Installed at the base of the backstay to enable adjusting its tension, backstay adjusters are, arguably, one of the least appreciated sailing accessories with the greatest benefit for performance sailing.
As you use the backstay adjuster to increase rig tension, you'll experience immediate results: forestay tension increases, roller furling gear operates more efficiently, and headsail shape improves -- allowing you to sail faster and point higher.
Harken integral backstay adjusters come in four sizes to fit boats with 7/32" - 3/8" (5-10 mm) wire. They are typically installed on sailboats in the 30 to 60 ft range (9 to 18 m).
Harken adjusters feature a unique double-action pump that delivers oil when the handle is both pushed and pulled.
This moves oil through the system twice as fast as the single-action pumps used on other integral backstay adjusters.
When releasing backstay tension, the rate of tension release can be controlled by how far open the knurled pressure release knob is turned.
Unlike competing models, the release knob cannot be over-tightened by hand when closing the pump, thus preventing oil leaks and damage to the valve.
A passive pressure relief valve is factory set to prevent the crew from over-tensioning the backstay.
An analog gauge with pressure increments reading 0-5 (0-5000 psi) is prominently mounted at the top of the cylinder, where it's easy to see.
The gauge can be oriented to four different viewing positions to suit your cockpit layout.
The complete kit includes:
A black hardcoat-anodized aluminum cylinder and pump, valve, gauge, stainless pump handle with three attachment options ranging from removable to permanently attached, user manual. The lower toggle is sold separately.
• All cylinders terminate in a clevis fitting; rod terminal options include a clevis or a low profile lashing eye
• All pins and plugs are stainless steel
• Clear anodized (silver) cylinders are available by special order
• Harken strongly recommends attaching a toggle to the cylinder's lower clevis to provide two axes of articulation to reduce fatigue of the aluminum cylinder clevis due to stay movement. Standard eye-jaw toggles fit all Harken cylinders. Note: Toggles are sold separately
• For most new installations, the diameter of your backstay and chainplate pin diameter will determine the size of the adjuster to purchase
Heavy on the technical side...
Integral backstay adjusters incorporate the hand pump and hydraulic cylinder in a single unit, installed at the base of the backstay.
Backstays can also be adjusted using a component-style hydraulic system with the hand pump, valves, and gauge(s) located in a remote mounted panel - perhaps in the wall of the cockpit well - and only the hydraulic cylinder installed at the base of the backstay. These systems can be valved, so the same pump can be used with separate cylinders to adjust other rigging components such as halyards, Cunninghams, mast jacks, travelers, vangs, or outhauls.
Sizing - Integral Backstay Adjusters are sized according to the breaking strength of the cylinder rod, which is comparable to the breaking strength of the maximum diameter wire they are used with — measured in thousands of pounds.
The prefix "-" is called the "dash size" and is placed before the rated strength, so -12 (dash twelve) rod has a rated strength of 12,000 lb.
For most new installations, the diameter of your backstay and chainplate pin diameter will determine the size of the adjuster to purchase.
When replacing an existing adjuster, or if your backstay incorporates single sideband insulators, you might try to match pin to pin distances, stroke lengths, or known desired pull forces for your particular rig. (Don't forget to take the toggle length into account when calculating.)
• Maximum pressure relief valve is factory set at 5,000 psi