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Forum Index : Windmills : wing sections, cord lengths
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rotorhed Newbie  Joined: 29/01/2007 Location: AustraliaPosts: 36 |
Hi everyone (newbie here) Just have a little question to anyone who has built a vawt project. Is there a specific (naca) wing section profile that you would suggest for a small vawt and what is the best cord length to use ? ( my aim is to get as many rpm as possible) I'm very interested in gizmos vawt any info on that would be greatly appreciated. Cheers Marge the Winds are here Ah McCaine............. |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
Hi rotorhead. That vertical I use is called a Lenz2, designed by Ed Lenz. His web site is here. Worth a visit, Ed has a few clever designs out there. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| rotorhed Newbie Joined: 29/01/2007 Location: AustraliaPosts: 36 |
Hi Glenn Thanks for the reply. I looked at the site and it got my brain juices flowing a little faster. Just wondering What is the diameter & wing height of your vawt. And if you know the cut in speed of the device. Conrats on a great site Cheers Christian Marge the Winds are here Ah McCaine............. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
Hi rotohed. That one is 1.3 meters diameter and 1.2 meter high. Cut in speed is stuffed if I know, but it starts in the lightest of winds and is charging at just over 20 rpm. I have started on a bigger one, 2.1 meters diameter by 2.4 meters high, but its on the back burner for a while, need to finish off a few other projects first. Have a look at this one built by another forum member, thefinis, its a monster! http://www.thebackshed.com/windmill/FORUM1/forum_posts.asp?T ID=418&PN=2 Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| thefinis Regular Member  Joined: 23/08/2006 Location: United StatesPosts: 53 |
Hey a loaded lenz2 is never going to hit very high rpms but the smaller diameter ones will reach workable rpms pretty easy. My big one will be going into a 1:6.5 gearbox to speed up the rpms to hopefully a workable number. But not until I get a new tower. Check out the link Glenn posted and look at the drawing with ratios from Ed. On vawts thin bladed air foils will reach a much higher rpm but are poor self starters. The USA gov did many studies on vawts at the Sandia Labs and have lots of good info available on the web. It seems to me that what it is happening is that the low rpm large chord wing vawts are showing promise while the problems with the high speed thin bladed vawts make a high speed hawt a better choice. A hawt is probably easiest for a small high rpm machine and has many detailed write ups on how to build. Best of luck Finis Texas born and bred |
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| rotorhed Newbie Joined: 29/01/2007 Location: AustraliaPosts: 36 |
Hi Guys Thanks for all the replies. I will check out those sites. As self starting is not an issue for my project maybe a thin wing airfoil would be more suitable. Since i have so much information now it's getting petty close to the fun stuff. Cheers Christian Marge the Winds are here Ah McCaine............. |
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vawtman Senior Member  Joined: 14/09/2006 Location: United StatesPosts: 146 |
Rotorhed hello Why wouldnt self starting be a issue? What size turbine does your project call for? Has far airfoils go thats where one needs to be creative. Workin on a project this spring too darn cold here now. You dont want the chords too narrow or profiles too thin unless its small. Thats just from a darrius lover.  |
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| rotorhed Newbie Joined: 29/01/2007 Location: AustraliaPosts: 36 |
Hi vawtman The turbine would be about 1m or smaller in diameter and maybe 1.5m tall. I'm thinking about using a nacca 4418 profile with a cord length of about 150 - 200mm. not sure if I should use a complete wing or an open wing like the lenz type. Might try both! Self starting is not an issue because it is going to be for a propulsion system. And I have the ability to start it when its needed. When I finally get round to stating I'll post some pictures. Cheers Christian Marge the Winds are here Ah McCaine............. |
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| vawtman Senior Member Joined: 14/09/2006 Location: United StatesPosts: 146 |
I know nothing about these nacca profiles since planes dont fly in little circles. Design the profile for the rotation of your turbine. For that little guy maybe 5 blabes at around 100mm chord and 50mm profile. 25mm is around an inch right?Me no metric Selfstarting wont be a problem with either but testing both would be cool A propulsion system????Please explain  |
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| rotorhed Newbie Joined: 29/01/2007 Location: AustraliaPosts: 36 |
Hi Vawt An inch 25.4mm. yeah 25mm is close enough. its good to hear that self starting won't be an issue. Just quietly I'd like to use the vawt to power a small water craft. I live very close to the bay and do a lot of paddling on my sufski and would like to enjoy the water with something a little less conventional. An ordinary sail boat is even to much work. It probably wont be a power house but it will be a fun little experiment. But before i can even get to the boat part I'll start with the easy part and test the vawt first. P.S. have you heard about the areotecture vawt their site is www.areotecture.com just a fantastic revolution in vawt technology. Cant wait till the start selling them in Australia. Marge the Winds are here Ah McCaine............. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5116 |
That sounds like a interresting project. I would go for a sav or Lenz windmill, lots of torque. You cold use a paddle wheel to make it a real easy project. Now for a brain teaser type of question. How do you think it would go up wind? Would the force of the wind against the wind turbine be greater than the thrust provided by the prop/paddle wheel and push you backwards? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| rotorhed Newbie Joined: 29/01/2007 Location: AustraliaPosts: 36 |
Hi Gizmo That is a very bake your noodle kind of question. However I have seen some very promising projects that suggest it can be done. I don't know what it is called but there is a video of a little wind powered car on you tube that has a fixed hawt driving the wheels and the video shows it driving directly up wind on a road it's almost unbelievable. found another video but not the i'm thinking of must have taken it off just search for wind turbine car it should come up. Suppose i'll find out the hard way. Christian Marge the Winds are here Ah McCaine............. |
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