The Seldén Furlex is a jib furling system. When you want to furl the jib, you pull the furling line — that line is stored on a drum at the base of the forestay. Getting those 30 turns wound onto the drum correctly is the kind of thing that takes five minutes to do wrong and a lost afternoon to fix.
This post walks through section 6.2 of the Furlex 200 S manual — Winding the line onto the drum — using a 3D model built directly from the exploded-view schematics.
From schematics to Three.js
The assembly manual (595-111-E) has a detailed exploded-view diagram on page 5 with 22 labeled parts. There are no CAD files. The approach is to read the 2D drawings carefully and reconstruct each part’s shape using Three.js primitives:
- CylinderGeometry for the bearing housing, luff extrusion, drum barrel, and flanges
- LatheGeometry (a profile rotated around an axis) for the dome-shaped line guard housing
- TubeGeometry along a helix for the furling line itself
- Dimensions come directly from the spec tables — the Furlex 200 S has a drum Ø 186 mm and height between flanges of 120 mm
The result isn’t photorealistic. It’s a schematic in the same visual language as the manual — readable, measurable, and interactive.
Overview — Furlex 200 S drum assembly
All 22 parts, from the forestay eye terminal at the top to the fork toggle at the bottom. The white flanged spool is the line drum (Ø 186 mm). The large plastic dome is the line guard housing. The small horizontal fitting at the drum's equator is the line guide fitting. Drag to explore.
Step 1 — Thread the furling line
Feed the furling line through the hole in the line guide fitting (the oval bushing at the drum equator, part 21), then through the hole in the line drum half that has a clip. Undo the clip, seat the line in the oval space, and fasten the clip securely.
Step 2 — Choose winding direction
The direction depends on which side the sail's UV protection strip faces. The arrow shows the rotation direction when viewed from above.
Step 3 — Wind 0 / 30 turns
Turn the luff extrusion by hand. Wind approximately 30 turns of furling line onto the drum. The line guide fitting keeps the line centred and distributed evenly.
Step 4 — Secure the line
Secure the free end of the furling line in the tack snap shackle at the base of the lower bearing assembly. This prevents accidental unfurling at anchor or under sail. The first turning block must be at least 300 mm from the drum.
Why the direction matters
When you furl the sail, the luff extrusion rotates. The drum rotates with it, winding the furling line on as the sail wraps up. The exit side of the line is determined by which direction the drum turns — and that’s fixed by the UV protection strip:
- UV strip on starboard → sail furls to starboard → extrusion turns clockwise (viewed from above) → line exits port side of drum
- UV strip on port → counter-clockwise → line exits starboard
Getting this wrong means the line winds in the wrong direction and the sail won’t furl evenly. The 30-turn requirement is a minimum — enough wraps that friction from the coiled line prevents slipping under load.
References
- Seldén Furlex 200 S & 300 S Manual (
595-104-E, 2014) — Section 6.2, p. 26 - Seldén Furlex Assembly Manual with rod forestay (
595-111-E, 2011) — p. 5 exploded diagram