Cockpit Ergonomics: 3D-Printed Cup Holders, Phone Mounts and Helm Accessories
Most cockpits are designed around the hull, not around the people in it. The one drink holder is on the wrong side, the phone with the anchor alarm slides off the seat every tack, and the winch handle lives wherever it landed last. None of these are safety-critical problems, which is exactly why they're a good fit for 3D printing: low load, high annoyance, and highly specific to your boat.
This guide covers the small helm and cockpit accessories that print well, how to size them to your rails and bulkheads, which material survives a summer in the sun, and the handful of things you should leave to bought hardware.
What belongs in this category
Cockpit accessories share three traits: they carry light loads (a drink, a phone, a handheld VHF), they mount to surfaces you already have (stainless rails, pushpit tubes, bulkheads, coaming faces), and they live outdoors. That last one drives the material choice more than anything else.
Good candidates: cup and can holders, phone and tablet cradles, handheld VHF or GPS holsters, winch-handle pockets, sunglasses and sunscreen caddies, chart-weight clips, binocular cradles, and small trays that sit in a cockpit locker lid. Less good candidates: anything you'll grab when you lose your footing. A grab handle deserves its own approach, covered in Grab Handles and Handholds: What 3D Printing Can and Can't Do.
Three ways to mount, and when to use each
Rail and tube clamps
A two-piece clamp around a stainless rail is the most useful mount on a boat. Pushpit, pulpit, bimini frame, wheel pedestal guard: almost every cockpit has 22, 25 or 30 mm tube somewhere within reach of the helm. A printed clamp sized to the exact tube diameter grips without marking the stainless and leaves no holes behind.
Measure the tube with calipers, not a tape. Nominal 25 mm rail is often 25.4 mm (1 inch); a clamp printed for 25.0 will crack or refuse to close. The clamp bore should equal the measured diameter plus 0.2–0.3 mm, with a 1–1.5 mm gap between the two halves when bolted up so the bolts do the clamping rather than the halves bottoming out. Our tube/rail mount device holder and the tube-mount clip holder are both generated from the measured diameter, which is how these should work.
Bulkhead and coaming mounts
Flat vertical surfaces take a screwed or adhesive plate. Screwed is more secure but every hole in a cored deck or coaming is a future leak. If you drill, seal the core: oversize the hole, fill with thickened epoxy, then drill the pilot through the epoxy plug. If you'd rather not drill, VHB tape on a properly prepared surface holds a phone or cup holder for years; see Drill-Free Mounting for the prep routine that makes it stick. The adhesive device holder is designed with a flat tape land for exactly this.
Modular rails
If you want more than one thing at the helm, print one rail and hang holders on it instead of mounting each item separately. A single bar with a snap or dovetail profile lets you move the phone cradle to port when the sun is to starboard, or swap the cup holder for a VHF holster on a delivery. The modular cylinder holder kit and modular rail device holder kit work on this principle, and the rail-mount cross bar puts the same rail on a pushpit tube.
Sizing a cup holder that actually holds
The standard 355 ml can is 66 mm across. A typical insulated tumbler is 75–90 mm at the base and tapers wider. An open-top holder sized for a can will spit a tumbler on the first wave. Two practical solutions:
- Tapered bore. Make the holder 92 mm at the top and 68 mm at 60 mm depth. Cans sit on the step at the bottom; tumblers wedge partway down. One holder, both drinks.
- Drain hole. Always. A 6–8 mm hole at the lowest point, or three slots, so rain and spilled coffee don't sit in it.
