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TELEDYNMCS(at)aol.com
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 Posted: Wed May 09, 2007 4:09 am Post subject: seals |
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In a message dated 5/9/2007 2:59:30 AM Eastern Daylight Time, europa-list(at)matronics.com writes:
| Quote: | My understanding is that preventing the air going over the flap, in
cruise, reduces drag, resulting in higher cruise speed, which I have
experienced. I don't have the engineering background to completely
understand what is happening to the wing, in flight. That's why I
depend on the guys on the list to keep me straight. I'm more of a "try
it and see" kinda guy...  John's advice is based on the success that
the glider guys have had, sealing the gaps. It seems to have worked on
Baby Blue, as well. Continued testing will tell to what degree of
advantage the seals make. It may very well prove that the extra few
knots is not worth the float upon landing. I won't know until I satisfy
myself that I've explored all the angles (and strip widths)...  |
Hey Jeff, et al,
The concept behind seals is pretty simple. In flight the wing creates a low pressure area on the top and high pressure on the bottom. (Bernoulli at it again) This pressure differential will try to equalize through the gap in the flap area and the hinge line of the ailerons. This is also true to some extent on the rudder hinge line and the trim tabs when they are deflected. This equalization causes drag, a lot of drag. So, the idea behind seals, both flap gap and positive seals on ailerons (and rudder and trim tabs), is to prevent this pressure equalization.
On N245E I used PVC weather-strip to create the flap gap seal. The size will depend on how big your gap is between the leading edge of the flap and the flap closeout when retracted. Choose a foam that is slightly thicker than the widest spot in the gap you have. The XS flap closeout looks as if it were designed to be sealed, given the flat area at the bottom rear of the closeout. If you apply the foam strip to the area where the flap "noses" into the closeout when up it will seal this area for cruise flight, but still allow air to flow over the flap when extended. Use a foam that crushes easily when the flap comes in contact with it. You don't want to use a foam that is too stiff or too thick or else your flaps won't fully retract. PVC weather-strip is soft and pliable and works quite well. It is also fairly UV resistant and is very cheap. It's available at any hardware store in various thicknesses. We've found that open cell foams tend to not last very long due to UV and they don't seal as well as closed cell foams like PVC. I also used weather-strip on the ends of my flaps so that they seal against the side of the fuselage when they are in the up position. According to Bruce Carmichael, renowned Aerodynamicist who wrote a book on drag reduction in homebuilts, the wing root/fuselage junction is another area of high drag on most airplanes. Sealing it up helps, too.
Aileron seals are a bit more tricky to employ. Some folks apply Mylar strips over the hinge lines and think they've sealed their ailerons. This is not true. Mylar is not a seal, but rather is applied to help the boundary flow stay attached over the hinge line. Mylar is also somewhat cosmetic in that it hides the hinge line. At high speeds the Mylar will lift up off the wing due to the pressure equalization, thus negating the effects of any sealing the Mylar might be offering. In some cases the Mylar will "buzz" at high speeds.
For sealing ailerons you need to install what are known as positive seals. These seals go from the leading edge of the aileron to the rear of the closeout. There are commercially available materials for this, including various types of cloth and Teflon tapes. Some folks even use cloth tape along the length of the aileron on the undersurface. This is fine on low speed gliders, but I think at the speeds we fly this method likely creates more drag. Personally, I like parachute cloth for making positive seals. Whatever you use it needs to be zero porosity, i.e., allowing no airflow through the material. Parachute cloth is thin, flexible, zero porosity and fits the bill here perfectly. Here at the 'Possum Werks we use Parachute cloth almost exclusively to fabricate positive seals. (it also helps that we have a parachute manufacturer a few miles down the road that gives us their scraps)
First remove the aileron. Then, cut a strip of parachute cloth about 3" wide exactly the length of the aileron. The width you use might take some trial and error to get it right. You don't want it so wide the the material bunches up when the aileron is deflected. 2.5' to 3" width should work on most Europas. Then, yellow contact cement is applied to the leading edge of the aileron, the rear of the closeout and the mating surfaces of the cloth. We use a brand of glue called Plio-bond. It's handy in that it comes in a small bottle with a brush applicator. 3M also makes good contact cement if you can find it. Avoid the water based stuff. It is crap.
