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klaus(at)utdallas.edu
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 Posted: Sun Mar 22, 2009 8:36 am Post subject: Seals for wing lockers of 601HDS |
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Hi,
Over the years I have wondered how much the air leakage
from the wing lockers onto the top of the wing impacts
performance. Particularly for the 601HDS that I have,
with its small wing area, the leakage might have a
significant effect.
This weekend I conducted a test to find out,
using 1/8 in. thick 1/4 wide adhesive foam strips
on the locker doors.
The foam is a bit like memory foam, in that it gives way
and collapses to the right size, without exerting much
pressure once it has the correct size.
A first inkling that things had changed came
immediately after takeoff. Even with reduced
power, the plane kept climbing at a
comparatively high rate. In level flight,
the cruise speed seemed quite a bit higher.
Measuring with GPS into and against the prevailing
winds using a total of four runs,
the plane cruised with 4,800 rpm (Rotax 912,
80 hp) at exactly at 100 kts,
which is 2-3 kts higher than before.
Load was pilot only, fuel tanks 75% filled.
Temperature 70 deg F, altitude 2,500 ft,
fuel consumption 4 gph.
Never ever before, regardless of load, temperature, or
altitude, had I seen that cruise speed at 4,800 rpm.
Conclusion: The air leakage of the wing locker doors
apparently has a significant impact on the lift characteristics
of the 601HDS wing. The effect should be even more
pronounced on 601HDS planes with heavier engines like
Subaru or Corvair, since they require higher angles
of attack. I suspect there is a similar
but somewhat reduced effect for
the 601HD and 601XL due to the larger wing area.
At least testing the effect of seals for those models
seems like a good idea.
Happy flying,
Klaus
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Jeyoung65(at)aol.com
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| Posted: Sun Mar 22, 2009 8:54 am Post subject: Seals for wing lockers of 601HDS |
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If this kind of improvement, have you sealed the metal strip covering the wing to center section with some kind of sealant? If so, what did you use? Jerry of Ga.
DO NOT ARCHIVE
In a message dated 3/22/2009 11:37:10 A.M. Eastern Standard Time, klaus(at)utdallas.edu writes:
| Quote: | --> Zenith-List message posted by: Klaus Truemper <klaus(at)utdallas.edu>
Hi,
Over the years I have wondered how much the air leakage
from the wing lockers onto the top of the wing impacts
performance. Particularly for the 601HDS that I have,
with its small wing area, the leakage might have a
significant effect.
This weekend I conducted a test to find out,
using 1/8 in. thick 1/4 wide adhesive foam strips
on the locker doors.
The foam is a bit like memory foam, in that it gives way
and collapses to the right size, without exerting much
pressure once it has the correct size.
A first inkling that things had changed came
immediately after takeoff. Even with reduced
power, the plane kept climbing at a
comparatively high rate. In level flight,
the cruise speed seemed quite a bit higher.
Measuring with GPS into and against the prevailing
winds using a total of four runs,
the plane cruised with 4,800 rpm (Rotax 912,
80 hp) at exactly at 100 kts,
which is 2-3 kts higher than before.
Load was pilot only, fuel tanks 75% filled.
Temperature 70 deg F, altitude 2,500 ft,
fuel consumption 4 gph.
Never ever before, regardless of load, temperature, or
altitude, had I seen that cruise speed at 4,800 rpm.
Conclusion: The air leakage of the wing locker doors
apparently has a significant impact on the lift characteristics
of the 601HDS wing. The effect should be even more
pronounced on 601HDS planes with heavier engines like
Subaru or Corvair, since they require higher angles
of attack. I suspect there is a similar
but somewhat reduced effect for
the 601HD and 601XL due to the larger wing area.
At least testing the effect of seals for those models
seems like a good idea.
Happy he es y - MATRONICS WEB FORUMS =========================< - List Contribution Web Site ; =========================
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Feeling the pinch at the grocery store? Make dinner for $10 or less.
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jaybannist(at)cs.com
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| Posted: Sun Mar 22, 2009 9:04 am Post subject: Seals for wing lockers of 601HDS |
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Klaus,
Could you be a bit more specific about that foam tape you used ? I can think of several applications for a tape like that.