Depth matters more than diameter for heeling. A holder 50 mm deep is decorative; 90–100 mm keeps a half-full can in at 20 degrees. If space is tight, angle the holder 10–15 degrees back toward the mount so gravity pulls the drink into the rear wall.
| Item | Typical size | Suggested bore / cradle | Depth |
|---|---|---|---|
| 355 ml can | 66 mm | 68 mm | ≥ 80 mm |
| 500 ml bottle | 70–73 mm | 75 mm | ≥ 90 mm |
| Insulated tumbler | 75–90 mm | tapered 92 → 68 mm | ≥ 90 mm |
| Handheld VHF | 60–70 × 30–40 mm | measured + 1 mm each way | ≥ 100 mm |
| Phone in case | 75–85 × 10–15 mm | measured + 1 mm width | lip ≥ 8 mm |
| Winch handle grip | 25–30 mm shaft | 32 mm slot, open front | ≥ 120 mm |
Phone and tablet mounts: retention beats convenience
A phone at the helm does three jobs: navigation, AIS or anchor alarm, and the occasional photo. All three end badly if the phone goes over the side. Design the cradle for retention first:
- Positive lip of at least 8 mm on all sides that face outboard, not just the bottom.
- Landscape and portrait are different cradles unless you print a rotating base; for most chartplotter apps, landscape is what you'll use.
- Charging cutout at the bottom, sized for your specific cable plug plus 2 mm. Angled cables need a wider slot.
- Sun and heat. A black phone in a black PETG cradle in direct sun will thermal-throttle or shut down. Print in a light colour, add ventilation slots behind the phone, and expect to shade it anyway.
Tablets are heavier and the lever arm on a rail clamp is long. A 10-inch tablet in a case is around 700 g; on a 150 mm arm that's a real bending moment every time the boat slams. Use two clamps on the rail spaced 80–100 mm apart, or mount to a bulkhead. Our wall mount device holder is generated to the device's measured width, height and thickness so the cradle grips rather than relying on a spring.
Materials: this is deck exposure
Cockpit accessories live in the harshest place on the boat short of the masthead: full sun, salt spray, and the occasional boot. PLA is out; it softens in a closed cockpit on a summer afternoon and chalks under UV within a season. PETG works if it's out of direct sun or you accept replacing it every couple of years. ASA is the right answer for anything permanently exposed: it holds colour, stays rigid to 95 °C and doesn't get brittle. For a cup holder that will be knocked, a TPU liner or a TPU insert ring stops rattles and keeps a metal tumbler from scratching the print.
For the longer comparison, see Best Materials for 3D Printing Boat Parts and, for keeping colour on deck, Make Your 3D Prints UV-Resistant.
Print settings that survive the cockpit
- Walls: 4 perimeters minimum (1.6–2 mm at 0.4 mm nozzle). Clamps and cradles fail at the wall, not the infill.
- Infill: 25–35 % gyroid. Higher isn't stronger in a meaningful way; more walls are.
- Orientation: print clamps so the bolt axis is perpendicular to the layers, and print cradle lips so the lip is not a stack of layers waiting to peel. Print Orientation and Strength covers why.
- Hardware: stainless A4 bolts with nyloc nuts or heat-set inserts; never let a stainless bolt bear directly on a thin printed flange without a washer. Details in Heat-Set Inserts and Marine Hardware.
- Rounded corners everywhere. Anything at knee or shin height in a cockpit will be hit. A 3 mm fillet on every outer edge saves skin and stops the print cracking at the corner.
What to leave alone
Don't print anything you would instinctively grab in a knockdown: handholds, pedestal guards, lifeline attachments. Don't print a tablet mount that clamps to the wheel or blocks a compass. And keep printed accessories clear of winch drums, sheet leads and the traveller; a cup holder that fouls a sheet in a gybe is worse than no cup holder.
Safety note: 3D-printed parts are not certified marine equipment. Verify the material and design are suitable for the load and exposure before use, keep printed accessories away from running rigging and safety gear, and never rely on a printed part to retain a person or as a handhold.
Start here
Measure your rail diameter, your phone with its case, and the drink you actually bring aboard. With those three numbers you can generate a clamp, a cradle and a cup holder that fit your boat instead of a generic one. Browse the Interior & Cabin and Navigation & Electronics collections for parametric holders, or the free files if you want to test-print a clamp on your rail before committing. Questions about a specific fitting: info@marinelab3d.com.