Reprofiling LS6 wings

[Ben C]

Hi all,

Given that down the track I will need to refinish my wings, I am
curious about
the process. I understand that LS/DG will not provide profile
information to
allow accurate reprofiling of the wings. Is it standard practice to
just
reinstate the profile that the wing had prior to refinish? Has anyone
taken a
profile from another aircraft to use, for example using a later LS6-c
to
reprofile an LS6-b? What about using an LS8 profile on an LS6, since
they are
supposed to be the same forward section?

Thanks, Ben

[Bob Kuykendall]

On Jun 19, 3:28*pm, Ben C > wrote:

> Is it standard practice to just reinstate the profile that
> the wing had prior to refinish?

That's pretty much what you do. Make sure the wing profile is round in
front, pointy in back, and the waviness is below .004", and it will
probably be fine.

> ...Has anyone taken a profile from another aircraft to use, for
> example using a later LS6-c to reprofile an LS6-b?

They're the same profile. Or at least the LS6-c left is the same as
the LS6-b left, and likewise for the corresponding right wings. I've
done template checks on several LS6 and a couple of LS8 to validate
it.

> What about using an LS8 profile on an LS6, since they are
> supposed to be the same forward section?

As you note, they're also pretty much the same, within the
qualifications noted above.

My advice: Don't bother trying to do a full profile job. The LS6 and
LS8 go like stink, generally fly very straight, and handle very well.
There is just about nothing a full profile job will do to change that.
It will defnitely add a bunch of weight and expend hundreds of hours
and thousands of dollars.

About the only things that would make much of a difference are the
leading edge profile back to about 15% chord, and getting the waviness
down to under .004". And my bet is that both of those are probably
already in pretty good shape.

Thanks, Bob K.
http://www.hpaircraft.com/hp-24

[KN]

On Jun 19, 9:04*pm, Bob Kuykendall > wrote:
> On Jun 19, 3:28*pm, Ben C > wrote:
>
> > Is it standard practice to just reinstate the profile that
> > the wing had prior to refinish?
>
> That's pretty much what you do. Make sure the wing profile is round in
> front, pointy in back, and the waviness is below .004", and it will
> probably be fine.
>
> > ...Has anyone taken a profile from another aircraft to use, for
> > example using a later LS6-c to reprofile an LS6-b?
>
> They're the same profile. Or at least the LS6-c left is the same as
> the LS6-b left, and likewise for the corresponding right wings. I've
> done template checks on several LS6 and a couple of LS8 to validate
> it.
>
> > What about using an LS8 profile on an LS6, since they are
> > supposed to be the same forward section?
>
> As you note, they're also pretty much the same, within the
> qualifications noted above.
>
> My advice: Don't bother trying to do a full profile job. The LS6 and
> LS8 go like stink, generally fly very straight, and handle very well.
> There is just about nothing a full profile job will do to change that.
> It will defnitely add a bunch of weight and expend hundreds of hours
> and thousands of dollars.
>
> About the only things that would make much of a difference are the
> leading edge profile back to about 15% chord, and getting the waviness
> down to under .004". And my bet is that both of those are probably
> already in pretty good shape.
>
> Thanks, Bob K.http://www.hpaircraft.com/hp-24
>

Hi Bob,
I am a newbie in the sport and wondering how much wing surface
deformity would one
expect to see in this era glass ships. The deformity is caused by
shrinking/ settling of fiberglass
through time or there is a different mechanism? The more recent ships
with carbon fiber wings suffer
just a much? BTW, I enjoy following your work. Thanks
Khanh

[JJ Sinclair[_2_]]

On Jun 19, 3:28*pm, Ben C > wrote:
> Hi all,
>
> Given that down the track I will need to refinish my wings, I am
> curious about
> the process. I understand that LS/DG will not provide profile
> information to
> allow accurate reprofiling of the wings. Is it standard practice to
> just
> reinstate the profile that the wing had prior to refinish? Has anyone
> taken a
> profile from another aircraft to use, for example using a later LS6-c
> to
> reprofile an LS6-b? What about using an LS8 profile on an LS6, since
> they are
> supposed to be the same forward section?
>
> Thanks, Ben

