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SAE Aero Design 2024 — AeroJC Micro-Class Team 313 (complete specs)

Cheat sheet

Printable study sheet: formulas → definitions → topic notes → traps.

Formulas

Wing loading: W/S = ½ ρ V_s² Cl

L = ½ ρ V² S Cl ; D = ½ ρ V² S Cd

Static margin ≈ (x_np − x_cg)/MAC ; report loaded SM ≈ +17% chord

Elevator area ≈ 25% of horizontal stabilizer (report elevator planform 12.59×0.787 in → area ≈9.209 in²)

Rudder area ≈ 25% of vertical stabilizer (report rudder ≈4.475 in²)

Cl_max ≈ 1.77 (XFLR5) used in propulsion matching

With slats: Cl ≈ 1.33 @ 8°, 1.49 @ 10°; without: 1.12 @ 8°, 1.28 @ 10°

Servo torque model (report): τ ∝ (C² V² L sin²S1) / (cos S1 · tan S2)

Aspect ratio AR = b²/S ≈ 4.92 (b=40.56 in, S=334.21 in²)

Empty ≈2.65–2.86 lb class; payload water 0.992 lb (15.2 oz) in 67 oz bag; budget ≈$813 / ~5 months

W/S=½ρV²Cl ; Cl_max≈1.77 ; AR≈4.92 ; S≈334 in² ; b≈40.56 in

SM≈(x_np−x_cg)/MAC ≈ +17% loaded

Slats Cl 1.33@8° / 1.49@10° vs clean 1.12 / 1.28

Empty ~2.65–2.86 lb ; payload 0.992 lb water ; budget ~$813

FOS≈2.01 structural; motor Cobra 930 kV; APC 13×6

Definitions

Team AeroJC #313: JSS Science and Technology University — SAE Aero Design East Micro-Class 2024
Micro-Class STOL: All-electric RC; span/payload/empty-weight scoring; ≤10 ft takeoff target
FX 63-137: Selected high-lift low-Re airfoil after trade vs S1223RTL and FX 63-143
Flaperon: Combined flap+aileron on EPS thermocol — lift + roll for short takeoff
Slat: Leading-edge high-lift device; styrofoam hot-wired with balsa guides
Taildragger: Landing gear giving ~10–11° ground AoA for takeoff
Water bag payload: 15.2 oz water in 67 oz bag; ribbons + de-aired fill vs 2.05 lb baffled 3D tank
Pendulum stability: High wing + CG below wing for lateral/cross-wind behavior
Cobra C2826/10: Motor 930 kV; prop APC 13×6; battery 1000 mAh (tech data sheet)
Emax ES08MDII Metal: Servos for flaperons, rudder/LG, elevator — 22.1981 oz·in each
STOL: ≤10 ft takeoff target Micro-Class

Topic-wise short notes

Study these first — one block per syllabus topic. Then read the deep notes below.

Competition & iterations

Team 313 Micro-Class East 2024; ~$813; ~5 months; 3 iterations.
Fail: printed tank + 32.7 in → ~4.08 lb, ~25 ft TO.
Win path: water bag 0.992 lb + 40.55 in + slats/flaperons + balsa → ~10 ft.

Trades

Rectangular high wing + pendulum CG; conventional tail + 3D attach.
Pusher→tractor/taildragger (~11° AoA); payload outside avionics + epoxy.
Span score hit offset by ~48% empty weight cut.

Airfoil & wing

FX 63-137 over S1223RTL / FX 63-143 @ Re=2e5; Cl_max~1.77.
b=40.55–40.56 in; c~8.14; S=334.21; AR=4.92; halves 20.28 in.
Slats raise Cl to 1.33/1.49 @ 8°/10° vs 1.12/1.28 clean.

Empennage, prop, servos

Elevator 12.59×0.787 (~25% HT→9.21 in²); rudder ~4.48 in².
Cobra C2826/10 930 kV; APC 13×6; 1000 mAh.
Emax ES08MDII Metal 22.2 oz·in on flaperons, rudder/LG, elevator.

Analysis & CG

SM ~+17% loaded; empty ~+9.22%; NP~12.31; FOS~2.01.
Length 33.24; width 40.56; height 12.95; empty sheet 2.651 lb.
Thrust rig + CG balancer + LG jig; de-aired ribbon-strapped bag.

Exam traps & quick notes

Source: AeroJC Team 313 TDR — SAE Aero Design East 2024 (full fact dump on this page).
Result narrative: 3rd place Florida 2024 Micro-Class.
Tools: SolidWorks, XFLR5, MATLAB scoring, Ansys/SimScale FEA+CFD, ground thrust rig + CG balancer + LG jig.
Three iterations: printed tank+32.7 in span failed → bag+40.55 in span+slats/flaperons+balsa succeeded.
Story: heavy printed tank failed → bag + span + slats/flaperons.
Tools: XFLR5, MATLAB score, SimScale, SolidWorks, thrust/CG rigs.

