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Forum Index : Windmills : New wing build
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| Air Bender Senior Member  Joined: 25/01/2011 Location: AustraliaPosts: 206 |
Hi Smithy I added the wings to boost the rpms up in lower winds. It never had any trouble with it starting up in low winds but when it did start it spun very slowly. I am not shore how much the extra wings are capping the higher rpms, at the moment I think that it is being restricted more by the loading on the alternator by having it set up with a low cut in speed. At the moment it is puting out around 40-60 watts but it is doing it day in day out. I have it connected to a 100 ah deep cycle battery and from this we are running a small TV, a UHF radio, a CD player, and some lights, so far I havnt seen the battery drop lower than 13V. If I had have known that I would be adding the extra wings I would have used a more high speed profile on the large wings, something like a naca 18. But at the moment the mill is a good work horse. I still plan to do some more experimenting with different stators and maybe a voltage booster to raise the cut in a bit. 
I took this picture yesterday during a very strong wind storm. I dont know how many rpms it was doing but it was spinning very fast. As you can see the wings stayed standing true apart from centrifical force pushing the tops of the small wings out slightly. All the best Dean. |
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| smithy Regular Member  Joined: 30/01/2011 Location: AustraliaPosts: 52 |
Thanks Dean, I have my 3 new 2m airfoils turning up soon, and I have the option of also putting them up in tandom with the existing ones, so will be interesting to see what the result is. I will post some updated photos of the 6 winged AirBlenda when she is done. Certainly an interesting exercise, and well done. Smithy "The answer my friend is blowing in the wind, the answer is blowing in the wind" Bob Dylan |
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| itsandbits1 Regular Member Joined: 13/08/2010 Location: CanadaPosts: 81 |
Good job on the build Air Bender, It looks like it will stand up for some time if you don't try to take too much power out of it because the wing tops will try to run forward 2 times every revolution, during the power portion of the circle. Most of the power is produced across the front but the symetrical wing gives you about 1/2 -2/3 the power across the back too. I wish you had let me know you were going to try (with mods) my design; I would have given you #7 which is what you see on the later mill on my site. They put out about 30% better. The vortex inducers I am trying also make the wind stick to the wing longer as it's going round and seem to help with power. Message me if you want to talk about MA and MP and chord for that wing Lloyd |
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| Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206 |
Hi itsandbits, I have thought that increasing the cord a bit by extending the trailing edge may be an improvment, but what I am going to try next is to test some differnt stators. I am working on the small hawt build at the moment which hopfully will be up next to the vawt soon and I am thinking the two outputs will be much the same so I think I will end up with the two competing against each other and I will start to work on the one that is puting out the least, I think wind wills are taking over my life 
Hopfully one day I will end up with two very good wind mills , the best of both worlds. When it comes time to do some modifications to the wings I will send you a message, working on wing and blade design is my main interest here. All the best Dean. |
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| itsandbits1 Regular Member Joined: 13/08/2010 Location: CanadaPosts: 81 |
How much weight did the wings eventually have with paint and all. I could see hollowing them out to 1/8" skin and put a good polyurethane paint on for strength but leave bars of strength across the chord every ft or so and leave it beefy at the mount. It will be nice to see the final output power of the unit once you get the angles optomized. If you get a chance would you mind getting a picture of the wing end closeup so we can see how the joint between the halves turned out. I started making drag blades but when I found lift I thought I found heaven, I didn't realize how much power you could get from the wind pushing something faster than it in the vertical mode. It Kind of takes over your life sometimes. If you want me to remove this I will Lloyd I'm not trying to hijack your thread and I hope you don't mind me putting this here for a reference of wing size comparisons and performance. the wings on mine are 9" chord x 20%thickness x 48" tall x 43"dia Remkick wing test for those that haven't seen it, this is the Remkick #7 wing version during some start stop tests in gusty 10mph winds. I have run this profile at 72 " with a 14" chord and it ran some pretty good tsr with no gen atached but a guy snapped when I wasn't there and the wind took it apart. Your unit would have a lot more power at your diameter with the longer chord in the 125-200 rpm range under load; I would go about 9-10", 125-175 being the power band for these. I have found that the MA; mount angle, for these varys a bit for diameter so from 0 degrees off the chord line, LE out to 8 degrees is common. this variability is determined by the MP; mount point, on the chord, with 30% being common but I always mount it at the fat part of the wing. So being able to adjust the MA slightly helps. The ma I use is a straight line from LE to TE and then the intersecting line of the mount arm if it is coming straight out from the rotor being 0-8 degrees, and adjust it a bit if it isn't. |
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| Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206 |
