April 10, 2015

What is the difference between VENDIA marine plank and plywood?

There are certain similarities and differences between VENDIA marine plank and plywood. Few weeks ago we wrote (link) about the differences between sliced and peeled veneer. VENDIA is always made of sliced veneer and this is one of the most important differences between VENDIA and plywood. But there are also other differences, for example structure, glue, raw material, form of the final product, and finishing.


Structure


Glued structure is the common feature of VENDIA and normal plywood but there are also essential differences. Plywood is completely made of cross-laminated veneers, which means that every second veneer is lengthwise and every second is crosswise veneer. The idea of cross-lamination is to reduce the tendency of solid wood to crack and also to make the panel stiff across all directions. The crack resistance, longevity, and longitudinal stiffness of marine plank are important features when building a wooden boat. Many boatbuilders prefer VENDIA to the plywood because VENDIA has the maximized longitudinal stiffness whereas plywood is stiff across all directions. VENDIA marine plank has crosswise veneers only the amount what ensures the crack resistance of the marine plank. Depending on the thickness, there are 1-2 crosswise veneers in VENDIA. This structure ensures the crack resistance but keeps the other good characteristics of solid wood and increases the longitudinal stiffness of the marine plank. Plywood is made of veneers that have the same thickness, so after the calibration the face veneer will be the thinnest. Compared to VENDIA the normal plywood is harder to work with because of the thin face veneer and the crosswise veneer right below the face veneer. In VENDIA the face veneer is always the thickest. 

The structure: VENDIA on the left and softwood plywood on the right. (The picture on the right borrowed from: lahdenmaki.fi)


Glue 


Commonly used glue in plywood panels is water resistant, brown phenol resin adhesive. In VENDIA we use water resistant, colourless MUF adhesive (melamine-urea-formaldehyde). MUF adhesive is commonly used for example in traditional marine plywood, so it is very suitable also for nautical environment. Clear advantage of MUF adhesive is its’ neutrality. When working with plywood the phenol resin adhesive appears as a dark seam in the edges and joints of the plank because of the plywood’s structure. Colourless MUF adhesive is in turn indistinguishable. 

birch plywood
Commonly used glue in birch plywood is brown phenol resin adhesive.

vendia, wooden boat, boatbuilding, marine plank, MUF
In VENDIA we use colourless MUF adhesive.


Raw material


Raw material of VENDIA marine plank is Finnish, old-grown pine butt logs, which means that the raw material is the same high-quality wood as traditionally used in wooden boatbuilding. The vast majority of plywood is manufactured from lower quality raw material, which weakens the longevity of plywood when considering boatbuilding. Wood species have also an impact on the longevity. Birch and Okoumé are faster decaying species while conifers are generally more resistant to decay.


Form of the final product


The fact that VENDIA looks more like natural solid wood and plywood doesn’t, results mainly from the differences between sliced and peeled veneer. Also the form of the final product affects in the appearance. Plywood is manufactured and sold in large sheets while VENDIA already in finished planks. Each VENDIA marine plank is handmade and sliced veneer is centralized in the middle of the plank according to veneer’s pattern. 

Spruce plywood on the left and Okoumé on the right.

vendia, wooden boat, marine plank, boatbuilding


Finishing 

There is also a difference in the features of impregnation. In absorption test of impregnating agents, the absorption of impregnation agent was 1 ½-2 –fold better in VENDIA than in birch plywood.

2 comments:

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