Comprehensive notes

Executive summary, iterations, budget, goals

Team 313 / AeroJC, JSS Science and Technology University — SAE Aero Design East Micro-Class 2024. All-electric RC STOL with water payload scoring.

Three iterations in ~5 months; budget ≈$813.

Iter 1: 3D-printed baffled water container + ~32.7 in span → empty/plane weight ≈4.08 lb, takeoff ≈25 ft (missed ≤10 ft). Container alone ≈2.05 lb with 32.63 oz payload attempt.
Later: water bag (15.2 oz / 0.992 lb water in 67 oz bag), span 40.55 in, chord ≈8.14 in, slats + flaperons, balsa build → weight ≈2.86 lb (~48.3% reduction), takeoff toward ≤10 ft.

Objectives: takeoff ≤10 ft; maximize flight score under span-limited scoring; water container that fights slosh; cost without killing performance.

Constraints: optimize span vs takeoff for 0.992 lb water (MATLAB scoring); max payload / min empty weight; 4S LiPo propulsion battery + independent Rx battery (electronics weight); leakage risk to avionics.

Discriminators: custom LG jig; water bag + ribbons; styrofoam slats; flaperons.

Risk mindset (TDR): risk assessment + trade-offs from day one (Table 3); schedule held via three planned iterations and late spares/presentation window.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Schedule, design flow, tools

Five-month deadline; three design iterations planned; ~1 month for report; last ~3 weeks for spares + technical presentation (Gantt in TDR Table 4).

Flow: MATLAB scoring → weight/payload/propulsion targets → wing/tail/LG design loops → XFLR5 control surfaces & stability → Ansys/SimScale structures + CFD → materials by strength-to-weight & availability.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Planform, tail, electronics, payload, overall trades

Wing planform: rectangular high wing (manufacture + stall with slats/flaperons fixing classic rectangular stall/uneven lift). CG below wing → pendulum lateral/cross-wind stability. Morphological matrix (Table 6) documented.

Tail: conventional over T-tail and V-tail (weight, stability, control, manufacturability — Pugh Table 7). Risk: glued empennage only → gust rupture → mitigated with 3D-printed mechanical attachment.

Electronics / prop layout: early pusher (high T/W) abandoned — prop strike risk + forced tricycle. Moved to tractor path with taildragger. Water leakage → payload outside avionics bay; bag inner layer epoxy coated.

Payload Pugh: printed baffled tank (heavy, 25 ft takeoff) vs bag + external ribbon partitions (slosh mitigation, weight cut 4.08→2.86 lb).

Overall: span increase to 40.55 in costs score points but enables 10 ft takeoff; ~48% empty-weight cut compensates and allows more payload attempts.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Scoring strategy & optimization levers

MATLAB scoring aimed at ~16 points/flight by:

Trade larger span S + flaperons/slats for Z (takeoff ≤10 ft).
Cut W_empty (water bag + balsa) to offset span score hit.
Lower empty weight → raise W_payload each attempt for score.

Key optimization factors: (1) span for lift of 0.992 lb + 10 ft TO; (2) thrust vs drag; (3) taildragger ~11° ground AoA; (4) payload enclosure/attachments.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Environmental considerations

Temperature ↑ → density ↓ → performance ↓.
Humidity ↑ → fewer molecules for given volume → lift ↓.
Cross-winds → control/TO/landing/maneuver risk; Lakeland winds comparable to Mysuru test site.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Airfoil selection & wing design — every number

Requirements: high Cl_max; low Re; high stall α; less negative Cm.

Shortlist: S1223RTL, FX 63-143, FX 63-137 @ Re=200000 (XFLR5 batch). S1223RTL: higher Cl but strong nose-down moment, small drag bucket, very thin TE → rejected. FX 63-143: OK Cl, wide bucket, worse than FX 63-137 → FX 63-137 selected.

Wing param	Value
Planform	Rectangular high wing
Span (final)	40.55 in (tech sheet 40.56 in)
Span (first)	32.67 in
Chord	8.14 in (MAC sheet 8.24 in)
Wing area	334.21 in²
Aspect ratio	4.92
High-lift	Slats + flaperons (25 ft → 10 ft TO)
Cl_max (XFLR5)	≈1.77

Wing build geometry: two spanwise sections each 20.28 in, joined on carbon spars — matches 40.56 in total span on the tech sheet.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Empennage, propulsion matching, servos

Elevator: 12.59 × 0.787 in; sized ≈25% of HT area → ≈9.209 in². Rudder: ≈4.475 in² (≈25% of VT). Inverted T-tail manufactured (see mfg).

