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Forum Index : Windmills : Furling?
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yahoo2 Guru  Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Thanks for the welcome Rastus. I regretted that post as soon as I put it up, too much detail and not enough pics for a newbie post. OK here's a pic, cant take the credit for this,its one of my dads projects. We were shifting it one windy day and the manual furl cable broke, I had her on two wheels for about 100 metres. 
I'm confused, no wait... maybe I'm not... |
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Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Yahoo2, Your post was informative!Others more familier with blade performance and flying will be up to speed with your comments and may join the discussion.I'm still comming to terms with the basics.I don't know how you handled it,but a truck on 2 wheels would have me sweating bullets!Just goes to show how much power mills are catching.Thanks for the pics!Cheers Rastus see Rastus graduate advise generously |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Not much skill involved from Me, the self furling mechanism cut in very quickly, but it took an eternity for the disc to slow down (no load on the pump).If it hadn't furled straight away, it would have pile driven itself into the ground in an instant. They certainly have plenty of torque, I remember seeing an IDIOT chain a 20 footer, it snapped a 2 inch D-shackle like a carrot. Haha "sweating bullets" No, this was a pussy compared to Version one, it was moved with a crane and just squeezed under the 32,000 Volt power lines, except on a hot day when the lines sagged. That was a mandatory brown trousers moment  
Slightly more on topic "I expect Wind seeking is addressed by the tail" The tail's job is to hold the turbine into the wind, the force created by the blades pushes against this making the mill furl, its a subtle but important difference to what most punters think.When you adjust the tail you are actually changing it's ability to hold into the wind. A true wind seeking mill will mostly face the wind with no tail attached at all, except for a few crazy loop-da-loops to keep the spectators interested 
cheers I'm confused, no wait... maybe I'm not... |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Yahoo2, I have no trouble shifting anything around my block or neighbours,no power lines in site.Have a petrol alternator and used it a handfull of times over the last 10 yrs,mainly for visitors.So I'm in the dark in more ways than one.  Your last comment interests me concerning a mill facing the wind largely on its own.Is that related to the inherent tendency of some blades to seek the wind because of their angle of attack?as stated earlier.Could you ellaborate further,please try to keep it as simple as possible.
Hi Jim, From your comment about furling adjustments,the acid test seems to be full blown storms.In my location they are predominantly august/september,so would it be worth my while to plan to do final adjustments within this time frame?I'm not normally deterred by the weather,But have no experience with wind turbines yet!I did Picture winter as a good season to set furling becuase the winds are consistanly stronger and the air density is heavier.I'm looking for advise,cheers Rastus. see Rastus graduate advise generously |
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JimBo911 Senior Member  Joined: 26/03/2009 Location: United StatesPosts: 262 |
Ratus Truth be told, when a storm rolls in that has very high winds you will then know what kind of mill you've built. If your a mill head like (me)some of the rest of us Yes it is worth your while. I know thats when my mill came off it's purch during a storm. You just got to watch and make adjustments. My first build I couldent keep the blades balanced so I went back to the drawing board and came up with a new hub and rods clamps. After that things got a lot easier. Jim |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Jim, Thanks for support with aug/sept suggestion.I'll make it so when ready. Some further understanding needed,in practical terms how is furling affected with different rearward tail angles.While lift of the tail position will vary along with Tail weight,surely it affects the head movement for better or worse?What would the differences be?Can anyone help!Cheers Rastus see Rastus graduate advise generously |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Yahoo2, Its been a while since I've been able to catch up.If you've had a chance to read Tim's windmill pg6 there's a discussion about blade activity.Could they be talking about "blade wind seeking" that you referred to and in my ignorance didn't grasp what you meant?Hope life's treating you well,Cheers Rastus see Rastus graduate advise generously |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Yahoo2, vawt going in a big way pg6 is the correct page!Cheers Rastus see Rastus graduate advise generously |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi to all, I hope this post irregularly cropping up isn't annoying!I've read that yaw to main shaft offset should be 4% to6% of blade diam.Are these figures relevant to F&P mills?Also Blade rotation CW/CCW to left or right yaw offset, can improve the mill coming out of the furled possition and reduce mast strikes in higher wind situations.Is there any truth to these claims? I'm looking for supportive confirmation or thumbs down comments.Can you help,Cheers Rastus see Rastus graduate advise generously |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
