Is there a drag rake guru out there?

[nimbusgb]

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

[jphoenix]

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

[John Galloway]

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
>
>

[Wayne Paul]

Here is a link that may be helpful.
http://www.soaridaho.com/Schreder/Technical/Drag_Rake/Dick_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
>

[Ian Molesworth]

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

[Brian]

How much do you want for it?

Brian

[Brian]

What are you using for meter?

Thanks

Brian

[nimbusgb]

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

[jphoenix]

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

[Bob Salvo]

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
>

[Bob Salvo]

Have you seen:
http://www.glidingmagazine.com/FeatureArticle.asp?id=199

Bob

"Bob Salvo" > wrote in message
...
> 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
> >
>
>

[nimbusgb]

Yup, been doing a LOT of reading lately!

Ian

[nimbusgb]

Pretty much.

2 * 10 pitots each over a 33mm span with a 'missing' tube a the
midpoint. Gives the rake a 75mm span. The plenum chambers are seperate
on each side of the wing and averaged by a tube running down the rear
edge of the chamber.

Ian

[Bob Salvo]

Do you intend to use it to find the optimum flap position?

Bob

"nimbusgb" > wrote in message
oups.com...
> Pretty much.
>
> 2 * 10 pitots each over a 33mm span with a 'missing' tube a the
> midpoint. Gives the rake a 75mm span. The plenum chambers are seperate
> on each side of the wing and averaged by a tube running down the rear
> edge of the chamber.
>
> Ian
>

[nimbusgb]

Yes, thats the general idea.

Ian