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Mike Welch
Joined: 13 Feb 2011
Posts: 272
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 Posted: Thu Mar 13, 2014 5:58 am Post subject: Drag Reduction Paradox |
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Pat, So did I, Pat.
I'm not trying to speak completely on behalf of Robert (who said "just learned that drag is not a factor at higher speeds" ), but what I "think" he meant was, (since he said something we all know is wrong),
"in regards to the additionof VGs and their affect on the top end of "my" plane's speedranges; "I just learned that drag (of only the VGs) is not a factor at higher speeds".
Yeah, took me reading what he said about three or four times before I figured out what he "may" have meant.
If I'm incorrect, and he meant precisely what he said, well.............maybe he will explain what I missed, too.
Mike Welch
do not archive
From: pj.ladd(at)btinternet.com
To: kolb-list(at)matronics.com
Subject: Re: Re: Drag Reduction Paradox
Date: Thu, 13 Mar 2014 04:49:05 -0700
<<just learned that drag is not a factor at higher speeds. >>
Huh!,
I thought drag increased by the square of the speed (or something like that) In essence the faster you go the MORE drag you create..
Pat
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rickofudall
Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA
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| Posted: Thu Mar 13, 2014 7:37 am Post subject: Drag Reduction Paradox |
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From: http://en.wikipedia.org/wiki/Drag_equation
where FD is the drag force, which is by definition the force component in the direction of the flow velocity,[1] ρ is the mass density of the fluid, [2] v is the velocity of the object relative to the fluid, A is the reference area, and CD is the drag coefficient – a dimensionless coefficient related to the object's geometry and taking into account both skin friction and form drag.
It's that V squared that increases the drag with velocity; i.e. go twice as fast and you produce 4 times the drag.
Rick Girard
On Thu, Mar 13, 2014 at 8:57 AM, Mike <mdnanwelch7(at)hotmail.com (mdnanwelch7(at)hotmail.com)> wrote:
| Quote: | Pat, So did I, Pat.
I'm not trying to speak completely on behalf of Robert (who said "just learned that drag is not a factor at higher speeds" ), but what I "think" he meant was, (since he said something we all know is wrong),
"in regards to the addition of VGs and their affect on the top end of "my" plane's speed ranges; "I just learned that drag (of only the VGs) is not a factor at higher speeds".
Yeah, took me reading what he said about three or four times before I figured out what he "may" have meant.
If I'm incorrect, and he meant precisely what he said, well.............maybe he will explain what I missed, too.
Mike Welch
do not archive
From: pj.ladd(at)btinternet.com (pj.ladd(at)btinternet.com)
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Subject: Re: Re: Drag Reduction Paradox
Date: Thu, 13 Mar 2014 04:49:05 -0700
<<just learned that drag is not a factor at higher speeds. >>
Huh!,
I thought drag increased by the square of the speed (or something like that) In essence the faster you go the MORE drag you create..
Pat
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Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be unhappy.
- Groucho Marx
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ThermalHunter
Joined: 13 Dec 2012
Posts: 9
Location: Cleveland, TN
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| Posted: Thu Mar 13, 2014 10:41 am Post subject: Drag Reduction Paradox |
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You are right, Mike...in the CONTEXT of what I was writing, naturally I was referring to the associated drag factor of the VG's... not drag IN GENERAL. That would make me look stupid if I said that. Do you see that Pat? Discussion... How Much Drag would those 1/2 inch high, slightly angled VG's produce at a position 'about' 10" behind the leading edge with the wing at an angle of attack commensurate with , say, 65 MPH?? I believe there would be a vacuum there. Hmm. Where (and when) does the air separate?
On Thursday, March 13, 2014 10:05 AM, Mike <mdnanwelch7(at)hotmail.com> wrote:
Pat, So did I, Pat.
I'm not trying to speak completely on behalf of Robert (who said "just learned that drag is not a factor at higher speeds" ), but what I "think" he meant was, (since he said something we all know is wrong),
"in regards to the addition of VGs and their affect on the top end of "my" plane's speedranges; "I just learned that drag (of only the VGs) is not a factor at higher speeds".