Jay Bannister
--
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hills(at)sunflower.com
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| Posted: Sun Mar 22, 2009 9:08 am Post subject: Seals for wing lockers of 601HDS |
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Klaus;
Very impressive test, and something I had never even heard about, wing
locker leakage affecting performance. Any ideas how those of us with a
flying 601HDS could eliminate the air leak, but still be able to open the
wing lockers normally?
Roger Hill
--
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Terry Phillips
Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT
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| Posted: Sun Mar 22, 2009 10:11 am Post subject: Seals for wing lockers of 601HDS |
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Hi Klaus
This is a very interesting subject. Back in 2007, Peter Chapman posted a
video showing tuft tests on his HDS providing graphic evidence of
significant lift destroying leaks at the wing locker cover joints. I
believe the video link is still active. Your results nicely confirm the
impressions left by the video. I'm pasting in my response to Peter just below:
Terry
| Quote: | >Date: Thu, 30 Aug 2007 08:37:45 -0600
>To: zenith-list(at)matronics.com
>From: Terry Phillips <ttp44(at)rkymtn.net>
>Subject: Re: tuft test video - 601 HDS
>
>Peter, thank you for posting the video. Very interesting results there.
>It is really great when someone takes the time and effort to produce real
>data, rather than just speculating--like I am doing 
>
>Your study reminds me of the work that Klaus Truemper did on his HDS--see:
>
>http://www.utdallas.edu/~klaus/Airplane/airplane.html
>
>and follow the link to the wing root fairing. Klaus used a manometer to
>look at the pressure at various points on his HDS and demonstrated that
>the curvature of the fuselage over the wing creates a low pressure region
>at the wing root aft of the widest part of the fuselage. Klaus built wing
>root fairings that reduced the effect of the low pressure zone and
>improved the performance and stall behavior of his aircraft. Is it
>possible that the inward flow at the aileron is caused by the low
>pressure region all the way in at the wing root? I plan to put fairings
>on my 601XL, but I'm hoping that someone will start selling them before I
>get to that point so that I don't have to make them myself.
>
>The turbulence around the wing locker is troubling. I am putting in the
>wing lockers, and I am planning to use flexible tape to cover the hinge.
>Soaring pilots commonly use tape to seal gaps, see, e.g.,
>
>http://www.wingsandwheels.com/page29.htm
>
>My goal was primarily to seal the rain out. However, there might be a
>fringe benefit of reducing boundary layer separation caused by the locker
>door hinge. The separation along the inboard side of the wing locker door
>could be caused by air leakage from the inside of the wing. The bottom of
>the wing is a high pressure area. I'm guessing that the inside of the
>wing is pressurized through any small opening on the bottom of the wing.
>There appears to be a gap along the inside edge of the locker door.
>Leakage through that gap could induce separation, and your video suggests
>that is a problem area on that wing. It would be interesting to know if
>taping that gap would affect the separation in that zone. If leakage is
>causing the problem, possible fixes might be to use more Dzus fasteners
>along the door edge, putting a thin gasket to improve the seal, or
>stiffening the door by gluing or riveting on longitudinal doubler strips
>to the inside of the door.
>
>Thanks again for posting the video. Nice work.
>
>Terry
>At 03:54 PM 8/29/2007 -0400, you wrote:
>>
>>
>>
>>I finally got around to doing a little video of some tuft testing on the
>>601 HDS I fly, filmed with a 0.3 wide angle lens on the camcorder.
>>
>>It is posted online at http://pcxstuff.blip.tv/file/356716/ and can also
>>be downloaded as a 13MB .wmv file. It's not a particularly clear video.
>>
>>It was an unprofessional test, a flight with no detailed plan, on a
>>dark, turbulent day, quickly done before the weather got any worse. But
>>I haven't seen anything better, so this will have to do until I get
>>around to trying again.
>>
>>In its nearly 2 minutes, the video basically shows slow flight,
>>throttled back, with a few approaches down to incipient stalls. Audio
>>was removed (including a lot of oil canning noise near the stall!), but
>>some indicated speeds called out by the pilot are shown in text on
>>screen. Speeds are typically low, eg 70 mph indicated before slowing
>>down, then down to 50 or 40 indicated (naturally likely inaccurate) for
>>the slow flight. The pitch angle against the horizon is an indication of
>>the speed.
