Choose a Selden block by matching the bearing type to your load: ball-bearing blocks for moderate, dynamic loads that need fine-tuning, plain-bearing blocks for heavy static loads, roller-bearing blocks for high dynamic loads, and ratchet blocks where you hold a loaded sheet by hand. Selden builds every block from glass fiber reinforced polymer and marine-grade stainless steel for a high strength-to-weight ratio, so the right choice comes down to your application and working load, not brand quality.
Selden block types at a glance
| Block type | Best for | Load character | Typical applications |
|---|---|---|---|
| Ball bearing | Fine-tuning under load | Moderate, dynamic | Genoa/jib sheets, spinnaker sheets, mainsheet, pole |
| High load ball bearing | High load in a small block | High, dynamic | Halyards, tackles, runners on keelboats and dinghies |
| Plain bearing | Heavy static loads | High, static | Halyard tuning, mainsheet systems, boom vangs |
| High load plain bearing | Wire / Dyneema core lines | Very high, static | Backstays and rig-loaded control lines |
| Roller bearing | Low friction at high dynamic load | High, dynamic | Backstay tackle, mainsheet, spinnaker halyard, kicker |
| Ratchet | Holding a loaded sheet by hand | Moderate, hand-held | Dinghy main and spinnaker sheets |
What are the main Selden block types?
The Selden block range consists of plain bearing blocks, roller bearing blocks, high load ball bearing blocks, high load plain bearing blocks, and ratchet blocks, plus standard ball bearing and halyard blocks. Each component is designed for top performance and precise interaction with the rig under all conditions, using only top-quality materials like glass fiber reinforced polymer and marine-grade stainless steel.
How do ball bearing and high load ball bearing blocks differ?
Standard ball bearing blocks are used where loads are more moderate and dynamic, ideal where the line needs continual fine-tuning under load. The ball bearings give good sheave rotation with the lowest possible friction, and they come in 20, 30, 40, and 60 mm sheave diameters; the bigger the bearing diameter, the lower the sheave friction. They are mainly used for spinnaker poles, spinnaker sheets and tacks, genoa/jib sheets, mainsheet, and mast tracks.
High load ball bearing blocks carry a very high working load for their size thanks to stainless steel sides and ball bearings, making them ideal for halyard applications, tackles, and runners on keelboats and performance dinghies. The 60 mm version uses Ø5 mm stainless ball bearings with Ø60 mm acetal sheaves and cages to cut friction and weight, with glass fiber reinforced composite cheeks for maximum performance.
When should I use plain bearing or roller bearing blocks?
Plain bearing blocks use acetal sheaves and stainless steel straps for the best strength and long service life, with stiff glass fiber reinforced composite cheeks that keep lines from wedging and a sliding swivel locking mechanism. Available from Ø50-100 mm sheaves, they suit heavy, static loads in halyard tuning, mainsheet systems, and boom vangs.
Roller bearing blocks are built for low resistance at high, dynamic loads, using Torlon rollers and acetal ball bearings to stabilize the sheave under side loads. They make quick release of a highly loaded backstay tackle, mainsheet, spinnaker halyard, or kicker fast and safe, and are available for Ø60 and Ø80 sheaves. For wires or Dyneema/Spectra core, choose the high load plain bearing block: stainless steel with electro-polished cheeks, an anodized aluminum V-shaped sheave, and a polymer plain-bearing bushing for rig-loaded lines like backstays.
Which Selden block should I choose for my boat?
Match the block to the load and the job. Use ball bearing blocks for sheets and control lines that you trim constantly under moderate load, and step up to high load ball bearing blocks for halyards, tackles, and runners. Reach for plain bearing blocks on heavy static loads such as vangs and mainsheet systems, and roller bearing blocks where a high dynamic load must release quickly. Ratchet blocks are the answer on dinghies where a sailor holds a loaded main or spinnaker sheet by hand — the sheave shifts automatically from free-turning to ratchet as load builds, giving control and convenience together.
Frequently asked questions
What materials are Selden blocks made from?
Selden blocks use glass fiber reinforced polymer and marine-grade stainless steel, giving a high strength-to-weight ratio and long service life under full rig loads.
Which Selden block is best for a mainsheet?
Ball bearing blocks suit a continually trimmed mainsheet, while plain bearing blocks are better for heavier, more static mainsheet systems and boom vangs.
What is a ratchet block used for?
Ratchet blocks make it easier to hold a loaded sheet by hand, automatically switching from free-turning to ratchet as load increases — typically on dinghy main and spinnaker sheets.
What are high load plain bearing blocks for?
They are optimized for wire or Dyneema/Spectra core lines subject to rig loads, such as backstays, with a V-shaped anodized aluminum sheave and stainless steel construction.
How does sheave diameter affect friction?
On ball bearing blocks the larger the bearing diameter, the lower the sheave friction, so bigger sheaves run more freely under load. Selden offers 20, 30, 40, and 60 mm options.
What is a Selden 2:1 halyard block for?
The halyard 2:1 block provides a 2:1 purchase for a Code 0 or main halyard with a captive pin, and its 30, 40, and 50 mm sheaves match the CX15, CX25, and CX45 furlers respectively.