Home » Public Forums » GMCnet » Opinions from Rocket Scientists Please (Really ??)
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| Re: [GMCnet] Opinions from Rocket Scientists Please [message #208828 is a reply to message #208821] |
Sun, 26 May 2013 10:46   |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Matt,
I agree, with all the crap (TV antenna mirror, roof A/C, pod, Fantastic Fan, luggage rack, ladder, spare tire) these things wouldn't
do diddley squat.
Regards,
Rob
-----Original Message-----
From: Matt Colie
Steve,
They may be of some value on a squared truck (or maybe an SOB), but I do not believe that they would be any value on a GMC as the
important corners are already round.
Just the opinion of a naval architect and marine engineer
Matt -
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Opinions from Rocket Scientists Please [message #208834 is a reply to message #208821] |
Sun, 26 May 2013 11:31 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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Vortex generators are somewhat commonly used
on aircraft. IIRC, they serve to hold airflow
to the wing and horizontal stabilizer surfaces.
This adds to "lift" and stability and will
reduce any tendency for control surfaces
(elevators and ailerons) to "flutter." I think
they had even been added to the B-52Fs in which
I flew back in the 1960s.
As a side note, it was a common practical joke
played on new maintenance troops to send them
on a long walk from flight line to base supply
for "a vortex generator." Supply would then ask
whether they were AC or DC and send the newbie
troop on a long walk back to the flight line.
Crew chief would choose AC or DC and send newbie
on the long walk back to the supply office. Of
course they had the OTHER type of current. Then
the "joke" would be explained.
In the last few years, large vertical ones have
been added to wingtips and it is claimed that
they improve fuel economy 5% or even more.
That is VERY substantial.
Will these help on our GMCs? I have no idea. I
note that the maker claims they will help on any
vehicle with a rear window steeper than 30 degrees
from vertical. That would include the GMC M/H.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ~ TZE166V101966 ~ ~ ~ ~
~ ~ ~ '76 ex-Palm Beach ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
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> To: gmclist@temp.gmcnet.org
> From: matt7323tze@gmail.com
> Date: Sun, 26 May 2013 10:12:13 -0500
> Subject: Re: [GMCnet] Opinions from Rocket Scientists Please
>
>
>
> SteveW wrote on Sun, 26 May 2013 10:50
> > http://www.airtab.com/about.html
> >
> > I guess I believe this... Maybe.
> >
> > Thoughts ??
> >
> > Steve W
> > Southern California
> > 1973 23'
>
> Steve,
>
> They may be of some value on a squared truck (or maybe an SOB), but I do not believe that they would be any value on a GMC as the important corners are already round.
>
> Just the opinion of a naval architect and marine engineer
>
> Matt - only 50 miles from home
> --
> Matt & Mary Colie
> '73 Glacier 23 Chaumière (say show-me-air)
> Now with 4 working Rear Brakes
> SE Michigan - Twixt A2 and Detroit
> _______________________________________________
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| Re: Opinions from Rocket Scientists Please [message #208836 is a reply to message #208815] |
Sun, 26 May 2013 11:50 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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First I am not a Rocket Scientist. I also haven't stayed in a Holiday Inn lately. I also have no formal training in aerodynamics. But I have read a lot on the Internet and am a bit skeptical of claims of items like this.
A quick review of what I think I know about aerodynamics: Any object that passes through the air has drag. At above a certain speed, that varies by size and shape, a very large percentage of this drag is caused by a vacuum space behind the object. This vacuum is caused by the inability of the air flowing past the object to quickly replace the object as the object is traveling. A boundary layer of air next to the object can provide a cushion of air that is not moving as quickly as the surrounding air. This boundary layer has the ability to expand enough to reduce the vacuum space... lowering the drag on the object.
An example of this effect is the golf ball. Years ago, golf balls were smooth. Then golfers discovered that their old golf balls went farther than the new, smooth ones. "It wasn't long before golfers were intentionally pitting their brand-new balls to improve their games. By 1905, golf balls were being manufactured with dimples, as they have been ever since."
<http://phys.org/news101660458.html>
So... a beat up motorhme should have less drag than a nice one? I do not think so... there is a little difference between golf ball and a motorhome. While golf balls are not sent through the air in a particular direction... in fact spinning in desired, a motorhome travels nose first. (We hope!)
I understand with automotive aerodynamics there is a big difference in drag and "air flow separation" with anything greater than a 30 degree change in the surface. So creating a little turbulent boundary layer just before any changes in the body shape greater than 30 degrees should reduce total drag.
So... I disagree with Matt and Robert and say it "It couldn't hurt."
BUT... I might be agreeing with them a little as it might not help enough at the speeds we travel to be noticed.
But for the land speed record coach.... 
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Opinions from Rocket Scientists Please [message #208931 is a reply to message #208821] |
Mon, 27 May 2013 08:41 |
Kudzu
Messages: 377
Registered: November 2011
Location: Marshville, NC
Karma: 0
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Senior Member |
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I agree. Plus they wouldn't help with the "bow wave" of a truck hitting
the front of the GMC either, which I find produces the bigger "pucker"
moments.
Dan in NC
1976 Eleganza II
On 5/26/2013 11:12 AM, Matt Colie wrote:
>
> SteveW wrote on Sun, 26 May 2013 10:50
>> http://www.airtab.com/about.html
>>
>> I guess I believe this... Maybe.
>>
>> Thoughts ??
>>
>> Steve W
>> Southern California
>> 1973 23'
> Steve,
>
> They may be of some value on a squared truck (or maybe an SOB), but I do not believe that they would be any value on a GMC as the important corners are already round.
