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place for venturi -in air duct?

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graeme bird

Joined: 15 Jul 2010
Posts: 434

Posted: Sat Apr 09, 2011 4:47 am Post subject: place for venturi -in air duct?

I am planing fitting a venturi to drive a vac AH & DI has anyone any suggestions as to the best place to put the venturi. I am tempted to put one or two smaller ones in the bottom of the air duct under the prop as I have a few inches space under the radiators.



I am also tempted to ditch the heavy vac instruments and fit a trutrak AH/DI

_________________
Graeme Bird
kit4 (Wagstaff) TBD
Kit3 G-CLXU (Gregory) mono 914 xs Woodcomp
Kit2 G-PATS - (kesterton) Mono Classic 912 warpdrive
Kit 1 G-UMPY - Mono Classic/XS 912S, Woodcomp G(@)gdbmk.co.uk

gholland(at)content-strea
Guest

Posted: Sat Apr 09, 2011 5:11 am Post subject: place for venturi -in air duct?

Graeme

Fit a TruTrak

Gerry

pjeffers(at)talktalk.net
Guest

Posted: Sat Apr 09, 2011 5:34 am Post subject: place for venturi -in air duct?

Graeme,  

I thought we had left venturi’s in the history books.  My experience with them goes back to Luscombes and Austers.  They were always rather dudious bits of kit that only work at all, at reasonably high speeds. That was when they were fitted externally on the wing L/E or side of the fuselage.  In this position they create significant drag.   

As you intend fitting it/them within the cooling duct be aware that on the basis of ‘not getting something for nothing’ you will be interfering with the engine cooling. Though I have not seen actual pictures of it you will find that the flow lines within the air intakes under the engine will be very turbulent which will not be appreciated by a venturi which relies on smooth or even laminar flow to work well.  

I personally think you would be much better off with a new fashioned Vac pump or all electric/electronic instruments.  

Just my input for further comment.  

   

         

  

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of graeme bird

 Sent: 09 April 2011 13:48

 To: europa-list(at)matronics.com

 Subject: place for venturi -in air duct?  

  

   

--> Europa-List message posted by: "graeme bird" <graeme(at)gdbmk.co.uk>

 

 I am planing fitting a venturi to drive a vac AH & DI has anyone any suggestions as to the best place to put the venturi. I am tempted to put one or two smaller ones in the bottom of the air duct under the prop as I have a few inches space under the radiators.

 

 I am also tempted to ditch the heavy vac instruments and fit a trutrak AH/DI

 

 --------

 Graeme Bird

 G-UMPY

 Mono Classic/XS FWFD 912ULS/Warp drive FP

 Build nearing completion

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=336442#336442

 

 

 

 

 

 

 

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 Europa-List Email Forum -

 href="http://www.matronics.com/Navigator?Europa-List">http://www.matronics.com/Navigator?Europa-List

 ===========

 bsp;   - MATRONICS WEB FORUMS -

 href="http://forums.matronics.com">http://forums.matronics.com

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 bsp;                  -Matt Dralle, List Admin.

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No virus found in this message.

 Checked by AVG - www.avg.com

 04/09/11  

       [quote][b]

grahamsingleton(at)btinte
Guest

Posted: Sat Apr 09, 2011 8:26 am Post subject: place for venturi -in air duct?

Graeme

why try to drag your nice modern Europa back into the steam age? Go solid state electronic, lighter, more reliable and without adding a large piece of built in headwind.

The time when you need an AH may well include icing conditions, poor light et al.

Graham

From: Peter Jeffers <pjeffers(at)talktalk.net>

To: europa-list(at)matronics.com

Sent: Saturday, 9 April, 2011 14:29:40

Subject: RE:  place for venturi -in air duct?



        place for venturi -in air duct?               

Graeme,   

I thought we had left venturiâ€™s in the history books.  My experience with them goes back to Luscombes and Austers.  They were always rather dudious bits of kit that only work at all, at reasonably high speeds. That was when they were fitted externally on the wing L/E or side of the fuselage.  In this position they create significant drag.    

As you intend fitting it/them within the cooling duct be aware that on the basis of â€˜not getting something for nothingâ€™ you will be interfering with the engine cooling. Though I have not seen actual pictures of it you will find that the flow lines within the air intakes under the engine will be very turbulent which will not be appreciated by a venturi which relies on smooth or even laminar flow to work well.   

I personally think you would be much better off with a new fashioned Vac pump or all electric/electronic instruments.   

Just my input for further comment.   

     

           

  

From: owner-europa-list-server(at)matronics.com [mailto:owner-europa-list-server(at)matronics.com] On Behalf Of graeme bird

 Sent: 09 April 2011 13:48

 To: europa-list(at)matronics.com

 Subject: place for venturi -in air duct?   

  

     

--> Europa-List message posted by: "graeme bird" < graeme(at)gdbmk.co.uk >

 

 I am planing fitting a venturi to drive a vac AH & DI has anyone any suggestions as to the best place to put the venturi. I am tempted to put one or two smaller ones in the bottom of the air duct under the prop as I have a few inches space under the radiators.

 

 I am also tempted to ditch the heavy vac instruments and fit a trutrak AH/DI

 

 --------

 Graeme Bird

 G-UMPY

 Mono Classic/XS FWFD 912ULS/Warp drive FP

 Build nearing completion

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=336442#336442

 

 

 

 

 

 

 

 ===========

 Europa-List Email Forum -

 href="http://www.matronics.com/Navigator?Europa-List">http://www.matronics.com/Navigator?Europa-List

 ===========

 bsp;   - MATRONICS WEB FORUMS -

 href="http://forums.matronics.com">http://forums.matronics.com

 ===========

 bsp; - List Contribution Web Site -

 bsp;                  -Matt Dralle, List Admin.

 href="http://www.matronics.com/contribution">http://www.matronics.com/contribution

 ===========

 

        

  

No virus found in this message.

