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Dimples On Model Aircraft Could Greatly Extend Range



 
 
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  #1  
Old November 4th 08, 08:04 PM posted to sci.energy,rec.aviation.homebuilt,rec.aviation.military,rec.aviation.marketplace,sci.engr.mech
Bret Cahill
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Posts: 11
Default Dimples On Model Aircraft Could Greatly Extend Range

Have they tried dimples on radio controlled aircraft? The size and
speed could designed around the magic Reynolds number = 100,000 where
the coefficient of drag drops precipitously.

Dimpling could vastly extent the range of large and slow as well as
small and fast radio controlled aircraft.

A competitive cyclist is the right size and speed for Nre = 100,000 so
dimple suits can work. Same for golf balls.

Nre = 100,000 for widebodies going 0.5 knots so dimples won't work
except on the runway.

From fluid mechanics the Reynolds number is the ratio of inertial
forces/viscous forces.

N re = Diameter X velocity X density of fluid/viscosity of fluid.


Bret Cahill



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  #2  
Old November 4th 08, 08:32 PM posted to sci.energy,rec.aviation.homebuilt,rec.aviation.military,rec.aviation.marketplace,sci.engr.mech
Gregory Hall
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Posts: 26
Default Dimples On Model Aircraft Could Greatly Extend Range


"Bret Cahill" wrote in message
...
Have they tried dimples on radio controlled aircraft? The size and
speed could designed around the magic Reynolds number = 100,000 where
the coefficient of drag drops precipitously.

Dimpling could vastly extent the range of large and slow as well as
small and fast radio controlled aircraft.

A competitive cyclist is the right size and speed for Nre = 100,000 so
dimple suits can work. Same for golf balls.

Nre = 100,000 for widebodies going 0.5 knots so dimples won't work
except on the runway.

From fluid mechanics the Reynolds number is the ratio of inertial
forces/viscous forces.

N re = Diameter X velocity X density of fluid/viscosity of fluid.


Bret Cahill




We competitive cyclists use dimples already on our disk wheels. And some
skinsuits incorporate them. But they don't look like the dimples on a golf
ball. They are shaped differently and they are shallow.

Check out Zipp disk wheel dimples he
http://www.zipp.com/wheels/detail.php?ID=33

Over a 40K ITT this rear wheel can give you a 30-40 second advantage over
smooth disk wheels.

--
Gregory Hall



  #3  
Old November 4th 08, 08:53 PM posted to sci.energy,rec.aviation.homebuilt,rec.aviation.military,rec.aviation.marketplace,sci.engr.mech
[email protected]
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Posts: 10
Default Dimples On Model Aircraft Could Greatly Extend Range

Have they tried dimples on radio controlled aircraft? � The size and
speed could designed around the magic Reynolds number = 100,000 where
the coefficient of drag drops precipitously.


Dimpling could vastly extent the range of large and slow as well as
small and fast radio controlled aircraft.


A competitive cyclist is the right size and speed for Nre = 100,000 so
dimple suits can work. �Same for golf balls.


Nre = 100,000 for widebodies going 0.5 knots so dimples won't work
except on the runway.


From fluid mechanics the Reynolds number is the ratio of inertial
forces/viscous forces.


N re = Diameter X velocity X density of fluid/viscosity of fluid.


Bret Cahill


We competitive cyclists use dimples already on our disk wheels. And some
skinsuits incorporate them. But they don't look like the dimples on a golf
ball. They are shaped differently and they are shallow.

Check out Zipp disk wheel dimples hehttp://www.zipp.com/wheels/detail.php?ID=33

Over a 40K ITT this rear wheel can give you a 30-40 second advantage over
smooth disk wheels.


A model plane about the size of a cyclist would benefit most from
dimples if it only went cycling speeds, 20 - 25 knots.

Smaller aircraft would need to be designed to go faster inverse with
size.

A golf ball sized aircraft would have to go 200 mph for dimples to
work.


Bret Cahill

  #4  
Old November 4th 08, 09:05 PM posted to sci.energy,rec.aviation.homebuilt,rec.aviation.military,rec.aviation.marketplace,sci.engr.mech
Gregory Hall
external usenet poster
 
Posts: 26
Default Dimples On Model Aircraft Could Greatly Extend Range


wrote in message
...
Have they tried dimples on radio controlled aircraft? ? The size and
speed could designed around the magic Reynolds number = 100,000 where
the coefficient of drag drops precipitously.


Dimpling could vastly extent the range of large and slow as well as
small and fast radio controlled aircraft.


A competitive cyclist is the right size and speed for Nre = 100,000 so
dimple suits can work. ?Same for golf balls.


Nre = 100,000 for widebodies going 0.5 knots so dimples won't work
except on the runway.


From fluid mechanics the Reynolds number is the ratio of inertial
forces/viscous forces.


N re = Diameter X velocity X density of fluid/viscosity of fluid.


