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David.Lehman
Joined: 10 Jan 2006
Posts: 265
Location: "Lovely" Fresno CA
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 Posted: Fri Feb 03, 2006 5:36 am Post subject: Kolb-List: |
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Thanx Tom...
Definitely "food for thought"...
Back to the drawing board...
DVD
On 2/2/06, kuffel(at)cyberport.net <kuffel(at)cyberport.net> wrote:
| Quote: |
DVD asks:
<<don't need the "tube" because the bulkhead fitting is forward of the
nose about 7/8" and should be in undisturbed air?>>
As in most things aeronautic, "not exactly". 7/8" in front of the wing or
nose cone the air is relatively undisturbed *relative to the surface*. In
other words, almost static. Unfortunately, what you need to measure is
air undisturbed relative to the ground (+/- wind of course). The general
rule is to reach such air you should be as far away from the nearest
surface as the radius of curvature of that surface.
This effect caused a very low and nervous first flight for a friend in his
new Mark III. He had mounted a commercial combined static/pitot probe on
the front of his nose cone. It was about 6 " long which is more than
enough for a wing mounting but in front of the much larger radius nose
cone put it in stagnant air. The resulting low pitot pressure had him
thinking he was on the verge of stall all the way around the pattern when
it turns out he was doing over 80 mph.
The good news is you don't have to abide by the "general rule" to get
useful, repeatable airspeed indications. The airplane will stall at the
same indicated airspeed at the same g loading every time. Just don't
expect the airspeed to be accurate or the same error through out its
range. Use a GPS to find out the actual speed of your 1 g stall and then
use the GPS to find out which indicated airspeed is 1.3 times the stall
speed. This indicated speed is then your normal approach speed (says the
FAA).
My friend increased the range of his indicated airspeeds by disconnecting
the static part of the commercial probe and using the interior of the nose
cone as his static source. This worked fine except for the errors in
caused in his altimeter.....
Tom Kuffel
Whitefish, MT
Building Original FireStar
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do not archive
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ô¿ô
"Both optimists and pessimists contribute to the society. The optimist invents the aeroplane, the pessimist the parachute."
--- George Bernard Shaw |
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David.Lehman
Joined: 10 Jan 2006
Posts: 265
Location: "Lovely" Fresno CA
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| Posted: Fri Feb 03, 2006 7:10 am Post subject: Kolb-List: |
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I guess some of the pitot tube science is "by gosh, by golly"... I'm
starting out with an 8" long 1/4" diameter aluminum tube... Tubing's cheap,
I'll cut until I find the airspeed indicator is affected...
DVD
On 2/3/06, robert bean <slyck(at)frontiernet.net> wrote:
| Quote: |
That same effect is what will make me reform the front of my handmade
aluminum nose cone. At easy cruise and below the airspeed works ok.
If I crank it
up the nose tips down and the ASI starts doing a little dance.
The probe is located 15" back of the front and 3 1/4" standoff from the
bottom.
The air should be linear at that point, fast or slow.
Eventually I may know how fast I'm going.
-BB
On 3, Feb 2006, at 2:26 AM, kuffel(at)cyberport.net wrote:
>
>
> DVD asks:
>
> <<don't need the "tube" because the bulkhead fitting is forward of the
> nose about 7/8" and should be in undisturbed air?>>
>
> As in most things aeronautic, "not exactly". 7/8" in front of the
> wing or
> nose cone the air is relatively undisturbed *relative to the surface*.
> In
> other words, almost static. Unfortunately, what you need to measure is
> air undisturbed relative to the ground (+/- wind of course). The
> general
> rule is to reach such air you should be as far away from the nearest
> surface as the radius of curvature of that surface.
|
do not archive
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
ô¿ô
"Both optimists and pessimists contribute to the society. The optimist invents the aeroplane, the pessimist the parachute."
--- George Bernard Shaw |
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David.Lehman
Joined: 10 Jan 2006
Posts: 265
Location: "Lovely" Fresno CA
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| Posted: Fri Feb 03, 2006 7:54 am Post subject: Kolb-List: |
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Yeah, the more I thought about this, the more it made sense...
When I walk down the ramp and look at twin engine airplanes, the pitot tube
is either under the wing or UNDER the nose... When I look at pictures of
test vehicles with nose mounted pitots, they're always long tubes... My
AT-6 had a wing leading edge mounted pitot tube and it was long enough for a
kid to do chin-ups on (this actually happened at an airshow, I taught the
kid some adult words!)... I eventually shortened the wingspan 7' and
mounted the pitot under the wing, using a short "L" type tube...
DVD
On 2/3/06, Rick Miles <ultrastarrick(at)yahoo.com> wrote:
| Quote: |
Look at a F-16 the tube is mounted on a boom that brings it well infront
of the nose cone into cleen air
robert bean <slyck(at)frontiernet.net> wrote: --> Kolb-List message posted
by: robert bean
That same effect is what will make me reform the front of my handmade
aluminum nose cone. At easy cruise and below the airspeed works ok.
If I crank it
up the nose tips down and the ASI starts doing a little dance.
The probe is located 15" back of the front and 3 1/4" standoff from the
bottom.
The air should be linear at that point, fast or slow.
Eventually I may know how fast I'm going.
