(This might be because there's little wind to deflect at the hub. Also: deflecting it also increases the wind speed at the root, which makes it mismatch the twist and foul the angle of attack - possibly losing what was gained.)
Might lower your drag just a tad - which is only a help for the bearing load and support guys.
Flux[ Parent ]
Same story with the hub: It's such a small part of the swept area that it makes little sense to try to scavenge it. Make the blades a half inch longer instead. B-)[ Parent ]
Different applications will recognize the improvements or not. The majority here charging batteries looking only for a specific cut-in speed (unloaded until then) and then not stalling too bad under load to charge probably wouldn't see a big improvement or at least think they could so yes,(why bother ?)
It's more work to carve twisted blades with the large drop at the root and also it's work to fabricate some kind of a custom nose cone that might be benificial. There is really no way to tell just how much power is lost while charging or was also lost (waiting longer for the flatter blades to come up to speed) without controlled testing of these variables.
I have no doubt that a nose cone properly designed to compliment the blade profile at the root could improve overall performance. Again, this is just too hard to prove and apply for most of us. I think few would disagree though that a nose cone can be attractive and lessen the "home brew" look if that's important. Just my thoughts. Dave B. [ Parent ]
The blade calculators indeed don't lie. But they assume the wind speed is the same at all radii.
if you use less twist at the root for a given formula your blade design will be less efficient overall
When you deflect the wind with a nosecone you RAISE the wind speed near the hub. As a result you require still MORE twist than the calculators give you to get the angle of attack right.[ Parent ]
I'll add a couple thoughts. We've found that the nose cones offer some other minor benefits. They protect the blade hardware quite a bit from corrosion, and in some cases bushings and hub fasteners . And, they similarly protect the blunt, end-grain portion of the blades where, long term, weather takes its toll.
They can be problematic as well especially if they are big (corroded attachment fasteners, loosening up, making noise, falling off, etc).
Lastly, a turbine without a nose-cone is out half dressed IMHO ;-)
~kitestrings
