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Mylar seals and stall speed?

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frans(at)privatepilots.nl
Guest

Posted: Mon Jul 30, 2012 3:38 am Post subject: Mylar seals and stall speed?

Recently I have put mylar seals on all the controls. I thought that if

it is good on gliders it would also be good on my Europa, and it also

enhances the look of my Europa, concealing the gaps and hinges (and

hiding some imperfections at the same time).



I vould not really find an increase in performance, or maybe it was too

small to measure in the rather unstable turbulent summer conditions.



Thinking back about my recent trip to the Alps, I suddenly recognized

that all my landings had an excessive flare. All of them. I also

remembered that on take off the airplane started flying while my Talking

Airspeed Indicator was still reporting speeds in the 30's.



Obviously I need to investigate my stall speeds, but I didn't think

about it during my last trip, not having realised that the mylar seals

could affect the stall speed of the airplane in some way. I just

contributed extended flares to sudden winds or thermals. Only when I was

back home I recognized the pattern.



Important here is that I also applied the mylar seals on the top of the

gap between the flaps and the wing. The idea here was to smoothen the

transition between the flaps and the wing and to prevent air from

seeping through when the flaps are retracted. When the flaps are

deployed the seals are just extending the wing 1.5cm (about 1/2 inch)

and I didn't think that this could affect the effectivety of the flaps

in some way.



So, my question is: Is it possible al all that mylar seals over the flap

gap are able to significantly reduce the stall speed? Or should I look

for some other reason?



I can make a picture to show how it looks like.



Frans

pete(at)lawless.info
Guest

Posted: Mon Jul 30, 2012 6:00 am Post subject: Mylar seals and stall speed?

Hi Frans



I have had the Mylar gap seals since new in 2003.  Mine were fitted to the

flap gap, as well as the ailerons and rudder, but my inspector was not happy

and checked with the PFA/LAA.  They were not happy either about possible

effects on the stall speed and the seals were removed from the flap gap

before the first flight.



Regards



Pete

G-RMAC



--

Fred Klein

Joined: 26 Mar 2012
Posts: 503

Posted: Mon Jul 30, 2012 6:07 am Post subject: Mylar seals and stall speed?

On Jul 30, 2012, at 5:30 AM, Frans Veldman wrote:

 	  Quote: 	
		  Recently I have put mylar seals on all the controls. I thought that if

it is good on gliders it would also be good on my Europa, and it also

enhances the look of my Europa, concealing the gaps and hinges (and

hiding some imperfections at the same time). 	




	Frans,

	I have forwarded your post to John Lawton who no longer monitors europa-list but has direct Europa and motorglider experience w/ seals.

	Fred



 [quote][b]

frans(at)privatepilots.nl
Guest

Posted: Mon Jul 30, 2012 6:36 am Post subject: Mylar seals and stall speed?

Hi Pete,



 	  Quote: 	
		   I have had the Mylar gap seals since new in 2003.  Mine were fitted to the

 flap gap, as well as the ailerons and rudder, but my inspector was not happy

 and checked with the PFA/LAA.  They were not happy either about possible

 effects on the stall speed and the seals were removed from the flap gap

 before the first flight.


	


I can imagine someone fearing that the stall speed increases... but here

the stall speed decreases. Is that a bad thing, to lower the stall speed?



Isn't that the holy grail of wing design, to lower the stall speed

without hurting the cruise and top end performance?



I can imagine that with heavy cross wind the airplane keeps flaring

beyond the point where the rudder can keep the plane straight. This

might be more of a problem for the mono than for the tri-gear. For the

tri gear one can opt to land with the flaps up or partially deployed if

a higher stall speed is desired.



At the next occasion I will do some checks to see if indeed the stall

speed has been affected by these seals. I didn't know that a STOL-kit

was so easy to make for an Europa. 



Oh, and I just assumed that with seals on the flap gap you mean seals on

the upperside of the wing. Not on the huge gap on the lowerside of the

wing, right? In the latter case, I can see how that could increase the

stall speed as you effectively change the fowler flaps into non-fowler

flaps. I didn't apply seals on the lowerside of the wing for exactly

this reason.



Do you still have the seals on the rudder? I only did the starboard

side, because at the port side the gap opens up quite a bit with full

right rudder, and the seals might be sucked inside the gap and block the

rudder. I would like to hear if someone indeed tried seals on the port

side of the rudder. I have quite a nasty transition there as the rudder

is less wide than the rear of the fuselage. I would love to smooth out

this transition but I'm not going to be the one who finds out whether

this is a good idea or not. 



