Wind Generator

The only practical way to mount a wind generator on a ketch is on the mizzen mast. On a sloop a roughly 12 foot mast is often erected for the wind generator. On a ketch there is no room aft of the mizzen mast due to the mizzen boom.

Placement Options

The main mast is taller than the mizzen and a good choice from the standpoint of best wind. Due to the main sail and masthead jib the only option on the main mast would be on top of the mast which is impractical. This is where the wind transducer is mounted which needs unobstructed air flow. The VHF antenna is also atop the main mast.

The mizzen mast is the only viable option. Although there is no currently mounted on the top of the mizzen mast, a top mount is impractical. A disadvantage of using the top of the mast is difficulty mounting or unmounting the wind generator when stepping or unstepping the masts. The front of the mizzen mast is unobstructed by the mainsail and provides better access. The wind generator has to be mounted far enough forward of the mast that the blades or tail cannot hit the mast. As high as possible is best but below where the blades could hit the triadic stay. Mounting or unmounting can be aided by installing mast steps.

Measurements and Approximate Placement

Measurements of the mast, boom & backstay provide the means to plan placement. Another consideration for both the wind generator and the radar is where the mounts will be when the masts are stored on the boat. A scanstrut LM-2 has been purchased for the radar which allows the radar to be easily removed. The mounting for the wind generator is a bit more of an obstruction when the masts are down.

There is enough room to mount the radar above the level of the speaders and mount one or even two wind generators below the top of the mast but above the radar. The wind generator will be mounted so that the top of the blades at least 2" below the level of the masthead. Since the triadic stay slopes up this provides enough room. Each wind generator mount at least 54" (4'3") of room to provide 3" above and below the range of the blades if a 4 ft wind generator was mounted. Since the generator being installed is 3 ft in diameter this will provide plenty of clearance.

The wind generator mount can be mounted with the masts down with the wiring put in place at that time. The mast steps can be mounted at the same time. The wind generator itself can be mounted after the masts are raised by going up the mast steps.

Electrical Connections

The Air Breeze wind generator has a very primitive charge controller. It appear to be a voltage regulator with a potentiometer to adjust maximum voltage. Turn clockwise to increase voltage. The range is 54.4V to 68V. It would be very difficult to hold a voltmeter, stay out of the way of the blades, and adjust a potentiometer on the side of the unit while standing on mast steps some 30 feet or more above the cockpit sole.

An alternate to using the Air Breeze charge controller is to use the ability to lock the Air Breeze by presenting a short circuit. A SPDT solenoid can be used to disconnect the wind generator from the battery bank and connect it to ground if voltage exceeds 59.1V (just under the high end of the battery charging range). Hysterysis will be needed on this voltage transition. If this limit is exceeded too often then the potentiometer on the Air Breeze can be turned slightly counterclockwise on a windless day. With ⅛ turn producing a 2.4V change, fine adjustment of the Air Breeze is nearly impossible making the solenoid and very accurate charge voltage measurement on the boat a better choice.

Mast wiring can lead to a waterproof connector in the mounting assembly or on the mast. At the bottom of mast another connector is needed. Beyond this lower connector would be the solenoid and then a shunt to measure charge current, then a fuse and then the charging circuit breaker and the batteries.

Wire size should be sufficient to carry the full load of the wind generator with 1% loss. The wind generator has AWG #10 wires so that is likely what will be used. At 0.9988 &ohm/kft or 0.0009988 &ohm/ft per ft (about 0.001 &ohm/ft) the roughly 40 ft of wire (mast is 37 ft tall, but wind generator is not on the top) would have a resistance of 0.04 Ω. At full power of 400W at 48V the current would be roughly 8.3A so 330 mV drop out of 48V so well under 1% (under 0.7%). Once inside the boat larger AWG #8 or AWG #4 wire can be used. AWG #8 or #6 cuts losses by roughly 40% or 60% relative to AWG #10 but costs more and is harder to work with.

The shore power charger would kick off if voltage gets too high due to the wind generator and stay off. The solar charger would kick into float mode but with a LFP battery BMS the solar charger float voltage can be set to 59.0-59.2V to match ideal charge voltage for the BMS.