Scuff the area to be glued with 180 to enhance the adhesion. Apply the glue in a swath about 3/8" wide to both the seal, the aileron and closeout. Use masking tape to keep your glue line to the prescribed width and remove the tape once the glue is dry. You can also use the masking tape to provide a guide when you scuff the area to be glued, but wipe it with acetone to remove dust before putting the glue on. Allow the glue to dry, usually about 20 minutes, remove the masking tape, then stick the seal to the leading edge of the aileron first, preferably while on your work bench. If you screw something up Xylene will remove the glue easily without harming your paint. The next part takes an extra set of hands.
With one person holding the aileron close to the wing, attach the other half of the cloth to the closeout forming an "S" pattern. Avoid wrinkles. See this drawing for details: http://wingsandwheels.com/page28.htm
Then, reattach the aileron as you would normally do. Check the throw and make sure you are not binding! If you apply the seal correctly you will not even know it is there. I have also sealed my rudder in a similar fashion as well as the trim tabs. They create similar drag when deflected.
I can't say specifically what improvements have occurred in N245E as a result of the seals since I've not ever flown it without them. I can tell you that I exceed Europas published numbers with a fixed pitch prop. I can also tell you that on gliders we generally see 2 to 4 points increase in glide and a noticeable decrease in sink rate, even on the old "woodies", after the application of seals. In power planes this translates to faster cruise, better climb rates and better fuel economy.
Anyway, hope it helps!
Regards,
John Lawton
Dunlap, TN (TN89)
N245E - Flying
See what's free at AOL.com.
[quote][b]
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fklein(at)orcasonline.com
Guest
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| Posted: Wed May 09, 2007 7:44 am Post subject: seals |
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John,
Thanks for the comprehensive "treatise" (and I use the word with utmost
respect) on this fascinating subject.
Fred
do not archive
On Wednesday, May 9, 2007, at 05:08 AM, TELEDYNMCS(at)aol.com wrote:
| Quote: | In a message dated 5/9/2007 2:59:30 AM Eastern Daylight Time,
europa-list(at)matronics.com writes:
My understanding is that preventing the air going over the flap, in
cruise, reduces drag, resulting in higher cruise speed, which I have
experienced. I don't have the engineering background to completely
understand what is happening to the wing, in flight. That's why I
depend on the guys on the list to keep me straight. I'm more of a "try
it and see" kinda guy... John's advice is based on the success that
the glider guys have had, sealing the gaps. It seems to have worked on
Baby Blue, as well. Continued testing will tell to what degree of
advantage the seals make. It may very well prove that the extra few
knots is not worth the float upon landing. I won't know until I
satisfy
myself that I've explored all the angles (and strip widths)...
Hey Jeff, et al,
The concept behind seals is pretty simple. In flight the wing creates
a low pressure area on the top and high pressure on the
bottom. (Bernoulli at it again) This pressure differential will try to
equalize through the gap in the flap area and the hinge line of the
ailerons. This is also true to some extent on the rudder hinge line
and the trim tabs when they are deflected. This equalization causes
drag, a lot of drag. So, the idea behind seals, both flap gap and
positive seals on ailerons (and rudder and trim tabs), is to prevent
this pressure equalization.