Yeah, took me reading what he said about three or four times before I figured out what he "may" have meant.
If I'm incorrect, and he meant precisely what he said, well.............maybe he will explain what I missed, too.
Mike Welch
do not archive
From: pj.ladd(at)btinternet.com
To: kolb-list(at)matronics.com
Subject: Re: Re: Drag Reduction Paradox
Date: Thu, 13 Mar 2014 04:49:05 -0700
<<just learned that drag is not a factor at higher speeds. >>
Huh!,
I thought drag increased by the square of the speed (or something like that) In essence the faster you go the MORE drag you create..
Pat
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neilsenrm(at)gmail.com
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| Posted: Thu Mar 13, 2014 11:49 am Post subject: Drag Reduction Paradox |
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I asked the question of drag from VG at a drag reduction form at Oshkosh a few years ago. The response was that VGs when properly used clean up aerodynamic issues to the point that they don't increase drag at speed and sometimes even decrease drag.
Rick Neilsen
Redrive VW Powered MKIIIC
On Thu, Mar 13, 2014 at 2:37 PM, Robert Gillisse <thermal_hunter2002(at)yahoo.com (thermal_hunter2002(at)yahoo.com)> wrote:
[quote]
You are right, Mike...in the CONTEXT of what I was writing, naturally I was referring to the associated drag factor of the VG's... not drag IN GENERAL. That would make me look stupid if I said that. Do you see that Pat? Discussion... How Much Drag would those 1/2 inch high, slightly angled VG's produce at a position 'about' 10" behind the leading edge with the wing at an angle of attack commensurate with , say, 65 MPH?? I believe there would be a vacuum there. Hmm. Where (and when) does the air separate?
On Thursday, March 13, 2014 10:05 AM, Mike <mdnanwelch7(at)hotmail.com (mdnanwelch7(at)hotmail.com)> wrote:
Pat, So did I, Pat.
I'm not trying to speak completely on behalf of Robert (who said "just learned that drag is not a factor at higher speeds" ), but what I "think" he meant was, (since he said something we all know is wrong),
"in regards to the additionof VGs and their affect on the top end of "my" plane's speedranges; "I just learned that drag (of only the VGs) is not a factor at higher speeds".
Yeah, took me reading what he said about three or four times before I figured out what he "may" have meant.
If I'm incorrect, and he meant precisely what he said, well.............maybe he will explain what I missed, too.
Mike Welch
do not archive
From: pj.ladd(at)btinternet.com (pj.ladd(at)btinternet.com)
To: kolb-list(at)matronics.com (kolb-list(at)matronics.com)
Subject: Re: Re: Drag Reduction Paradox
Date: Thu, 13 Mar 2014 04:49:05 -0700
<<just learned that drag is not a factor at higher speeds. >>
Huh!,
I thought drag increased by the square of the speed (or something like that) In essence the faster you go the MORE drag you create..
Pat
| Quote: |
get="_blank">http://www.matronics.com/Navigator?Kolb-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
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Larlaeb
Joined: 02 Apr 2013
Posts: 75
Location: League City, Texas United States
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Thu Mar 13, 2014 4:20 pm Post subject: Drag Reduction Paradox |
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Wonder how that relates to a Kolb? and what is "at speed" for a Kolb?
Most of the feedback I get from Kolb owners that install VGs is a slight reduction in top speed. Don't know about cruise speed. Not much difference between cruise speed for me, when I am flying Kolbs, and top speed.
Top speed in a Kolb in normally never comfortable. They were not designed for speed.
I have a normal "sweet spot" cruise speed, and a "get to the next way point a little quicker" cruise speed.
In my MKIII, anything over 90 mph starts to get uncomfortable and is wasting a lot of fuel. Normal cruise, 5,000 rpm, 912ULS, is 80 to 85. High cruise, 5,200 rpm 912ULS, is 85 to 90, depended on I am loaded.
