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Forum Index : Windmills : Furling?
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Rastus Guru  Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi to all, The forums advise to avoid danger and damage with furling is obvious.General furling functions are not as clear to me!Does having a larger head offset result in a smooth furling action compared to a closer offset, or is it visa-versa?Does a longer tail hold the mill into the wind better than a shorter one?What happens when different rearward tail hinge angles are used,say 20deg compared to 10deg?Also is the tail side angles principle use to have the tail boom clear the alternator as a precaution?What is the reason behind some tails having an end flap?The desciptive terms I've used probably aren't correct,but will be sorted as information is provided.I'm looking forward to understanding these aspects better with your help!Cheers Rastus see Rastus graduate advise generously |
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KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
Read the article furling explained then come back with questions Its on the backshed homepage. Most easily described as an artform as far as i can tell, a few principals sure but smooth, relaible etc are signs of a mmill that has had lots of time spent on it. -Oh and they are rarely perfect Luck favours the well prepared |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah furling is a bit of a art, all the maths do is give you a ball park figure, but the only way to get it working spot on is through trial and error. Phill has done a lot of experimentation on furling, and we both agree the tails should be as long as possible. The further out the back the tail is, the cleaner its wind and the better leverage it has to act against the nacelle. My most stable wind turbine had a tail boom that was 6 feet long, on a 6 foot turbine. I've had shorter tails and they tend to swing around too much and furl erratically or violently. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
Hmm RUTLAND look left loor right look lef then right Do they ever point into the wind? Luck favours the well prepared |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi karlJ, Thanks,the questions I've raised are the result of reading the furling page and forum references numerous times without finding plain answers.This thread is intended to draw on the exsperience of generators who have made adjustments and can compare before and after results,or have had different mills and noticed advantages.I'm sorry I don't understand your second response! Hi Glen, Thankyou for exsplaining that longer tail length helps stabilize mill operation, compared to short which is more eratic with harsh furling action.The specific length helps me know what would be considered a long tail.I'm not looking for calculations as answers,instead I'm hoping for descriptions,like you have provided,on performance by varying components settings/make-up. Cheers Rastus see Rastus graduate advise generously |
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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Rastus et al Here's a hot link to that article KarlJ mentioned you read. I thought I'd toss it up here to help you and any others who might need to brush up on stuff. Furling Basics . . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Mac, The hot link does make it convenient to access the furling aricle!Thanks for putting in the time to help.Cheers Rastus see Rastus graduate advise generously |
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Andy R. Newbie  Joined: 07/05/2010 Location: United StatesPosts: 18 |
Rastus said: "What is the reason behind some tails having an end flap?" Yeah, I noticed a little flap on the tail of a 10K Bergey XL about a month ago. It was furling maybe 75 or more degrees and holding really smooth. (Maybe that's why they cost almost 50 grand US.) Does anyone know why some tails have a "flap"? |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Thats partly due to the flap. A normal flat tail needs to be deflected 10 or so degrees before it's turned enough to catch enough wind to have an effect. The flap makes the tail wider, it needs to turn less to come into play, so it tents to follow the wind better. I've seen some tails that have two flaps, like a wedge, but you only really need one. The flap has the effect of making the furl smoother, sort of like a damper. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Catch66 Newbie Joined: 13/03/2010 Location: United StatesPosts: 27 |
I have also noticed the extra Vertical vane only on the one side.. That info about tail length also helps. weather permitting tomm.I will also do some adjustment to this theory. Watching Hugh's turbines furl (on video) truly a thing of beauty.. Thanks Gizmo Chuck |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Andy and Chuck, Your posts have opened up more info for those of us who can't "take things for granted" just yet!I'm still in the planning stage so a tail flap will now be included. Hi Glen, I'll apply your explanation to my build.Thanks for the heads up! Cheers Rastus see Rastus graduate advise generously |
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| JimBo911 Senior Member  Joined: 26/03/2009 Location: United StatesPosts: 262 |
Ratus At the start set your mill to furl early,(for safety and controlling RPM etc) watch how she responds to the winds if all goes well you can then make changes to keep it in the winds a little more work your way up. Every mill will respond different. Jim |
