Spinnaker forces can be measured, displayed and recorded in real time using TVM (Tension Vector Measurement) units.

• Titanium Tension Measurement Link
• 3 Axis strapdown magnetometer
• 3 Axis MEMS accelerometer
• Microcontroller
• RF Link
• Battery power source

Theory and Operation

In operation, a TVM unit is put in series with each of the three corners of the spinnaker utilizing standard snap shackles. These three units measure the tension force applied by either the halyard, sheet or guy. They also each measure the direction of this force using the 3 Axis magnetometer and accelerometer combination.
This combination allows determination of the tension vector (force and direction) for each corner of the sail. These 3 data streams are radioed once per second to a deck located unit, which contains its own 3 axis magnetometer/accelerometer as well as radio receiver.
This unit then determines the spinnaker forces relative to the yacht centerline (by taking the difference between the force heading and the yacht heading) and transmits this information via RS232 to an on board computer.

Features and Benefits:

• Small, lightweight, battery powered and easy to use
• Real Time output of Spinnaker thrust for trimming guidance
• Force measurements for Spinnaker Code validation
• Force measurements for VPP force inputs
• Force measurements for Rapid Spinnaker Development and Optimization
• Internal Antenna (Range approx 50 m)
• Internal Rechargeable Lithium Ion Battery

Options

• 1500Kg, 2000Kg, 3500Kg, 6000Kg

System Consists of:

• 3 TVM Corner Measurement Units
• Deck Unit (contains Compass, Data Receiver, RS232 instrument interface
• PC_VFM_LOG PC Software to capture, display and log the data from the Deck Unit
• PC_TVM_CAL PC Software for Unit Setup, Calibration
• Lithium-Ion Battery Charger and Cables

Preliminary Specifications:

TVM units (used at each spinnaker corner):

• Force range: 2000Kg
• Link Length (Hole to Hole): 87 mm
• Battery: 3.7 V Lithium Rechargeable (approx 10hr)
• Output rate: 1 Hz
• Output data: Tension, Heading, Inclination (from Horizontal)
• Weight: Approx 200 gm, incl battery
• Size: 55 x 55 x 40 mm
• Accuracy:
• Tension: +/-0.5%
• Heading: +/-2 deg
• Inclination: +/2 deg

Central Deck Unit

• Battery: 9 V Lithium, more than 50 hours
• Size: Approx 100 x 50 x 25 mm
• Output type: RS232 19200
• Output Data: Each Corner's Raw Data (Bearing, Inclination, Tension) Yacht Heading, Heel

This picture shows the compass heading of each of the 3 corners

This picture shows the inclination angle (from horizontal, negative pointing downwards) from the 3 corners

This picture shows the tension in the 3 corners and also the computed total thrust for the entire sail, in the direction of the boat.
(Data have been hidden for proprietary reasons)