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Forum Index : Windmills : Added some "Winglets" to the Lenz2
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I made some winglets ( Is that how its spelt? ) to the Lenz2 on the weekend. Ed pointed out they can improve efficiency, so I drew up a desing in CAD and used the cnc router to cut out a set from 3mm ply wood. 
Painted them blue to match the rest of the wings. Held on with pop rivets. While I was at it I added a meter to the tower, it was a little short at 1.5 meters high 
Will see how it goes over the next couple of weeks. The winds are starting to pick up, finally! Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Prof Newbie  Joined: 01/12/2005 Location: AustraliaPosts: 33 |
Hi Gizmo and Co, I love to see the "Lenz2" subject at the top of the page, not that this the only reason for this post. The great thing about the "Lenz2" design is the simplicity of the wing shape such that it is easy to virtual make it from off the shelf/recycled components. There is of course a certain amount of trade off in performance with this simplicity. By just adding things such as "winglets" keeps to the simple concept but can "tweak" the performance some what. In keeping with this "K.I.S" approach, I think that by attaching "trim tabs" near the trailing edge of the underside of the wing, without changing the chord length, would also increase the performance of the wing with an easy addition. The trim tab should be approximately 0.25 of the chord length in length. The trim tab should be set at a angle such that at the trailing edge (T.E.) point of the trim tab, it is at 90 degrees to a line to the axis of the rotor. When the wing is moving into the wind (the upstroke), the air moving across it would have a change of direction when it encounters the trim tab and there would be an increase in its velocity. The air being ejected from the T.E. of the trim tab would be in line with the arc of movement of the rotor rather than just spilling off the wing at a tangent. This would create a "jet" like tail thrust to the wing, i.e. a performance improvement. Simple. But wait, there's more!! On the downstroke, the trim tab would create more "drag" on the wing, and this would also help push the rotor around and thus gain some more thrust. The hardest thing about this is that you would again have to pull you VAWT out of the sky to attach the trim tabs. What do ye think? (No, I have not tried this.) Prof. I know boats!! |
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windstuffnow Newbie Joined: 30/06/2006 Location: United StatesPosts: 31 |
Prof, I worked with something similar in the wind tunnel with the small model. It wasn't real professional and the attatchments were flimbsy at best. Anyway, they didn't seem to do very well. I had plans to try a different approach similar to a drooped aileron to help deflect some of the trailing edge air but haven't tried it yet. Also, I tried a crude "slat" on the leading edge thinking it would carry lift farther around on the upwind side. That did actually work to a small degree but the increase in performance didn't seem worth the complexity. Possibly a much better (less crude) version would help significantly. I think there is potential in the diversion of trailing edge air as well. Have fun! |
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