Only the first 4" are critical and I would make 'quickie' templates
before stripping the wing. Set wing leading edge up on saw-horses and
mark span locations every 18" then make rough cardboard templates
starting at the root. Place wax-paper over L/E and goop up your rough
template with Bondo and lower them onto each indicated location. After
the Bondo dries remove and sand the edges to leave only the center
1/4" template. Be sure to mark each template 1 through 16, or so.
Then start the fun part, with a Porter-Cable, variable speed electric
orbital sander using 60 grit, 6" sticky back
disks..................remove all the gelcoat down to, but not
including the fiberglass structure. Check back after the 2 weeks this
may take and I'll give you the next step in you all Winter project.
Cheers,
JJ

[jsbrake[_2_]]

Before I make myself out to be too much of an idiot with a mostly-
likely-obvious question... is there a quick quide on the process of re-
profiling? My search in Google just now was fruitless, so I'm doing
something wrong. I'm not planning on doing it, but I'm curious about
the process.

Thanks!
- John

[Luke[_4_]]

On 06/21/2011 10:11 AM, jsbrake wrote:
> Before I make myself out to be too much of an idiot with a mostly-
> likely-obvious question... is there a quick quide on the process of re-
> profiling? My search in Google just now was fruitless, so I'm doing
> something wrong. I'm not planning on doing it, but I'm curious about
> the process.
>
> Thanks!
> - John
Hi John,

this is probably the best article to give you an idea of the work involved.

http://www.archive.jimphoenix.com/archive09/jimphoenix2/pages/Nimbus/LH%20UP%20wing/subLH%20UP%20wing.html

Luke Szczepaniak

[[email protected]]

On Jun 21, 10:11*am, jsbrake > wrote:
> Before I make myself out to be too much of an idiot with a mostly-
> likely-obvious question... is there a quick quide on the process of re-
> profiling? *My search in Google just now was fruitless, so I'm doing
> something wrong. *I'm not planning on doing it, but I'm curious about
> the process.
>
> Thanks!
> - John

Yep.
Reprofiling only.
Identify and fill low areas- usually due to shrink over time.
Identify and remove high areas- rare, but it does happen.
Where are they? Ah that is the question.
Throw in refinishing and that is a whole different question.
The first time you do this you will do well not to make the glider
worse. Many do.
Few do it the second time.
UH

[mattm[_2_]]

On Jun 21, 11:37*am, wrote:
> On Jun 21, 10:11*am, jsbrake > wrote:
>
> > Before I make myself out to be too much of an idiot with a mostly-
> > likely-obvious question... is there a quick quide on the process of re-
> > profiling? *My search in Google just now was fruitless, so I'm doing
> > something wrong. *I'm not planning on doing it, but I'm curious about
> > the process.
>
> > Thanks!
> > - John
>
> Yep.
> Reprofiling only.
> Identify and fill low areas- usually due to shrink over time.
> Identify and remove high areas- rare, but it does happen.
> Where are they? Ah that is the question.
> Throw in refinishing and that is a whole different question.
> The first time you do this you will do well not to make the glider
> worse. Many do.
> Few do it the second time.
> UH

That's the thing -- not to make it worse. Is it worth it to try
though?
My plane seems to fly about 10-12% worse than the Johnson
measured polar. The gelcoat is in pretty good shape overall
after 33 years though; it looks like a reprofiling is basically
a refinish project, which I'm not planning on doing anytime soon.

-- Matt

[jsbrake[_2_]]

Okay, I think need to be an idiot and ask the questions (I beg your
indulgence)...

I understand the part about getting the correct profile templates and
shaping the wing to the correct profile. However, doesn't that mean
that the wing will be thicker than profile once the gelcoat is sprayed
on? Or are the templates made deliberately thinner to account for
this added thickness? But then how would one know how thick to lay on
the gelcoat?

It seems to me that "re-finish" and "re-profile" are being used nearly
interchangeably, i.e. in both cases, the gelcoat is completely
removed.

Can it be that the gelcoat can be only partially sanded off, filled in
somehow (more gel?) to meet profile, then bond in another layer of
gelcoat? I've seen a wing repaired: new foam core, glass layers,
bondo then gelcoat, so I know small patches can be done this way (I
didn't get to see the gelcoat being applied).

