Impregnating agents and VENDIA

Impregnation of wooden boat is important to guarantee the decay resistance and longevity. We have made an absorption test of impregnating agents to see how VENDIA marine plank reacts with different impregnating agents. The test was made in accordance with Cobb-test, in which the impregnating agents were absorbed 168 hours (seven days) into the test materials. The test materials were normal structured 9 mm VENDIA (called evo1 in the pictures), 9 mm VENDIA Pro (called evo2 in the pictures) and birch plywood. The tested agents were Owatrol, Hempel, linseed oil mixed with zinc naphthenate and tar.

To increase the moisture and decay resistance the impregnating agent should be absorbed deep into the marine plank. For effective absorption it is essential how easily the impregnating agents can penetrate the glue layers of the marine planks or plywood.

The test results showed that all the tested impregnating agents were absorbed into VENDIA marine planks (red and blue bars in the picture) better than into birch plywood. The MUF adhesive used in VENDIA marine plank let the impregnating agents through whereas the phenol formaldehyde used in birch plywood didn’t have the same feature. In practise this meant that the impregnating agents couldn’t be absorbed deep into the plywood.

The absorption test results of tar were interesting – tar wasn’t absorbed into the wood as well as generally has been thought. The absorption of the tar used in the test into VENDIA or birch plywood was low. The tar only formed a layer on the marine plank’s surface which became thicker when the treatment was repeated. If tar is used it should be greatly diluted to enable proper absorption into the wood.

When impregnating a wooden boat, time and diligence are the key factors, no matter what impregnating agent is used. To increase moisture and decay resistance it is essential to have multiple treatments and a lot of time. The best result can be achieved by spreading the impregnating agent carefully and giving enough time for absorption between the treatments.

The MUF adhesive used in VENDIA marine plank

Phenol formaldehyde adhesive is the most commonly used glue in marine plywood. It is water-resistant and commonly used in plywood industry. Originally the phenol formaldehyde adhesive is colourless but effect of air and oxygen convert the phenol into brown. That is why the dark glue seams stand out in plank board joints and edges if wooden boat is made of normal marine plywood.

When developing VENDIA marine plank our goal was to create a marine plank that is beautiful and durable. We wanted to get rid of the dark seams of normal marine plywood. When we started to develop VENDIA marine plank, one of the criteria in addition to the water-resistance was that the glue should be colourless. Our choice was MUF adhesive because of its colourless feature, water-resistance and strong references. MUF adhesive is commonly used among high-quality marine plywood producers.

The MUF adhesive is a two-component glue including adhesive and hardener. It is Weather Boil Proof (WBP) glue and meets the requirements of British Standard 1088 for marine plywood. The glue has passed the boiling test, which means that the glue must withstand boiling of 24 hours. In addition to boiling test, we have also made the absorption test of impregnating agents. In the test we had Owatrol, Hempel and linseed oil mixed with zinc naphthenate and it proved that all these impregnating agents were absorbed well also through the glue layers.