Frans

pete(at)lawless.info
Guest

Posted: Mon Jul 30, 2012 9:43 am Post subject: Mylar seals and stall speed?

Evening Frans



My seals are all on the top surface and the hinge line of the rudder.  I

agree with you about the effect on the stall speed but was not prepared to

argue the case - at the time I just wanted to get the aeroplane flying. They

did not actually say no just that we would have to do a lot of flight

testing.



I will be most interested to hear the results of your stall speed tests. I

would have expected hot and high to have had an opposite effect on

performance.



My rudder is also a poor fit at the bottom, the fuselage is too wide, how

ever it is probably in turbulent air off the prop. 



Regards



Pete



--

Fred Klein

Joined: 26 Mar 2012
Posts: 503

Posted: Mon Jul 30, 2012 10:03 am Post subject: Mylar seals and stall speed?

On Jul 30, 2012, at 8:29 AM, Frans Veldman wrote:

 	  Quote: 	
		  Oh, and I just assumed that with seals on the flap gap you mean seals on

the upperside of the wing. Not on the huge gap on the lowerside of the

wing, right? In the latter case, I can see how that could increase the

stall speed as you effectively change the fowler flaps into non-fowler

flaps. I didn't apply seals on the lowerside of the wing for exactly

this reason.

	




Frans,

If memory serves, I believe the kind of seals you describe are appropriate for the ailerons, and not necessarily for flaps. I seem to recall reading that flap seals function best when...at some point along the gap between the wing and flap...there is a linear compressible rod which runs the length of the flap...it is designed to maintain the pressure differential between the air along the top of the flat and that along the bottom of the flap when the flap is retracted. The flap seal is not intended to "smooth" the airflow across the top of the flap when the flap is either deployed or retracted. 

But I'm not the expert, and I hope John Lawton will comment further,

Fred



 [quote][b]

frans(at)privatepilots.nl
Guest

Posted: Mon Jul 30, 2012 10:20 am Post subject: Mylar seals and stall speed?

Hi Pete,



 	  Quote: 	
		   My seals are all on the top surface and the hinge line of the rudder.


	


Ah, I also did the underside of the ailerons and the underside of the

tailplanes.



 	  Quote: 	
		   I will be most interested to hear the results of your stall speed tests. I

 would have expected hot and high to have had an opposite effect on

 performance.


	


What do you mean? You expected the performance to get worse by using

seals? Or the other way around?



 	  Quote: 	
		   My rudder is also a poor fit at the bottom, the fuselage is too wide, how

 ever it is probably in turbulent air off the prop. 


	


Well, after I applied seals on the hinge line of the rudder, I noticed

that I need more right rudder than before. I have a small trim tab to

get a neutral rudder during cruise, but I had to bend the trim tab quite

a bit more to the left after I applied the seals. So at least the seal

is doing something, be it good or bad.



More right rudder needed is actually the opposite effect of what I

expected. Can't explain why this is or what the implication is.



The rudder is anyway a mystery to me. I have a vent opening in the

D-panel and connected a scat hose to it to a similar opening to the

rudder closeout. The idea here is that the rudder closeout is a low

pressure area, due to the shape and also due to the gaps, and helps the

air vacate the cabin to improve ventilation. Oddly enough though, the

D-panel opening not sucks the air out of the cabin but actually blows a

lot of air *into* the cabin! My doors don't leak, I have no other

openings in the cabin. I have no idea where that air coming in from the

rudder is going and why the rudder closeout is a higher pressure area

than the cabin. Really weird. If anyone has an idea I would love to hear.



Regards,

Frans

grahamsingleton(at)btinte
Guest

Posted: Mon Jul 30, 2012 10:32 am Post subject: Mylar seals and stall speed?

Frans

agree it's surprising that there is higher pressure in the rudder closeout. It is probably due to the reduction in pressure

as the airflow accelerates to pass the wide fuselage, then slows down as it rejoins the ambient air. That implies

good pressure recovery on the rear fuselage so less drag!

Graham

         From: Frans Veldman <frans(at)privatepilots.nl>

 To: europa-list(at)matronics.com 

 Sent: Monday, 30 July 2012, 20:13

 Subject: Re: Mylar seals and stall speed?

