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Is there a drag rake guru out there?



 
 
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  #1  
Old March 31st 05, 11:18 AM
nimbusgb
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Default Is there a drag rake guru out there?

Can anyone help with the design and installation details of a drag
rake?

I'm interested in:
Pitot tube sizing ( ID and length )
Span of the rake.
Positioning of the dynamic pressure port.
Plenum chamber/s dimensions.
Positioning of a rake on or behind the trailing edge.

Ian

  #2  
Old March 31st 05, 01:49 PM
jphoenix
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Ian,

Here's a link I was given last year, looks like a pretty good
description:

http://www.owp.us/Althaus/AlthausDragProbe.asp

Jim

nimbusgb wrote:
Can anyone help with the design and installation details of a drag
rake?

I'm interested in:
Pitot tube sizing ( ID and length )
Span of the rake.
Positioning of the dynamic pressure port.
Plenum chamber/s dimensions.
Positioning of a rake on or behind the trailing edge.

Ian


  #3  
Old March 31st 05, 02:31 PM
John Galloway
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You could buy mine:-) Made by Replogle in the late
eighties to Dick Johnson's specifications - with meter
and tubing. Used once.

John Galloway
Scotland

At 13:00 31 March 2005, Jphoenix wrote:
Ian,

Here's a link I was given last year, looks like a pretty
good
description:

http://www.owp.us/Althaus/AlthausDragProbe.asp

Jim

nimbusgb wrote:
Can anyone help with the design and installation details
of a drag
rake?

I'm interested in:
Pitot tube sizing ( ID and length )
Span of the rake.
Positioning of the dynamic pressure port.
Plenum chamber/s dimensions.
Positioning of a rake on or behind the trailing edge.

Ian





  #4  
Old March 31st 05, 02:35 PM
Wayne Paul
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Default

Here is a link that may be helpful.
http://www.soaridaho.com/Schreder/Te...ck_Johnson.htm

Wayne
http://www.soaridaho.com/

"nimbusgb" wrote in message
ps.com...
Can anyone help with the design and installation details of a drag
rake?

I'm interested in:
Pitot tube sizing ( ID and length )
Span of the rake.
Positioning of the dynamic pressure port.
Plenum chamber/s dimensions.
Positioning of a rake on or behind the trailing edge.

Ian



  #5  
Old March 31st 05, 05:18 PM
Ian Molesworth
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Default

Thanks Wayne,Jim

I am already aware of Johnson articles and Althaus's improved version.
Neither article actually discusses any of the maths behind the design
and positioning of a rake. I'm looking for a little more detail. I have
a prototype rake I built and I'll be testing its operation this weekend.
www.internationalsoaring.org/dragrake1.htm

Regards
Ian




  #6  
Old March 31st 05, 06:00 PM
Brian
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Default

How much do you want for it?

Brian

  #7  
Old March 31st 05, 06:01 PM
Brian
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Default

What are you using for meter?

Thanks

Brian

  #8  
Old March 31st 05, 06:33 PM
nimbusgb
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Default

I have a differential pressure gauge built around a Honeywell DUXL01D.
Measuring 0 - 1" H20 which is the same range that I've seen used on the
old 80's repogle systems and in Dick Johnsons tests.

At the moment, during testing I'll be using an analog meter, my
amplifier outputs a signal between .6 and 4 volts. Ultimately it'll go
into an A/D converter on a digital system I have.

Ian

  #9  
Old April 1st 05, 12:47 AM
jphoenix
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Nice looking rake Ian.

It appears to be per the Althaus drawing?

Jmi

Ian Molesworth wrote:
Thanks Wayne,Jim

I am already aware of Johnson articles and Althaus's improved

version.
Neither article actually discusses any of the maths behind the design
and positioning of a rake. I'm looking for a little more detail. I

have
a prototype rake I built and I'll be testing its operation this

weekend.
www.internationalsoaring.org/dragrake1.htm

Regards
Ian


  #10  
Old April 1st 05, 03:07 AM
Bob Salvo
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Default

An analog meter does a nice job of smoothing the information in mild
turbulence. Additional smoothing may be needed with a digital system. If a
pitot that is used to sample the airspeed at the other port of the pressure
gauge has the same hose size and length as the hose coming from the rake,
the pressure gauge output should be smoother. You might consider using a
Kiel tube for the pitot and mounting it on you drag probe. I hope to hear
more about your tests.

Bob

"nimbusgb" wrote in message
ups.com...
I have a differential pressure gauge built around a Honeywell DUXL01D.
Measuring 0 - 1" H20 which is the same range that I've seen used on the
old 80's repogle systems and in Dick Johnsons tests.

At the moment, during testing I'll be using an analog meter, my
amplifier outputs a signal between .6 and 4 volts. Ultimately it'll go
into an A/D converter on a digital system I have.

Ian



 




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