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About this calculator
Before the resin is mixed, the store needs to know what to issue. Enter the size of the largest ply and get the cut size and quantity of every layer, plus the sealant tape. Each overlap is yours to change, so it matches your manual.
Runs in your browser. Tap an example or enter the size of the largest ply; the PDF is a cut list for the store.
How it works it out
The stack. Peel ply, release film, bleeder if the SRM asks for it, breather, tape and bag, in the order of the vacuum bagging guide and FAA-H-8083-31 Vol. 1 pp. 7-20 to 7-22.
Cut sizes. Each piece is the repair plus twice the sum of the overlaps under it. Peel ply is L + 2 × peel overlap. Bleeder is cut to the size of the release film.
Sealant tape. The perimeter along the tape's centre line, plus the joint overlap you enter.
The bag. The outer edge of the tape, plus what you leave past it, plus your pleat allowance on the length and on the width.
Off the roll. With roll widths entered, it takes the shorter of the two ways round. A piece wider than the roll is split into strips to join, and the sheet says how many.
Where the overlaps come from. The Handbook gives the stack but no overlaps. Peel ply, film and breather start at 2 in, the top of the 1 to 2 in in our guide. The tape gap starts at 3 in, our reading of the guide's "a few inches". These are shop practice, not a standard. Tape width starts at 1/2 in, the size of Airtech AT-200Y. Bag past the tape, tape joint, pleats and waste have no published figure, so they start at 0, the bare geometry.
Worked example
A 12 × 8 in repair with the starting overlaps: 2 in for peel ply, film and breather, 3 in to the tape, 1/2 in tape.
- Peel ply: 16 × 12 in. Release film: 20 × 16 in. Breather: 24 × 20 in.
- Tape centre line: 3 1/4 in past the breather on each side, so 30.5 × 26.5 in. Perimeter 114 in, or 9.5 ft.
- Bag: to the outer edge of the tape, 31 × 27 in, or 5.81 ft² before pleats.
Limits — when NOT to use this
- The manual governs. Materials, bleeder plies and overlaps come from the SRM or the material sheet.
- Pleats are your figure. With 0 % the bag is the flat size, and a contour or a corner takes more.
- Rectangles only. A round repair is cut from a square. Offcuts are not nested back in.
- Not counted: the breather pad under each port, an edge bleed strip, thermocouple pass-throughs.
- Not in our catalog yet. We list no bagging consumables or roll sizes, so none are quoted here.
Sources
- FAA-H-8083-31, AMT Handbook — Airframe, Volume 1, Chapter 7 — pp. 7-20 to 7-22, vacuum bag materials and their order; the Handbook prints no overlaps between layers.
- Airtech AT-200Y data sheet — sealant tape size, 1/8 × 1/2 in.