bjvarley
New member
I agree with Chinita, our 913 is almost silent, nearby boats have even commented on this..don't know why some have found them noisy though
Wind generators
- Thread starter CptBlood
- Start date
DipperToo
Active member
There has been a lot of discussion over the past year on these forums.
From my experience there are several issues;
1. Above decks noise is primarily down to the blade design and speed of spinning.
2. Transmitted noise is intrusive but livable with during the day, but many systems will need the blades stopping at night. Rubber mounting pads or neoprene pads with isolation collars for the bolts will certainly help things.
3. Resonance is a real killer. The gennys work with having coils passing magnets, and at the point of charging starting, there is a resistance when the coils pass the magnets which can lead to the vibration mentioned above. However, a side effect is that resonance can be triggered in the mounting structure and noise above decks is loud and below decks intolerable - even with rubber isolation mounts. There are also questions about damage when the structure resonates as well.
Based on the above, it may be worth seeing if a wind genny supplier has a mounting kit which is guaranteed not to resonate - then you only have to address the questions of transmitted noise with isolation pads.
I would love to find a structural engineer with personal interest in this topic and most mounting poles are similar size and material. Based on a few variants with several wind genny data, it would be good to be able to find out pole/mounting sizes to avoid! Also, a method of working out something for a tuned mass damper. I am usre that someone could come up with a desihn that would clamp to a pole of between 1.75 and 2" with adjustable weights to cover a resonable spectrum to dampen .... but that is probably asking too much!
I have been trying for several years to find a solution but to no avail as yet.....
From my experience there are several issues;
1. Above decks noise is primarily down to the blade design and speed of spinning.
2. Transmitted noise is intrusive but livable with during the day, but many systems will need the blades stopping at night. Rubber mounting pads or neoprene pads with isolation collars for the bolts will certainly help things.
3. Resonance is a real killer. The gennys work with having coils passing magnets, and at the point of charging starting, there is a resistance when the coils pass the magnets which can lead to the vibration mentioned above. However, a side effect is that resonance can be triggered in the mounting structure and noise above decks is loud and below decks intolerable - even with rubber isolation mounts. There are also questions about damage when the structure resonates as well.
Based on the above, it may be worth seeing if a wind genny supplier has a mounting kit which is guaranteed not to resonate - then you only have to address the questions of transmitted noise with isolation pads.
I would love to find a structural engineer with personal interest in this topic and most mounting poles are similar size and material. Based on a few variants with several wind genny data, it would be good to be able to find out pole/mounting sizes to avoid! Also, a method of working out something for a tuned mass damper. I am usre that someone could come up with a desihn that would clamp to a pole of between 1.75 and 2" with adjustable weights to cover a resonable spectrum to dampen .... but that is probably asking too much!
I have been trying for several years to find a solution but to no avail as yet.....
bjvarley
New member
Yes if the generator itself doesnt sound noisy from outside(ie its not
blade noise/bad bearing/something hitting something) resonance would be an explanation.. but the resonant frequency of the generator mast itself is quite high (hang one up and hit it) so this would have to power secondary resonances in the boat structure at lower frequencies to explain the sorts of noise problems people are describing here (quite possible).. solution is still the same.. stop the mast resonating in the first place.
Our gen mast is exactly as DipperTwo describes.. 1.75m long 2inch diam. but is clamped in 4 or 5 places (deck, lower and upper rear pushpit rails, manufacturers point near gen. plus a strut to the backstay..all cushioned by 2 or 3mm of rubber where appropriate, and there is no noise inside the boat.
Possible solution for those with problems is to to try and put in more damping/clamping on the gen. mast.
We do get a low hum if we let our gen. turn when it is 'electronically off' ie when the battery is full. This we traced to the backstay resonating at these low speeds with high resistance on the gen. .. good reminder to to tie the fan down!
bjvarley
New member
Oh and the best place to try and damp is probably 1/4 way from top or bottom of longest free section of gen. pole.
DipperToo
Active member
Good insight. One suggestion I omitted from my post was to have the pole cut and joined using bolts and an inner connecting tube, plus as bjvarley has done, multiple supports, all isolated.
Agree about secondary resonance. I have 2 large 2" shaft anodes which I have tried to position on the possible nodes but to no real avail.
The main pole is also filled with builders foam except for a small cable conduit to try and eradicate air resonance within the tube. I know that has also worked for some people.
I know there are specialist vibration measuring systems, but a crude attempt to identify the prominent frequency analysing an audio recording showed the main peak at around 160/170 Hz and the next lower peak at around 520Hz. This is rather a black science at the end of the day!
Thanks for the comment.
bjvarley
New member
Neat way of doing it, I was thinking oscilloscopes and frequency analysers.. not readily available on most cruising yachts!
Black science is usually the most fun in my experience.
DipperToo
Active member
There is quite a good free bit of software called Audacity which has a frequency analysys feature wherre you can set sample rates, see peaks, plot correlation etc under the analyze tab. Takes a little playing around with but rather good software at the end of the day.
Been using the software for ages - you can also doenload via the site the various plugins to do MP3 and other audio formats apart from WAV.
Link is here>> http://audacity.sourceforge.net/ and you need the latest beta version 1.3.13
bjvarley
New member
Thanks for that Dippertoo
silver-fox
Active member
We have a 913 mounted on a gantry directly above our aft cabin. No precautuions have been taken to minimise noise or vibration and its simply not a problem. Sure we can hear it when the wind gets up, but its no more or less intrusive than the wind in the rigging.
OldBawley
Active member
Would not want to miss the windgen. The sky is covered since a week, the big Chinese solar panels are delivering 4,5 Amps instead of the 9 Amps in summer. The days are short, sun is low and orientating the panels is difficult when on anchor or on a mooring.
The Areogen 4 is going steady, day and night. Yesterday changed anchoring spot to have more uniform wind. The gen is humming, I like humming.
The Areogen 4 is going steady, day and night. Yesterday changed anchoring spot to have more uniform wind. The gen is humming, I like humming.
bjvarley
New member
Hmm.. just looked up an ad. for aerogen 4.. claims 19 amp continuous charging in a 60 kt wind..ie near hurricane..very useful! otherwise looks similar to 913.
Alixora
Alixora
OldBawley
Active member
The 19 Amp for a Aerogen 4 is *******s. Mine who is an older version ( Now they have helicoid placed magnets and maybe more modern magnets ) Gives most of the time only one Amp. Still enough to keep our fridge going. ( Uses 24 Ah day. Is self made and only 32 l capacity ) In stronger winds the Aerogen gives 3-4 Amps, and the max I have measured was 7.5 Amp. There was 9 Bf blowing.
The 913 is about the same, the output is directly depending on diameter of the fan and the sort of blades. That is way I am building a low wind strength generator. Diameter 1,5 meter Two blade.
Think I start with 1.7 meter and than eventually cut down the blades. Do not want more than 5 Amp, we do not need more. Now waiting for a big Schottky diode. Winter therapy.
The 913 is about the same, the output is directly depending on diameter of the fan and the sort of blades. That is way I am building a low wind strength generator. Diameter 1,5 meter Two blade.
Think I start with 1.7 meter and than eventually cut down the blades. Do not want more than 5 Amp, we do not need more. Now waiting for a big Schottky diode. Winter therapy.