Plywood For Puddle DucksBy John Bridges #512 "Lavender Duck" (28es 18eo 20ea 43ad 50ar)
Marine grade plywood is the obvious answer if only cost were not a factor and most Puddle Duckers have opted for cheaper grades of plywood at about $20 per sheet compared to quotes as high as $95 for 1/4” Marine grade plywood.
Over the past several years members of CABBS and others have successfully used Lauan underlayment (with exterior glues) for building small boats such as Weekend Skiffs and Optimists. These have stood up well providing they were kept well painted and stored in the dry and out of the weather between use.
Unfortunately the quality of the Lauan plywood sold in many Lumber yards has gone rapidly down hill in the last couple of years. Home Depot and Lowes now stock a 5 ply Lauan with paper thin surface veneers. If this fails when bent over the stern bulkhead a weak cross grain will be left to produce an ugly far from smooth curve and a repair job probably needing fibreglass and Epoxy.
Other stores stock a 3 ply with a thick core of another species and thinner- than- traditional face and back. Even when painted this sort of plywood can be porous as water squeezes through invisible core gaps and knot holes. Note! Lauan is a collective name for various red species growing in tropical areas such as the Philippines. It is sometimes sold as Philippine Mahogany. Now the term is used even more loosely and I have even seen some “Lauan “ plywood with Oak as the face veneer
Home Depot also stock a product from Ecuador called SANDEPLY. It is well made with good quality veneers and adhesive. It is softer than Lauan, but has been used successfully for several Puddle Ducks.
Exterior grade Pine Plywood is readily available from most lumber yards and stores and has been used for many Puddle Ducks judging from the “Reached 3 D” Photos. The adhesive is good, but the quality of the veneers allows a lot of knot holes to be included in the core and back veneer. Incidentally the BC classification refers to the quality of the back and face veneers and not to the specie of wood. This fairly coarse grained softwood also does not weather well and even if kept painted will tend to allow the growth rings to separate in use and break the paint film over the course of time.
Another alternative being suggested is the use of DURAPLY. This is a heavy 5 ply construction made of Eucalyptus in Argentina. Again the outer veneers are paper thin and I suspect could give problems; but I have not tried it myself.. The adhesive used should give good results if used for bulkheads and without risk of de lamination.
ARAUCO PLY is another newcomer to the market, this time from Chile. It is made from the very fast growing Radiata Pine so for the greens amongst you it is definitely from a renewable sustained forestry source. The face veneer on the panels I have seen are beautifully smooth and free from defects but the back veneers contained large knot holes up to 3” diameter. It will therefore produce a good looking duck from the outside but you shouldn't look too closely at the inside. For the quality, the price is high. However a recent Forest Fire damaged the factory and this product is likely to be off the market for a while.
Finally some good news if you can get a group together to build perhaps 6 Puddle Ducks for a “Hatch” This way by placing a bulk order you can obtain a very attractive price from a company like BOULTER PLYWOOD bringing the price down to the neighbourhood of $40 which is admittedly almost double the price of the cheaper alternatives, but will result in a longer lasting Duck. How many years of use do you want to get from your duck? Are the kids going to grow up and lose interest? Are you going to want to replace your Duck with a newer one incorporating all those improvements you dreamed up in the winter months? Have you been bitten by the sailing bug and now want a bigger faster sail boat? Will it be protected from sun and rain during storage? You are the one that has to make the decision,
Whatever sort of plywood you use you should consider ways of protecting the edges. If these are exposed there will be a tendency for the end grain exposed to suck water into the cell structure faster than into the adjacent veneers. This will produce stresses and a desire for the laminations to want to separate.
It is always a good idea to cover the chines with a 4” wide strip of Fibreglass cloth impregnated with Epoxy Resin. This will also help to prevent abrasion when the boat is pulled up a sandy beach. Similarly I always try to cover any exposed plywood edges at the gunwale, or line where the sides and deck meet. A conventional cover moulding can be used here to good effect.
Some builders cover the entire bottom and sides with Fibreglass cloth and this will add to the water resistance, strength and appearance of the Duck but will also increase the weight.
One last comment regards painting plywood. You may find that paint will take better on one area than another of the same sheet. This is because the veneers are peeled from a cylindrical log and when this veneer is flattened what was the inner side will be stretched and develop small cracks. This is called the loose face and the other the tight face. No attention is paid to the placing of the tight or loose face when the plywood veneers are assembled for making into a panel of plywood. Paint will take better on the tight face especially if you follow instructions and use a good primer followed by a couple of coats of top coat.
Best results will be obtained by using a Marine Epoxy enamel, followed for durability by an oil based enamel. However many Puddle Ducks are resplendent in just a coat of Latex Exterior House Paint. As the English say “You pays your money and you takes your choice”
|Exterior grade Pine Plywood||$22|
|Store bought Lauan 3 ply||$24|
|Store bought Lauan Underlayment||$17|
|Single sheet Marine Ply||$95|
|Bulk purchase Marine Ply||$40|