A boom vang controls leech tension and boom height by applying downward force on the boom, and the four main types are flexible (block-and-tackle), rigid (air-spring/pneumatic), Gnav (inverted), and hydraulic. The right choice depends on your boat size, sailing style, and whether you want to eliminate the topping lift.
Boom vang types at a glance
| Type | How it works | Topping lift needed? | Best for |
|---|---|---|---|
| Flexible | Blocks with purchase apply downward force; simplest design | Yes, on midrange boats | Dinghies and midrange cruisers |
| Rigid (Hard Vang) | Air-spring (pneumatic) telescopic tube supports and de-powers the boom | No | Cruisers and racers wanting boom support |
| Gnav | Inverted strut pushes down on the boom from above | No | Small sport boats needing cockpit room |
| Hydraulic | Piston-in-cylinder driven by a plumbed hydraulic system | No | Large yachts with heavy booms |
What is a boom vang and what does it do?
A boom vang applies a downward force on the boom to control leech tension at all points of sail, independent of the mainsheet. By holding the boom down when the mainsheet is eased, it flattens the mainsail leech and keeps the sail powered up correctly off the wind. Depending on your sailing style, one of the four main vang types will suit your boat best.
How does a flexible vang differ from a rigid vang?
A flexible vang is the simplest type: it is built from blocks with a purchase system that pulls the boom down, and it lets you control leech tension regardless of mainsheet load. On midrange boats it still needs a topping lift to support the boom. A rigid vang, also called a Hard Vang, is an air-spring (pneumatic) telescopic tube with purchase building. It de-powers the sail quickly and holds the boom up on its own, so no topping lift is required.
What is a Gnav vang?
The Gnav ("vang" spelled backward) is an inverted vang: a rigid strut extends obliquely upward from the boom to the mast, exerting a force that pushes down on the boom. It delivers the same leech control as a conventional vang but from above, which frees up cockpit space. It is commonly used on small sport boats such as the Melges 15, where the open room lets the crew move freely during maneuvers.
When should I choose a hydraulic vang?
Hydraulic vangs are the least common type because of their cost and complexity, but the principle is the same: a stainless steel piston rod with an aluminum piston rides inside an anodized aluminum cylinder, sealed by a series of seals that need periodic servicing. Whether double-acting push-pull for large yachts with heavy booms or a gas-return design, the system requires the boat to be plumbed with hoses, a reservoir, and a control panel. These installations should be done professionally and can cost as much as the most expensive mechanical vang.
Which boom vang should I choose for my boat?
Choose a flexible vang for a simple, economical setup on a dinghy or midrange boat where a topping lift is acceptable. Choose a rigid vang if you want to eliminate the topping lift and gain quick de-powering plus boom support. Consider a Gnav on a small sport boat where cockpit space matters, and reserve hydraulic vangs for large yachts with heavy booms that already run a hydraulic system.
Frequently asked questions
What does a boom vang actually control?
It controls the downward force on the boom, which sets leech tension in the mainsail at all points of sail, independent of the mainsheet.
Do I still need a topping lift with a boom vang?
Flexible vangs on midrange boats still need a topping lift to support the boom, but rigid, Gnav, and hydraulic vangs support the boom themselves.
What is a Gnav and why use one?
A Gnav is an inverted vang whose strut pushes down on the boom from above; it is popular on small sport boats because it opens up cockpit room for the crew.
Are hydraulic vangs worth it for a cruiser?
Hydraulic vangs are costly and require professional installation with hoses, a reservoir, and a control panel, so they are usually reserved for large yachts with heavy booms.
What is a rigid vang made of?
A rigid vang is an air-spring (pneumatic) telescopic tube with purchase building, letting you de-power the sail quickly while supporting the boom.