The mandrel
If it flexes, it binds.
The mandrel carries the concentrated furling load, so it is the stiffest part of the boom: high-modulus prepreg carbon.
SparsFurling booms
Stiff enough to reef cleanly.
Mandrel, shell and furling system, engineered as one structure under mainsheet load.
01What it is
A beam when sailing.
A machine when reefing.
With the mainsail set, the boom is a structural beam carrying mainsheet and vang load. The moment you reef or drop sail it becomes a mechanism, and a mechanism only runs smoothly inside a beam that has not bent. If the boom flexes, the mandrel binds, the sail furls unevenly and the shape goes with it. Stiffness is what makes the furling work.
Section, laminate and mandrel are set to your mainsail area, boom length and mainsheet geometry. Send us the specification form and we size the structure with you against the full load case.
Send us your specification
02Intentional design
Two ways
to reef.
Reef anywhere, not at a cringle.
Continuous furling has no discrete reefing points, so the mainsail can be shortened to any point along the luff and set exactly for the conditions. For most vessels and most programmes this is the right answer, and the simplest.
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03How we build
Two processes.
One boom.
- 01
Mandrel: high-modulus prepreg
The mandrel is built from high-modulus prepreg carbon, cured at controlled temperature for the highest stiffness at the lowest mass.
- 02
Shell: resin infusion
The outer shell is resin-infused, which suits the tapered section, gives a clean finish and keeps the cost sensible.
- 03
One model for both
FEA models how mandrel and shell share the load, so the boom behaves as one component rather than two parts bonded together.