sorry I have not replied Rastus. Things have been a bit hectic here lately and my old computer decided to cash in its pension cheque, its taken a while to get my new server up and running. i will have a look at your posts when I get home, I have to do an emergency dash to the Adelaide hills to pick up some parts for my seeding machinery.  I'm confused, no wait... maybe I'm not... |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Rastus I have found that 4" works ok on my mill with a 3.9 Meter diameter, thats with 5 degrees lay back and 10 degrees side lift. All the best Bob Foolin Around |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Yahoo2, Never a dull moment for you by the sound of it!I dropped off the net for couple of weeks had bugs in the machine,couldn't use insecticied, had to get IT specialist.I have no idea when it comes to that stuff but have used seed drills.They're probably called something else now to keep up with the times. Thanks Bob, If I've calculated correctly the 4" is 2.56%,aprox half recommended offset,so that shoots that out the window.I'm wondering if the mainshaft is close to centred with the yaw centre because you gain mast clearance with the 5% lay back?Out of curiosity which direction does it rotate and side furl?Cheers Rastus see Rastus graduate advise generously |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Rastus Looking from the front of the blades on mine it is offset to the left and the blades rotate clockwise. Philm has tried opposite rotation anti clock and found that it furls a bit better, I fiddled with mine till I got it to furl at 12 ms so haven't tried to change rotation. On the next mill I get from Phil I will try the anti clock rotation, this may help it furl without all the other modifications I have done to mine. My next mill will rotate clockwise also as I can't reverse the blades, but will make a adjustable side offset angle. The offset 5 " to the left blade diameter 4.2 meters. The lay back of the blade disk for mast clearance will be 5 degrees, as I have found it makes little if no difference to power collected. All the best Bob Foolin Around |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Bob, It was late at night and a bit premature to ditch the suggested 4% to 6% offset default, without considering tail length and weight as likely many readers would tell me!Having others exchange info and exsperience gives me a broader scope to consider.Having the 5 deg lay back with little difference in power,is something I wasn't sure about.I suppose the dia.could be slightly increased to compensate for loss if a builder is finicky.Anti-clockwise rotation improving LH furl is interesting.Your description is easier to follow than others I've read.It was clear that furling can be improved by matching rotation to direction,what wasn't clear was weather rotation should be towards the mast or with the furl direction as you have described in Philm's case.I'm partial to conformity,so I'd prefer clockwise rotation and have the mill furl to the right even though power is generated in either direction.Thankyou very much for your help!Cheers Rastus see Rastus graduate advise generously |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
There used to be a "rule of thumb" Half the rotor diameter in Feet is the offset in inches. example 16 Foot rotor is 8 inches offset. I cant remember where I heard it, could be a load of rubbish. Here's a bit of brain cell exercise. A link to an auto-gyro page, there is a paragraph or two on wind flowing over a blade rotating at an angle to the wind. If you read that and then look at the pic (from the basic furling page)and imaging the angles of the wind flowing over the blades it may help to explain why rotor dive around so much. Autogyros- How they work, a brief history, and why they were never excepted 
My opinion, for what its worth, is you don't need to stress about all this to much, concentrate on building a really good tower that you can lower in 5 or 10 minutes by yourself. All your problems go away when you can fiddle with your mill at a minutes notice. Sounds kinky, but it works. cheers, Yahoo. I'm confused, no wait... maybe I'm not... |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi yahoo2 There are so many different things effecting furling that it is hard to make a hard and fast rule that suits all situations. I have heard the same offset rule and I believe it is a good starting point but still subject to tail length and weight and bias angles. The only thing I have seen with large offsets is they can furl very quickly once the furl starts and if this isn't controlled, can cause tail strikes. All the best Bob Foolin Around |
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fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
