Plywood is a strong material made out of many wooden sheets. This is also used as engineering material. Though not very attractive, it is extremely strong for boat making. Depending upon its thickness, plywood can resist damages.
Plywood is used in different applications including boat construction. This is a wood product made from many sheets of veneer or plies. It undergoes the process of pressing together, glued and grains going in multiple directions.
Plywood is a high quality wooded sheet that has resistance to:
•cracking
•breaking
•twisting
•warping
•bending and
•shrinkage
In boat building, it is not practical to discuss all types of lumber. There are specific woods common in each country yet imported lumbers can also be found.
The common rule:
Any lumber in the locale that becomes successful in boat making can be applied.
Although there are some characteristics of the wood that need to be considered like:
•weight
•strength
•decay resistance
Look for wood that will match these requirements. If the boat designer wants a lightweight lumber like Sitka Spruce, do not give him white oak. It would double the weight of Sitka Spruce. White oak weighs heavier. Weight will affect the performance of the boat. You can use woods of similar weight and strength as substitute. They must also prove to be successful for boat making.
In buying Lumber
Determine first the required thickness of wood material to be used. The designer must note in the plan or material listing the specific lumber thickness. The thickness of the lumber is usually the first dimension. It is called the sided dimension. For practicality, the designer must give specific standard for lumberyard dimensions like:
•1” material refer to four quarters or
•1” material to 1” NET
When asking for a quotation, note these to your lumber supplier. You can also purchase just one big board and re saw them into desired pieces to save money.
Example:
Specified three 1” x 2” members, group these together. You can cut this from one big board sized 1” x 6” + extra allowance.
To re saw this board, you will need a power saw. It can be a:
•table saw or
•radial arm saw
In Selecting Lumber
Select the actual board to use after deciding on the type of lumber. Wide width is mostly preferable. Long length is advantageous. When the plan needs a member 20’ long but the available is only 12’, it can be formed by:
•Scarf joint or
•Butt joint
The builder must check his plan to assure that the joint be found at a strategic location.
Example:
By using a butt joint and butt lock, a two 10’ length can be used to make 20’ member. It is probable that the joint be found in the location of the hull. It has stern curvature that will make the joint more difficult to make. On the other hand, 12’ and 8’ length makes 20’ member also. It could be manipulated to locate the joint outside curvature. It will simplify the joint.
To select appropriate material, the builder must check all choices against the plan. The lumber for boat making project must be seasoned. It means removing moisture from the wood. It is done to improve its purpose.
The two methods of lumber seasoning are Air drying and Kiln drying. The characteristics of the two methods:
1. Air drying process
•It is the best process
•It requires year or more of drying time
2. Kiln drying process
•It is acceptable if done correctly
•It can leave more moisture in the wood if rushed or
•It removed too much moisture in the wood that makes it brittle if cooked
If it is cooked, the wood will no longer be suitable for boat building. And, if the wood contains much moisture after seasoning, the wood will shrink or split. If possible, select boards that have vertical grain also called edge grain or rift sawn stock. These boards expand and contract without too much distortion.
Look for lumber defects
Defects must be checked. People confused with blemish as defects. Blemish affects only the appearance but not the service it gives. A defect is an irregularity on the wood that may affect strength. It is sometimes limited to a certain area only. It can be cut away.
Two types of defects:
•Those caused by seasoning
•Those caused by the way of tree growth
Seasoning defects are caused by removing moisture and shrinkage. Common seasoning defects include checking and warping. Natural defects caused by growth depend on the species of lumber.
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