>>
>>At about 37 and 49 seconds seconds there are clear stall recoveries,
>>after a lot of wing rock. I don't know if there was an actual stall
>>break or the pilot simply let the stick forward once the bucking was
>>getting enough.
>>
>>
>>
>>I haven't thought through it all yet myself, but a few observations are
>>possible:
>>
>>-- One can clearly see the region of separated airflow spread outboard
>>and forward as the wing gets closer to a stall.
>>
>>-- Even when in slow flight not right at a stall, a large area near the
>>wing root doesn't have straight fore to aft flow. I'm not current on my
>>aerodynamics, but a waving yarn might only indicate an area of a
>>turbulence within a thick boundary lager, and not fully separated flow.
>>One can't see the actual wing/fuselage junction, but even outboard of
>>that, the flow isn't all front to back.
>>
>>-- It doesn't take much to mess up airflow right down on the wing
>>surface, if closer to the leading edge.
>>There's a yarn just behind of the aft, inboard Dzus fastener on the wing
>>locker. Even when the plane dives with speed when recovering from a
>>stall, that yarn doesn't like to stay straight. On the other hand, the
>>yarn behind the top of the main wheel strut, also behind an obstacle,
>>does stay straight. A quick guess is that the slight upwards bulge of
>>the wing locker near the front of the locker is what's actually causing
>>a flow problem, not the Dzus fastener. The slight bulge is far enough
>>forward on the airfoil that the shape becomes critical, unlike for the
>>gear strut which is further back. The yarn that is forward of the
>>"behind the Dzus" one, is right on the locker, and it shows a tendency
>>to lift off the surface rather than stay flat on the wing.
>>
>>-- There is substantial inwards flow near the trailing edge of the wing.
>>Some is expected near the tip as the tip vortex rotates up and inwards.
>>But at low speed there's some inwards flow component along the aileron
>>pretty much all the way inboard. Some inwards flow can be expected from
>>a sharply forward swept trailing edge wing, but the amount is much more
>>than I expected.
>>
>>-- Right when the plane is about to stall, it is impressive how many of
>>those little yarns are trying to go the wrong way, to jump the
>>aerodynamically sinking ship!
>>
>>
>>
>>Peter Chapman
>Toronto, ON
|
At 11:26 AM 3/22/2009 -0500, Klaus wrote:
| Quote: |
Hi,
Over the years I have wondered how much the air leakage
from the wing lockers onto the top of the wing impacts
performance. Particularly for the 601HDS that I have,
with its small wing area, the leakage might have a
significant effect.
This weekend I conducted a test to find out,
using 1/8 in. thick 1/4 wide adhesive foam strips
on the locker doors.
The foam is a bit like memory foam, in that it gives way
and collapses to the right size, without exerting much
pressure once it has the correct size.
A first inkling that things had changed came
immediately after takeoff. Even with reduced
power, the plane kept climbing at a
comparatively high rate. In level flight,
the cruise speed seemed quite a bit higher.
Measuring with GPS into and against the prevailing
winds using a total of four runs,
the plane cruised with 4,800 rpm (Rotax 912,
80 hp) at exactly at 100 kts,
which is 2-3 kts higher than before.
Load was pilot only, fuel tanks 75% filled.
Temperature 70 deg F, altitude 2,500 ft,
fuel consumption 4 gph.
Never ever before, regardless of load, temperature, or
altitude, had I seen that cruise speed at 4,800 rpm.
Conclusion: The air leakage of the wing locker doors
apparently has a significant impact on the lift characteristics
of the 601HDS wing. The effect should be even more
pronounced on 601HDS planes with heavier engines like
Subaru or Corvair, since they require higher angles
of attack. I suspect there is a similar
but somewhat reduced effect for
the 601HD and 601XL due to the larger wing area.
At least testing the effect of seals for those models
seems like a good idea.