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| KarlJ Guru Joined: 19/05/2008 Location: AustraliaPosts: 1178 |
the second response the rutland has a vane but no tail as such hence it waves about alot and doesnt track the wind well Luck favours the well prepared |
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| Catch66 Newbie Joined: 13/03/2010 Location: United StatesPosts: 27 |
Gizmo Thanks for your comments. Pulled turbine down Yesterday and I added a 12" length now @ 5' which actually looks quite nice. repositioned tail 18" x 24" from vertical to horizontal and added the vertical vane you suggested tracks much better Since yesterday's change.. Thanks again Glenn for commenting about furling help and tracking. Chuck |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
No problems Chuck, good to hears its made an improvement. I spoke to Phill the other night, he's done A LOT of testing with furling, and plans to put it all down on paper one day soon, which I hope to share on the site. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi to all, My computer is preaty sick from the junk vandels have put in it,so waiting for a tech to work it over.Using another one on loan just now. Hi Jim, If I'm able to get a mill with a large offset furling at peak efficiency,will the larger yaw radius exstend the yaw bearings life and dissipate the forces better than a short offset? Hi Chuck, It's great to know you've made changes based on the threads content and given possitive feedback straight away.Well done! Hi karlJ, I guess the commecial guys don't always get it right either by the look of your follow-up post.I'd like to aim for something at least better than a Rutland,but only time will tell.As you can see I'm trying to learn some of the basics that are taken for granted by exsperienced members,but seem to be hidden between the lines. I'm gratefull to all of you for sharing what you know.cheers Rastus see Rastus graduate advise generously |
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| JimBo911 Senior Member Joined: 26/03/2009 Location: United StatesPosts: 262 |
Rastus It's difficult to say how long and type of machine will last, depends on how well it is built and of course the type of weather conditions she will be flying in. Play it on the safe side, work your way up watch and adjust till all works well. You have to be able to adjust the off set of the alternator and blade set this will give you room for experimentation. It's took me the better part of a year and then some to get it right lots of variables time, money, patience, work, the wife. Make an adjustment then you have to wait for however long it takes for a storm to blow in thats when the truth comes out. Make sure she has BRAKES.  Jim |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
PC healthy again, Hi Jim, The mill will run in fairly harsh conditions,will put it up 60ft(19mt) to find cleaner air.I can see your point about the brake and tried another thread on that subject.The general consensus was get it furling right and no feedback from anyone using brakes.I'm not planning to include a break,and yes, I hope the mill doesn't break!So I'm learning as much as I can about furling.Thanks for your feedback,Cheers Rastus see Rastus graduate advise generously |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
"wrote this a week ago late at night,  ' it seems to make sense in the daylight so I decided to post it". Any thoughts?
There are three things that I think have a bearing on furling that don't get a lot of air time in the discussions. Increasing the distance from the offset point to the blade hub (lengthening the axle the fan is on) should increase the leverage on any offset, making a mill harder to bring out of a furled position. Aerodynamic lift plays a large part in the force pushing the blades towards the tower. This means that reducing the load on the alternator will increase the blades rpm increasing the lift and causing a furl. This seems to be more obvious on blades with no twist. The third is a bit harder to get my head around, the reason some blades "seek the wind". My latest theory is it happens to twisted blades that are designed to have the perfect "angle of attack" along their entire length. Works great when the fan is faced directly at the wind but at a furl angle the blades seem to loose lift in the part of the circle away from the wind. I talked to some blokes that fly autogyro's, which is the closest thing I can think of to a wind turbine. They assure me the leading side creates more lift than the lagging side and the side flying towards the wind has vastly more lift than the one flying away (top and bottom on a turbine). I'm confused, no wait... maybe I'm not... |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Yahoo2, Good on you for jumping onboard!The forces mills are subject to are numerous and complicated.The offset point to hub distance is generally set, by a standard F&P shaft unless it is docked shorter and blade to mast clearance (safety margin).It could be hard to quantify the losses due to return from furl resistance.On the other hand the losses of not being furled when needed are obvious.Main shaft offset has a significant affect on furling,along with tail specs.I think lift is taken care of when productive furling is set.I expect Wind seeking is addressed by the tail,however your comments hold more insite than I can comment on.I hope other members can find the time to elaborate further.Welcome to the community!Cheers Rastus see Rastus graduate advise generously |
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