The Harken Single-Acting Integral Backstay Adjuster is a self-contained hydraulic tensioner that lets you tune mast bend and headstay tension quickly by pumping an integrated handle, with no external hoses to snag or leak. Designed for sailboats roughly 30 to 60 feet, it puts precise, repeatable backstay control within reach for both racers chasing sail shape and cruisers seeking smoother furling.
Harken integral backstay adjuster at a glance
| Feature | What it does | Why it matters |
|---|---|---|
| Single-acting integral pump | Pumping the handle pushes fluid to increase tension; a release knob bleeds pressure back | Fast, one-handed adjustment on the fly |
| Internal hydraulic system | Self-contained cylinder with no external hoses | Nothing to snag or leak; low maintenance |
| Pressure relief valve | Caps maximum load automatically | Prevents over-tensioning and protects the rig |
| Compact, integral body | Adjuster is built into the backstay run | Saves space and blends into existing rigging |
| Multiple attachment options | Flexible handle and end connections | Adapts to different boats and layouts |
What is a single-acting integral backstay adjuster?
A backstay adjuster changes the tension on the backstay, which in turn controls mast bend and headstay sag. "Single-acting" means the built-in pump does work in one direction only: each stroke of the handle drives hydraulic fluid to raise pressure and increase tension, while a separate release knob lets you ease it back in a controlled way. "Integral" means the hydraulic cylinder and pump are a single self-contained unit that sits in-line with the backstay, rather than a remote pump connected by hoses.
How does the Harken integral adjuster work?
To add tension you pump the handle, which pushes fluid inside the sealed cylinder and extends the ram, tightening the backstay and bending the mast. To reduce tension you open the release knob and the pressure bleeds off smoothly. Because the system is fully internal, there are no external hoses to route, snag, or leak, and a built-in pressure relief valve prevents you from over-loading the rig. All the working components are readily accessible, which keeps routine maintenance simple.
Which size do I need?
Harken offers the integral adjuster in several sizes, matched to the load your rig will see and the pin and bore dimensions of your fittings. Smaller boats typically use the lower-numbered sizes, while larger, higher-load rigs step up. Always match the adjuster to your backstay wire diameter, clevis pin size, and the manufacturer's working-load guidance rather than choosing by boat length alone.
Who is it for — racing or cruising?
The adjuster suits both. Racers use fast backstay changes to flatten the mainsail, open the leech, and reduce headstay sag as the breeze builds, optimizing sail shape mode by mode. Cruisers benefit from easing backstay tension to reduce headstay sag for smoother, lower-effort headsail furling, then adding tension for better upwind performance. In both cases the single-acting integral design delivers reliable, repeatable adjustment with minimal upkeep.
Frequently asked questions
What does a single-acting backstay adjuster do?
It increases backstay tension with each pump of the handle and releases it through a control knob, letting you tune mast bend and headstay sag on demand.
Does the Harken integral adjuster have external hoses?
No. The hydraulic system is fully internal, so there are no external hoses to snag or leak, which keeps it durable and low-maintenance.
What size boats is it designed for?
The adjuster is intended for sailboats of roughly 30 to 60 feet, with different sizes matched to rig load and fitting dimensions.
Can it be over-tensioned?
A built-in pressure relief valve caps the maximum load automatically, helping prevent over-tensioning and protecting the rig.
Is it hard to maintain?
No. All the working components are readily accessible, so routine maintenance is straightforward.
How do I choose the right size?
Match the adjuster to your backstay wire diameter, clevis pin size, and bore, following Harken's working-load guidance rather than boat length alone.