composite panel engineered to replace plywood in demanding marine, construction, and fabrication applications. 

Manufactured from high-density closed-cell polyurethane foam reinforced with continuous strand fiberglass and woven roving, Bluewater 26 delivers the highest strength-to-weight ratio in the Coosa product line. 

At 26 lbs per cubic foot, Bluewater 26 is over 30% lighter than plywood while offering superior stiffness and structural integrity. It will not absorb water, rot, swell, or develop mildew — making it the preferred composite panel for transoms, bulkheads, and any application where structural performance and moisture resistance are both critical.

For non-structural or semi-structural applications where weight savings are the priority, compare it to Bluewater 20 to choose the right density for your build.

Coosa Bluewater 26 vs. Coosa Bluewater 20

Bluewater 26 is the denser and more structurally capable of the two Coosa composite panel options. It’s the right choice when the panel will bear load, resist impact, or serve as a direct plywood replacement in a structural role. 

If your project is non-structural or semi-structural — hatch lids, wall panels, slide-outs — Bluewater 20 composite panels provide a lighter and more economical alternative at 20 lbs per cubic foot. For transom replacement, bulkhead construction, heavy-duty flooring, and direct plywood substitution, Bluewater 26 is typically the right call.

Common Applications for Coosa Board 26

• Transom boards and transom replacement 
• Bulkheads 
• Direct plywood replacement (structural) 
• Boat deck flooring and floor panels 
• Stringers 
• Heavy-duty construction and marine fabrication 
  

Bluewater 26 is available in 1/2” and 3/4” thicknesses and sold in 2’ x 4’ panels, with quantity discounts starting at 5 sheets.

Note: Coosa Board is not currently manufactured in 4’ x 8’ sheets.

For bonding, laminating, or sealing your installation, browse marine resins and coatings that pair well with composite panels.

Coosa Board 26 FAQ 

What is Coosa Board? 

Coosa Board is a brand of fiberglass composite panels used as a lightweight, non-absorbent alternative to marine plywood. The panels are made from closed-cell polyurethane foam reinforced with fiberglass, making them resistant to water, mildew, and rot.

What is Coosa Board made of? 

Coosa Board is constructed from high-density closed-cell polyurethane foam reinforced with continuous strand fiberglass and woven roving. This construction provides strength comparable to or exceeding plywood at a fraction of the weight.

How does Bluewater 26 compare to plywood? 

Bluewater 26 is over 30% lighter than marine plywood and offers superior stiffness and compressive strength. Unlike plywood, it will not absorb water, swell, delaminate, or develop mildew — making it a permanent solution in marine and high-humidity environments.

What’s the difference between Bluewater 20 and Bluewater 26?

Bluewater 20 is lighter (20 lbs/ft³) and more economical, best suited for non-structural and semi-structural applications. Bluewater 26 is denser (26 lbs/ft³) with higher compressive strength and stiffness, making it the structural-grade option for transoms, bulkheads, and direct plywood replacement. Both are available in 1/2” and 3/4” thicknesses. 

Can Coosa Board be used as a transom replacement? 

Yes. Coosa Board—especially Bluewater 26 and Bluewater 20—is widely used for transom replacement because it won’t rot or absorb water like wood. Bluewater 26 is the preferred option for transoms due to its structural-grade density and compressive strength.

Is Coosa Board available at Home Depot or Lowe’s? 

Coosa Board is a specialty composite panel and is not typically stocked at Home Depot or Lowe’s. Fibre Glast carries it in stock with volume pricing and ships direct.