Posted by Bob F on August 3, 2009, 7:16 pm
It looks like they still are.
You should be able to heat the blades and twist the tips flatter, then cool them
and they will retain the new shape. But maybe PVC just is to flexable for bigger
The blade angle needs to vary inversly as the speed of that section of the blade
travels. The tips travel faster, so they need less angle. That way, they slice
through the same distance of air traveling through the blade as the center blade
angle does in each revolution, even though they are moving much faster through
Photos, like those you posted can help tell if the tip angle is correct. The
blade should not flex towards the wind at the tip. It should optimally flex
slightly in the direction the wind is pushing on the blade if it is flexible
material, although this amount of flex may not be visable.
I suppose some amount of mismatch like you have could be used to self-regulate
the blade speed in high winds to avoid overspeed damage, at the cost of lowered
efficiency at lower speeds.
All the above is only my educated opinion. I am not a windmill expert in any
way, just an interested engineer.
Posted by z on August 3, 2009, 11:09 pm
I wonder if you could coat them with fiberglass, like autobody mesh with
resin to stiffen them up once they were in the shape you wanted.
I love that stuff..
Posted by Morris Dovey on July 27, 2009, 4:14 pm
Yup. There are folks who will do whatever to make a buck. Any bets as to
whether they even tried to identify the original author?
A Google search should turn up at least /this/ thread (which is why I
adjusted the subject line) :)
No worry. I have a lot more curiosity than need, and I'm pretty sure you
have more important things to do than satisfy my idle curiosity.
The PVC pipe blade strike me as the best kind of creative
problem-solving. Optimal performance would be nice, but generally has a
significant associated cost. Sometimes, quick and dirty is needed - and,
as someone once pointed out: "Perfection is the enemy of good."
Yuppers - and I learned something new and interesting. Thanks again.
DeSoto, Iowa USA
Posted by Ulysses on July 27, 2009, 4:39 pm
I may have more "urgent" things to do but without idle curiosity a lot of
the stuff we make not never have been thought of ;-) Who knows, you might
get an idea that you can incorporate into a solar collector. Besides that,
I OWE it to just about anyone who asks for whatever limited knowledge and
experience I have which I might not have if others had not taken the time to
explain things to me and/or bother to post it on a web site.
That makes me feel a lot better about some of the half-assed stuff I've
Posted by Morris Dovey on July 27, 2009, 6:02 pm
Strange how that works out sometimes... :)
DeSoto, Iowa USA