Hi itsandbits, I cant remember how much the wings weighed after painting but I think it was around 2.5 kg. I think that increasing the chord and then increasing the MA to suit the longer chord would give it it a bit more power in the range where I need it. It is on the drawing board. It is good to have someone to confirm this. I can see where the MP can have a big influence on mounting angle. I will get a try and get a good shot looking straight up at the wing when it stops raining. The speed that your mill runs at is very impresive, mine is not geting up to those kind of rpms even when the wind blows hard but it is reaching battery cut in at between 13-14 volts at about 80 rpm in under 10mph winds but it is not realy pushing much past this unless we get storm conditions. Any advice on improving the mill will be much appreciated even if I dont get around to implimenting it for a while. All the best Dean |
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| itsandbits1 Regular Member Joined: 13/08/2010 Location: CanadaPosts: 81 |
I like the way you made the unit. You really have to concentrate with the vawt wings on keeping them smooth; that's why I use aluminum sheet to cover my foam blanks. My 43"x 48" was pushing enough power at 10mph into a 18v battery bank to continuously light 100 w of 12v bulbs I have hooked up in the one video. if you look carefully at the subtle differences between the one in the private link I'm posting here and compare the charts to the one you built, you can see the variables that give it the power. Remkick7 wing This is a somewhat obscured picture of the true wing and I don't mind someone using it for their own personal use but I plan to get it extruded when everything gets finalized and if anyone beats me to it I wouldn't mind a bone being thrown my way. |
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| Air Bender Senior Member Joined: 25/01/2011 Location: AustraliaPosts: 206 |
Hi itsandbits, I am wondering what you use to stick your aluminum sheet to your foam blanks. I am thinking that if I were to extend the chord on my current wings I could go something along the lines of fitting some short ribs extending out from the existing trailing edge and then covering the extended area with light sheet aluminum. If I were to get a bit more power out of these wings it wouldnt take to much work to reduce the diameter a bit to give me a few more rpms. We are starting to become reliant on the on this windmill to power the kids cubby which is becoming more like a small house, which makes it hard to take it down for periods of time to make modifications, thats where the second wind mill will come in very handy. When I get the two mills up and running together I hope to run some wireing to my shed. This mill will need to come down soon as I have noticed a small amount of movement when I push up and down on the rotor arms, It must be in the rotor hub or in or around the bearings. I cant see any movement but I can feel it. When I put the new wings up this part of the mill wasnt touched and has been running for nearly two years know. So when I pull it apart to check this part out it will be a good time to do some other modifications as well. I still havnt got a picture looking directly up from under the wing yet but hopfully I will soon. In its latest configeration I dont think I have had a day were the mill hasnt spun for at least part of the day. Thanks for your help. All the best Dean. |
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| itsandbits1 Regular Member Joined: 13/08/2010 Location: CanadaPosts: 81 |
Hi Dean. I use a water based contact cement and it seems to be allright for my purposes. I am usually in a bit of a hurry and don't do it as per directions so I have had some seperation but if your going on to something solvent won't melt, you can use the solvent based stuff. I think it "bites" better. I'm glad to see the second set of wings are keeping it running steady, with the larger wing chord on mine it runs in less than 1/2ms so doesn't take much to get up to cutin. the USVAWT alt I have on it has 21v @ 100rpm series delta with 2.9 ohm. res. I tweaked the alt a little and get close to 27v now and that.s the one I have running in the stop/start tests. Bearings on the alts are always a pain because if they let go too much you'll take a chance on wiping out the mags and coils so your smart to take it apart when you can that's for sure and the loading you put on it with the wings up there is hard on a single bearing system. My next unit is going to have a long center shaft with a bearing top and bottom so the load gets spread out more. Even now with the short chord; if you shorten the arms , you might be surprised and find the unit actually puts out more. they will be flying in higher lift and give more rpm at the same time and you could take a look at putting some small adjustment in the end plates somehow. I don't know how you are mounting the arms to the altbut you could do it there by tipping the arm forward or back from perpendicular with the center pole or by moving the wings forward or back on the chord line. I have found as little as a degree can make a huge difference. Just some thoughts, hope it helps Lloyd |
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| itsandbits1 Regular Member Joined: 13/08/2010 Location: CanadaPosts: 81 |
I just went back over the build again and I guess the best placee to change any angle would be at the end of the arms or where you go into the square tube. By the definition of the AOA or as I say the MA; because that takes the wind out of the equation, just going by the centerline of the chord LE to TE in relation to the perpendicular from the center of the alt, what do you think the wing angle is? On the one picture it looks in the 6-8 degree range which might be steep for that shape but again, that depends on where on the chord the mount point is. Hope that helps or at least is understandable Lloyd |
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