Wind generator noise abatement

[skipgundlach]

Prompted by a plea for having no wind generators in another thread:

KISS Balancing and wind generator noise abatement

Wind generator noises aren't entirely the fault of blade design.
Sometimes it's also a matter of balance.

I have one of the large-fan versions, a KISS, with which we are well
pleased, despite its having been very abused in our 14 years of use
(which included a 12-hour salt water immersion and an extended fresh
water immersion, both of which responded to a spraydown with fresh
water, an air-dry, and spray with Corrosion Block before reassembly).

However, a balancing axle is available. A static balance may match by
weight, but does not include rotational forces. If you have a
different model wind generator, you may have to fabricate a balancing
axle; it will be well worth the effort.

KISS is no longer made, but new blades and hub are available from the
prior manufacturer (now retired). The blades are gram-matched,
ostensibly meaning that when you mount them, all is good.

Not so fast, Bucko. Dynamic balance that rig!

I used lead tape. In order to balance (see below on my modus), it
took over a foot on two of the blades. It has to be done in a
windless environment, of course. And, natch, I attach at the back
side of the blade so as to not muck with the aerodynamics.

Here's how I measure whether I'm truly balanced or not:

My not-perfectly straight-flat workbench in the walkthrough has a
fiddle. I find a level spot (how full the tanks are, and davits, and
so on affects that) for one end of the axle, and use an aluminum
torpedo level for the other. If both ends are level, it should not
rotate if it's balanced. When it IS balanced, a slight tilt of the
level (max bubble-touch, not way off) will cause the blade to rotate
with the axle heading downhill. As my axle ends are about 1/4 inch,
you can imagine that it takes a fair amount of torque to move a 30"
blade - but, while slow, it WILL rotate, but not do so when level.

I put on the tape in amounts I estimate will work (it comes with a
plastic sheet backing, like you'd find on double-stick tape rolls),
sticking the ends lightly, initially. I start with one end relatively
close to the hub. Some fiddling with how far out the tape is, and I'm
close. When I have it reasonably close, with tape on two of the three
blades, I get down to fine tuning.

By "close" I mean that the blades will rotate, but only slowly, with
the bare blade light. By that I mean that regardless of whether I
start the blade at 8 or 4 in clock position, it wants to rise to the
top from there. I then remove all the protective tape and fully
attach the lead.

I then start, with a utility knife, removing segments of the tape from
the ends to balance (slice gently so as to not damage the blade).
Keep your pieces; you likely will have to fiddle with matching up the
two weighted blades; mine are as small, as I get close, as 1/8" - but
if handled carefully, will re-adhere. I start relatively large and
get smaller as I approach nirvana

In the end, my metric is that the unweighted (now "heavy") blade, from
either 10 or 2 clock positions, takes a minute or more to reach
bottom - and that I can make the smallest adjustment to 'level' and
also have it turn.

The difference, at least in our KISS, is stark. A mere
Whiiiiissssshhhh, instead of a moan or groan or roar.

I suspect that any blade set could be similarly balanced, whether KISS
or not. If you can put your hand on however it's mounted, and can
feel vibration in the pole, likely your blades are not really
balanced, even if your blade weights are within micrograms of each
other...

L8R

Skip

[Mike OReilly]

There are plenty of quiet(er) wind gen now available. There really is no reason to put up with the old Air-X style that would scream like a banshee* once the wind go going.

I've had a Silentwind for many years now. It isn't "silent" but it's pretty darn quiet. It sits above our cockpit on its own mast and we carry on normal conversation with it whirling away. A couple of boat lengths away it is completely silent.

But there are lots of others out there as well which are also similarly quiet. The D400 comes to mind. Superwind has a good reputation, as do Rutland and the KISS and a few others. Even the Air versions have apparently become much better.

These days noisy wind gens are more likely caused by poor installation and, as Skip says, unbalanced blades.

*I know about the Air-X because I used to have one.

[Bill O]

I'm not going to argue that balanced blades are good to have, but getting them balanced isn't going to be that easy unless you have a good balance.
Even then, doubtful that one would get them down to the microgram level (one millionth of a gram) as Skip mentioned without an analytical lab available.
Mike's approach to buy a quieter wind gen is a more reasonable approach for most people. Out of the box years ago, our Rutland was very quiet and remains quiet w/the somewhat sun damaged/deteriorated blades. Will say we have changed the bearings when they were starting to make noise, but that is unrelated to blade balance.
I did chuckle at Mike's description of the old Air-X sounding as if it screamed like a banshee when the wind came up. I think of the Air-X noise more like a mass of howler monkeys going at it in the trees.

[Chili Palmer]

Originally Posted by Bill O

I'm not going to argue that balanced blades are good to have, but getting them balanced isn't going to be that easy unless you have a good balance.
Even then, doubtful that one would get them down to the microgram level (one millionth of a gram) as Skip mentioned without an analytical lab available.
Mike's approach to buy a quieter wind gen is a more reasonable approach for most people. Out of the box years ago, our Rutland was very quiet and remains quiet w/the somewhat sun damaged/deteriorated blades. Will say we have changed the bearings when they were starting to make noise, but that is unrelated to blade balance.
I did chuckle at Mike's description of the old Air-X sounding as if it screamed like a banshee when the wind came up. I think of the Air-X noise more like a mass of howler monkeys going at it in the trees.