Bret Cahill


We competitive cyclists use dimples already on our disk wheels. And some
skinsuits incorporate them. But they don't look like the dimples on a golf
ball. They are shaped differently and they are shallow.

Check out Zipp disk wheel dimples
hehttp://www.zipp.com/wheels/detail.php?ID=33

Over a 40K ITT this rear wheel can give you a 30-40 second advantage over
smooth disk wheels.


\ A model plane about the size of a cyclist would benefit most from
\ dimples if it only went cycling speeds, 20 - 25 knots.
\
\ Smaller aircraft would need to be designed to go faster inverse with
\ size.
\
\ A golf ball sized aircraft would have to go 200 mph for dimples to
\ work.

I wonder if anybody has thought of putting the appropriate dimples on the
surface of propellers? Seems like reducing drag there would increase RPM and
reduce HP required.

A bicycle wheel spins much faster than 20-25 knots apparent to the air it
interfaces with. At 30 knots, for example, the surface of the wheel might be
moving closer to 100 knots apparent to the wind.

--
Gregory Hall


  #5  
Old November 4th 08, 09:53 PM posted to sci.energy,rec.aviation.homebuilt,rec.aviation.military,rec.aviation.marketplace,sci.engr.mech
[email protected]
external usenet poster
 
Posts: 10
Default Dimples On Model Aircraft Could Greatly Extend Range

Have they tried dimples on radio controlled aircraft? ? The size and
speed could designed around the magic Reynolds number = 100,000 where
the coefficient of drag drops precipitously.


Dimpling could vastly extent the range of large and slow as well as
small and fast radio controlled aircraft.


A competitive cyclist is the right size and speed for Nre = 100,000 so
dimple suits can work. ?Same for golf balls.


Nre = 100,000 for widebodies going 0.5 knots so dimples won't work
except on the runway.


From fluid mechanics the Reynolds number is the ratio of inertial
forces/viscous forces.


N re = Diameter X velocity X density of fluid/viscosity of fluid.


Bret Cahill


We competitive cyclists use dimples already on our disk wheels. And some
skinsuits incorporate them. But they don't look like the dimples on a golf
ball. They are shaped differently and they are shallow.


Check out Zipp disk wheel dimples
hehttp://www.zipp.com/wheels/detail.php?ID=33


Over a 40K ITT this rear wheel can give you a 30-40 second advantage over
smooth disk wheels.


\ A model plane about the size of a cyclist would benefit most from
\ dimples if it only went cycling speeds, 20 - 25 knots.
\
\ Smaller aircraft would need to be designed to go faster inverse with
\ size.
\
\ A golf ball sized aircraft would have to go 200 mph for dimples to
\ work.


I wonder if anybody has thought of putting the appropriate dimples on the
surface of propellers? Seems like reducing drag there would increase RPM and
reduce HP required.


I'm not certain dimples would make much difference in a well designed
airfoil wing or prop or fusalage. Maybe something that had an awkward
shape, i. e., a strut, would benefit the most.

I may recant.

A golf ball goes 4 times further with dimples but a golf ball isn't
aerodynamic in the first place.

A bicycle wheel spins much faster than 20-25 knots apparent to the air it
interfaces with. At 30 knots, for example, the surface of the wheel might be
moving closer to 100 knots apparent to the wind.


It's just double the speed of the hub.


Bret Cahill

  #6  
Old November 4th 08, 10:05 PM posted to sci.energy,rec.aviation.homebuilt,rec.aviation.military,rec.aviation.marketplace,sci.engr.mech
[email protected]
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Posts: 2,878
Default Dimples On Model Aircraft Could Greatly Extend Range

In rec.aviation.marketplace Gregory Hall wrote:

I wonder if anybody has thought of putting the appropriate dimples on the
surface of propellers? Seems like reducing drag there would increase RPM and
reduce HP required.


While reducing drag would be a goal, fixed propeller systems are designed
to keep the tip velocity under mach 1.

For constant speed props, the RPM is whatever you set it to, again
under mach 1.


--
Jim Pennino

Remove .spam.sux to reply.
  #9  
Old November 5th 08, 01:29 AM posted to sci.energy,rec.aviation.homebuilt,rec.aviation.military,rec.aviation.marketplace,sci.engr.mech
[email protected]
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Posts: 1,130
Default Dimples On Model Aircraft Could Greatly Extend Range

On Nov 4, 4:26*pm, "daestrom"
wrote:
wrote:
In rec.aviation.marketplace Gregory Hall wrote:


I wonder if anybody has thought of putting the appropriate dimples
on the surface of propellers? Seems like reducing drag there would
increase RPM and reduce HP required.


While reducing drag would be a goal, fixed propeller systems are
designed to keep the tip velocity under mach 1.


For constant speed props, the RPM is whatever you set it to, again
under mach 1.


True, but reducing Hp requirements would still be an advantage.


There's an outfit that markets a perforated tape for
propeller leading edges. The perfs act like dimples. They claim
performance improvements with their stuff, of course. See http://www.dimpletape.com/

Dan
 




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