TPU on Board: Flexible 3D Prints for Chafe Guards, Gaskets and Bumpers

Most guides to 3D printing boat parts talk about stiffness: which filament holds a load, which one survives the sun, which one doesn't snap when a sheet loads up. Fair enough — we wrote one of those ourselves in our guide to the best materials for 3D printing boat parts. But some of the most useful parts on a boat aren't stiff at all. They're the rubbery bits: chafe guards, gaskets, bumpers, grips, anti-rattle spacers. On a production boat these are moulded rubber or bought as generic marine accessories that never quite fit. With a roll of TPU, you can print them sized to your hardware exactly.

What TPU actually is

TPU (thermoplastic polyurethane) is a flexible filament that prints on almost any FDM machine and comes out of the printer behaving like a tough rubber. Two properties matter for marine use:

• Shore hardness — the squishiness rating. TPU is sold from about 85A (soft, very rubbery) to 95A and beyond (firm, like a shoe sole). Softer grips and seals better; firmer prints more easily and holds shape under load.
• Toughness — TPU has outstanding abrasion resistance and tear strength. It shrugs off exactly the kind of rubbing, flexing and vibration that cracks rigid prints. It also doesn't mind saltwater, and UV resistance is decent for a printed plastic, especially in darker colours.

The trade-off: TPU creeps under sustained load, so it's the wrong choice for anything structural. Think of it as printable rubber, not printable metal.

Five jobs TPU does better than any rigid filament

1. Chafe guards

Anywhere a line rubs — a bow cleat, a fairlead edge, a stanchion base where the jib sheet drags — a printed TPU sleeve or saddle takes the wear instead of the line or the gelcoat. A 95A guard, 2–3 mm thick, printed to wrap the exact radius of your hardware, outlasts tape and stays put. Pair it with organizers from our deck & rigging collection and the foredeck stops eating dock lines.

2. Gaskets and seals

A printed gasket seals a deck plate, an electronics box lid or a locker hatch that has started to weep. Print at 100% infill, 85A–90A if you can, and size the gasket to compress about 20–30% when the fastener is tightened. We covered gasket design in more depth in our article on sealing 3D prints with PTFE tape, epoxy and TPU gaskets — the short version is that flat, evenly compressed TPU beats any amount of sealant re-applied every season. For threaded plumbing joints, though, keep using PTFE tape on the threads; a gasket seals faces, not threads. Fittings live in our plumbing & pumps collection.

3. Bumpers and edge protectors

Companionway corners, locker lids that slam, an outboard tiller that whacks the transom, the sharp corner of a battery box: a TPU bumper turns a bang into a thud. These are trivially quick prints — often under 30 minutes — and they save both varnish and shins.

4. Anti-rattle and anti-vibration spacers

Boats vibrate. Engine hours loosen everything, halyards slap, and anything printed rigid and bolted to a bulkhead near the engine eventually fatigues. A TPU washer or sleeve between a rigid printed mount and the hull kills the buzz and isolates the part from vibration. If you've printed instrument or device mounts, a thin TPU pad behind the base is a one-gram upgrade that noticeably extends their life.

5. Grips and handles

A TPU sleeve over a stainless grab rail, a printed grip for a washdown pump handle, or non-slip feet under a galley cutting board. 85A TPU with a textured surface pattern grips wet hands far better than smooth plastic or bare metal.

Printing TPU without the headaches

TPU's reputation for being hard to print comes from bowden-tube machines and old firmware. On a modern direct-drive printer it's almost boring. The settings that matter:

Two extra tips from our own bench: print gaskets slowly with a slightly higher flow rate (102–105%) to guarantee watertight walls, and skip the brim — TPU sticks to PEI sheets aggressively enough that removal, not adhesion, is the usual problem.

Hardness cheat sheet

• 85A — gaskets, grips, non-slip feet. Softest common grade; slowest to print.
• 90A — the all-rounder: seals well, prints reasonably, good bumpers.
• 95A — chafe guards, spacers, protective sleeves. Prints nearly like PETG.

If you'll only stock one spool aboard, make it 95A: it covers the most jobs and prints reliably even on a small travel printer. It also earns a place in the ditty bag next to the parts from our onboard spares kit list.

Where to start

Print a bumper first — any bumper. It's a five-gram part, it can't fail in any way that matters, and it teaches you how your printer handles flexible filament before you attempt a gasket that needs to be watertight. Several of our free files are good TPU candidates even though they were designed for rigid filament; browse the free collection and think about which parts on your own boat would rather bend than break.

Safety note: 3D-printed parts are not certified marine equipment. TPU creeps under sustained load and softens with heat, so never use printed flexible parts for load-bearing, life-safety or below-the-waterline applications. Verify material suitability for your specific use before installing, and inspect printed seals regularly. Questions? Write to us at info@marinelab3d.com.