On N245E I used PVC weather-strip to create the flap gap seal. The
size will depend on how big your gap is between the leading edge of
the flap and the flap closeout when retracted. Choose a foam that is
slightly thicker than the widest spot in the gap you have. The XS flap
closeout looks as if it were designed to be sealed, given the flat
area at the bottom rear of the closeout. If you apply the foam strip
to the area where the flap "noses" into the closeout when up it will
seal this area for cruise flight, but still allow air to flow over the
flap when extended. Use a foam that crushes easily when the flap comes
in contact with it. You don't want to use a foam that is too stiff or
too thick or else your flaps won't fully retract. PVC weather-strip
is soft and pliable and works quite well. It is also fairly UV
resistant and is very cheap. It's available at any hardware store in
various thicknesses. We've found that open cell foams tend to not last
very long due to UV and they don't seal as well as closed cell foams
like PVC. I also used weather-strip on the ends of my flaps so that
they seal against the side of the fuselage when they are in the up
position. According to Bruce Carmichael, renowned Aerodynamicist who
wrote a book on drag reduction in homebuilts, the wing root/fuselage
junction is another area of high drag on most airplanes. Sealing it up
helps, too.
Aileron seals are a bit more tricky to employ. Some folks apply Mylar
strips over the hinge lines and think they've sealed their ailerons.
This is not true. Mylar is not a seal, but rather is applied to help
the boundary flow stay attached over the hinge line. Mylar is also
somewhat cosmetic in that it hides the hinge line. At high speeds the
Mylar will lift up off the wing due to the pressure equalization, thus
negating the effects of any sealing the Mylar might be offering. In
some cases the Mylar will "buzz" at high speeds.
For sealing ailerons you need to install what are known as positive
seals. These seals go from the leading edge of the aileron to the rear
of the closeout. There are commercially available materials for this,
including various types of cloth and Teflon tapes. Some folks even
use cloth tape along the length of the aileron on the undersurface.
This is fine on low speed gliders, but I think at the speeds we fly
this method likely creates more drag. Personally, I like parachute
cloth for making positive seals. Whatever you use it needs to be zero
porosity, i.e., allowing no airflow through the material. Parachute
cloth is thin, flexible, zero porosity and fits the bill here
perfectly. Here at the 'Possum Werks we use Parachute cloth almost
exclusively to fabricate positive seals. (it also helps that we have a
parachute manufacturer a few miles down the road that gives us their
scraps)
First remove the aileron. Then, cut a strip of parachute cloth about
3" wide exactly the length of the aileron. The width you use might
take some trial and error to get it right. You don't want it so wide
the the material bunches up when the aileron is deflected. 2.5' to
3" width should work on most Europas. Then, yellow contact cement is
applied to the leading edge of the aileron, the rear of the closeout
and the mating surfaces of the cloth. We use a brand of glue called
Plio-bond. It's handy in that it comes in a small bottle with a brush
applicator. 3M also makes good contact cement if you can find it.
Avoid the water based stuff. It is crap.
Scuff the area to be glued with 180 to enhance the adhesion. Apply the
glue in a swath about 3/8" wide to both the seal, the aileron and
closeout. Use masking tape to keep your glue line to the prescribed
width and remove the tape once the glue is dry. You can also use the
masking tape to provide a guide when you scuff the area to be glued,
but wipe it with acetone to remove dust before putting the glue
on. Allow the glue to dry, usually about 20 minutes, remove the
masking tape, then stick the seal to the leading edge of the aileron
first, preferably while on your work bench. If you screw something up
Xylene will remove the glue easily without harming your paint. The
next part takes an extra set of hands.
With one person holding the aileron close to the wing, attach the
other half of the cloth to the closeout forming an "S" pattern. Avoid
wrinkles. See this drawing for details:
http://wingsandwheels.com/page28.htm
Then, reattach the aileron as you would normally do. Check the throw
and make sure you are not binding! If you apply the seal correctly you
will not even know it is there. I have also sealed my rudder in a
similar fashion as well as the trim tabs. They create similar drag
when deflected.
I can't say specifically what improvements have occurred in N245E as a
result of the seals since I've not ever flown it without them. I can
tell you that I exceed Europas published numbers with a fixed pitch
prop. I can also tell you that on gliders we generally see 2 to 4
points increase in glide and a noticeable decrease in sink rate, even
on the old "woodies", after the application of seals. In power planes
this translates to faster cruise, better climb rates and better fuel
economy.