>
> Just the opinion of a naval architect and marine engineer
>
> Matt - only 50 miles from home
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1976 Eleganza II
1996 Chevy Impala SS
1999 Kawasaki Vulcan Nomad
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| Re: Opinions from Rocket Scientists Please [message #208943 is a reply to message #208815] |
Mon, 27 May 2013 11:36 |
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John Heslinga
Messages: 632
Registered: February 2011
Location: Edmonton, Alberta, Canada
Karma: 4
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In My Humble Opinion:
They look Ugly and would ruin the design of the coach. I have a GMC because of its great looks and style, not necessarily for its efficiency.
Sorry: No Rocket Science Justfication. 
John and Cathie Heslinga
1974 Canyonlands 260
455, Manny tranny and 1 ton, 3:70 LS,
Red Seal Journeyman, DTE, BEd. MEd.
Edmonton, Alberta
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| Re: Opinions from Rocket Scientists Please [message #209069 is a reply to message #208815] |
Tue, 28 May 2013 19:21 |
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SeanKidd
Messages: 747
Registered: June 2012
Location: Northern Neck Virginia
Karma: 4
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I was a US Navy airframe mechanic, vortex generators are typically used to control boundary layer eddys, (minute cusion of air between aircraft skin and high velocity air stream)this forces airflow into an area behind the airfoil, typically a wing to control drag, if the air were allowed to flow naturally along an aircraft wing; it actually tends to run towards the trailing edge of the wing toward the centerline to fill the vacuum created by the displaced air from the fuselage. The vortex generators help direct the air off the wing. The aggregate drag reduction is negligible, the drag is just evenly controlled and dispersed.
Sean and Stephanie
73 Ex-CanyonLands 26' #317 "Oliver"
Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.
Colonial Travelers
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| Re: [GMCnet] Opinions from Rocket Scientists Please [message #209084 is a reply to message #209069] |
Tue, 28 May 2013 23:33 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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My senior Summer semester was taking the wind tunnel class lab.
I can tell you that some things are so tricky to gain , that in some cases
we recorded negative results.
Placement of these devices are so critical, that I feel they would need to
show me exactly where to place them on our coach to pay back the cost of
the devices.
I have not seen many on trucks on the road, so it must not be that great.
On Tue, May 28, 2013 at 5:21 PM, Sean Kidd <fiatkidd@yahoo.com> wrote:
>
>
> I was a US Navy airframe mechanic, vortex generators are typically used to
> control boundary layer eddys, (minute cusion of air between aircraft skin
> and high velocity air stream)this forces airflow into an area behind the
> airfoil, typically a wing to control drag, if the air were allowed to flow
> naturally along an aircraft wing; it actually tends to run towards the
> trailing edge of the wing toward the centerline to fill the vacuum created
> by the displaced air from the fuselage. The vortex generators help direct
> the air off the wing. The aggregate drag reduction is negligible, the drag
> is just evenly controlled and dispersed.
>
>
> --
> 73 Ex-CanyonLands 26' #317 "Oliver"
> Hubler 1-Ton, Quadra Bags, Rear Disc, Reaction Arms,
> Fluorescent Mineral Capital of the World, New Jersey
> _______________________________________________
> GMCnet mailing list
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--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Opinions from Rocket Scientists Please [message #209119 is a reply to message #209112] |
Wed, 29 May 2013 08:39 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Michael Leipold wrote on Wed, 29 May 2013 08:33 |
When we build "Fuel Economy Test Trucks" we use these.
They make the truck look weird, probably because we do not paint them to match. Whether they work or not, I never really asked anyone. But I do know that the "Supertruck" we are building for the government to show what kinds of Fuel Efficiencies can be realistically gained is covered with these. So somebody here has bought into them.
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Micheal,
You are talking about the Government there....
The same people that like alcohol in motorfuel and curly fried light bulbs with mercury....
Nuff Said.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Opinions from Rocket Scientists Please [message #209120 is a reply to message #209112] |
Wed, 29 May 2013 08:35 |
Jp Benson
Messages: 649
Registered: October 2011
Location: Fla
Karma: 2
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Senior Member |
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I found a good deal of info on "supertruck". A lot of interesting things were tried. It seems that most of the aerodynamic improvements were attributed to modified body and trailer shape. Searching supertruck program + vortex generators led me to a discussion on the RVNetwork. http://www.rvnetwork.com/index.php?showtopic=102395
One person who claimed to have built an aerodynamically efficient truck had this to say about vortex generators:
"Vortex Generators work to a very small extent. But I am a big
bang-for-the-buck- kinda guy, and I think they are a waste of money."
This doesn't really prove anything but is an interesting anecdotal observation.
Also found a LaFerrari webpage that claimed VG's were used to "boost downforce and efficiency". So opinions vary.
Wikipedia has a good discussion on the use of vane type VG's on aircraft used for delaying flow separation over the wing.
Is there a link to information about the VG covered truck?
Thanks,
JP
>________________________________
> From: Michael <lilmyk@gmail.com>
>To: gmclist@temp.gmcnet.org
>Sent: Wednesday, May 29, 2013 8:33 AM
>Subject: Re: [GMCnet] Opinions from Rocket Scientists Please
>
>
>
>
>When we build "Fuel Economy Test Trucks" we use these.
>They make the truck look weird, probably because we do not paint them to match. Whether they work or not, I never really asked anyone. But I do know that the "Supertruck" we are building for the government to show what kinds of Fuel Efficiencies can be realistically gained is covered with these. So somebody here has bought into them.
>--
>1973 GMC 26' Glacier - Unknown Mileage - Has a new switch pitch transmission with Powerdrive :)
>_______________________________________________
>GMCnet mailing list
>Unsubscribe or Change List Options:
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>
>
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