Author Topic: Blades stalling  (Read 2862 times)

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Offline oztules

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Re: Blades stalling
« Reply #15 on: December 10, 2016, 02:13:15 PM »
Carving looks good so far....... very good.
Was that roughed with the chainsaw?

I am a bit twitchy around the bung hole about 10' with no furling. A big wind through those blades will be 30kw and more to try to look after. If your alternator is very stiff, you will possibly control it.... if not stiff enough, it will leave the coils smashed and tangled.

50mph winds here are common, and if shorted, my 4m unit was no problem, but if it was running without furling, it would end up in New Zealand, no hope of keeping it under control if I didn't short it out in big winds. Furling gives a good degree of safety, but it is not infallable. The physics look good, but in the real world, the mill can do odd things in wild winds, and can track without a tail for short times.... enough to cause problems..... but it is a far cry from no furling.

You really need a plan B... so try furling ..........of any kind... better than no kind. Big winds are scary when they get out of hand, and a well carved set of blades can rally take advantage of them....... the toy plastic ones are just not the same.



................oztules
Flinders Island...... Australia

Offline bj

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Re: Blades stalling
« Reply #16 on: December 11, 2016, 05:15:06 AM »
   Your carving looks great.
   Have to agree with Oztules about furling.  Been there  with a crazy wind, and there wasn't much left.
"Even a blind squirrel will find an acorn once in a while"
bj

Offline TurboMiles

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Re: Blades stalling
« Reply #17 on: December 11, 2016, 07:38:41 AM »
Roughed cut with a chain saw, but with the help of a jig I made, then 10 minutes with a belt sander,  Picture!
No Furling is a bad idea.  Didn't take much looking to find good information.  I'll fab up something to make the existing tail pivot and rise.
I would like nothing more then to finish these blades but work schedule doesn't allow right now.

Offline niall

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Re: Blades stalling
« Reply #18 on: December 13, 2016, 03:11:17 PM »
the blades look spot on ......heres a link to one furling method , used on Piggott mills i think and works well ......theres a few others

http://www.thebackshed.com/windmill/Docs/Furling.asp

it doesent have to be exact , but closer is gooder than nothing 

if the 2 tower pivot angles and tail/boom weight are in harmony the tail will lift and drift in a clean vertical line ...or...if the welding is a bit ( i,m going to have a go at this right now with the welder ) it may rotate a bit as it lifts....its still furling though  ???

the tail may go on some kind of a sponsered walk of kinds in high winds....but a sponsered walk is often........... just fine

as was mentioned furling is an odd thing   .....theres a vid of a Proven 3k downwind machine running upwind in a storm when it had no earthly business doing so......

hopefully you can update more later  :)   

Offline TurboMiles

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Re: Blades stalling
« Reply #19 on: December 13, 2016, 03:36:50 PM »
Probably not the best pictures, but not the best photographer.
I understand furling, but the problem I have is the turbine is centered over the tower.  All furling systems I've seen are offset.  So I thought about disconnecting the generator from the pivot housing and making a bracket to offset it. 
Or I can leave it as it is, make smaller blades for out and save the big blades for an axial.

Offline niall

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Re: Blades stalling
« Reply #20 on: December 13, 2016, 04:07:04 PM »
modify and go for a offset ........furling will work better that way

Offline bj

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Re: Blades stalling
« Reply #21 on: December 13, 2016, 06:43:58 PM »
Niall is quite correct.   You need the offset.  The tail fights the offset to keep it into the wind, until the offset over
powers, and lifts the tail.  Once lifted, the tail no longer has the leverage to hold it into the wind, and things tame
down until the wind subsides enough for the tail to fall, and it starts all over again.  There are angles, lengths etc
in the Dan's book, and they work, but I think I lent mine out, and it is lost. (or permanently adopted)
"Even a blind squirrel will find an acorn once in a while"
bj

Offline TurboMiles

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Re: Blades stalling
« Reply #22 on: December 13, 2016, 07:01:22 PM »
I own 2 Hugh Piggot books.  Everything I need to design a furling system is in the books.  It's actually a simple design and I believe I can make a good rig out of my existing genny.

Offline TurboMiles

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Re: Blades stalling
« Reply #23 on: December 18, 2016, 10:20:18 AM »
Does it matter if the blades have a curve to them?  I finished the blades and one have about a 3" bow into the wind. Would it be ok to use?

Offline niall

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Re: Blades stalling
« Reply #24 on: December 18, 2016, 07:44:15 PM »
i,d say it,d be ok ......i wouldnt drop a blade just because it fished a bit from the other side of the river 

3" inchs is a fair bit in tracking .....it might tend to rock the mast a little bit  ....not sure about that though

my 3.7m had one blade tip off by about 1.5 " .....it never seemed that bothered about it at all  ( the least of its worries )......i wouldnt let it hold you back ,

balance them as well as possible and let them run ....wood will change its shape and balance with moisture anyway

once the blades are out in the open they will all change a bit ........but wood is pretty adaptable at surviving in the wind

i,d worry more about joining the blades at the hub and to the alt ......2 nice disks of strong ply front and back and plenty of stainless ( ideally ) screws 

( you might be able to correct the bend a bit by off setting that blade at the hub ....sand off a little and shim it a bit .....that might take the tip tracking back to about an inch )

Offline TurboMiles

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Re: Blades stalling
« Reply #25 on: December 19, 2016, 04:48:08 PM »
What I have so far.

Offline niall

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Re: Blades stalling
« Reply #26 on: December 19, 2016, 06:53:05 PM »
very nice work ......you wont get a set of those of ebay ...ideal for Hughs 2.4m design ...methinks
its good to see someone carving blades......



 

Offline TurboMiles

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Re: Blades stalling
« Reply #27 on: December 19, 2016, 07:04:49 PM »
2.4?  These blades are 5' lol should I cut them down to 2.4m or leave it at 3m.  I'm building a furling system
Thanks for the help niall.

Offline bj

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Re: Blades stalling
« Reply #28 on: December 20, 2016, 05:36:48 AM »
  Turned out very nice.   Just opinion, but I wouldn't cut them down just yet.  You can always
do it later if you need to.
"Even a blind squirrel will find an acorn once in a while"
bj

Offline TurboMiles

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Re: Blades stalling
« Reply #29 on: December 20, 2016, 06:35:04 AM »
I'm sure it's important that all blades be very close to the same dimensions, but how important is it?  They are all close, but is the airfoil identical on all, no.  Does it matter much if they balance out? 
Would there be any downside to having blades to large for the generator if it furls? 
The factory blades would produce 100 watts at ~11mph, 200 at ~15mph, could you tell me what I could expect to see with the new blades?