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Old 11-11-2006, 15:44   #1
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Wind Generator Mounting Location

The sticks are down on my Spencer 44 CC ketch with a stoutly rigged mizzen that is about 33 feet off the deck. There is no room astern for a dedicated tower - so aloft it shall go. I purchased a Rutland 913 and now await delivery. I will fabricate the mounting hardware. The options and considerations are 1) below the radar dome - this has the least effect on heeling moment from both windage and weight aloft (about 25 lbs total with mount and hardware), but greatest interference from (and to) sails while underway, and least clean air at anchor. 2) Above the radar dome - which trades off cleaner air (when on the wind) for a higher weight and windage effect, or 3) at the mizzen masthead, which gets the cleanest air of all, for the greatest effect on stability and load on the rig.

The mast head mount on a straignt pole would have less torsional load on the mount - anyone experienced problems with this? The heavier cables for the longer run are not a big concern, and my mizzen stays'l will still see plenty of use with that arrangement. My real question is - just how much of an effect on stability will the unit cause at the various locations, and how much less would it be halfway up? I am not engineer and don't know how to do the math to figure it out, nor interpret the significance of the results. Can anyone help me?

Re the mizzen stays'l - it appears that I'll perhaps still be able to fly it with the generator mounted part way up either above or below the radar, as the sail flys outside the twin mainmast backstays and I just have to be careful when hoisting and dousing. Is this a mistake? Does anyone have experience with this?
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Old 12-11-2006, 03:53   #2
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Basically, inasmuch as I’m no engineer, either:

The kinetic energy, exerted by the 25 Lb wind turbine will vary as the square of the mounting height.

Hence:
Doubling the mounting height will quadruple the forces exerted on the mast & rig.
Mounting the turbine at 23.3 Ft will result in roughly one-half the loading as mounting at 33 Ft.

Perhaps one of our Engineer, Physicist, or Mathematician members can describe and explain the vectorial kinetic energy calculations.
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Old 16-02-2007, 12:15   #3
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Settled on about 40 per cent of the way up, just below the first spreaders. This was based more on the strength of the rig and minimizing loads than anything else.
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Old 16-02-2007, 12:40   #4
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I too was pondering where I locate a wind gen device. I've seen some CC Ketchs rig using a seperate pole out on the cap rail just forward of the main back stays and almost level with the mizzen. Support, fore and aft, with conventional means, and lateral support to the mizzen with some adjustable supports off the main mizzen support to the shrouds and one of the main backstays.

Dunno ... otherwise, mostly ABOVE the radar dome on the mizzen.
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Old 16-02-2007, 18:54   #5
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Just out of reach of your fishing pole, boat hook, or gaff is good.

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Old 17-02-2007, 01:12   #6
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I also am mounting my 403X. I have a Ketch and to me, the best place is just below the spreaders on my Mizzen for many reasons. 1)If I dismast, it is likely to break just above the spreader. 2)The shorter the run of wire, the less the guage of said wire. 3)With Ratlines, the unit it at least servicable. Good luck.
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Old 15-03-2007, 17:05   #7
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There's another factor to consider. Wind velocity seems to increase a whole lot as you get higher off the water. Also, while weight aloft increases heeling moment(bad for racers), it also increases the moment of inertia, contributing to a slower, more comfortable rolling motion(maybe good for cruisers). Early small boat circumnavigator Capt. Voss would sometimes haul an anchor part way up the mast to deal with violent rolling! Some (Including Steve Dashew) even contend that a heavy rig can help prevent capsizing by slowing the boats roll-down from a breaking sea. I think I'm going to put my wind gen atop my mizzen. I've got a heavy boat with a relatively short mizzen. I'll let y'all know how it works out.
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Old 02-05-2008, 11:04   #8
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Resurrecting an old thread:

I'd preparing to purchase a wind generator (most probably, SWWP's Air Breeze), and want it mounted at the mizzen masthead.

I could probably fabricate a mount, but I've also been searching around to see if I could find something similar to a mount for a vertical base station antenna for hams - a bit beefier version of the mount for my Diamond X50A dual-band vertical antenna (pdf here).

What have our readers done?
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Old 05-05-2008, 23:51   #9
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looking at also installing a generator, and trying to figure out if just to put it off the arch over the pushpit or up the mast somewhere
as I was thinking of more wind the higher up also
thoughts will be good for this decision
thanks guys
I will keep watching wait for your mistakes and then make my own
as we all do
well hopefully will learn from you all have achieved to date
thanks again
hooked
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Old 06-05-2008, 00:35   #10
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Saw one in La Conner today on the MAIN masthead... couldn't quite believe it! Thought it was a giant wind instrument at first (hmmm, actually... wonder if they have a N2K interface for those things?). Anyway, quite a startling sight, but it did find clear air way up there (though at that dock, that's less an issue). Steve
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Old 06-05-2008, 03:32   #11
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wind gen

Kinetic energy = 1/2 mass times velocity squared confused about height issue.Height has more to do with torque?
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Old 06-05-2008, 09:22   #12
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Quote:
Originally Posted by marc2012 View Post
Kinetic energy = 1/2 mass times velocity squared confused about height issue.Height has more to do with torque?
Wind speeds are normally higher aloft than at the surface, due to friction as wind passes over the surface of the water, and any other disturbances it finds in its path.

Of course, adding mass aloft increases the torquing moment (is that the right expression?), and increases loading on the shrouds when the wind pipes up. Granted, the additional forces are slight, but still real.
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Old 06-05-2008, 09:53   #13
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Wind velocity is often assumed to vary as the 1/7 power of height above the surface for planning wind turbine tower sites. The power that can be extracted from the wind varies as the third power of the wind velocity. I generated a little chart that shows the expected wind speed at different heights compared to a height of 30 feet. It revealed that one would expect to lose about 2% of the power available at 30 feet above the surface per foot of decrease below 30 feet. For example at 20 feet above the surface the wind speed would be about 94% and the available power would be 84% of the values at 30 feet. At 10 feet or 20 feet lower the theoretical wind speed would be 85% and the power produced would be 62% of that at a 30 foot height.
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Old 06-05-2008, 10:44   #14
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Interesting that this thread is up again. As promised I have pictures here for you all. This is a Mizzen mounted bracket I found on e-bay for $150. It was apparently made for a windbugger and had the original store stickers on it for $795!!! The only mod I made was welding a smaller tube inside of the manufacturers socket, to accomodate the 403. I was lucky the width of the bracket was very close to that of my mizzen mast. I mounted it lower than the spreaders and high enough that there hopefully will not be a problem with the mainsail.
Let me know what you think.
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Old 07-05-2008, 20:12   #15
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Thanks cowboy
fantastic calculations for us to work with
now got to look for a clear place in front of the mast that wont fowl the jib
or maybe end up on a post off the arch on the pushpit
see what I can do
near spreaders sounds very good if I can swing it
Thanks hooked
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