GOOD FURLING - It seems everone wants the answer, or wants a caculation that will give them a perfect furl in their first attempt at building a wind generator of their "OWN DESIGN", and I would have to say that there is no caculation that will give you that kind of infomation that I have seen to date . The secret to getting it right is to build as much adjustability into YOUR DESIGN as you can for the blades and alternator you are using, then it is down to good old trial and error . This is probably the main reason why furling is a black art, because we are all not on the same playing field . If everyone had the same standard materials, design and blades, tail length and weight, alternator and loading, then as a group it would be easy to come up with a turbine that furls and performs, but when a person comes along and wants the answer to be given for the perfct furling dimensions and angles for their particular build, it is virtually an impossible ask for others to say what is going to work as there are to many variables. I have trialed quite a few options , RH Furl , LH furl , Adjustable ofset , Adjustable X-Y on the tail pivot and watched them for endless hours with fleeting spurts of enlightenment , but only to have it blown away when the idea is put to paper. My opinion for what it is worth, whether it is RH or LH furl , CW or CCW rotation it doesnt matter as all forces are counterbalanced in a spinning blade set with wind being the driving force. Propeller effect , northern/sthern hemisphere gyroscopic effects and all other off beat reasons that are said to hinder or perfect furling are a myth in my eyes . Differing Blade types and loaded rotational speed at the furl point change furling characteristics, and the relation to the force of the tail weight & surface area resistance through the tail pivot angles counter acting the force of the blade offset, untill at a given wind speed that force overcomes the opposing tail weight and wind resistance force and the turbine starts to furl. Off course there are a number of other angles and dimensions that can be thrown in to the equasion just to mess with your head. All this can leave Joe Bloggs and his one off turbine build standing in the middle of the field, alone and searching the internet for the answer, instead of build it and then trial and error to get it working. It is good to get advice from others who have been there and have experence but it can also backfire with all the variables. I don't recomend trying to lower a mill in a howling wind when it is all going wrong , it definatly tightens up the sphincter. And tail strikes are more caused by flimsy tails and blades with incorrect stops. It comes back to a level playing field with lots of players going with a tried and proven design, EG-: Hugh Piggots designs which are constantly being upgraded and worked on and has a huge following and if built to the plans should perform the same in each location. If advice is given on the best furl angles be sure they also give their blade / alternator type and rpms at point of furl, the tail weight, length and surface area as well as blade offset and all the other revelant info to be able to make a desision if the infomation is going to be revelant. The best advice I can give in regards to getting furling working well from my experience with the "ALU GOE222 BLADES" and I believe this to be somewhat relevant to other differing blades - The back tail pivot angle should be minimal 1 to 3deg, basicly enough to bring it of the top stop, to much angle back causes the tail to increase its opposing force applied in the first 30 to 45deg of furling. As the blades furl they are loosing wind force so the the force applied through the tail pivot should deminish to give a smooth furl . If you play arround with a mock tail you will see what I mean. All the other angles and dimensions are in the builders court, but I would suggest as I did before, is to build with adjustability on the Blade Offset 80-140mm and 5-20deg side angle on the tail pivot and leave the back angle set @2deg at first , start with a max blade offset and almost min side angle, then start to tune it from there, and make sure the tail stops are set correctly. Below is a PDF instructions I send to those who buy the 500w kits and it shows setting the furl angles and a few other things, it might be revelant info here. 2011-05-29_140439_Tail_Angles_&_Mods.pdf PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| Rastus Guru Joined: 29/10/2010 Location: AustraliaPosts: 301 |
Hi Yahoo2, I tried the brain ex. and found out it's very lethargic!The tower I'm keen on is 19mt high and is climable but not easily lowered.Due to present health I don't have good balance,so I'm not looking to work on the mill very often at 60ft up.People make choices that don't always add up to others and this is probably one of those times.I do realise your advise is sound! Hi Bob, you've provided the answer to a previous question "how larger offset effects furl action".It can result in faster and harsher head movement which surely is not ideal. Hi Phill M, Hugh Piggots mills seem almost revered amongst generators and with the success biulders have its fairly well deserved.Your comments concerning the number of variables in individual biulds are justified,and your exsplanation about furling angles and benefits you've noted are particularly helpfull to me,along with the additional link.I feel your comments are worthwhile for those of us not considering AxFx mills and designs that are possibly more "Aussy"(F&P) if I can get away with saying that!Thanks to each of you for exspanding the discussion,Cheers Rastus see Rastus graduate advise generously |
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