  

 

--> Europa-List message posted by: Frans Veldman <frans(at)privatepilots.nl (frans(at)privatepilots.nl)>



Hi Pete,



 	  Quote: 	
		   My seals are all on the top surface and the hinge line of the rudder.


	


Ah, I also did the underside of the ailerons and the underside of  the

tailplanes.



 	  Quote: 	
		   I will be most interested to hear the results of your stall speed tests. I

 would have expected hot and high to have had an opposite effect on

 performance.


	


What do you mean? You expected the performance to get worse by using

seals? Or the other way around?



 	  Quote: 	
		   My rudder is also a poor fit at the bottom, the fuselage is too wide, how

 ever it is probably in turbulent air off the prop. 


	


Well, after I applied seals on the hinge line of the rudder, I noticed

that I need more right rudder than before. I have a small trim tab to

get a neutral rudder during cruise, but I had to bend the trim tab quite

a bit more to the left after I applied the seals. So at least the seal

is doing something, be it good or bad.



More right rudder needed is actually the opposite effect of what I

expected. Can't explain why this is or what the implication is.



The rudder is  anyway a mystery to me. I have a vent opening in the

D-panel and connected a scat hose to it to a similar opening to the

rudder closeout. The idea here is that the rudder closeout is a low

pressure area, due to the shape and also due to the gaps, and helps the

air vacate the cabin to improve ventilation. Oddly enough though, the

D-panel opening not sucks the air out of the cabin but actually blows a

lot of air *into* the cabin! My doors don't leak, I have no other

openings in the cabin. I have no idea where that air coming in from the

rudder is going and why the rudder closeout is a higher pressure area

than the cabin. Really weird. If anyone has an idea I would love to hear.



Regards,

Frans

http://www.matronics.com/Navigator?Europa-Li> http://foru             - List Contribution Web Site -<bbsp;                         -Matt Dralle, List =========

kheindl(at)msn.com
Guest

Posted: Mon Jul 30, 2012 10:46 am Post subject: Mylar seals and stall speed?

Hi Frans,



I am with you on this one. If there is one thing that always puzzles me, is when someone says that you can't do this, but doesn't give any reasoning as to why.

Karl



[quote] Date: Mon, 30 Jul 2012 17:29:07 +0200

 From: frans(at)privatepilots.nl

 To: europa-list(at)matronics.com

 Subject: Re: Mylar seals and stall speed?

 

 --> Europa-List message posted by: Frans Veldman <frans(at)privatepilots.nl>

 

 Hi Pete,

 

 > I have had the Mylar gap seals since new in 2003.  Mine were fitted to the

 > flap gap, as well as the ailerons and rudder, but my inspector was not happy

 > and checked with the PFA/LAA.  They were not happy either about possible

 > effects on the stall speed and the seals were removed from the flap gap

 > before the first flight.

 

 I can imagine someone fearing that the stall speed increases... but here

 the stall speed decreases. Is that a bad thing, to lower the stall speed?

 

 Isn't that the holy grail of wing design, to lower the stall speed

 without hurting the cruise and top end performance?

 

 I can imagine that with heavy cross wind the airplane keeps flaring

 beyond the point where the rudder can keep the plane straight. This

 might be more of a problem for the mono than for the tri-gear. For the

 tri gear one can opt to land with the flaps up or partially deployed if

 a higher stall speed is desired.

 

 At the next occasion I will do some checks to see if indeed the stall

 speed has been affected by these seals. I didn't know that a STOL-kit

 was so easy to make for an Europa. 

 

 Oh, and I just assumed that with seals on the flap gap you mean seals on

 the upperside of the wing. Not on the huge gap on the lowerside of the

 wing, right? In the latter case, I can see how that could increase the

 stall speed as you effectively change the fowler flaps into non-fowler

 flaps. I didn't apply seals on the lowerside of the wing for exactly

 this reason.

 

 Do you still have the seals on the rudder? I only did the starboard

 side, because at the port side the gap opens up quite a bit with full

 right rudder, and the seals might be sucked inside the gap and block the

 rudder. I would like to hear if someone indeed tried seals on the port

 side of the rudder. I have quite a nasty transition there as the rudder

 is less wide than the rear of the fuselage. I would love to smooth out

 this transition but I'm not going to be the one who finds out whether

 this is a good idea or not.

pete(at)lawless.info
Guest

Posted: Mon Jul 30, 2012 11:26 am Post subject: Mylar seals and stall speed?