 Checked by AVG - www.avg.com

 04/09/11   

       [quote]http://www.matronics.com/Navigator?Europa-Listllow" target="_blank" href="http://www.matronics.com/contribution">http========================


[b]

ptag.dev(at)tiscali.co.uk
Guest

Posted: Sun Apr 10, 2011 6:33 am Post subject: place for venturi -in air duct?

Hi! I'll second that Gerry but do it with crimp connections, please.

(not soldered! been there got the feckin "t" shirt !

regards

Bob Harrison G-PTAG  from Swedish Lapland Courtesy Ryanair and 1000 

mile o/night train sleeper !



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		  Fit a TruTrak


	


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graeme bird

Joined: 15 Jul 2010
Posts: 434

Posted: Mon Apr 11, 2011 12:34 pm Post subject: Re: place for venturi -in air duct?

thanks for the advice. It is appreciated. The point about smooth air is a good one. I plan to have an electronic centre piece, a gps and moving CAA map.

The thing is, a venturi and vac instrument is such a very simple arrangement; doesn't need power, software update, emit RF, have parts that go obsolete, be dependent on a supplier that will disappear, be hard to read in sunlight, have connections that corrode, wires and components that vibrate off, rely on GPS satellites and cant be jammed. 



The drag caused by a venturi must be tiny based on its forward cross section.

Graeme Bird, Electronics engineer, satellite processors,  Astrium Space (EADs)

grahamsingleton(at)btinte
Guest

Posted: Mon Apr 11, 2011 3:11 pm Post subject: place for venturi -in air duct?

<The drag caused by a venturi must be tiny based on its forward cross section.>

Not true, the drag of a Europa is quite low for it's csarea, drag of a venturi is high, unless you totally re design it. you could easily add 10% to your cruise drag but don't ask me, I didn't do the sum.

think of th coist of a year of extra fuel.

my humble opinion

Graham

From: graeme bird <graeme(at)gdbmk.co.uk>

To: europa-list(at)matronics.com

Sent: Monday, 11 April, 2011  21:34:14

Subject: Europa-List: Re: place for venturi -in air duct?



-



The drag caused by a venturi must be tiny based on its forward cross section.

Graeme Bird, Electronics engineer, satellite processors,  Astrium Space (EADs)



--------

Graeme Bird

G-UMPY

Mono Classic/XS FWFD 912ULS/Warp drive FP

Build nearing completion





Read this topic online here:



http://forums.matronics.c;  --> http://forums.matronics.com [quote][b]

graeme bird

Joined: 15 Jul 2010
Posts: 434

Posted: Tue Apr 12, 2011 9:11 am Post subject: Re: place for venturi -in air duct?

Graham, I do value your comments but I would like to understand this, there are already two, three inch holes and a vast letter box with radiators in plus the mono wheel, 8 flap hinges hanging down into the air flow. The amount of energy the ventrui needs to extract to spin the gyro is tiny. Is it because the air is rotating around the fuselage and thus the drag the venturi causes is due to a larger area?



The icing aspect is interesting - wouldnt really want that to ice first in cloud.

grahamsingleton(at)btinte
Guest

Posted: Tue Apr 12, 2011 2:49 pm Post subject: place for venturi -in air duct?

Hi Graeme,

first as someone said the venturi might not work too well inside a duct, I would want to redesign it as a letter box venturi perhaps? However I suspect that the inefficient air motors driving the two gyros may well need a good half horsepower to give enough suction.(correction, pressure, there's no such thing as suction is there?) A good venturi would be more efficient than a vacuum pump, nevertheless, a solid state system would be inherently more reliable and less energy wasteful.

Agree about all the stuck on ducts, this is why people like Frans Veldman et al worked so hard to optimize their cooling, I'm sure with gratifying results.

Not worth the effort to reinvent a well designed wheel, ( the factory cooling system was OK but could have done better !

Graham

From: graeme bird <graeme(at)gdbmk.co.uk>

To: europa-list(at)matronics.com

Sent: Tuesday, 12 April, 2011 18:11:39

Subject: Europa-List: Re: place for venturi -in air duct?



--> Europa-List message posted by: "graeme bird" <graeme(at)gdbmk.co.uk (graeme(at)gdbmk.co.uk)>



Graham, I do value your comments but I would like to understand this, there are already two, three inch holes and a vast letter box with radiators in plus the mono wheel, 8 flap hinges hanging down into the air flow. The amount of energy the  ventrui needs to extract to spin the gyro is tiny. Is it because the air is rotating around the fuselage and thus the drag the venturi causes is due to a larger area?



The icing aspect is interesting - wouldnt really want that to ice first in cloud.



--------

Graeme Bird

G-UMPY

Mono Classic/XS FWFD 912ULS/Warp drive FP

Build nearing completion





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=336719#336719





http://www.matronics.com/Navigatorsp;              - MATRONICS WEB FORUMS -

=   -->  [quote][b]

graeme bird

Joined: 15 Jul 2010
Posts: 434

Posted: Mon Apr 18, 2011 12:36 pm Post subject: Re: place for venturi -in air duct?

well, in spite of the collective wisdom, I already had all the bits tubed up and installed so I may as well give it a go with the venturi. I tried it in the car and it seems to work ok and the drag doesnt seem so great at 70mph. If I keep changing the baseline I'll never get to fly it. 

The whole caboodle is 3Kg DI & AH.

The more I think about modern electronics TV, computer, mobile, camera, printer, GPs etc it all goes in the obsolete draw after a couple of years.

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