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Wing Contour?



 
 
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  #1  
Old July 31st 19, 05:00 AM posted to rec.aviation.soaring
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Default Wing Contour?

Can anyone tell me specifically how to tell how closely a wing is following its intended shape or to know if it has "issues"? Also, if I'm sanding, polishing or refinishing it, how do I accurately correct for any deficiencies? Asking for a friend... : )
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  #2  
Old July 31st 19, 12:05 PM posted to rec.aviation.soaring
AS
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Default Wing Contour?

On Wednesday, July 31, 2019 at 12:00:34 AM UTC-4, wrote:
Can anyone tell me specifically how to tell how closely a wing is following its intended shape or to know if it has "issues"? Also, if I'm sanding, polishing or refinishing it, how do I accurately correct for any deficiencies? Asking for a friend... : )


The best way I am aware of is to get top and bottom templates made for several stations from the root outwards to check the actual profile against the theoretical one. Not sure if any of the manufacturers offer that sort of help but if you know the airfoil designation, someone in the know can calculate the coordinates. It takes a good 'smoothing' or interpolation algorithm to get the wrinkles out of that curve. With access to a large CNC router one can then mill such template set from a thin AL-sheet.

Uli
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  #3  
Old July 31st 19, 11:19 PM posted to rec.aviation.soaring
SoaringXCellence
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Default Wing Contour?

All,

two stories:

One of my fellow pilots wanted to re-finish his LS-4. He loved the way is glider handled and other performance so he made templates from the existing wing surface and maintained it when refinishing.

Another friend and I both have Mini Nimbus or Mosquito wings, that ostensibly were created from the same molds. He took the time to plot and make templates for the supposed airfoil. When compared to either of our ship, the templates don't fit the wing and in a different way on each glider!

YMMV, and most likely will.

Mike B.
  #4  
Old July 31st 19, 11:34 PM posted to rec.aviation.soaring
Bob Kuykendall
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Default Wing Contour?

On Tuesday, July 30, 2019 at 9:00:34 PM UTC-7, wrote:
Can anyone tell me specifically how to tell how closely a wing is following its intended shape or to know if it has "issues"? Also, if I'm sanding, polishing or refinishing it, how do I accurately correct for any deficiencies? Asking for a friend... : )


It depends entirely on the nature of the wing. For aggressively laminar profiles like the old FX67, it can matter a lot. For others, it matters a lot less.

In my direct experience, freedom from waviness (Johnson reading below 0.004" per linear inch) is a lot more important than absolute fidelity to contour. Time spent trying to impose some sort of theoretically ideal contour with filling and sanding is a lot better spent just getting any big waves out and then concentrating on soaring strategy and tactics.

Case in point: Do a template check on any LS6 or LS8. I can probably loan you the templates for that, though I haven't seen them for a while. Anyhow, what you find is that the camber lines for the right and left wings are substantially different. The template for one wing fits the opposite wing like maybe they're from two different gliders. This applies to all of the six or eight ships I've checked, and all of them have been different in pretty much the same ways, so I'm pretty sure that's how they come out of the molds.. But these are not dogmeat gliders-- they go like stink, fly arrow straight if they're tuned properly, and have won regional and national contests. Who's to say whether the right or the left wing has the correct profile and the other not? They both seem to work pretty damn well.

--Bob K.
  #5  
Old August 1st 19, 12:30 AM posted to rec.aviation.soaring
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Default Wing Contour?

On Wednesday, July 31, 2019 at 6:34:52 PM UTC-4, Bob Kuykendall wrote:
On Tuesday, July 30, 2019 at 9:00:34 PM UTC-7, wrote:
Can anyone tell me specifically how to tell how closely a wing is following its intended shape or to know if it has "issues"? Also, if I'm sanding, polishing or refinishing it, how do I accurately correct for any deficiencies? Asking for a friend... : )


It depends entirely on the nature of the wing. For aggressively laminar profiles like the old FX67, it can matter a lot. For others, it matters a lot less.

In my direct experience, freedom from waviness (Johnson reading below 0.004" per linear inch) is a lot more important than absolute fidelity to contour. Time spent trying to impose some sort of theoretically ideal contour with filling and sanding is a lot better spent just getting any big waves out and then concentrating on soaring strategy and tactics.

Case in point: Do a template check on any LS6 or LS8. I can probably loan you the templates for that, though I haven't seen them for a while. Anyhow, what you find is that the camber lines for the right and left wings are substantially different. The template for one wing fits the opposite wing like maybe they're from two different gliders. This applies to all of the six or eight ships I've checked, and all of them have been different in pretty much the same ways, so I'm pretty sure that's how they come out of the molds. But these are not dogmeat gliders-- they go like stink, fly arrow straight if they're tuned properly, and have won regional and national contests. Who's to say whether the right or the left wing has the correct profile and the other not? They both seem to work pretty damn well.

--Bob K.