Hi Frans



No I was thinking if your take off performance has improved when you were

hot and high (a bad combination for performance) that there may be a greater

improvement closer to sea level.



And yes I forgot mine also has strips on the top of the trim tabs.  Nothing

at all underneath.



Unfortunately I have never flown the aeroplane without the strips so I can't

make a judgement as to their effectiveness.  But I do get a 120 kt + cruise

at 14.4 litres per hour off an 80hp 912ul with an NSI vp prop.  Cruise revs

4,200.



Pete

--

frans(at)privatepilots.nl
Guest

Posted: Mon Jul 30, 2012 11:45 am Post subject: Mylar seals and stall speed?

On 07/30/2012 09:25 PM, Pete Lawless wrote:



 	  Quote: 	
		   And yes I forgot mine also has strips on the top of the trim tabs.  Nothing

 at all underneath.


	


Oh, I have the opposite. The hinge line (on top) matches perfectly with

the tail plane and trim tab so I decided to leave that alone. On the

underside thouph is quite a gap so I installed the seals there.



 	  Quote: 	
		   Unfortunately I have never flown the aeroplane without the strips so I can't

 make a judgement as to their effectiveness.  But I do get a 120 kt + cruise

 at 14.4 litres per hour off an 80hp 912ul with an NSI vp prop.  Cruise revs

 4,200.


	


I don't know the 912ul but this sounds pretty good to me! I can't get

120kt out of 14.4 liters with my 914.

Do you have a mono?



Frans

kheindl(at)msn.com
Guest

Posted: Mon Jul 30, 2012 12:58 pm Post subject: Mylar seals and stall speed?

Hi Frans,

Talking about fuel consumption again, I am surprised to learn that you can get 4 1/2 hour legs. You mentioned that in your optimum cruise at 125 kts the engine uses 18l/hour, and of course for takeoff and climbout the consumption is always a lot more. So that makes about 86 litres ? Are you using the long range tank ?

Karl

 	  Quote: 	
		   Date: Mon, 30 Jul 2012 22:38:15 +0200

 From: frans(at)privatepilots.nl

 To: europa-list(at)matronics.com

 Subject: Re: Mylar seals and stall speed?

 --> Europa-List message posted by: Frans Veldman <frans(at)privatepilots.nl>

 On 07/30/2012 09:25 PM, Pete Lawless wrote:

 > And yes I forgot mine also has strips on the top of the trim tabs.  Nothing

 > at all underneath.

 Oh, I have the opposite. The hinge line (on top) matches perfectly with

 the tail plane and trim tab so I decided to leave that alone. On the

 underside thouph is quite a gap so I installed the seals there.

 > Unfortunately I have never flown the aeroplane without the strips so I can't

 > make a judgement as to their effectiveness.  But I do get a 120 kt + cruise

 > at 14.4 litres per hour off an 80hp 912ul with an NSI vp prop.  Cruise revs

 > 4,200.

 I don't know the 912ul but this sounds pretty good to me! I can't get

 120kt out of 14.4 liters with my 914.

 Do you have a mono?

 Frans

&g=======================

&g=======

 	  Quote: 	

  [quote][b]

pete(at)lawless.info
Guest

Posted: Mon Jul 30, 2012 1:56 pm Post subject: Mylar seals and stall speed?

Hi Frans



Yes it's a mono.  No speed kit fitted.



Regards



Pete



--

frans(at)privatepilots.nl
Guest

Posted: Mon Jul 30, 2012 11:08 pm Post subject: Mylar seals and stall speed?

On 07/30/2012 10:57 PM, Karl Heindl wrote:

 	  Quote: 	
		   Hi Frans,

 

 Talking about fuel consumption again, I am surprised to learn that you

 can get 4 1/2 hour legs.


	


No, I didn't say that (sorry if I gave that impression). I made one

tankstop. 4 1/2 hour was the total flying time to get home. The point I

tright to make was that the engine behaved normally for the 4 1/2 hours

flown after the fuel pressure drop.



 	  Quote: 	
		   You mentioned that in your optimum cruise at

 125 kts the engine uses 18l/hour,


	


Well, actually slightly less than 18l/hour, and the 125 kts is the

indicated airspeed, so at FL85 on this trip I was looking at ground

speeds close to 140 kts. But still I need to make one stop, not only to

refuel the airplane, but also because my personal "range" is also about

3 hours. It feels good to get out of that cramped cockpit once in a

couple of hours. 



Frans

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