Laminated hulls

APPLICATIONS: Laminating

Wood is especially strong when thin layers can be glued together, forming laminated members. Cutting lumber into thin layers also allows selective use of lumber so that ordinary defects, such as knots, shakes, checks, and grain deviations can be minimized or eliminated. This results in stronger members or members of smaller size for similar strength compared to members taken from single pieces of wood.

In addition, laminating can be done for aesthetic effect. For example, beautiful laminated members can be made by alternating grain patterns and colors. Such versatility allows the builder to select lumber in more readily available sizes, instead of having to locate larger sizes of lumber that may not be available or available only at high cost.

Gluing up laminated members (other than making laminated hulls as noted in the following) involves basically the same procedures as previously described (see Glue Application Methods) using the 2-step process. Either "POXY-GRIP" or POXY-SHIELD® can be used. However, as long as mating surfaces fit firmly and closely, the use of thickened POXY-SHIELD® is not necessary other than for convenience to prevent excessive running. Completed members that are to be encapsulated must be coated afterward with at least 2 coats of POXY-SHIELD® (see heading, Coating & Encapsulating).

LAMINATED HULLS

A laminated hull is any hull made by bonding thin layers of wood, wood veneers, or plywood together. These include designs with planking systems often referred to as "cold molded" or double or multi-diagonal planking. Double diagonally or multi-diagonally planked hulls use solid wood veneers or plywood cut into strips, successive diagonal layers oriented at 90^o angles to the preceding layer. Any design where a wood/epoxy composite system is specified using these layers to form the planking skin is made easy by using POXY-SHIELD®.

Staples, nails, or any suitable type fastenings are used to hold the layers in place against the framework and subsequent laminations. With laminated hulls, many or most of these fastenings can be removed after bonding each of the layers in place. In this case, ordinary cheap steel staples or nails (frequently driven pneumatically for speed and simplicity) can be used. Small "washer blocks" of thin wax-coated plywood, pieces of cardboard, strips of thick plastic, etc., are usually used between the hull surface and fastening head to prevent the fasteners from being driven too far into the wood; this makes the fastening easier to remove. Remember, if waxed plywood is not used for washer blocks, or a parting film is not used under the fastenings, they may stick after the resin cures.

A basic premise with the GLEN-L Epoxy Encapsulation System is that every surface of every member in the boat be coated with POXY-SHIELD®. Does this mean the surfaces of layers that will be within the planking skin laminate should be pre-coated? Our feeling is that pre-coating of surfaces that will be concealed in the planking skin is optional, but not necessary. While there certainly is no harm in this, it can add to the complexity and difficulty of the procedure, requiring considerably more time plus more resin. Usually the actual adhesive bonding layer used will provide sufficient protection within the layers.

When building laminated hulls, use thickened POXY-SHIELD® between all layers as the laminating adhesive. Any of the fillers can be used, however, don't use too much filler if you intend to use a roller for application (some prefer applying the resin with a notched trowel). We prefer the use of Microspheres or Silica for this filler. Although #1 Silica is more expensive you may wish to use it if you have a problem with the mixture running on vertical surfaces. The use of Microspheres or Silica expands the resin, forms a lightweight adhesive, fills gaps and indentations well, and applies more smoothly than Fibers when added to form the right consistency. The mixture is preferably applied to both mating surfaces.

The subject of building hulls using these methods is involved and beyond the scope of this manual. Several texts exist concerning the "cold molded" method (using both plywood and solid wood veneers), and the builder who needs more information is advised to read these. For information, contact the designer of your boat or GLEN-L Marine Designs for current texts recommended on this subject.

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