Measuring Flex - V1 - Weight Belt Test

Legacy

Goal

Measure the load required to make the tip vertical (90°) and observe where the blade bends (root, mid, tip).

Specifications / Dimensions

• Clamp depth ≈80 mm on the blade root
• Marks at 0.3 L (root), 0.6 L (mid), and 0.9 L (tip)
• Weights applied in a 2:1 ratio (tip:mid)

Time needed

Type	Hours
Implementation	0.25 h
Waiting	0 h

Bill of Materials

Material	Quantity	Unit Cost	Line Cost
Weight belt with pockets Consumable Holds weights in place to load the fin tip and mid-span	1 belt
Dive weights Consumable Individual weights to create the 2:1 tip-to-mid loading ratio	Mix of weights to reach target load
Rigid ruler or printed grid Consumable Visual reference to observe bend angles along the blade span	1 reference board
Masking tape Consumable Secures the grid or ruler to the support structure	1 roll

Tools Required

Tool	Purpose
Clamp with rubber pads	Secure the blade without marking the rails
Camera or smartphone	Record the deflection for later comparison
Angle finder or protractor	Measure the bend angle at the target load

Instructions

• Step 1 — Load until tip is vertical
  Add weights to tip and mid (2:1 ratio) and stop when the last 20 mm of the tip points straight (≈90°). Record the total weight.

Formula:
F90 = m × 9.81 (N)

• Step 2 — Measure bend at 3 zones
  Take a side photo at the load and estimate local slope (angle) at each zone:
• θ_root at 0.3 L
• θ_mid at 0.6 L
• θ_tip at 0.9 L

Data to Record

• Clamp depth (mm)
• Blade span L (mm)
• Load method: belt with weights on top (tip + mid, 2:1 ratio)
• F90 (N)
• θ_root, θ_mid, θ_tip (degrees at F90)

Limitations

• Dive weights limit fine-tuning of the scale