Anyway, hope it helps!
Regards,
John Lawton
Dunlap, TN (TN89)
N245E - Flying
<image.tiff>
|
| Quote: |
See what's free at AOL.com.
|
| | - The Matronics Europa-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?Europa-List |
|
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| Back to top |
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Dave Miller
Joined: 10 Jan 2006
Posts: 51
|
| Posted: Wed May 09, 2007 9:36 am Post subject: seals |
|
|
Yes, good stuff.
I've got Mylar strips on the top of my ailerons, no sign of lifting or buzzing.
Also per the local glider guy, I used white "duct" cloth tape on the underside hinge line, I really don't think it causes any drag that far back on the wing.
No idea if this makes any difference to speed, but it does make the aileron response crisper.
Dave A061
Fred Klein <fklein(at)orcasonline.com>
Sent by: owner-europa-list-server(at)matronics.com
05/09/2007 11:43 AM
Please respond to europa-list
To: europa-list(at)matronics.com
cc:
Subject: Re: Re: seals
John,
Thanks for the comprehensive "treatise" (and I use the word with utmost
respect) on this fascinating subject.
Fred
do not archive
On Wednesday, May 9, 2007, at 05:08 AM, TELEDYNMCS(at)aol.com wrote:
> In a message dated 5/9/2007 2:59:30 AM Eastern Daylight Time,
> europa-list(at)matronics.com writes:
>
> My understanding is that preventing the air going over the flap, in
> cruise, reduces drag, resulting in higher cruise speed, which I have
> experienced. I don't have the engineering background to completely
> understand what is happening to the wing, in flight. That's why I
> depend on the guys on the list to keep me straight. I'm more of a "try
> it and see" kinda guy... John's advice is based on the success that
> the glider guys have had, sealing the gaps. It seems to have worked on
> Baby Blue, as well. Continued testing will tell to what degree of
> advantage the seals make. It may very well prove that the extra few
> knots is not worth the float upon landing. I won't know until I
> satisfy
> myself that I've explored all the angles (and strip widths)...
>
>
> Hey Jeff, et al,
>
> The concept behind seals is pretty simple. In flight the wing creates
> a low pressure area on the top and high pressure on the
> bottom. (Bernoulli at it again) This pressure differential will try to
> equalize through the gap in the flap area and the hinge line of the
> ailerons. This is also true to some extent on the rudder hinge line
> and the trim tabs when they are deflected. This equalization causes
> drag, a lot of drag. So, the idea behind seals, both flap gap and
> positive seals on ailerons (and rudder and trim tabs), is to prevent
> this pressure equalization.
>
> On N245E I used PVC weather-strip to create the flap gap seal. The
> size will depend on how big your gap is between the leading edge of
> the flap and the flap closeout when retracted. Choose a foam that is
> slightly thicker than the widest spot in the gap you have. The XS flap
> closeout looks as if it were designed to be sealed, given the flat
> area at the bottom rear of the closeout. If you apply the foam strip
> to the area where the flap "noses" into the closeout when up it will
> seal this area for cruise flight, but still allow air to flow over the
> flap when extended. Use a foam that crushes easily when the flap comes
> in contact with it. You don't want to use a foam that is too stiff or
> too thick or else your flaps won't fully retract. PVC weather-strip
> is soft and pliable and works quite well. It is also fairly UV
> resistant and is very cheap. It's available at any hardware store in
> various thicknesses. We've found that open cell foams tend to not last
> very long due to UV and they don't seal as well as closed cell foams
> like PVC. I also used weather-strip on the ends of my flaps so that
> they seal against the side of the fuselage when they are in the up
> position. According to Bruce Carmichael, renowned Aerodynamicist who
> wrote a book on drag reduction in homebuilts, the wing root/fuselage
> junction is another area of high drag on most airplanes. Sealing it up
> helps, too.
