A caravan owner in Queensland asked for a replacement front window after a stone cracked the original. The quote he had was for flat sheet cut to size. The window was curved with a 1400 mm radius, and a flat panel would have popped the seal within one trip. That single misunderstanding is the most common failure in acrylic caravan window replacement.
Replacement work starts with the old panel, not the new one. Trace the outline on card, mark hinge centres, hinge radius, seal line and any cut-outs for blinds. Then record the chord and rise so the fabricator can derive the radius. A formed panel that is 3 mm out on radius will fight the frame everywhere.
Acrylic caravan window thickness and forming
Most touring caravan side windows are 3 mm acrylic; front and large panoramic panels move to 4 mm or 5 mm because they see more wind load and more stone impact. Going thicker without changing the frame is a mistake: a 5 mm panel needs a deeper seal bed or it will stand proud and leak.
- 3 mm: side windows up to 900 x 700 mm
- 4 mm: front windows and panels over 1 m wide
- 5 mm: panoramic or roof-level glazing, frame permitting
- Forming: 160 C to 180 C, radius no tighter than 150 times thickness
Heat forming is where cheap suppliers take shortcuts. A radius tighter than about 150 times the sheet thickness will thin the outer wall and leave visible striations. We press-form against a matched male and female tool, then anneal at 80 C before trimming, which is the step that keeps a formed window from cracking at the hinge line two seasons later.
Fixing detail that decides whether it leaks
Acrylic moves. A 900 mm window at noon in the sun will be 3 to 4 mm wider than the same window at dawn. If the panel is clamped between a rigid aluminium frame and a hard gasket, the movement has nowhere to go and the sheet crazes at the screw line. The professional detail is a floating bed: EPDM gasket, 2 mm hole clearance, screws snug not driven, and a neutral-cure silicone bead at the outer edge only.
Sealant choice matters as much as the frame. Acetoxy silicone releases acetic acid while curing, which stress-cracks acrylic. Use neutral-cure, and never apply solvent-based contact adhesive near a masked panel.
If the caravan also needs interior panels, the cleaning routine becomes a design input: our acrylic and PC cleaning guide lists the agents that are safe on a formed window, and the ones that turn a stressed panel hazy in one season.
For buyers replacing glazing across a fleet rather than one unit, custom size acrylic sheets can be supplied cut and formed to the trace, with each panel numbered to the vehicle.
Send a photo of the old window, its radius and the hinge layout to oversales@rpplexiglass.com for a formed panel quote.
Frequently Asked Questions
Is acrylic suitable for caravan windows?
Yes. It weighs about half of glass at the same thickness, survives stone impact without shattering, and can be heat-formed to the original curve. The limits are scratch resistance and heat, so fit it with a floating frame, not a rigid clamp.
How do I measure a curved window?
Trace the old panel onto card, mark the hinge centres and the seal line, then send the trace plus the chord and rise of the curve. Radius matters more than area, because it sets whether the panel is press-formed or vacuum-formed.
Why does a replacement window crack at the fixing holes?
Holes drilled without clearance, or screws tightened against a flat frame. Acrylic expands about 0.065 mm per metre per degree C, so a 900 mm window moves roughly 3 mm across a 40 C swing. Holes should be 2 mm oversize and the panel should sit on a gasket.