Unbalanced blades will wear out the bearings faster. That's not a boat thing, that's a science thing.

[Bill O]

Our wind gen is 20 yrs old and we replaced the bearings once. Some of that is due to iced up blades causing them to be unbalanced, but mostly it was just age of the bearings.

To clarify what I said before "getting them balanced isn't going to be that easy unless you have a good balance." May seem odd to use the term balance twice, but the second "balance" is referring to an analytical scale used in a lab. Some were accurate enough to weigh micrograms of chemicals.

To Chili Palmer, Be Cool. ("Get Shorty" and "Be Cool" are the cult classic movies that the character Chili Palmer appeared and was portrayed by John Travolta).

[Tomodore]

Agree that getting a quiet one is good start. We were at anchor near a noisy wind gen set and dinghy over to see what one we don't want. Turned out that boat had a quiet one (Marine Kinetics) and the noisy one was even further away and screaming. We have had Marine Kinetics unit for 5 years now and are very pleased.No doubt the boat with the loud one went crazy or deaf!

[skipgundlach]

Originally Posted by Bill O

Our wind gen is 20 yrs old and we replaced the bearings once. Some of that is due to iced up blades causing them to be unbalanced, but mostly it was just age of the bearings.

To clarify what I said before "getting them balanced isn't going to be that easy unless you have a good balance." May seem odd to use the term balance twice, but the second "balance" is referring to an analytical scale used in a lab. Some were accurate enough to weigh micrograms of chemicals.

To Chili Palmer, Be Cool. ("Get Shorty" and "Be Cool" are the cult classic movies that the character Chili Palmer appeared and was portrayed by John Travolta).

Unless your manufacturing is entirely uniform, even very balanced weights can behave as unbalanced on a moving 'wheel' - which is why I emphasized doing dynamic balancing - where it can turn.

If one blade has slightly more weight toward one end and the other the reverse, despite their being identical in piece weight, it will wobble. Any irregularity in construction (variance of any weight at any given location of the blade, if that makes any sense) will have to be balanced...

If you had a means to very accurately measure to the point, you could find the balance point for each blade (pinpoint somewhere in the middle-ish); if they were identical, likely that would be better than, say, a half-inch variance (which in itself isn't terribly accurate, but it illustrates why to dynamic balance; you could make them the same by slightly weighting both of their light sides, e.g.)...

[Clivevon]

I found that about 30 feet of rope, tossed over the blades & tied off to the base of the mizzen, was the perfect solution. Eventually I got a chap to remove the bl**dy thing in exchange for taking it away - no problems since with wind generator noise.

[Bill O]

QUOTE=skipgundlach;3435629]Unless your manufacturing is entirely uniform, even very balanced weights can behave as unbalanced on a moving 'wheel' - which is why I emphasized doing dynamic balancing - where it can turn.

If one blade has slightly more weight toward one end and the other the reverse, despite their being identical in piece weight, it will wobble. Any irregularity in construction (variance of any weight at any given location of the blade, if that makes any sense) will have to be balanced...
[/QUOTE]

Skip,
I can't disagree that a poorly manufactured blade in theory could be out of wack and would perform poorly in a high speed wind gen application.

Luckily, the better manufacturers have better QC protocols when making their blades. When the material is homogeneous/well mixed/uniform one avoids the weight distribution issues you mention and can manufacture tight spec blades. The down side is there could be lot to lot (batch to batch) variation. While the blades are the exact same size, shape, etc. the density of the material in lot X may not exactly match the density of lot YY. If you mixed blades from the 2 lots, the gen would most likely have a vibration/be slightly out of balance. Generally this is why you need to purchase a whole new set if you damage a single blade so they match.

There are plenty of good wind gens that out of the box (they will have matching blades) and work well.

[Wallaby]

Six blade Airmaax--silent and powerful, high quality construction. The direct opposite of my old Air-X generator.

[Tellie]

SuperWind. They took care of all this years ago.

[Jentine]

Balance the blades and the generator will run quietly. This is the simplest way:

https://www.youtube.com/watch?v=eO_i60bczfw

[Tomodore]

Sounds a lot like anchor threads where old style works but rough edges and later generation much better, love my US made Marine Kinetics but many quality brands out there.

[skipgundlach]

Originally Posted by Jentine

Balance the blades and the generator will run quietly. This is the simplest way:

Heh. That's where I learned how.

However, not everyone has a nice hard, level setup as John does...

[Jolly Roger]

When I first fitted an old KISS generator on my boat it wobbled badly, so I dismantled it and found the bearings, front and back on the stator were worn out—probably original. These cost peanuts from Amazon, and the stator rotated better after re-assembly. But the blades were also out of balance, so I bought a balancing mandrel from Hotwire.com (the US distributor at that time), and balanced them meticulously myself. The thing then worked perfectly and silently, apart from the whooshing noise of the air passing over it. Another thing I did was install a thrust bearing between the body and the support shaft, which was a source of friction, but now the slightest wind shift and the thing rotates into the wind. It’s obviously important that any windmill should face into the wind, and any variance can cause wobbling and noise.
I wrote an article for a British sailing magazine about rebuilding a KISS generator, which included balancing, which can now be read on my site. http://schooner-britannia.com/wind_generator.html