-BB
On 3, Feb 2006, at 2:26 AM, kuffel(at)cyberport.net wrote:
>
>
> DVD asks:
>
> <> nose about 7/8" and should be in undisturbed air?>>
>
> As in most things aeronautic, "not exactly". 7/8" in front of the
> wing or
> nose cone the air is relatively undisturbed *relative to the surface*.
> In
> other words, almost static. Unfortunately, what you need to measure is
> air undisturbed relative to the ground (+/- wind of course). The
> general
> rule is to reach such air you should be as far away from the nearest
> surface as the radius of curvature of that surface.
|
do not archive
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kolb-List |
|
_________________
ô¿ô
"Both optimists and pessimists contribute to the society. The optimist invents the aeroplane, the pessimist the parachute."
--- George Bernard Shaw |
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pj.ladd(at)btinternet.com
Guest
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| Posted: Fri Feb 03, 2006 8:49 am Post subject: Kolb-List: |
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I'll cut until I find the airspeed indicator is affected...>>
What are you going to do then, Dave? Stick a bit back on?
Cheers
Pat
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David.Lehman
Joined: 10 Jan 2006
Posts: 265
Location: "Lovely" Fresno CA
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slyck(at)frontiernet.net
Guest
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| Posted: Fri Feb 03, 2006 9:02 am Post subject: Kolb-List: |
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I had the choice of sticking it out front or underneath.
The very great possibility of someone walking into it at a flyin
made me opt for second best..... down where the weeds
whack it. Now I'm thinking a wing strut mount would be even
better. I only fold and unfold once each season so that wouldn't
be a big obstacle.
-BB, go ahead and archive pitot
On 3, Feb 2006, at 10:10 AM, David Lehman wrote:
| Quote: |
I guess some of the pitot tube science is "by gosh, by golly"... I'm
starting out with an 8" long 1/4" diameter aluminum tube... Tubing's
cheap,
I'll cut until I find the airspeed indicator is affected...
DVD
On 2/3/06, robert bean <slyck(at)frontiernet.net> wrote:
>
>
>
> That same effect is what will make me reform the front of my handmade
> aluminum nose cone. At easy cruise and below the airspeed works ok.
> If I crank it
> up the nose tips down and the ASI starts doing a little dance.
> The probe is located 15" back of the front and 3 1/4" standoff from
> the
> bottom.
> The air should be linear at that point, fast or slow.
>
> Eventually I may know how fast I'm going.
> -BB
> On 3, Feb 2006, at 2:26 AM, kuffel(at)cyberport.net wrote:
>
>>
>>
>> DVD asks:
>>
>> <<don't need the "tube" because the bulkhead fitting is forward of
>> the
>> nose about 7/8" and should be in undisturbed air?>>
>>
>> As in most things aeronautic, "not exactly". 7/8" in front of the
>> wing or
>> nose cone the air is relatively undisturbed *relative to the
>> surface*.
>> In
>> other words, almost static. Unfortunately, what you need to measure
>> is
>> air undisturbed relative to the ground (+/- wind of course). The
>> general
>> rule is to reach such air you should be as far away from the nearest
>> surface as the radius of curvature of that surface.
do not archive
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Fri Feb 03, 2006 9:34 am Post subject: Kolb-List: |
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| Now I'm thinking a wing strut mount would be even
| better. | -BB, go ahead and archive pitot
Modrning Bob B/Gang:
I mounted my pitot/static system below the outboard end of the right
hand lift strut on the MKIII. Works fine.
I have also had them on the nose of the nose cone, under the nose
cone, and in the middle of the lift strut. System worked well in all
locations, except under the nose cone when I let the FS go up on its
nose. 
Best system for up to 75 mph was the Winter Venturi ASI designed
primarily for sail planes. A very accurate instrument from nearly 0
to 75 mph. Operated on a venturi and not pitot pressure and static
pressure. Takes the error out of airspeed systems for our little
airplanes. Careful interpolation will allow you to read up to 85 mph
as the needle begins its second trip around the dial.
The Winter Venturi ASI in the photo shows 100 mph, but when it come to
ordering, it only gives a choice of 0 to 75 mph. Would be nice to
have one 0 to 100 or 110 mph. The beauty of this gauge is its extreme
accuracy on the low side of the scale. Allowed us to play close to
the stall in our FS's and US's.
http://www.airstuff.com/eshop/10Browse.asp
Take care,
john h
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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Steve Boetto
Joined: 11 Jan 2006
Posts: 364
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| Posted: Fri Feb 03, 2006 9:55 am Post subject: Kolb-List: |
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In a message dated 2/3/06 11:34:43 AM Central Standard Time,
jhauck(at)elmore.rr.com writes:
| Quote: | Best system for up to 75 mph was the Winter Venturi ASI designed
primarily for sail planes. A very accurate instrument from nearly 0
to 75 mph.
|
thanks for the idea John, what does the sender look like and how big? It is
not shown on the website
Steve B
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Fri Feb 03, 2006 10:22 am Post subject: Kolb-List: |
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| thanks for the idea John, what does the sender look like and how
big? It is
| not shown on the website
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| Steve B
Hi Steve B/Gang:
The venturi is small and placed 90 deg to the mounting tube. Easily
mounts to the lift strut, or it will also mount down through the
bottom of the nose cone.
Tried to find a photo of the venturi online, but failed. I may have
one stuck away in the bottom draw somewhere. If I come across one, I
will post it to the List.
john h
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kolb-List |
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_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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