Propulsion: wing loading W/S = ½ρV²Cl with Cl_max 1.77; Sadraey-style matching for RoC, Vmax, Vstall (Table 13). Tech data sheet:

Item	Spec
Motor	Cobra C2826/10, 930 kV
Propeller	APC 13×6
Battery capacity	1000 mAh (4S LiPo class rule)
Empty weight (sheet)	2.651 lb

Servos: XFLR5 hinge moments → lightest motors meeting torque. All Emax ES08MDII Metal @ 22.1981 oz·in for flaperons, rudder & landing gear, elevator.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Takeoff, stability, structures, aero analysis

Takeoff: MATLAB trajectory; slats+flaperons → 10 ft. First printed container forced ~20–25 ft margin and score loss. Fix: water bag + taildragger ~10° AoA.

Static stability (XFLR5): Cm–α → static margin ≈17% of chord; neutral point ≈1.383 and related LE offsets (sheet: NP at 12.31; fully loaded CG 10.92 with SM +17%; empty CG 11.55 with SM +9.22%). Cn–β: Cn=0 at β=0 with restoring yaw.

Dynamic / slosh: fold bag, strap with ribbons, remove air before fill → little impact on dynamic stability.

Structures (SimScale): deformation, von Mises, FOS ≈2.01; LG and tail-boom safe for flight loads.

Aero: SimScale pressure/velocity + XFLR5 streams. Cl with slats: 1.33 @ 8°, 1.49 @ 10°; without: 1.12 / 1.28.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Materials, manufacturing sequence, interfaces

Materials selected by strength-to-weight and availability (Tables 16–17). Manufacturing as mini assembly line (Table 18).

Fuselage: SolidWorks; 0.157 in balsa; laser cut; trusses for strength/weight.
Wing: 1.96 in styrofoam hot-wire; two 20.28 in halves joined by 0.12 in Ø carbon tubes + glass fiber tape; EPS thermocol flaperon taped; slats hot-wired with balsa guides, sanded, spanwise spacing.
Empennage: inverted T-tail, 0.157 in EPS thermocol; glued + 3D attachment.
Landing gear: Al rods taildragger; 3D-printed jig folds front LG into inverted-U; rear LG on tail boom via 3D prints.

Interfaces/attachments catalogued (Figure 10). Custom jigs for repeatability.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Mass properties, CG, testing, tech data sheet

Excel mass build-up from LE origin (Table 19). Tech sheet moments (sample):

Component	Weight (lb)	Arm (in)	Moment
Motor	0.337	8.6	2.89
Battery	0.187	4.5	0.84
Payload	0.992	−1.43	−1.41
Fuselage	0.078	4.35	0.34
Tail	0.121	−19.96	−2.41

Aircraft envelope (sheet): length 33.24 in; width 40.56 in; height 12.95 in; wing area 334.21 in²; AR 4.92; MAC 8.24 in.

Testing: weight sensitivity Pareto; static thrust rig; CG balancing apparatus; half-filled de-aired water bag strapped externally.

External: SAE Aero Design ↗ Engineering Toolbox ↗

Interview Q&A — SAE Aero 2024 (full answers)

Q. Biggest failure and fix?

Heavy 3D-printed baffled tank (~2.05 lb) + 32.7 in span → ~4.08 lb plane and ~25 ft takeoff. Switched to 0.992 lb water in a bag with ribbons, grew span to 40.55 in, added slats/flaperons and balsa, cut weight ~48%, hit ~10 ft. MATLAB showed the span score hit was worth the weight/payload gain.

Q. Why FX 63-137 and those wing numbers?

Needed high Cl_max, low Re, high stall α, mild Cm. S1223RTL Cl was higher but thin TE and harsh Cm; FX 63-137 won XFLR5 at Re=2e5. Final: 40.55×8.14 in class, S=334 in², AR≈4.92, Cl_max≈1.77; slats raise Cl to ~1.49 at 10° vs ~1.28 clean.

Q. Stability and slosh?

High wing + low CG pendulum; conventional tail with 3D mechanical attach after glue-only risk; XFLR5 SM ~17% loaded; bag folded, de-aired, ribbon-strapped outside avionics with epoxy liner.

Q. Propulsion and servos?

Matching chart + Cl_max 1.77. Sheet: Cobra C2826/10 930 kV, APC 13×6, 1000 mAh. Emax ES08MDII Metal 22.2 oz·in on flaperons, rudder/LG, elevator — lightest that met hinge-moment torque.

Q. Structures and manufacturing talking points?

SimScale FOS≈2.01 on load path; laser-cut 0.157 in balsa fuselage; hot-wire foam wing halves on 0.12 in carbon spars; EPS empennage; Al LG with printed jig. Same design→test→iterate loop as BAJA.

Q. Quote the CG story off the data sheet.

Fully loaded CG ~10.92 in from LE with SM +17%; empty CG ~11.55 with SM +9.22%; neutral point ~12.31; length 33.24 in. Payload arm negative (forward of LE origin in their sheet) so water placement was a CG lever.

External: SAE Aero Design ↗ Engineering Toolbox ↗