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#Post#: 4776--------------------------------------------------
Re: New Design for the DIY75
By: sut Date: November 16, 2014, 3:31 pm
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I would just take a small dc motor and mount the windmill to it
bet it would light a led!
The diy 175 looked like it was spinning pretty good, for 7 mph
wind
#Post#: 4783--------------------------------------------------
Re: Sail Blade VAWT
By: sut Date: November 17, 2014, 6:58 am
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What about when the ripstop gets covered in ice and snow But it
could just act like another blade and shed it
#Post#: 4785--------------------------------------------------
Re: Sail Blade VAWT
By: lynx wind Date: November 17, 2014, 9:02 am
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The concerns raised here are real.
The circular disk will collect so much snow and ice it probably
wont startup enough to throw off the weight. So probably the
three arm rotor is still best.
The swept area is what we calculate potential power in the wind,
but the blade area of triangular sails is less than straight
blades, unless the shape is adjusted for a wider base.
What happens if the material gets ice covered? It may not, it
is waterproof and would probably shed any precipitation, ice or
snow.
#Post#: 4788--------------------------------------------------
Re: Sail Blade VAWT
By: lynx wind Date: November 17, 2014, 3:26 pm
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Oooh be careful about quoting people's theory on how wings and
sails work. I don't subscribe to the whole low/high pressure
theory as the whole and complete story at all. It can be
disproven with a sheet of paper by a school kid.
Anyway, no a triangle isn't the only shape but it offers some
distinct advantages. The TE can be kept taut allowing the flat
sail to belly out. If the line between top of TE and bottom of
TE isn't close to straight it will flap like a flag.
Try some experiments with simple models.
#Post#: 4790--------------------------------------------------
Re: Sail Blade VAWT
By: lynx wind Date: November 17, 2014, 3:54 pm
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Got it...
Then you get back into keeping those two spars separated and
supported. I'd rather have just one spar flailing around, but
try it.
#Post#: 4793--------------------------------------------------
Re: Sail Blade VAWT
By: lynx wind Date: November 17, 2014, 9:20 pm
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The savonius is more of a drag type like an anemometer's cups.
A sailboat can run downwind but slightly slower than true
windspeed. It's my least favorite way to sail. Very slow and
no breeze.
It's interesting how you turn the blade angle just slightly and
then rotation is opposite the savonius.
If you study how a parachute works, at first it seems it's pure
drag. But it's not. The air rushing up and outside the
parachute circumference causes a coanda effect pulling up on the
top of the parachute.
#Post#: 4823--------------------------------------------------
Re: Sail Blade VAWT
By: nessprojects Date: November 18, 2014, 6:34 pm
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I love this simple concept, Once the 175 is finished I might try
this idea out on my old 75 alternator being as it is doing nowt
!.
#Post#: 4877--------------------------------------------------
Re: Sail Blade VAWT
By: baccula Date: November 25, 2014, 9:52 pm
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I'm also thinking of prototyping this, I'm sure my wife would be
happy to put her sewing skills to work to whip up some sails.
LW, are you thinking that fiberglass rods will be stiff enough
for this? I'd be using the Seagull 75 stator, so thinking 36"
height.
#Post#: 4879--------------------------------------------------
Re: Sail Blade VAWT
By: lynx wind Date: November 25, 2014, 10:25 pm
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They should flex and spill power just like a sail boat. I have
the material to build this but find myself up to my ears in
projects. Hopefully soon.
#Post#: 4883--------------------------------------------------
Re: Sail Blade VAWT
By: baccula Date: November 27, 2014, 4:16 pm
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I picked up some ripstop nylon at the fabric store, and my wife
was kind enough to sew these up for me this morning. Overall
height is ~17", 6.5" wide and sleeved to fit a 5/16" fiberglass
rod (driveway marker from HD). I'll be repurposing the rotor
from my SG75, which is just wide enough to accomodate the sails.
I purchased some SS eyelets that will screw into the rotor to
retain the sail at LE and TE using grommets that I will punch in
to the sail. Not sure if I need something to keep it pulled taut
at the top? I will be using shaft collars with set screws on
either side of the rotor to locate the spar. I think I will
epoxy the collars to the rotor to provide a bit more support as
well. Anything else I should be thinking about?
[IMG]
HTML http://i.imgur.com/PvpkRltl.jpg[/img]
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