Service & support
How to use hydraulic Mast Jacks
Selecting and using the right mast jack is not as simple as it seems. Modern rigs demand a lot of knowledge before you can trim them correctly.
Pre-tensioning the rig
Traditionally, tensioning the rig was a matter of adjusting it on the leeward side when sailing. With the introduction of rod and fibre rigging and carbon fibre the loads on masts have increased drastically, resulting in another way of pre-tensioning the rig. The rig is pushed upwards from the bottom using a hydraulic mast jack.
What is the principle of mast jacks?
The principle use of a hydraulic jack is to adjust the rigging screws without tension loads on them and then to lift the mast step with the hydraulic jack and put it on shims. Good pre-tensions can be achieved with some iteration on the length of the rigging screws. This method is much more certain and reliable than any other method.
Why do Mast jacks have a great value for adjusting the rig tension?
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A limiting factor of using turnbuckles is that it may be impossible to achieve the necessary tensions by turning the rigging screws with hand tools. The threads of the rigging screws may also be damaged in the procedure.
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When fibre rigging (like PBO) is introduced as standing rigging wires, this instantly eliminates the ability to apply torque on the wires.
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The pre-tensions of a rig become reproducible. That is very important for racing rigs with different pre-tensions for different wind speeds and seaways.
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Once the forestay, shrouds and mast butt location are tuned for the boat, you do not have to alter them. The rig tension is adjusted with the mast jack.
The 2 basic types of mast jack:
Holmatro Through Bar set: This set contains 2 hydraulic jacks and a hand pump. The jack will be placed parallel to the mast and the jacking bar (not supplied)goes through the mast. An economic system, with one set you can jack several rigs. Since the jacks can be stored in a dry place after use, these jacks can be manufactured out of aluminium, with standard high-pressure quick-connect couplers.
Holmatro In-Mast jack set. These are permanently mounted jacks which are mounted upside down inside the mast. Mostly used by racing yachts that will change the rig tension before each race. The mast jack is always ready for use and needs no storage space. The jack is made from 17/4 Ph stainless steel to have a long lifetime. As a standard, all Holmatro jacks are equipped with tilting saddles.
Quick-connect couplers (hydraulic connectors) are available in full stainless steel for working pressures of 720 bar (10.000 psi). Holmatro is also manufacturer of a range of pumps of professional quality.
Shims
The shims can vary in height to ensure that the foot of the mast, when resting, touches on all it's perimeter both fore and aft in order to distribute the load uniformly along the profile surface. If the mast touches only fore or aft, modify or add the wedge-shaped spacers to ensure that the load is evenly distributed.
Find a dealer
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