Bob said it well.
There is very little data available for the airfoils on the modern(last 20 years) ships.
Best bet is fill the spar shrink and don't screw up the leading edge.
If I'm doing a "serious" job I pull templates of the leading edge 4 inches back every 24 inches so it is back to "correct" before finish spraying.
Fair warning: More ships have been made worse by people who did not know what they were doing and the list of projects abandoned part way through is long.
UH
  #6  
Old August 1st 19, 05:03 PM posted to rec.aviation.soaring
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Default Wing Contour?

What technique do you use to make templates ("pull a set") for the leading edge as Hank states? Do you guys know if there are existing coordinates or templates for ASK21 and ASW24?

Doug
  #7  
Old August 1st 19, 05:23 PM posted to rec.aviation.soaring
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Default Wing Contour?

On Thursday, August 1, 2019 at 12:03:56 PM UTC-4, wrote:
What technique do you use to make templates ("pull a set") for the leading edge as Hank states? Do you guys know if there are existing coordinates or templates for ASK21 and ASW24?

Doug


I make templates out of 1/4 inch plywood cut to a very close profile to the leading edge.
I wax the wing well, then put a thick coating of aerodynamic fairing compound(body filler) on the inner surface of the wood template and squish into place.
When cured remove a clean up. Label immediately.
'21 has published airfoils. No idea why anyone would want to profile one.
Have '24 templates for B mod.
UH
  #8  
Old August 1st 19, 05:42 PM posted to rec.aviation.soaring
Papa3[_2_]
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Default Wing Contour?

On Wednesday, July 31, 2019 at 6:34:52 PM UTC-4, Bob Kuykendall wrote:
On Tuesday, July 30, 2019 at 9:00:34 PM UTC-7, wrote:
Can anyone tell me specifically how to tell how closely a wing is following its intended shape or to know if it has "issues"? Also, if I'm sanding, polishing or refinishing it, how do I accurately correct for any deficiencies? Asking for a friend... : )


It depends entirely on the nature of the wing. For aggressively laminar profiles like the old FX67, it can matter a lot. For others, it matters a lot less.

In my direct experience, freedom from waviness (Johnson reading below 0.004" per linear inch) is a lot more important than absolute fidelity to contour. Time spent trying to impose some sort of theoretically ideal contour with filling and sanding is a lot better spent just getting any big waves out and then concentrating on soaring strategy and tactics.

Case in point: Do a template check on any LS6 or LS8. I can probably loan you the templates for that, though I haven't seen them for a while. Anyhow, what you find is that the camber lines for the right and left wings are substantially different. The template for one wing fits the opposite wing like maybe they're from two different gliders. This applies to all of the six or eight ships I've checked, and all of them have been different in pretty much the same ways, so I'm pretty sure that's how they come out of the molds. But these are not dogmeat gliders-- they go like stink, fly arrow straight if they're tuned properly, and have won regional and national contests. Who's to say whether the right or the left wing has the correct profile and the other not? They both seem to work pretty damn well.

--Bob K.


Just to amplify what both Bob and Hank are saying, I'm currently in the midst of an LS3 refinish project with our club. While there ARE published coordinates (though even there some uncertainty exists about the intended thickness of the outer section), we are finding that there is a lot of work involved just in getting the templates correctly situated. This is a glider that won the sports class nationals last year, and so far we are finding a lot of very big deviations from the supposedly accurate profile in the outer third. It is much too blunt. The work involved to "fix" that would be significant. Could we actually make the glider worse - yup. Would anyone notice the difference if we got it "right". Probably not.

Meanwhile, we are paying a lot more attention to building up the spar lines to get rid of the shrinkage there and smoothing everything out.

We pulled the coordinates from Soaring articles published by Dick Johnson and updated later with "corrections". We cut the templates for the LE out of 1/4 inch ply on a CNC router. To do the full chord we will need a bigger router, but we've got plenty of guys in the club who have access to what we need. But, at this point (first pass of priming and filling), we're leaning toward smoothing and leaving the profile alone.

One group's experience...

  #9  
Old August 1st 19, 05:50 PM posted to rec.aviation.soaring
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Default Wing Contour?

Just to clarify, the 1/4 inch ply is "rough cut" as closely as possible and the filler adheres to the wood and gives the smooth surface needed to re-profile? How far back above, and below the wing do you go for a glider you want to perform well?

Doug
  #10  
Old August 1st 19, 06:11 PM posted to rec.aviation.soaring
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Default Wing Contour?

On Thursday, August 1, 2019 at 12:50:22 PM UTC-4, wrote:
Just to clarify, the 1/4 inch ply is "rough cut" as closely as possible and the filler adheres to the wood and gives the smooth surface needed to re-profile? How far back above, and below the wing do you go for a glider you want to perform well?

Doug


You understood correctly.
First 10% or so. About 3 inches inboard and 2-1/2 outboard.
Purpose of the templates is to have finished wing with same profile it started with. "Normal" sanding will usually make the leading edge too blunt.
UH
 




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