Carbon fiber tow and epoxy laminated to the wing will make it stiffer. What airfoil did you cut? A RC glider airfoil like one of the Dr. Drela foils is fast and clean in the air. Also, I like the Selig 3014 airfoil. It's almost the same. I don't know anything about what you are doing so the symmetrical airfoil might be best. The last catch term to google is UIUC. Lots of airfoils info there. Just thought I'd mention the airfoils in case you are not familiar. Fun project...good luck.
You may have already thought of this but, to strengthen the blades, you could make two rings from old coat-hangers. One for the top and one for the bottom, attached to the ends of the three blades. Or if the weight will be a problem, perhaps you could use strong fishing-wire; in a triangular shape.
Very nice! I wonder if performance would be improved by filling in the space between the disks, either with a simple cylinder (plastic wrapped around and taped or?), or even better perhaps, something with a profile to deflect the air up or down. I suggest this because I have found in my turbines (video's linked to this profile), that reducing whetted area of non lift producing surfaces can improve performance. In the space between the disks, the amount of turbulence
the amount of turbulence from the boundary layers is probably so great that the exposed foils are not likely contributing anything but drag, and so by enclosing the space, you would reduce the whetted area by the surface of the plates, the shaft, and any portion of the foils that aren't contributing. My design paradigm is to work on both sides of the equation, reduce drag, and increase lift. You might also get a slightly boosted wind velocity at the root of the foils
Cool. I'm glad wing stiffening worked. It just occured to me also of centrifugal forces. If the blades splay out from the axis, this will slow the rotation speed. I still think joining the wings with wire or even maybe foam spars will help spread the load evenly, like spokes on a bike wheel does. Thanks for the uploads. I have been watching quite while.
I've watched all 3 of your videos on the Vawt and still I see some wobble on the bottom circular section. Its not much, but at that speed im certain is doesn't help.
At 0.6 watts and 12 volts you're implied load resistance of the battery is 240 ohms. It would be interesting to run the turbine into a fixed series of resistors from 24 ohms up to 480 ohms instead of a battery, and compare the power curves of each resistor. Then you could guess which battery voltage will improve the match of the generator to the load by selecting which resistor did best. Maybe a 12 volt battery is not best, at those rotation speeds for that generator.
Looks Good! What type of foam? EPP is great foam that I would recommend taking a look at. It’s the type of foam you see for those swimming pool foam toys that some call noodles. You can literally run over it with a Mac Truck without damage. Another cool thing is that you can use the R/C covering that you iron on.
Interesting. This suggests the center of pressure, which moves fore and aft cordwise during rotation, was flexing the wing spanwise causing the outer portions to be stalled for much of the rotation. I bet there is also twist occuring due to the same effect, which is also hurting performance. Perhaps stiffen-up the wing cordwise and I bet you'll see further improvement. Ideally the wing would not flex to any significant degree in any direction. Try some stiff premade model aircraft wings.
@Fearlessthinker At this point, I'm targeting an overall efficiency of 5%. I'm not sure what is going to be the magic bullet, but when I get closer, I think I'll glass/epoxy the wing for improved stiffness.
not saying it didn't have any effect but surface smoothness makes a huge difference at the speed lift wings need to pass through the air, but so does wing flexing
Carbon fiber tow and epoxy laminated to the wing will make it stiffer. What airfoil did you cut? A RC glider airfoil like one of the Dr. Drela foils is fast and clean in the air. Also, I like the Selig 3014 airfoil. It's almost the same. I don't know anything about what you are doing so the symmetrical airfoil might be best. The last catch term to google is UIUC. Lots of airfoils info there. Just thought I'd mention the airfoils in case you are not familiar. Fun project...good luck.
leaktech1 1 month ago
You may have already thought of this but, to strengthen the blades, you could make two rings from old coat-hangers. One for the top and one for the bottom, attached to the ends of the three blades. Or if the weight will be a problem, perhaps you could use strong fishing-wire; in a triangular shape.
J2897Tutorials 3 months ago
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Very nice! I wonder if performance would be improved by filling in the space between the disks, either with a simple cylinder (plastic wrapped around and taped or?), or even better perhaps, something with a profile to deflect the air up or down. I suggest this because I have found in my turbines (video's linked to this profile), that reducing whetted area of non lift producing surfaces can improve performance. In the space between the disks, the amount of turbulence
drewartturbine 3 months ago
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to finish
the amount of turbulence from the boundary layers is probably so great that the exposed foils are not likely contributing anything but drag, and so by enclosing the space, you would reduce the whetted area by the surface of the plates, the shaft, and any portion of the foils that aren't contributing. My design paradigm is to work on both sides of the equation, reduce drag, and increase lift. You might also get a slightly boosted wind velocity at the root of the foils
drewartturbine 3 months ago
Cool. I'm glad wing stiffening worked. It just occured to me also of centrifugal forces. If the blades splay out from the axis, this will slow the rotation speed. I still think joining the wings with wire or even maybe foam spars will help spread the load evenly, like spokes on a bike wheel does. Thanks for the uploads. I have been watching quite while.
20RoyalSuperKing 3 months ago
I've watched all 3 of your videos on the Vawt and still I see some wobble on the bottom circular section. Its not much, but at that speed im certain is doesn't help.
Unsharpened 3 months ago
@Unsharpened Good point. I should get that disk running straight.
Caleb6543 3 months ago
At 0.6 watts and 12 volts you're implied load resistance of the battery is 240 ohms. It would be interesting to run the turbine into a fixed series of resistors from 24 ohms up to 480 ohms instead of a battery, and compare the power curves of each resistor. Then you could guess which battery voltage will improve the match of the generator to the load by selecting which resistor did best. Maybe a 12 volt battery is not best, at those rotation speeds for that generator.
definitionofis 3 months ago
@definitionofis Good idea.
Caleb6543 3 months ago
Looks Good! What type of foam? EPP is great foam that I would recommend taking a look at. It’s the type of foam you see for those swimming pool foam toys that some call noodles. You can literally run over it with a Mac Truck without damage. Another cool thing is that you can use the R/C covering that you iron on.
TheWindGinProject 3 months ago
Interesting. This suggests the center of pressure, which moves fore and aft cordwise during rotation, was flexing the wing spanwise causing the outer portions to be stalled for much of the rotation. I bet there is also twist occuring due to the same effect, which is also hurting performance. Perhaps stiffen-up the wing cordwise and I bet you'll see further improvement. Ideally the wing would not flex to any significant degree in any direction. Try some stiff premade model aircraft wings.
Fearlessthinker 3 months ago
@Fearlessthinker At this point, I'm targeting an overall efficiency of 5%. I'm not sure what is going to be the magic bullet, but when I get closer, I think I'll glass/epoxy the wing for improved stiffness.
Caleb6543 3 months ago
more than the smooth surface I would guess just stiffening solved most.
Try a carbon fiber spar imbedded in the middle
photolodge 3 months ago
@photolodge
not saying it didn't have any effect but surface smoothness makes a huge difference at the speed lift wings need to pass through the air, but so does wing flexing
itsandbits1 3 months ago
more than the smooth surface I would guess just stiffening solved most.
photolodge 3 months ago