Laminated wood panels are not a modern invention; layered wood has been found in ancient Egyptian tombs.  Musical instrument makers have used laminated wood since mid-1850.  It has been popular in boat building since the 1930’s, and World War II pushed the advance of plywood in both boat and aircraft construction.

Today, designs for plywood boats are abundant.  Fast becoming the material of choice for amateur builders for a variety of building techniques – tack-and-tape, stitch-and-glue, glued lapstrake – all offer a wide range of hull shapes.  Each year, thousands of amateur builders construct kayaks, canoes, small sailboats and rowboats from marine plywood.

What makes marine plywood different from construction grade plywood?  Marine plywood is specially made plywood that is designed to resist rotting in a high-moisture environment.  The advantages of marine plywood are durability, strength, workability and resistance to warping.  Truly the only disadvantage is the price in comparison to standard plywood.  A builder using inferior plywood risks the cost of not only the wood and other materials, but most important, the labour of the project.  In this instance, you do get what you pay for; the price for marine grade plywood is good insurance.  

It is important that any plywood used for boat construction be “balanced”.  This means that there is a centre-ply with an equal number of veneers on either side; and the corresponding veneers are all the same thickness.  With cross laminations, marine plywood gives high strength and stiffness to weight ratio, and high dimensional stability.  Resistance to impact damage is key.  High quality finishes can be accomplished.  And as with any wood, whether solid or laminated ply, care should be taken in applying protection, especially to the edges.   

International standards for grading marine plywood
There are few international standards for grading marine plywood.  Most commonly seen is marine plywood evaluated by Lloyd’s of London as compliant to British Standards.  The standard is associated with Lloyd’s of London as they perform the testing of products to this standard.  Although the initials BS are for “British Standard”, the finished product does not have to be “British made”. Two frequently seen marine grades are BS1088 and BS6566.  BS6655 standard has been withdrawn and replaced, but because this term is understood in the industry, it is still referred to.

• Domestic (American) marine plywood is made to standards formulated and monitored by the American Plywood Association (APA).  It is not a US government standard. 
  
  
• BS1088 sets down requirements for wood species, construction, lay-up and adhesives used.  These specs apply to plywood produced with untreated tropical hardwood veneers that have a set level of resistance to fungal attack.  Resistance to biodeterioration determines the wood species chosen.  Plies are bonded with WBP phenolic or melamine formaldehyde containing a phenol. BS1088 standards also limits the number of defects allowed in the face and inner plies.  There should be no voids or open splits, bubbles, checks or grain runoff on the face veneers.  The list of standards goes on.  BS1088 also requires that the manufacturer test occasional panels to ensure these standards be consistently met. 
  
  
• BS1088 uses more select material, and is a superior panel to BS6566.  However, having said that, there are many rough and tumble projects that can “afford” to use this lesser marine grade product.  Ensure you are using the product appropriate to your project. 

Boats are synonymous with pleasure; whether in the creation of the craft or in the on-the-water pursuit.  Enjoy your passion!!