Evaluating Your Work
Building something is only half the job. Knowing whether you built it well — and being honest about what went right and wrong — is what separates a craftsperson from someone who just got lucky.
Setting Evaluation Criteria Before You Start
This requirement says to determine evaluation guidelines with your counselor, meaning you agree on what “good” looks like before you start building. This is how professional composites manufacturing works too — quality standards are defined before a single ounce of resin is mixed.
Work with your counselor to set criteria in these categories:
Visual Quality
- Surface finish: Is the surface smooth, or are there rough spots, pinholes, or dry areas where resin did not fully wet the fibers?
- Fiber visibility: In a translucent fiberglass lay-up, are the fibers evenly distributed, or do you see bunching, wrinkling, or gaps?
- Color and clarity: Is the cured resin uniform in color? Milky patches indicate trapped moisture. Yellow or brown spots may indicate localized overheating.
- Edge quality: Are trimmed edges clean and smooth, or rough and splintered?
Structural Integrity
- Rigidity: Does the part feel solid, or does it flex more than expected? Excessive flex could mean too few layers, incomplete cure, or poor fiber orientation.
- Delamination: Tap the surface with a coin or your knuckle. A sharp, clear sound means good consolidation. A dull, hollow sound may indicate delamination — layers that have separated internally.
- Voids and bubbles: Hold translucent fiberglass parts up to a light. Air bubbles show up as bright spots. Large voids weaken the part significantly.
Dimensional Accuracy
- Shape: Does the part match the mold or intended shape? Warping during cure is common with thin parts and indicates uneven fiber placement or thermal issues.
- Thickness: Is the wall thickness consistent? Thick spots mean excess resin (adding weight without strength). Thin spots mean insufficient resin coverage.
Process Quality
Your counselor may also evaluate your process, not just the result:
- Did you follow safety procedures consistently?
- Were your mixing ratios accurate?
- Did you work methodically or rush?
- How did you handle problems during the lay-up?
Common Defects and What Caused Them
Understanding why a defect occurred is more valuable than achieving a flawless result. Here are the most common issues in beginner composites work:
| Defect | What It Looks Like | Likely Cause |
|---|---|---|
| Dry spots | White, opaque areas where fibers are visible and rough | Not enough resin applied, or resin did not wet all fibers |
| Air bubbles/voids | Circular or irregular voids visible in or under the surface | Incomplete rolling/consolidation, trapped air during lay-up |
| Delamination | Layers separate when tapped or flexed | Poor surface prep between layers, contamination, insufficient resin |
| Wrinkling | Visible creases in the fiber fabric | Fabric not smoothed before resin application, too much fabric for the contour |
| Warping | Part curves or twists after demolding | Unbalanced lay-up (fibers not symmetric), uneven cure temperature |
| Tacky surface | Surface stays sticky and does not fully harden | Incorrect resin-to-hardener ratio, curing temperature too low |
| Exotherm damage | Discolored, cracked, or melted areas | Too much resin mixed at once, left in a thick pool instead of spread thin |
Dry spots
- What It Looks Like
- White, opaque areas where fibers are visible and rough
- Likely Cause
- Not enough resin applied, or resin did not wet all fibers
Air bubbles/voids
- What It Looks Like
- Circular or irregular voids visible in or under the surface
- Likely Cause
- Incomplete rolling/consolidation, trapped air during lay-up
Delamination
- What It Looks Like
- Layers separate when tapped or flexed
- Likely Cause
- Poor surface prep between layers, contamination, insufficient resin
Wrinkling
- What It Looks Like
- Visible creases in the fiber fabric
- Likely Cause
- Fabric not smoothed before resin application, too much fabric for the contour
Warping
- What It Looks Like
- Part curves or twists after demolding
- Likely Cause
- Unbalanced lay-up (fibers not symmetric), uneven cure temperature
Tacky surface
- What It Looks Like
- Surface stays sticky and does not fully harden
- Likely Cause
- Incorrect resin-to-hardener ratio, curing temperature too low
Exotherm damage
- What It Looks Like
- Discolored, cracked, or melted areas
- Likely Cause
- Too much resin mixed at once, left in a thick pool instead of spread thin
The Evaluation Conversation
When you sit down with your counselor to evaluate your projects, treat it as a learning conversation, not a pass/fail test. For each project:
- Describe what you planned — materials, technique, and expected outcome
- Show the finished part — point out both successes and defects
- Explain what caused the defects — connect them to specific steps in your process
- Describe what you would do differently — this shows growth and genuine understanding
A Scout who builds an imperfect part but can explain exactly why each defect occurred and how to prevent it next time has learned far more than someone who followed instructions perfectly without understanding the process.
🎬 Video: A Simple Composite Material to Make at Home — https://youtu.be/vxKlbik4QjM
You have built, inspected, and evaluated your composite projects. The final requirement looks ahead — toward careers and hobbies where your new composites knowledge could take you.