The Marimo Labs Water Rocket Launcher

Designed in Cambridge, Massachusetts, USA
Free forever, everywhere
marimolabs.com
v1.42

A full-bore water rocket launcher system designed for easy assembly and universal compatibility.

For those without ready access to 3D printers, you can purchase a kit with all parts from the Marimo Labs Store.

Kits of non-printed parts are also available.

• Video instructions above.
• Written instructions on Instructables: [https://www.instructables.com/Simple-3D-Printed-Water-Rocket-Launcher/](https://www.instructables.com/Simple-3D-Printed-Water-Rocket-Launcher/)
• Detailed design discussions at: [https://www.marimolabs.com/water-rocket-launcher](https://www.marimolabs.com/water-rocket-launcher)
• Read the Safety Instructions PDF!
• Additional model files (for advanced variations, fins, payloads, etc) are at the main model page at Printables: [https://www.printables.com/model/86434-water-rocket-launcher](https://www.printables.com/model/86434-water-rocket-launcher)

Disclaimer

Hey. Pressurized systems are dangerous. Know what you are doing and take appropriate safety precautions. Make your own assessment about whether this project is appropriate for what you are trying to do, and use at your own risk. Do not attempt without appropriate experience, protective equipment, and tools. Most water rocket guides recommend not pressurizing past 60psi/4 bar. Always secure the launcher to the ground.

PARTS LIST

Non-Printed

Option 1: Marimo Labs Store (shipping in the US)

• Core Subkit with Non-Printed Parts
• Rubber Band and Launch Cord Subkit (or bring your own)

Option 2: Purchase off-the-shelf (sample Amazon links below)

• TR414 Tire valve stem
• O-ring 15mm ID x 3.5mm thickness x 22mm OD
• Schrader (car/mountain bike) valve hose extension
• Rubber bands, any, but silicone #33 (3 1/2" x 1/8") are nice
• String to tie to Launch Pin
• Reusable straw, 7.6-8mm OD (prevents water backflow into pump)

Printed

• Base
• Collar
• Clamp x6
• Core Type B
• Launch Pin
• Leg x3
• Peg x3 (don't skip securing the launcher to the ground!)
• Carrier

PRINT SETTINGS

Launcher Parts

• Line width: 0.4-0.45mm
• Layer height: 0.20mm
• Walls/perimeters: 2-3
• Infill: 20%
• Filament: PETG ideal (for temperature stability) but not required. PLA/PLA+ is fine, but you must protect from heat to prevent deformation.
• Supports: None
• Brims: Core B and the Launch Pin have small footprints and may benefit from brims if your bed has low adhesion. Generally not needed.

Printing tips

Consider slowing down print speeds and accelerations, especially if using PETG. Limit print speeds to 75mm/s with external wall 50mm/s or set max volumetric rate to 8mm^3/s. This allows better layer adhesion, bridges, and text quality. CoreXY is so blazing fast that PETG sometimes isn't able to stick to itself.