>
> Aileron seals are a bit more tricky to employ. Some folks apply Mylar
> strips over the hinge lines and think they've sealed their ailerons.
> This is not true. Mylar is not a seal, but rather is applied to help
> the boundary flow stay attached over the hinge line. Mylar is also
> somewhat cosmetic in that it hides the hinge line. At high speeds the
> Mylar will lift up off the wing due to the pressure equalization, thus
> negating the effects of any sealing the Mylar might be offering. In
> some cases the Mylar will "buzz" at high speeds.
>
> For sealing ailerons you need to install what are known as positive
> seals. These seals go from the leading edge of the aileron to the rear
> of the closeout. There are commercially available materials for this,
> including various types of cloth and Teflon tapes. Some folks even
> use cloth tape along the length of the aileron on the undersurface.
> This is fine on low speed gliders, but I think at the speeds we fly
| Quote: | this method likely creates more drag. Personally, I like parachute
> cloth for making positive seals. Whatever you use it needs to be zero
|
> porosity, i.e., allowing no airflow through the material. Parachute
> cloth is thin, flexible, zero porosity and fits the bill here
> perfectly. Here at the 'Possum Werks we use Parachute cloth almost
> exclusively to fabricate positive seals. (it also helps that we have a
> parachute manufacturer a few miles down the road that gives us their
> scraps)
>
> First remove the aileron. Then, cut a strip of parachute cloth about
> 3" wide exactly the length of the aileron. The width you use might
> take some trial and error to get it right. You don't want it so wide
> the the material bunches up when the aileron is deflected. 2.5' to
> 3" width should work on most Europas. Then, yellow contact cement is
> applied to the leading edge of the aileron, the rear of the closeout
> and the mating surfaces of the cloth. We use a brand of glue called
> Plio-bond. It's handy in that it comes in a small bottle with a brush
> applicator. 3M also makes good contact cement if you can find it.
> Avoid the water based stuff. It is crap.
>
> Scuff the area to be glued with 180 to enhance the adhesion. Apply the
> glue in a swath about 3/8" wide to both the seal, the aileron and
> closeout. Use masking tape to keep your glue line to the prescribed
> width and remove the tape once the glue is dry. You can also use the
> masking tape to provide a guide when you scuff the area to be glued,
> but wipe it with acetone to remove dust before putting the glue
> on. Allow the glue to dry, usually about 20 minutes, remove the
> masking tape, then stick the seal to the leading edge of the aileron
> first, preferably while on your work bench. If you screw something up
> Xylene will remove the glue easily without harming your paint. The
> next part takes an extra set of hands.
>
> With one person holding the aileron close to the wing, attach the
> other half of the cloth to the closeout forming an "S" pattern. Avoid
> wrinkles. See this drawing for details:
> http://wingsandwheels.com/page28.htm
>
> Then, reattach the aileron as you would normally do. Check the throw
> and make sure you are not binding! If you apply the seal correctly you
> will not even know it is there. I have also sealed my rudder in a
> similar fashion as well as the trim tabs. They create similar drag
> when deflected.
>
> I can't say specifically what improvements have occurred in N245E as a
> result of the seals since I've not ever flown it without them. I can
> tell you that I exceed Europas published numbers with a fixed pitch
> prop. I can also tell you that on gliders we generally see 2 to 4
> points increase in glide and a noticeable decrease in sink rate, even
> on the old "woodies", after the application of seals. In power planes
> this translates to faster cruise, better climb rates and better fuel
> economy.
>
> Anyway, hope it helps!
>
> Regards,
>
> John Lawton
> Dunlap, TN (TN89)
> N245E - Flying
>
>
>
<image.tiff>
>
> See what's free at AOL.com.
>
>
>
>
[quote][b]
| | - The Matronics Europa-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?Europa-List |
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