Free tools · 05
Resin & cloth
calculator.
How much to mix and how much to cut. Board length and width, polyester or epoxy, your lay-up, and you get grams of resin per stage, catalyst or hardener, and metres of cloth, before you open the tin.
Resin
| Stage | Cloth | Resin | Catalyst / hardener |
|---|---|---|---|
| Deck lamination (4+4 oz) | 209 g | 795 g ≈ 723 ml | 12 ml MEKP (1.5 %) |
| Bottom lamination (4 oz) | 105 g | 398 g ≈ 362 ml | 6 ml MEKP (1.5 %) |
| Hot coat, deck | — | 365 g ≈ 332 ml | 5 ml MEKP (1.5 %) |
| Hot coat, bottom | — | 365 g ≈ 332 ml | 5 ml MEKP (1.5 %) |
| Total, +10 % for the bucket and the brush | 2116 g ≈ 1.92 L |
Cloth to cut
3 pieces × 2.13 m
from a 76 cm roll: 6.4 m in total
Surface, one face
0.65 m²
0.77 m² with the rail laps
Rule used
3.8 g resin per g of cloth
hot coat 560 g/m² per side
- Hand lamination with a squeegee, resin soaking into the foam included. A tight, dry lam uses 10–15 % less; a wet one for a tint or a cutlap, 10–20 % more. Mix a little extra rather than run out mid-lam.
- Polyester: MEKP between 1 % (hot room) and 2 % (cold); never under 1 %. Epoxy: use your brand's exact ratio, by weight if the label says so; the figure here uses the volume ratio you picked.
- Cloth weights: 4 oz ≈ 136 g/m², 6 oz ≈ 203 g/m². Lengths include 6" of lap at each end; width assumes a 30" roll, enough for boards up to about 23" wide.
Questions
- How much resin does a surfboard take?
- A 6'0" shortboard glassed 4+4 oz on the deck and 4 oz on the bottom with polyester takes roughly 1.1 kg of lamination resin and another 0.7 kg for the two hot coats, so about 1.8–2 kg in total. A longboard with 6+6 / 6 is nearer 4 kg. The calculator does the arithmetic for your board and lay-up.
- Polyester or epoxy?
- Polyester goes on polyurethane (PU) blanks and is the classic feel and finish. Epoxy goes on EPS foam (polyester would melt it) and also works on PU; it is lighter, stronger and has no smell, but costs more and needs exact mixing by weight or volume. Never use polyester on EPS.
- How much catalyst (MEKP) for polyester?
- Between 1 % and 2 % by volume, depending on the room temperature: 2 % below 18 °C, 1.5 % in a 18–24 °C room, 1 % above 24 °C. Less than 1 % may never cure; more than 2 % goes off before you finish the lap.
- What do 4 oz and 6 oz mean?
- The cloth weight per square yard: 4 oz is about 136 g/m², 6 oz about 203 g/m². Lighter cloth is lighter and more flexible, heavier cloth is stronger and dings less. A common shortboard schedule is 4+4 deck / 4 bottom; a longboard 6+6 / 6.
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