Plywood

At the end of a street in a coastal suburb there sits a modest building. An observer glancing through a window would behold a scene of cheerful industry, complete with the competing sounds of power tools, recorded music, occasional laughter, and frustrated cursing (usually directed at the telephone).

Closer inspection would reveal five small craft under construction, along with a handful of repair jobs, spars, rudders and centerboards. If the watcher were astute, he or she would notice that although the boats are of differing design, there is a common thread – timber, epoxy, modest size, and traditional design.

The owner of the workshop tends to talk too much, but that is because he is passionate about small craft, and he is keen to encourage amateur construction. He believes that the most common impediment to successful amateur boatbuilding is not lack of space, nor is it shortage of money. He thinks that lack of confidence is the reason that the majority of projects remain unfinished, or are never even commenced.

Wandering through the workshop, the visitor will discover that many different forms of construction are compatible with the most commonly used materials. For example, each of the boats on the floor is being built differently – glued-lapstrake (clinker), strip-planking overlaid with double-diagonal ply, conventional stringer/frame, stitch-and-glue, and lapstrake ply in the dory form.

All of these building methods are suitable for the amateur working with a minimum of equipment, and with limited windows of working time. Admittedly, some of these methods are more complex than others, but all are within the realm of anyone who is willing to pay attention to detail, and to do the required homework.

Today’s builder has access to enormous reserves of information, and high-quality building materials are easy to obtain.

There is a commonly held belief that marine plywood is somehow inferior to natural plank stock, and that plywood boats are not the genuine article. A recent repair job demonstrated the error in this line of thought.

The boat in question was a beautifully built lapstrake (clinker) pulling boat of the Whitehall style. The planking was all of high-quality marine plywood, the plank laps having been glued with marine epoxy. As is normal with such construction, no bent frames or ribs were required, but she did have two small half-bulkheads fore and aft enclosing buoyancy tanks.

She had been hooked up on a pylon while slung in davits at the stern of a very large motor-sailer. As a result, she had suffered serious damage to her starboard side – the gunwale, clamp (or inwale), two planks and a laminated knee were all smashed, and absent from the boat. There was also damage to the planking on the port side, where a pad-eye had torn out a section of the sheer plank.

Amazingly, the remaining hull had retained its shape, and it was possible to carry out an economic, and complete, repair. Had this boat been built using natural timber planking, she would have been framed with dozens of bent ribs, floor timbers, and knees. The plank laps could not have been glued, and would have needed copper rivets or clench-nails.

I doubt whether a boat in this traditional way could have survived the same accident without loss of hull shape, and she would probably suffered terminal damage.

Ironically, the only parts of the repaired boat which remained doubtful were the fine copper clench-nails which had presumably been used to hold the laps during construction while the epoxy cured. Throughout the boat, there was evidence of paint cracking around these fastenings, and a subsequent path for water entry to the end grain of the planking. During examination of the damaged planking prior to repair, I was able to determine that the nails had added little or nothing to the damage resistance of the glued lapstrake construction.

Don’t try to save money by using exterior or structural plywood. The glue-line may be the same as that in marine ply, but nothing else is equal. The relevant standards for marine plywood (AS/NZ 2272 and BS 1088) specify allowable timber species, veneer tolerances, allowable defects and finish levels. As a result, the use of marine plywood will produce a stronger, longer-lasting and fairer boat. The money saved by using inferior grades of plywood amounts to a tiny fraction of the time and money invested in the boat.

Not all marine plywood is created equal. Some imported BS 1088 marine ply is of inferior construction, and suffers from wide variations in timber density. In my limited experience, I can thoroughly recommend all of the Australian Hoop Pine marine plywood (e.g.; Brims, Austral, Boral etc) made to AS/NZ 2272. Of the imported Pacific Maple marine plywood, Wayang Brand is of consistently high quality, and represents unbelievable value for money. Other brands can be good, but shop with great care.