Effects of Boat Tail Taper Angle on Model Rocket Drag During Free Flight
DOI:
https://doi.org/10.58445/fyf3fb51Keywords:
Boat tail optimization, Base drag reductionAbstract
Boat tails are tapered rear extensions that reduce base drag in vehicles, but their effectiveness depends on taper angle. Previous computational and wind tunnel studies predict an optimal subsonic boat tail angle near 14-16°. This study evaluated 0°, 7°, 14°, and 21° boat tails on an Estes Big Bertha model rocket. We hypothesized that the 14° boat tail would produce the lowest drag coefficient consistent with predictions of an optimum near 14-16°. Flight acceleration was recorded with a Vernier Go Direct Accelerometer, and velocity was determined by integrating acceleration over time. Drag coefficient was calculated during the unpowered coast phase after motor burnout, between 15 and 28 m/s. The mean experimental drag coefficients were 0.663 ± 0.016, 0.673 ± 0.016, 0.406 ± 0.016, and 0.572 ± 0.016 for the 0°, 7°, 14°, and 21° configurations respectively. The 14° boat tail produced the lowest drag, with a 38.7% reduction in drag coefficient relative to the 0° baseline. OpenRocket simulations based on launch site atmospheric conditions were compared with the experimental results. OpenRocket predicted smaller reductions, with mean drag coefficients of 0.604, 0.569, 0.572, and 0.589. The 7° and 14° boat tails had similar simulated drag. The experimental performance of the 14° boat tail is consistent with previous research describing airflow separation and reattachment near this taper angle. These results indicate the potential of low-cost model rocket flight tests for analyzing aerodynamic predictions under real flight conditions.
References
Hoerner, Sighard F. Fluid-Dynamic Drag: Practical Information on Aerodynamic Drag and Hydrodynamic Resistance. 2nd ed., Hoerner Fluid Dynamics, 1965.
Bawa, Vidit and Quentin Michalski. “An Experimental Framework for In-Flight Determination of Rocket Aerodynamic Drag.” 2025 AIAA Region VII Student Conference, 1–2 Dec. 2025, University of Sydney, Sydney, Australia. https://doi.org/10.2514/6.2025-104785.
Tran, The Hung, et al. “Effect of Boattail Angle on Near-Wake Flow and Drag of Axisymmetric Models: A Numerical Approach.” Journal of Mechanical Science and Technology, vol. 35, no. 2, Feb. 2021, pp. 563–573. https://doi.org/10.1007/s12206-021-0115-1.
Suliman, M. A., et al. “Computational Investigation of Base Drag Reduction for a Projectile at Different Flight Regimes.” 13th International Conference on Aerospace Sciences & Aviation Technology (ASAT-13), 26–28 May 2009, Military Technical College, Cairo, Egypt, paper ASAT-13-FM-05, pp. 1–13. https://doi.org/10.21608/ASAT.2009.23743.
Yang, Yunchao, et al. “Large Eddy Simulation of Base Drag Reduction Using Jet Boat Tail Passive Flow Control.” Computers & Fluids, vol. 198, 15 Feb. 2020, article 104398. https://doi.org/10.1016/j.compfluid.2019.104398.
Wong, D. T.-M. and W. A. Mair. “Boat-Tailed Afterbodies of Square Section as Drag-Reduction Devices.” Journal of Wind Engineering and Industrial Aerodynamics, vol. 12, no. 2, July 1983, pp. 229–235. https://doi.org/10.1016/0167-6105(83)90071-5.
Peterson, Randall L. Drag Reduction Obtained by the Addition of a Boattail to a Box Shaped Vehicle. NASA Contractor Report 163113, National Aeronautics and Space Administration, Aug. 1981. https://ntrs.nasa.gov/citations/19810020556.
Choi, Hyun A., et al. “Numerical Study on the Effect of Boat Tail Shape on Aerodynamic Drag of SUV.” International Journal of Automotive Technology, vol. 22, no. 1, Feb. 2021, pp. 165–172. https://doi.org/10.1007/s12239-021-0017-3.
Kim, Jeong Jae, et al. “Wind Tunnel Tests on Drag Reduction of Heavy Vehicles Using Sinusoidal Boat Tails.” Journal of Mechanical Science and Technology, vol. 34, no. 1, Jan. 2020, pp. 201–208. https://doi.org/10.1007/s12206-019-1221-1.
Chamberlin, Roger and Bernard J. Blaha. “Flight and Wind Tunnel Investigation of the Effects of Reynolds Number on Installed Boattail Drag at Subsonic Speeds.” 11th AIAA Aerospace Sciences Meeting, 10–12 Jan. 1973, Washington, D.C., AIAA Paper 73-139. https://doi.org/10.2514/6.1973-139.
Tran, The Hung, et al. “Effect of Boattail Angle on Pressure Distribution and Drag of Axisymmetric Afterbodies under Low-Speed Conditions.” Transactions of the Japan Society for Aeronautical and Space Sciences, vol. 62, no. 4, 2019, pp. 219–226. https://doi.org/10.2322/tjsass.62.219.
Pandey, Rohit and Rohan Pandey. “Amortized Inference for Model Rocket Aerodynamics: Learning to Estimate Physical Parameters from Simulation.” arXiv, 24 Dec. 2025, arXiv:2512.22248. https://arxiv.org/abs/2512.22248.
Niskanen, Sampo. OpenRocket Technical Documentation. 10 May 2013. https://openrocket.info/documentation.html.
Barrowman, James S. and Judith A. Barrowman. The Theoretical Prediction of the Center of Pressure. NARAM-8 R&D Project, 18 Aug. 1966.
Downloads
Posted
Categories
License
Copyright (c) 2026 Research Archive of Rising Scholars
This work is licensed under a Creative Commons Attribution 4.0 International License.
