Calculator Inputs
Example Data Table
These sample rows show typical inputs and outcomes.
| Scenario | Bed W × L | Overhang | Roll W × L | Tube | Core / Max D | Thickness | Outcome |
|---|---|---|---|---|---|---|---|
| Row cover, standard | 1.2 m × 8 m | 0.15 m | 1.8 m × 10 m | 1.6 m | 0.05 / 0.22 m | 0.35 mm | Good fit |
| Short tube | 1.5 m × 8 m | 0.15 m | 2.1 m × 10 m | 1.6 m | 0.05 / 0.22 m | 0.35 mm | Does not fit |
| Thick plastic | 1.2 m × 12 m | 0.10 m | 1.8 m × 15 m | 1.8 m | 0.05 / 0.18 m | 0.60 mm | Borderline |
Formula Used
- Required width: Wreq = Wbed + 2×Overhang + Overlap
- Required length: Lreq = Lbed + 2×EndAllowance
- Waste buffer: W = Wreq × (1 + Waste%), L = Lreq × (1 + Waste%)
- Usable tube length: TubeUsable = TubeLength − 2×Clearance
- Winding capacity (flat material): Lmax ≈ π×(Dmax² − Dcore²) / (4×Thickness)
Capacity is an estimate for evenly wound layers. Wrinkles, folds, and hardware can reduce real capacity.
How to Use This Calculator
- Measure your bed width and length in a single unit.
- Decide how much overhang and end allowance you need.
- Enter your cover roll width and roll length.
- Measure reel tube length, core diameter, and max diameter.
- Set a realistic thickness and a small clearance value.
- Submit and review fit checks and adjustment suggestions.
- Download CSV or PDF to save your plan.
What this fit check measures
This calculator compares your required cover size against three practical limits: available roll width, available roll length, and the reel’s usable tube length. Required width includes bed width, two overhangs, and an overlap allowance, then applies a waste buffer for trimming and handling.
Sizing inputs that change outcomes fastest
Overhang and end allowance strongly influence the pass/fail result because they add directly to required dimensions. For low tunnels or frost cloth, many growers use 10–20 cm overhang per side for pinning and soil contact. If you routinely re-cut edges, increase waste to 5–8% to reduce shortfalls.
Reel tube and clearance considerations
Tube length is reduced by clearance on both ends to avoid rubbing on brackets, end caps, and bearings. A modest clearance of 5–15 mm per side is common for smooth operation. If your setup has wide supports or crank hardware, use a larger clearance value to prevent binding.
Winding capacity and thickness effects
Winding capacity is estimated from core diameter, maximum diameter, and material thickness. Thin fabrics and light plastic wind more length before reaching the diameter limit. Thicker films and folded edges reduce capacity because each wrap builds diameter faster. If capacity is borderline, consider a larger maximum diameter, a thinner cover, or a longer reel.
How to interpret borderline results
A borderline warning means the cover might work, but real-world factors can reduce performance. Wrinkles, uneven tension, and moisture can increase effective thickness. If the tube length is only slightly short, a diagonal start may help, but it can introduce edge wrinkling. Use the “extra needed” values to choose the next size up confidently.
FAQs
1) What thickness should I enter for row cover?
Use the manufacturer thickness when available. If unknown, measure with calipers on a single layer. For woven fabrics, thickness varies with tension, so choose a slightly higher value for safer capacity estimates.
2) Why does clearance reduce tube length?
Most reels have brackets, end caps, or crank hubs that occupy space. Clearance prevents the wound cover from rubbing, which lowers wear and keeps the reel turning smoothly.
3) My roll width passes, but the tube fails. What now?
The cover can be wide enough but still not supported by the reel. Choose a longer tube, reduce overhang/overlap, or split the bed into two narrower sections with separate reels.
4) Does overlap always increase required width?
Yes, if you plan to overlap edges, seams, or reinforcement strips. If you do not overlap, set overlap to zero. Keeping it realistic improves both fit and capacity results.
5) How accurate is the winding capacity estimate?
It is a practical estimate for evenly wound layers. Real capacity can be lower due to wrinkles, damp fabric, folding, or uneven tension. Use it to compare options, then add a safety margin.
6) When should I allow a diagonal start?
Use it only when the tube length is slightly short and you can manage edge alignment. Diagonal starting can reduce initial width demand, but it may wrinkle edges and complicate rewinding.