Happy flying,
Klaus
|
Terry Phillips ZBAGer
ttp44~at~rkymtn.net
Corvallis MT
601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail, flaps, & ailerons
are done; waiting on the wings
http://www.mykitlog.com/N47TP/
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_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings. |
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larry(at)macsmachine.com
Guest
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| Posted: Sun Mar 22, 2009 10:49 am Post subject: Seals for wing lockers of 601HDS |
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Hi Guys,
The best approach to keeping leakage to a minimum would first be rigid
angle reinforcement
for the inside edges of the baggage door. The second thing, a well
installed set of Dzus fasteners that
grip the position of the lid at more places than the plans show. In the
link below notice the reinforcement
all round the door and then diagonals that cover the area. This is a
very effective tight fit.
http://www.macsmachine.com/images/wing/baggagearea/full/baggage-door-rear.gif
http://www.macsmachine.com/images/wing/baggagearea/full/luggageopenrear.gif
Larry McFarland 601HDS at www.macsmachine.com
Roger & Lina Hill wrote:
| Quote: |
Klaus;
Very impressive test, and something I had never even heard about, wing
locker leakage affecting performance. Any ideas how those of us with a
flying 601HDS could eliminate the air leak, but still be able to open the
wing lockers normally?
Roger Hill
|
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ashleyw(at)gvtc.com
Guest
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| Posted: Sun Mar 22, 2009 12:36 pm Post subject: Seals for wing lockers of 601HDS |
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Klaus,
Yesterday I made this video with my 601XL.
http://www.gvtc.com/~ashleyw/index.htm
Notice the strings are straight even around and across the rear of the wing
lockers.
At apporx the 35 seconds time on the video, seperation is begining at the
inboard wing root while indicating approx 35KIAS.
Floyd Wilkes
601XL
---
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klaus(at)utdallas.edu
Guest
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| Posted: Mon Mar 23, 2009 10:34 am Post subject: Seals for wing lockers of 601HDS |
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Hi,
There have been a number of issues raised by my earlier email.
I try to address them below.
*1. If this kind of improvement, have you sealed the metal strip covering the
wing to center section with some kind of sealant? If so, what did you use?
Jerry of Ga.
I did not seal that portion, but this may be another area of improvement.
It would depend on how tightly the strip is installed. In my plane,
there is little gap, even under high angles of attack. But clearly something
to look into.
2. *
*Could you be a bit more specific about that foam tape you used ?? I can think of
several applications for a tape like that.
Jay Bannister
**The tape is from Home Depot, under weather stripping. The foam material
is white, not black. The latter type cannot be much compressed, but the white
foam material can be compressed almost flat to paper thickness.
3. *
**Very impressive test, and something I had never even heard about, wing
locker leakage affecting performance. Any ideas how those of us with a
flying 601HDS could eliminate the air leak, but still be able to open the
wing lockers normally?
The doors can still be opened just as before. Where the doors touch
the wing, the strip is installed. It attaches only to the door, not the wing.
4. **
**This is a very interesting subject. Back in 2007, Peter Chapman posted a
video showing tuft tests on his HDS providing graphic evidence of
significant lift destroying leaks at the wing locker cover joints. I
believe the video link is still active. Your results nicely confirm the
impressions left by the video. I'm pasting in my response to Peter just below:
Terry
****I have not seen the video.
5. **
**The best approach to keeping leakage to a minimum would first be rigid
angle reinforcement
for the inside edges of the baggage door. The second thing, a well
installed set of Dzus fasteners that
grip the position of the lid at more places than the plans show. In the
link below notice the reinforcement
all round the door and then diagonals that cover the area. This is a
very effective tight fit.
http://www.macsmachine.com/images/wing/baggagearea/full/baggage-door-rear.gif
http://www.macsmachine.com/images/wing/baggagearea/full/luggageopenrear.gif
Larry McFarland 601HDS at www.macsmachine.com
Agree with all of the above. We used the material supplied with the kit,
added Ls to reinforce, bent the edges down a bit, but still had leakage.
For folks in that situation, the seal may be a fast way to solve the
problem.
6. **
**Yesterday I made this video with my 601XL.
http://www.gvtc.com/~ashleyw/index.htm <http://www.gvtc.com/%7Eashleyw/index.htm>
Notice the strings are straight even around and across the rear of the wing
lockers.
At apporx the 35 seconds time on the video, seperation is begining at the
inboard wing root while indicating approx 35KIAS.***
***Floyd Wilkes
601XL
Nice video! Clearly, there is little problem in your case. You must have
a tight seal already, and at any rate, the XL is less susceptible to the
problem than the HDS, which has much lower pressure above the wing.
Happy flying,
Klaus
**
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