If your Kolb is getting a speed boost with VGs, I am happy for you.
john h
mkIII
Titus, Alabama
I asked the question of drag from VG at a drag reduction form at Oshkosh a few years ago. The response was that VGs when properly used clean up aerodynamic issues to the point that they don't increase drag at speed and sometimes even decrease drag.
Rick Neilsen
Redrive VW Powered MKIIIC
[quote] [b]
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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jbhart(at)onlyinternet.ne
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| Posted: Tue Mar 18, 2014 8:13 am Post subject: Drag Reduction Paradox |
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John,
There are other benefits from vortex generators other than increased low
speed lift performance. The one benefit that may be of help to you is now
they seem to tame or remove high speed wing twitchness and improve aileron
effectiveness.
With VGs you may be able to move your "sweet spot" to a higher speed and an
increased comfort level.
Jack B. Hart FF004
Winchester, IN
.........................................
From: "John Hauck" <jhauck(at)elmore.rr.com>
Date: Thu, 13 Mar 2014 19:20:19 -0500
Wonder how that relates to a Kolb? and what is "at speed" for a Kolb?
Top speed in a Kolb in normally never comfortable. They were not designed for speed.
I have a normal "sweet spot" cruise speed, and a "get to the next way point a little quicker" cruise speed.
In my MKIII, anything over 90 mph starts to get uncomfortable and is wasting a lot of fuel. Normal cruise, 5,000 rpm, 912ULS, is 80 to 85. High cruise, 5,200 rpm 912ULS, is 85 to 90, depended on I am loaded.
If your Kolb is getting a speed boost with VGs, I am happy for you.
john h
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Tue Mar 18, 2014 2:31 pm Post subject: Drag Reduction Paradox |
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Jack H/Kolbers:
Thanks for that information.
I don't really care to land any slower than I do without VGs, nor do I
believe any improvement in cruise speed would be enough to go to the expense
and effort to mount VGs, nor the inconvenience of having to work around them
once mounted. I have hard enough time getting the MKIII washed and cleaned
now without having to deal with all those little things sticking up on the
wing and other places.
As far as "taming and removing high speed wing twitchiness and improving
aileron effectiveness", I have never flown a Kolb that had those particular
problems.
I believe one of the primary problems with higher cruise and top speed on
Kolb aircraft, other than the Ultrastar which used a different engine mount
system, is the engineering of the Lord Mount engine mount system. I have
shared this before and will share this with you again. Some 27 years ago I
did some experimenting with my original Kolb Firestar, quite by accident.
Cannot remember why I had the Firestar tied down or why I was doing the
engine run ups, but during this exercise I discovered how much the engine
was raised in the rear and canted down and to the left, I believe, as the
RPM was increased right up to full throttle. Up to a certain point all was
well, then the automatic divergence of the thrust line started eating up
most of the thrust being produced by the engine. The Lord mount density was
whatever was being shipped with the original Firestar kits way back then.
During my next test flight, at about 65 or 70 mph, I can't remember now, I
hit a brick wall. The Firestar would fly no faster on this flight, although
it had pegged 85 mph, WOT straight and level flight on previous flights. I
was a little upset with my airplane and reduced power slowly. As I did, the
aircraft started accelerating. As it accelerated, at this lower than WOT
power setting, I slowly increased power and the Firestar continued to
increase airspeed. To remedy this problem I got on the horn and talked to
Little Mike at old Kolb Aircraft. Asked him to find the hardest Lord Mounts
available and told him why I wanted them. Those hard Lord mounts fixed my
problem. My MKIII has always had the hardest Lord mounts, but with 80 and
100 hp engines, that much thrust still kicks the thrust line off center.
Once the Kolb gets to a certain amount of drag, the more power applied, the
more the thrust line is diverted from inline with the airframe. I believe
that is why I can fly to 88 mph at 5,200 rpm, but increased power to 5,500
rpm only pushes the MKIII to 95 mph. Of course there are other factors
involved, but the offset thrust line is one of the major problems.
