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cffd(at)pgrb.com
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 Posted: Thu Jul 20, 2006 9:20 am Post subject: Glide Ratio power off-an experiment |
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I decided to experiment with a small propeller and a fan.
With the fan blowing straight up I put a freewheeling prop on a stiff wire
held vertically, with the prop spinning it rose up the wire.
I stopped the prop from spinning with a thread taped to the end of one
blade and placed it over the fan. It did not rise as high as when spinning.
This tells me the of the non-spinning prop takes more wind speed (closer to
the fan) to support the prop's weight due to less drag. The spinning prop
was supported with less wind (farther from the fan) due to the higher drag.
Remember:
the force of drag = 1/2 *Cd* air density * Vsrqd * area. Since the force is
equal to the propeller weight in both cases but the velocity of the air is
less for the spinning prop either the Cd went up or the area increased which
means the total drag is higher to be supported by the slower wind.
Also in my 701 at idle and 50 mph, my descent rate was about 715 fpm for a
glide ratio of about 6 to 1. Which means at an altitude of 1000 feet you
have about a mile and a little over a minute to figure out what to do.
Chuck D.
N701TX
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cffd(at)pgrb.com
Guest
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| Posted: Fri Jul 21, 2006 4:15 pm Post subject: Glide Ratio power off-an experiment |
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There has been so much chatter about banning folks that nobody
has commented on my experiment.
Chuck D.
N701TX
do not archive
| Quote: |
I decided to experiment with a small propeller and a fan.
With the fan blowing straight up I put a freewheeling prop on a stiff wire
held vertically, with the prop spinning it rose up the wire.
I stopped the prop from spinning with a thread taped to the end of one
blade and placed it over the fan. It did not rise as high as when
spinning.
|
| Quote: |
This tells me the of the non-spinning prop takes more wind speed (closer
to
|
| Quote: | the fan) to support the prop's weight due to less drag. The spinning prop
was supported with less wind (farther from the fan) due to the higher
drag.
|
| Quote: |
Remember:
the force of drag = 1/2 *Cd* air density * Vsrqd * area. Since the force
is
|
| Quote: | equal to the propeller weight in both cases but the velocity of the air is
less for the spinning prop either the Cd went up or the area increased
which
|
| Quote: | means the total drag is higher to be supported by the slower wind.
Also in my 701 at idle and 50 mph, my descent rate was about 715 fpm for a
glide ratio of about 6 to 1. Which means at an altitude of 1000 feet you
have about a mile and a little over a minute to figure out what to do.
Chuck D.
N701TX
|
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http://www.matronics.com/Navigator?Zenith-List |
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