Straight boards are required to get precise project details, but this is only sometimes the case considering warping is a common wood problem. When boards warp, they bend towards a particular direction and lose their even layer. With uneven boards, finished projects are unappealing and would deviate from the correct dimensions.
One of the primary courses of a bowed board is the unequal water content in the parts of the wood. Depending on how they dry out the wood shrinks during the process and bends. If you have a bowed board, straightening it before using it for your project is vital.
Depending on which part of the trunk the board is cut from, the tendency of bowing rises as it moves to the other sections of the tree trunk. Bowed boards should be straightened before use to prevent a weak project, but before we see how to make these boards straight, let’s understand the concept of a bowed board.
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What is a Bowed Board?
Boards that are not flat are referred to as bowed boards, as their uneven surface can form a concave or convex curve. Sometimes, the unevenness may be a series of bends on the surface. A bowed board refers to the wood with a noticeable curve along its face.
With many different types of warping, bow warp is when the curve happens on the face of the board while the sides remain straight. In bow warp, the wood ends bend inwards or outwards to form a U-shape when viewed from the sides.
A bowed board will see the center higher or lower than the ends when placed on its face, making it challenging for your projects. It is difficult to align these boards when doing carpentry or construction, so straightening the wood first is the right solution.
Wood can have a slight or severe bow, which affects the repair method you can utilize. Woodworkers employ several means to fix bowed boards which may vary based on effectiveness and style. However, repairing the wood is rewarding as it becomes easier to handle, aligns correctly, and delivers impressive finished projects.
Causes of Bowed Boards
Bowed wood can occur naturally or induced by environmental factors. For naturally occurring bow, the tree growth pattern is often the culprit here as the tree seeks light and nutrients while avoiding obstacles. Here, we’ll highlight some causes of bowed boards that do not happen naturally.
1. Insufficient Drying
Moisture is the center of most bowed wood problems, with insufficient Drying among the causes. When wood dries, it shrinks as moisture leaves; however, when drying is inadequate, some parts of the wood will have more moisture content than others. This means some parts of the surface will shrink more than other sections leading to a curve.
Other times, wood is not dried correctly, leaving water content higher than the humidity. When this occurs, the wood will lose moisture when stored or even after building the project—however, this time in an uncontrolled environment which will often bow the board.
2. Changes in Humidity
More moisture in the wood makes the wood swell, while lower moisture content shrinks the wood, so high humidity increases the water in the wood and vice versa. It gets interesting when the humidity levels change frequently – the wood loses moisture and then gains liquid, all within a short period.
The sudden moisture loss and gain causes bowed boards as the humidity levels hitting the wood differ based on exposure. Places which rapid changes in humidity will see more warped wood.
3. Improper Storage
You can purchase straight woods for your project and store them, but see bowed boards when it is time to build your project. This is often due to poor storage practices employed when keeping the wood.
Storing wood requires the right environmental factors, which include lighting, humidity, and temperature, store lumber to prevent warping. Follow wood storage best practices to avoid damaging the wood during storage, especially when stacked correctly.
4. Exposure to Ultraviolet Rays
UV rays are rays from the sun, and they remove the lignin of wood, making the cell wall resilient. Wood loses its outward hardness without lignin, which means it can easily bend, especially with weight.
Overexposure to UV rays will break down and remove the lignin in the wood and make it weak. Its weakness will leave the lumber open to distortion with any slight pressure.
Tools Needed For Straightening a Bowed Board
You’ll need specific tools to achieve your bowed board’s straightening processes. Here are some of the tools to ready before embarking on this repair task:
- Heat lamp
- Pressing iron
- Paper towels
Methods For Straightening a Bowed Board
You can use several methods to straighten a bowed board ranging from simple tools to more specialized mechanisms. You can also use a combination of some of these methods for more efficiency.
1. Using Clamps or Weight
This method is sometimes called the pressure technique, which uses pressure to straighten curved boards. You’ll find this method particularly effective for thin panels that can bend. Ensure to get several clamps, damp paper towels, and a stable flat surface like a worktable.
Wrap the wood with a damp paper towel to keep a controlled environment within the wood, clamp the board firmly to the flat worktable and leave it for some days to straighten. Depending on the atmospheric temperature, cooler climes may take up to weeks.
2. Applying Water And Heat
Water and heat cause wood to warp, but they can reverse the issue in controlled environments. This method involves a heat source like a heat lamp and water applied on either side of the board to weaken and then reshape the wood.
Start by applying water to the concave side of the board while paying attention to the water quantity so as not to weaken wood glue for glued pieces. With the concave side properly wetted, turn it face down and apply heat to the convex side. The heat from a heat lamp is sufficient for this process.
Here is a similar method to the steam using the iron technique of straightening bowed boards; however, this uses sunlight as its heat source. To do this, wrap the curved wood in a damp towel with the concave side facing down. Leave it under the sun for days so the heat and moisture can repair the wood.
Steaming is an effective bowed board repairer when dealing with slight bows. For this technique, you need a steam source like the pressing iron and a damp towel. The moisture helps the heat to penetrate quickly, while the towel ensures the iron glides smoothly over the wood grain.
Lay the board on your flat worktable with the concave side facing up. You’ll need to spread a damp towel over the face of the board to facilitate the repair as you heat it with the iron. Go back and forth over the area with the iron to flatten it. With the wood flat, remove the towel and secure it between two flat boards using clamps.
5. Cutting The Board
Cutting the board is a little extreme and is hardly a straightening method but a way of getting straight wood, even from your bowed boards. If you work with smaller board pieces, this method will save you a lot of time trying to repair the wood.
Use a saw to cut the curved wood into smaller parts so each section is straight. This method is only applicable when you can use shorter board pieces.
Precautions And Safety Measures While Straightening a Bowed Board
The precautions you must take will vary depending on the method of straightening the bowed wood you use. However, here is a general take on safety measures and precautions to observe while repairing bowed board:
- Always sand your board after adding moisture to achieve a smooth surface. Liquid raises the wood grain.
- Techniques requiring the addition of water will need extra attention to avoid adding too much water.
- Ensure proper ventilation and lighting in your workspace while keeping the area clear.
- Select the most suitable technique based on the level of the bow and available materials.
- For methods that require heat, leave the board to cool down before handling it to avoid injury.
- Have a fire extinguisher nearby to protect against fire breakouts.
Boards will curve when exposed to certain environmental factors; while trying to rectify this problem, you may encounter some challenges. Here are the most common challenges and their answers:
Ans: Store in an area with excellent air circulation with minimal moisture exposure. Preventing humidity levels from changing rapidly will also help stop bowing.
Ans: Place the board on a surface and carefully observe its bow. It is a concave bow if it curves inwards, whereas outward bending is convex now.
Ans: Keep the wood in a well-ventilated area with minimal humidity changes and less exposure to moisture. Stack horizontally with a few other boards while ensuring an equal weight distribution.
Ans: Yes, jointers and planers can fix bowed wood; however, they tend to reduce the wood thickness. Using planers and jointers as repair tools will reduce the integrity of the wood.
If you expose wood to Moisture and subject it to improper or insufficient drying, it will bow. When this happens, you’ll need an effective technique to fix the curve. Heat, moisture, and clamps are popular materials for repairing bowed boards. You need to keep the safety measures in mind before using any method for straightening a bowed board.