Why the finish fails at all
The white surface on a classic glass sailplane is not paint. It is gelcoat — a relatively thick polyester layer laid into the mould before the structural laminate, so it forms the outer skin rather than sitting on top of one. It was chosen because it moulds beautifully, sands to the aerodynamic accuracy these aircraft depend on, and reflects sunlight, which matters more than it sounds when the alternative is a dark composite structure baking on a summer grid.
What it does not do is last indefinitely. Over decades of ultraviolet exposure and thermal cycling the layer shrinks slightly and becomes progressively more brittle, while the laminate beneath it does not move in the same way. Eventually the surface relieves that stress the only way it can, and a fine network of cracks appears — crazing. It usually shows first on the upper wing surfaces, which get the most sun, and around areas of stress concentration.
This is a normal end-of-life behaviour for a material doing a hard job for forty years, not evidence that anyone did anything wrong. Nearly every glass glider from the 1970s and 1980s has reached it or will.
Cosmetic, or not
The question that decides everything: is the crazing confined to the gelcoat, or has something moved underneath it?
Most crazing is exactly what it looks like — a surface finish at the end of its life over a structure that is entirely sound. It is ugly, it costs a little performance through increased surface roughness, and it can eventually admit water into the laminate, which is the reason it should not be ignored forever.
Some crazing is a symptom. Cracks that follow a spar line, radiate from a fitting, concentrate around a repair, or appear in a distinctly different pattern from the general craze field are telling you about the structure and not the surface.
You cannot resolve this from photographs, and neither can we. It needs someone who inspects composite sailplanes for a living, in person, with the wings out of the trailer and good light. If you are buying, that inspection is not an optional extra — it is the thing you are actually paying for. Our guide to buying a glider covers what a pre-purchase inspection should include and why a glider-experienced inspector is not the same as any A&P.
What it costs, in the only unit that lasts
We are deliberately not publishing a dollar total, and the reason is not caution. A total goes stale in a year, varies by a factor of two across regions, and gets quoted back at people in negotiations it has no business being in. The number that stays true is the labour.
Refinishing specialists put a full, properly executed job at upwards of 300 hours for the wings alone, and upwards of 500 hours for a complete aircraft. Multiply by the hourly rate you are actually quoted. That is your estimate, and it will be closer than anything you read in a forum thread.
Materials barely enter into it. Two gallons of polyurethane with catalyst and thinner — a few hundred dollars, mixing to more than enough for a 15-metre ship. When people say refinishing is expensive they are describing skilled labour measured in months, which is why the price does not fall and why the good shops have waiting lists.
Why the hours are so large
It is worth understanding where 500 hours goes, because it explains why "just spray it" quotes should worry you rather than delight you.
- Stripping. The old gelcoat comes off. Slowly, mechanically, and without cutting into the structural laminate beneath it — which is the entire skill and the reason this is not a job for an enthusiastic member with a sander.
- Filling and fairing. The surface has to be returned to the aerofoil. A sailplane wing's contour accuracy is a performance item, not a cosmetic one, and this is where most of the hours actually live.
- Finishing. Priming, applying, flatting, polishing — repeatedly, by hand, over a very large surface area.
- Everything else. Control surfaces off and rebalanced, seals, fittings, masking, and reassembly.
A quote that is dramatically below the others is not a bargain; it is a different job with the same name.
Gelcoat again, or polyurethane?
There is a genuine and long-running disagreement here, and anyone who tells you it is settled is telling you their preference.
New gelcoat is the original material, appropriate to the original design, and repairable by the same methods the aircraft was built with. It is heavy, and in time it will craze again.
Polyurethane paint systems are lighter and flexible enough that they do not craze in the same way. They are thinner, which means the surface underneath has to be right before they go on, and the repair and touch-up story is different from what a classic sailplane shop is used to.
Ask the shop what they use, why, and what they have seen come back after ten years. Ask specifically about weight and about repairs. A shop that answers those three questions concretely is a shop that has thought about it.
The re-weigh is not optional
Removing a heavy polyester layer and replacing it with something else changes the empty weight and can move the empty centre of gravity. The placarded weight and the weight-and-balance data in the aircraft's paperwork describe an aircraft that no longer exists.
The aircraft must be re-weighed and the documentation updated before it flies. If you fly at the light or heavy end of the cockpit load envelope this can change what you are legally able to carry — our cockpit load calculator works from the current placard, so make sure the placard is the current one.
The buyer's arithmetic
Now put it together, because this is what the page is for.
A 1970s standard-class glass ship in sound structural condition with tired gelcoat might be advertised well below the market for a clean example. The difference between those two prices is frequently smaller than the cost of a full refinish. In that situation the cheap aircraft is not cheap — it is the same aircraft with the bill deferred and the work still to arrange, at a shop with a waiting list, during a season you had planned to fly.
This does not make the tired one a bad buy. It makes it a different buy, and the question is simply whether you know which one you are making. Plenty of people knowingly buy a flyable aircraft with an ageing finish, fly it for eight seasons while polishing what is there, and never refinish it at all. That is a completely reasonable plan. It stops being reasonable when it was never a plan.
For clubs the same arithmetic applies with an extra term, because a refinish takes the aircraft out of service for a substantial part of a season. A club fleet aircraft that is unavailable for four months has a cost beyond the invoice, and it belongs in the fleet replacement plan as a line item with a date, not as a surprise.
Living with it instead
Refinishing is one answer and it is not the only one. The realistic middle ground, practised by a great many owners:
- Keep it out of the sun. The trailer, a cover, or a hangar. UV is the mechanism; shade is the intervention, and it is free.
- Keep water out. Sealing and filling the crazing so it does not admit moisture into the laminate buys years and is a fraction of the cost.
- Do the wings only. They take the sun and they carry the aerodynamics. A wings-only job at 300-odd hours is a serious expense but it is not 500, and it addresses most of what matters.
- Have it inspected, then decide with a date. Knowing the structure is sound converts an anxiety into a maintenance schedule, and a maintenance schedule can be saved for.
What does not work is treating it as an unknown indefinitely. The inspection is cheap relative to everything else on this page, it is the only thing that distinguishes the two cases that look identical from ten feet away, and until you have had it done you do not know whether you own a cosmetic problem or a structural one.