Centering Rings Guide: Sizing for 2.26 and 5.38 Airframes
By High Power Model Rocketry | Published: 2026-10-17
Category: Buying Guides
Learn how to size centering rings for 2.26-inch and 5.38-inch airframes. This guide covers fit, material thickness, and trade-offs for high-power rocket builds.
Quick answer
For a 2.26-inch airframe, choose centering rings that fit inside the tube and over your motor mount, typically 1/8-inch thick plywood. For a 5.38-inch airframe, opt for 1/4-inch thick rings to handle larger motors and heavier loads. Match the ring's inner diameter to your motor mount tube size, and confirm the outer diameter matches your airframe's inner diameter.
Why sizing matters for centering rings
Centering rings align the motor mount tube inside the airframe and transfer thrust loads to the body. A ring that's too loose can shift during flight, causing misalignment or failure. A ring that's too tight may crack or prevent assembly. Always measure your airframe's inner diameter (ID) and motor mount outer diameter (OD) before ordering.
Material thickness also affects strength and weight. Thinner rings (1/8-inch) work for smaller airframes and lighter motors, while thicker rings (1/4-inch) provide extra rigidity for larger airframes and high-power motors. Plywood is the standard material—it's strong, affordable, and easy to glue.
2.26-inch airframe rings: fit and trade-offs
A 2.26-inch airframe typically uses rings with a 1/8-inch thickness. These are light and easy to install, making them ideal for mid-power rockets or Level 1 certification builds. The trade-off is lower shear strength—if you plan to fly heavy motors or add a lot of nose weight, consider stepping up to a thicker ring or reinforcing with epoxy fillets.
Common motor mount sizes for this airframe include 24mm and 29mm. Verify the ring's inner diameter matches your mount tube. Some rings come with a Kevlar loop or screw eye for shock cord attachment, which can save you an extra step.
5.38-inch airframe rings: fit and trade-offs
A 5.38-inch airframe (often called 5.5-inch) demands sturdier centering rings. These rings are typically 1/4-inch thick plywood to handle the higher thrust and weight of large high-power motors. The extra thickness also provides a larger glue surface for a stronger bond.
Motor mount options for this airframe include 38mm and 54mm. Some ring packs include an eye bolt and Z-clip motor retention, which simplifies assembly. The downside is added weight and cost—these rings are heavier and more expensive than smaller ones, but the structural benefit is worth it for Level 2 and Level 3 rockets.
Decision rules for choosing centering rings
- Match inner diameter to motor mount: Measure your motor mount tube's outer diameter. The ring's inner hole must fit snugly—not loose enough to slide without glue, not so tight that it cracks when pressed on. Check the ring's listed motor mount size (e.g., 24mm, 29mm, 38mm, 54mm) against your tube.
- Match outer diameter to airframe ID: The ring's outer diameter must equal your airframe's inner diameter. For a 2.26-inch airframe, that's BT-2.14 (54mm ID). For a 5.38-inch airframe, that's BT-5.38 (136.7mm ID). Confirm the airframe tube size in the product description before buying.
- Choose thickness based on power level: Use 1/8-inch rings for mid-power and Level 1 rockets. Use 1/4-inch rings for Level 2 and above, or when flying heavy motors in larger airframes. Thicker rings add weight but prevent failure under high thrust.
- Consider included hardware: Some ring packs come with Kevlar loops, screw eyes, or motor retention clips. These can save time and reduce parts cost, but verify they match your build method. Hardware included can simplify assembly—check the pack contents.
Product facts
- Centering Rings For 2.26" Airframe: Centering rings for BT-2.14 (54mm) to 24mm motor mount, 1/8″ thick. 2 Pack includes SCM1 – Kevlar loop. Also available for BT-2.14 to 29mm motor mount with Kevlar loop and screw eye. These rings are sized for a 2.26-inch airframe (BT-2.14 inner diameter). The 1/8-inch thickness keeps weight low, and the included Kevlar loop or screw eye gives you a built-in shock cord attachment point.
- Centering Rings for 5.38" Airframe: Centering rings for BT-5.38 to 38mm mount, 2 pack 1/4″ thick, includes SCM3 1/4″ eye bolt and Z clip motor retention. Also available for BT-5.38 to 54mm mount. These rings are designed for a 5.38-inch airframe. The 1/4-inch thickness provides the strength needed for high-power motors, and the included eye bolt and Z-clip simplify motor retention installation.
Which centering rings are right for your build?
Best for
- 2.26-inch airframes with 24mm or 29mm motor mounts, especially for mid-power or Level 1 certification flights
- 5.38-inch airframes with 38mm or 54mm motor mounts for Level 2 or Level 3 high-power rockets
Not for
- Airframes with non-standard inner diameters—always measure before ordering
- Builds requiring metal or composite rings (these are plywood only)