Thanks!
-John
(and if these are _really_ stupid questions, just call me Hugo)
(no offense intended to anyone named Hugo)

[Grider Pirate]

On Jun 21, 11:54*am, jsbrake > wrote:
> Okay, I think need to be an idiot and ask the questions (I beg your
> indulgence)...
>
> I understand the part about getting the correct profile templates and
> shaping the wing to the correct profile. *However, doesn't that mean
> that the wing will be thicker than profile once the gelcoat is sprayed
> on? *Or are the templates made deliberately thinner to account for
> this added thickness? *But then how would one know how thick to lay on
> the gelcoat?
>
> It seems to me that "re-finish" and "re-profile" are being used nearly
> interchangeably, i.e. in both cases, the gelcoat is completely
> removed.
>
> Can it be that the gelcoat can be only partially sanded off, filled in
> somehow (more gel?) to meet profile, then bond in another layer of
> gelcoat? *I've seen a wing repaired: new foam core, glass layers,
> bondo then gelcoat, so I know small patches can be done this way (I
> didn't get to see the gelcoat being applied).
>
> Thanks!
> -John
> (and if these are _really_ stupid questions, just call me Hugo)
> (no offense intended to anyone named Hugo)

The best step-by-step I've ever found was on Jimphoenix.com. He
stripped, reprofiled, and refinished a set of Nimbus wings.
Unfortunately, I don't think it's still available, as he has moved to
Washington and is now more into boats. It might not hurt to email him
to see if he could send you the 'article'.
Cheers

[Grider Pirate[_2_]]

On Jun 21, 1:01*pm, Grider Pirate > wrote:
> On Jun 21, 11:54*am, jsbrake > wrote:
>
>
>
>
>
> > Okay, I think need to be an idiot and ask the questions (I beg your
> > indulgence)...
>
> > I understand the part about getting the correct profile templates and
> > shaping the wing to the correct profile. *However, doesn't that mean
> > that the wing will be thicker than profile once the gelcoat is sprayed
> > on? *Or are the templates made deliberately thinner to account for
> > this added thickness? *But then how would one know how thick to lay on
> > the gelcoat?
>
> > It seems to me that "re-finish" and "re-profile" are being used nearly
> > interchangeably, i.e. in both cases, the gelcoat is completely
> > removed.
>
> > Can it be that the gelcoat can be only partially sanded off, filled in
> > somehow (more gel?) to meet profile, then bond in another layer of
> > gelcoat? *I've seen a wing repaired: new foam core, glass layers,
> > bondo then gelcoat, so I know small patches can be done this way (I
> > didn't get to see the gelcoat being applied).
>
> > Thanks!
> > -John
> > (and if these are _really_ stupid questions, just call me Hugo)
> > (no offense intended to anyone named Hugo)
>
> The best step-by-step I've ever found was on Jimphoenix.com. *He
> stripped, reprofiled, and refinished a set of Nimbus wings.
> Unfortunately, I don't think it's still available, as he has moved to
> Washington and is now more into boats. *It might not hurt to email him
> to see if he could send you the 'article'.
> Cheers- Hide quoted text -
>
> - Show quoted text -

Oh wait! Here it is.....http://www.jimphoenix.com/nimbus/

[sisu1a]

> Before I make myself out to be too much of an idiot with a mostly-
> likely-obvious question... is there a quick quide on the process of re-
> profiling? *

Quick and reprofiling don't belong in the same sentence. Not sure why
it hasn't been linked yet, but here you go:

http://www.8kcab.com/Checklists_files/KK_ASW20_Refinish.pdf

It should at least give you an idea of what you're (thinking about)
getting into...

-p

[Andreas Maurer]

On Tue, 21 Jun 2011 09:09:20 -0700 (PDT), mattm >
wrote:

>My plane seems to fly about 10-12% worse than the Johnson
>measured polar. The gelcoat is in pretty good shape overall
>after 33 years though; it looks like a reprofiling is basically
>a refinish project, which I'm not planning on doing anytime soon.


Hi Matt,

don't rely too much on Johnson's polars. Dick did an amazing job, but
with his limited resources his polars are off more often than not.

The German Idaflieg polars are usually very precise, but it took ten
times more effort to measure them.

My advice:
Take a close look at the wing and try to find out if there's waviness
in front of the wing spar. The best way is to have a neon lamp over
the wing - by looking at its reflection you can see the slightest
waviness.
If you find serious waviness (which I doubt), come back to this group
and ask for an exchange between help and cash.
If you don't ... be happy and ignore Dick's polar. :)

In my opinion it is impossible to get a proper airfoil again if you
don't have some experienced guy at hand.


Andreas

p.s.
Do you happen to have a friend with a similar glider (ASW-20, Ventus
1) at hand that you could use to compare your performance to?