If I want to go faster, I need an airplane built for speed. If I want to
have a fun airplane that I can also make some incredibly long, exciting
flights, I'll stick with an 80 mph cruise and my MKIII.
The above is my opinion only, based on personal experience building,
breaking, and flying Kolb aircraft for the past 30 years.
Take care,
john h
mkIII
Titus, Alabama
There are other benefits from vortex generators other than increased low
speed lift performance. The one benefit that may be of help to you is now
they seem to tame or remove high speed wing twitchness and improve aileron
effectiveness.
With VGs you may be able to move your "sweet spot" to a higher speed and an
increased comfort level.
Jack B. Hart FF004
Winchester, IN
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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zeprep251(at)aol.com
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| Posted: Wed Mar 19, 2014 3:56 am Post subject: Drag Reduction Paradox |
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The dramatic difference in all aspects of flight below 40 mph have convinced me of the VG's worth on the MK -3C. You only have to fly it with & without to see it.
G. Aman MK3C jabiru 800+hrs
Sent from my iPhone
| Quote: | On Mar 18, 2014, at 12:13 PM, "Jack B. Hart" <jbhart(at)onlyinternet.net> wrote:
John,
There are other benefits from vortex generators other than increased low
speed lift performance. The one benefit that may be of help to you is now
they seem to tame or remove high speed wing twitchness and improve aileron
effectiveness.
With VGs you may be able to move your "sweet spot" to a higher speed and an
increased comfort level.
Jack B. Hart FF004
Winchester, IN
..........................................
From: "John Hauck" <jhauck(at)elmore.rr.com>
Date: Thu, 13 Mar 2014 19:20:19 -0500
Wonder how that relates to a Kolb? and what is "at speed" for a Kolb?
Top speed in a Kolb in normally never comfortable. They were not designed for speed.
I have a normal "sweet spot" cruise speed, and a "get to the next way point a little quicker" cruise speed.
In my MKIII, anything over 90 mph starts to get uncomfortable and is wasting a lot of fuel. Normal cruise, 5,000 rpm, 912ULS, is 80 to 85. High cruise, 5,200 rpm 912ULS, is 85 to 90, depended on I am loaded.
If your Kolb is getting a speed boost with VGs, I am happy for you.
john h
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jbhart(at)onlyinternet.ne
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| Posted: Fri Mar 21, 2014 6:12 pm Post subject: Drag Reduction Paradox |
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| Quote: | From: "John Hauck" <jhauck(at)elmore.rr.com>
Date: Thu, 13 Mar 2014 19:20:19 -0500
Top speed in a Kolb in normally never comfortable.
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John,
Why? What do you feel?
Jack B. Hart FF004
Winchester, IN
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Sun Mar 23, 2014 12:46 pm Post subject: Drag Reduction Paradox |
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| Quote: | Top speed in a Kolb in normally never comfortable.
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John,
Why? What do you feel?
Jack B. Hart FF004
Winchester, IN
At full power, primarily noise and burning a lot more fuel to gain a few
mph. I think another major factor is the engine being twisted with an
attitude change the more power applied, once the engine mounts have reached
their holding capability. At top speed it feels like it is dragging its
anchor. I imagine the high thrust line is killing a lot of speed and eating
up a lot of power also.
Power off, my MKIII is quiet and smooth as silk at speeds up to 105 mph.
That speed was unintentional during a rapid decent. At higher altitudes,
probably 5,000 feet and above, the sensation of speed is almost nil. Easy
to over speed. Slow cross check of the gauges will get my MKIII over VNE,
100 mph, in a blink. Power off it is trimmed neutral.
Don't believe Homer Kolb ever had any intention for his airplanes to fly
wide open. He was more interested in slower flight, STOL characteristics,
and enjoyable flying.
john h
mkIII
Titus, Alabama
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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