Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Project design and construction
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Project design and construction
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Subject: Wood-Work
Class: Senior Secondary 3
Term: 1st Term
Week: 13
Theme: Design And Construction
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Design to meet given specifications, and design problems. Make working• drawing, drawings of designs Prepare cutting lists and bills of materials Construct the project and apply wood finishes.
Design And Construction for communication in technical fields.
Purpose: To clearly communicate the exact size, shape, and features of a project, enabling precise marking out, cutting, and assembly.
Types of Drawings: Orthographic Projections: Show the object from different views (e.g., front, top/plan, end/side views) as if looking directly at each face. They provide true dimensions and shapes but require multiple views to describe the object fully. These are typically drawn in First Angle Projection (common in Nigeria and Europe) or Third Angle Projection (common in USA).
First Angle Projection: The object is placed in the first quadrant. The plan view is below the front view, and the end view is to the right of the front view.
Isometric Projections: A 3D drawing technique where all three axes (length, width, height) are shown equally foreshortened, usually at 30 degrees to the horizontal. It provides a visual representation of the object, showing multiple faces simultaneously. It gives a realistic impression.
Oblique Projections: Similar to isometric but one face (usually the front) is drawn true to size, and the depth lines recede at an angle (e.g., 45 degrees) and may be half-scale for realism (cavalier vs. cabinet). Less distorted than isometric for the front face.
Exploded Views: Show how individual parts of an assembly fit together, with parts separated along an axis but aligned to indicate their relative positions. Useful for complex assemblies and instructional manuals.
Conventions: Dimensions: Numerical values indicating sizes (length, width, thickness). Always placed clearly, usually outside the main outline, with extension and dimension lines.
Scale: The ratio of the drawing size to the actual object size (e.g., 1:1 for full size, 1:2 for half size).
Title Block: Contains essential information like project name, drawing number, scale, date, designer, and client.
Annotations: Notes providing additional information (e.g., material type, finish, specific joint details).
Worked Example 1: Orthographic Drawing of a Simple Wooden Block Problem: Draw the orthographic projection (Front, Plan, End views) of a wooden block with dimensions 100mm (Length) x 50mm (Width) x 40mm (Height) in First Angle Projection. Assume the 100mm side is the length and 50mm side is the width.
Solution:
1. Front View (Elevation): Will show the Length (100mm) and Height (40mm). Draw a rectangle 100mm wide and 40mm high.
2. Plan View (Top View): Will show the Length (100mm) and Width (50mm). Drawn directly below the front view. Project vertical lines from the front view's width. Draw a rectangle 100mm wide and 50mm deep.
3. End View (Side View): Will show the Width (50mm) and Height (40mm). Drawn to the right of the front view. Project horizontal lines from the front view's height and vertical lines from the plan view's depth (using a 45-degree projector line or compass arcs from the plan view). Draw a rectangle 50mm wide and 40mm high.
4. Add Dimensions: Clearly label the 100mm, 50mm, and 40mm dimensions on the respective views. (Self-correction: Cannot draw images here, but the description is clear enough for a teacher to understand and demonstrate. Emphasize the projection lines and alignment.) 2.
3. Cutting List A cutting list is a detailed tabular record of all individual wooden components required for a project, derived directly from the working drawings.
Purpose: To ensure efficient material usage, minimise waste, facilitate accurate cutting, and simplify material ordering. It is crucial for cost-effective production in Nigerian workshops.
Components of a Cutting List: | Part Name | Quantity | Thickness (mm) | Width (mm) | Length (mm) | Material Type | Remarks (Grain Direction, etc.) | | :--------------- | :------- | :------------- | :--------- | :---------- | :------------ | :------------------------------ | | Top Panel | 1 | 18 | 300 | 600 | Iroko | | | Side Panels | 2 | 18 | 282 | 450 | Iroko | | | Bottom Panel | 1 | 18 | 282 | 564 | Iroko | | | Back Panel | 1 | 6 | 450 | 600 | Plywood | | | Shelf | 1 | 18 | 282 | 564 | Iroko | | | Door Frame Stile | 2 | | :------------- | :--------- | :---------- | :------------ | :------------------------------ | | Top Panel | 1 | 18 | 300 | 600 | Iroko | | | Side Panels | 2 | 18 | 282 | 450 | Iroko | | | Bottom Panel | 1 | 18 | 282 | 564 | Iroko | | | Back Panel | 1 | 6 | 450 | 600 | Plywood | | | Shelf | 1 | 18 | 282 | 564 | Iroko | | | Door Frame Stile | 2 | 25 | 40 | 400 | Mahogany | | | Door Frame Rail | 2 | 25 | 40 | 250 | Mahogany | | Preparation Process:
1. Carefully examine each component in the working drawings.
2. Identify the nominal (rough cut) dimensions, which usually include an allowance for final trimming, planing, and jointing (e.g., add 5-10mm to length and width, 2-3mm to thickness). Emphasize that dimensions from drawings are usually finished dimensions, so allowances must be added.
3. Record the part name, quantity, and dimensions for each piece.
4. Specify the type of timber required (e.g., Iroko, Obeche, Plywood).
5. Add remarks for specific instructions (e.g., "grain runs lengthwise"). 2.
4. Bill of Materials (BOM) A bill of materials is a comprehensive list of all raw materials, components, and hardware (e.g., screws, hinges, sandpaper, glue, finish) required for a project, along with their estimated costs.
Purpose: Essential for budgeting, procurement, and project management, especially in Nigeria where material costs can fluctuate.
Components of a Bill of Materials: | Item No. | Description (Material, Size, Quantity) | Unit of Measure | Quantity | Unit Price (₦) | Total Cost (₦) | | :------- | :------------------------------------- | :-------------- | :------- | :------------- | :------------- | | 1 | Iroko Timber (18x300x600mm) | Piece | 1 | 3,500 | 3,500 | | 2 | Iroko Timber (18x282x450mm) | Piece | 2 | 2,800 | 5,600 | | 3 | Iroko Timber (18x282x564mm) | Piece | 2 | 3,200 | 6,400 | | 4 | Plywood (6x450x600mm) | Sheet | 1 | 2,000 | 2,000 | | 5 | Mahogany Timber (25x40x400mm) | Piece | 2 | 1,500 | 3,000 | | 6 | Mahogany Timber (25x40x250mm) | Piece | 2 | 1,000 | 2,000 | | 7 | Wood Screws (4.0x30mm) | Dozen | 1 | 300 | 300 | | 8 | PVA Wood Glue | 500ml | 1 | 1,500 | 1,500 | | 9 | Sandpaper (Grits 80, 120, 220) | Sheets | 3 | 100 | 300 | | 10 | Varnish (Clear Gloss) | 1 Litre | 1 | 2,500 | 2,500 | | TOTAL ESTIMATED COST | | | | | 27,100 | Preparation Process:
1. Transfer all material requirements from the cutting list.
2. List all additional hardware, consumables, and finishes.
3. Determine the unit of measure (e.g., piece, sheet, litre, dozen).
4. Obtain current unit prices from local suppliers (e.g., timber markets, hardware stores). This step often involves research in a Nigerian context.
5. Calculate the total cost for each item and sum to get the grand total. 2.
5. Construction This phase involves physically building the project based on the prepared drawings and lists.
Marking Out: Transferring dimensions and shapes from drawings to the actual timber. Accuracy is paramount.
Cutting: Using appropriate hand or power saws to cut components to size.
Jointing: Forming joints (e.g., mortise and tenon, dovetail, butt, rebate) to connect components securely.
Assembly: Bringing together all parts, ensuring squareness and rigidity.
Shaping and Finishing Prep: Planing, sanding, filing, and scraping to achieve desired forms and smooth surfaces, preparing for finishing. 2.
6. Wood Finishes The final stage of a project, applying a finish, protects the wood and enhances its appearance.
Purpose: Protection: Against moisture, abrasion, stains, UV light, and pests (e.g., termites, wood borers common in Nigeria).
Aesthetics: Enhances grain, changes colour, adds sheen.
Durability: Extends the lifespan of the project.
