Seldén composite and stainless steel sheave boxes for dinghy mast halyard exits, available in 21mm and 35mm sheave sizes with plain bearing, ball bearing and XSM bearing options for halyard turning, jib halyards and spinnaker halyards.
How to choose
Sheave box selection depends on three things: the application, the halyard type and the rig load. Start with the sheave diameter. The 21mm sheave boxes suit lower-load applications such as halyard turning points and boom outhauls. The 35mm sheave boxes are rated for wire and HMPE jib halyards and higher-load applications where a larger sheave reduces halyard wear and friction.
Within the 35mm jib halyard range, three bearing options are available. The plain bearing composite sheave is the standard option for most dinghy jib halyards. The plain bearing aluminium sheave improves wear resistance and increases the safe working load, the correct upgrade if you are replacing a worn composite sheave. The stainless steel ball bearing sheave is the highest performance option, suited to classes where rig tension is high and the halyard is adjusted while sailing, reducing friction at peak loads.
The stainless XSM bearing jib halyard sheave box (505-092-23) is in a separate category. It uses a solid XSM bearing rather than conventional ball bearings, developed specifically for the Fireball, 505 and Flying 15 where extremely high halyard tensions are standard. It is not a general-purpose upgrade, choose it only for these classes or equivalent high-tension applications.
The stainless spinnaker halyard sheave box (505-079) is a low-profile fitting for high line-speed applications such as spinnaker halyards and pole lifts, where a compact box with minimal friction is needed.
The wear guard (505-075) is a stainless steel insert that fits all 505-071 sheave boxes to protect the mast and box from halyard wear. It is recommended for any installation where the halyard runs over the top of the box.
Dinghy class applications
The XSM bearing sheave box (505-092-23) is specifically referenced for the Fireball, 505 and Flying 15 classes where 1:1 jib halyards are used at exceptionally high tensions.