Types of Finishes: * Varnishes: Clear, durable coatings (e.g., polyurethane varnish, yacht varnish for outdoor use in humid Shaping and Finishing Prep: Planing, sanding, filing, and scraping to achieve desired forms and smooth surfaces, preparing for finishing. 2.
6. Wood Finishes The final stage of a project, applying a finish, protects the wood and enhances its appearance.
Purpose: Protection: Against moisture, abrasion, stains, UV light, and pests (e.g., termites, wood borers common in Nigeria).
Aesthetics: Enhances grain, changes colour, adds sheen.
Durability: Extends the lifespan of the project.
Types of Finishes: Varnishes: Clear, durable coatings (e.g., polyurethane varnish, yacht varnish for outdoor use in humid climates).
Lacquers: Fast-drying, hard, and clear coatings (spray application).
Paints: Opaque coatings for colour and protection, often used on lower-grade timber or for decorative effects.
Oils: Penetrate the wood, providing a natural look and feel (e.g., Danish oil, linseed oil). Offers good protection against moisture but less against abrasion.
Stains: Change the colour of the wood without obscuring the grain. Applied before a clear topcoat.
Wax: Provides a soft sheen and some protection, often used over other finishes or on its own for a traditional look.
Application Process:
1. Surface Preparation: Thorough sanding through progressively finer grits (e.g., 80, 120, 180, 220) to achieve a smooth, blemish-free surface. Dust removal is crucial.
2. Sealing (Optional but Recommended): Applying a sanding sealer or a thinned first coat of the chosen finish to seal the wood pores and prevent blotching.
3. Application of Finish: Applying multiple thin coats as per manufacturer's instructions, allowing adequate drying time between coats and light sanding between coats for adhesion and smoothness.
3. Teaching and Learning Activities The following activities are designed to actively engage students with the concepts of project design and construction. 3.
1. Teacher Activities Introduction (10 mins): Begin by presenting a problem scenario common in Nigeria, e.g., "A local primary school needs simple, durable wooden stools for new pupils, but with a tight budget." Discuss with students what goes into creating such an item from idea to finished product.
Design Process Explanation (15 mins): Explain the stages of design (problem identification, research, ideation, sketching, refinement). Emphasise factors like function, aesthetics, material availability (local timber types), and cost relevant to the Nigerian context. Demonstration of Sketching and Design Principles (20 mins): Using a whiteboard or projector, demonstrate freehand sketching of different design options for the stool. Discuss how to incorporate stability, comfort, and simple aesthetics.
Explanation of Working Drawings (20 mins): Explain the importance of working drawings. Demonstrate how to create orthographic views (Front, Plan, End) using a simple object (e.g., a prepared wooden block or a model of a joint) and drawing tools. Emphasise First Angle Projection and correct dimensioning. Briefly introduce isometric and oblique views. Explanation and Demonstration of Cutting List Preparation (15 mins): Explain the purpose and components of a cutting list. Using a simplified design (e.g., a small box), demonstrate step-by-step how to extract dimensions from a drawing, add allowances, and populate a cutting list table. Explanation and Demonstration of Bill of Materials (15 mins): Explain the purpose and components of a BOM. Extend the small box example to include calculating timber requirements from the cutting list (e.g., how many linear metres of 18mm x 50mm timber needed), then add hardware (nails, glue) and finish (varnish), assigning hypothetical but realistic unit prices from Nigerian markets. Overview of Construction and Finishes (10 mins): Briefly explain the construction sequence (marking out, cutting, jointing, assembly, sanding) and the purpose and types of wood finishes, linking them to protection against local conditions (e.g., humidity, termites). Show samples of finished and unfinished wood.
Q&A and Clarification (5 mins): Address any questions or misconceptions. 3.
2. Student Activities Brainstorming and Problem Analysis (Group Activity - 10 mins): In small groups, students discuss the primary school stool problem. They list requirements, potential materials, and initial ideas. Initial Design Sketching (Individual - 15 mins): Students individually sketch at least two different design concepts for the stool, focusing on functionality and form. * Orthographic Drawing Practice (Individual - 20 mins): Given a simple drawing or a physical object (e.g., a simple wooden joint, a small