Re-curving mylar on a glider

My top surface mylar seems to have lost some of it's curvature, because
it doesn't quite touch the aileron and flaps when they are in positive
positions. Does anyone know a way to put the curve back into the mylar
without removing it? It's so well adhered and smoothly installed, I'd
like to leave it on if at all possible, but I think it may be degrading
my climb while thermalling. The mylar is almost 12 years old.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric, I would think that mylar that is 12 years old would have lost its
flexibility. It gets pushed up with upward aerleron or negative flap
settings and tends to stay there or very slowly flex back down to "neutral".
So going to positve settings will be difficult.

I don't know how you could put "life" back into the old plastic, but I would
be interested to hear.

BT

"Eric Greenwell" wrote in message
news:JfBYg.3919$5v5.3761@trndny08...
My top surface mylar seems to have lost some of it's curvature, because it
doesn't quite touch the aileron and flaps when they are in positive
positions. Does anyone know a way to put the curve back into the mylar
without removing it? It's so well adhered and smoothly installed, I'd like
to leave it on if at all possible, but I think it may be degrading my
climb while thermalling. The mylar is almost 12 years old.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric,

The Mylar is originally curved by passing the strip through a set of curved,
heated rollers. Complicated enough, all by itself (g) . . . to do the chore
with the Mylars still attached to the plane is beyond my admittedly limited
experience.

bumper

"Eric Greenwell" wrote in message
news:JfBYg.3919$5v5.3761@trndny08...
My top surface mylar seems to have lost some of it's curvature, because it
doesn't quite touch the aileron and flaps when they are in positive
positions. Does anyone know a way to put the curve back into the mylar
without removing it? It's so well adhered and smoothly installed, I'd like
to leave it on if at all possible, but I think it may be degrading my
climb while thermalling. The mylar is almost 12 years old.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org

bumper wrote:


The Mylar is originally curved by passing the strip through a set of curved,
heated rollers. Complicated enough, all by itself (g) . . . to do the chore
with the Mylars still attached to the plane is beyond my admittedly limited
experience.

I am interested in finding out more about this roller process?
Any pictures or detailed descriptions available?
For my projects in the past, I successfully made my own curved Mylar
strips in 5ft sections

Udo

A friend of mine tried to make his own curving machine, using
a length of steel pipe and a propane torch. We had great fun
watching as he burned his fingers and leaped about yelling
"Ouch ! Ouch !" and made all manner of wavy plastic, but it did
get a bit scary when he almost set his shop afire. After that he
ordered new pre-curved mylar from Germany.

See ya, Dave

PS: I'm sure Bumper could do better ! But not as entertaining.

PPS: Pipe is the wrong idea; as you pass the myler through
it heats the edges and not the area needing the curve...

PPPS: Bumper already knew that.

bumper wrote:
The Mylar is originally curved by passing the strip through a set of curved,
heated rollers. Complicated enough, all by itself (g) . . .

wrote:
A friend of mine tried to make his own curving machine, using
a length of steel pipe and a propane torch. We had great fun
watching as he burned his fingers and leaped about yelling
"Ouch ! Ouch !" and made all manner of wavy plastic, but it did
get a bit scary when he almost set his shop afire.
See ya, Dave

Dave,
Here is what I do.I buy the 7 mil sheets (I figure it provides less
friction than the 10 mil) and roll it up inside of a peice of carpet
roll tube.Then I bake it at about 160 in the oven for 30 minutes.Then
cut it into strips and use scotch 665 double sided tape to adhear it to
the wings and 3M 850 mylar tape for the safety strip.I can do top and
bottom of my flaps ailerons and tail a couple times over for about 50
bucks.I replace it every 3 to 5 years and I have never had a
problem.This does seem a little less entertaning than your buddys
method, but it works fine.
K Urban

Unless you've ot a *really* long oven, that leaves you with
a lot of small pieces, no ? Its a lot nicer (and easier to apply
with proper technique) to have longer strips, no ?
Best Regards, Dave

KM wrote:
Dave,
Here is what I do.I buy the 7 mil sheets (I figure it provides less
friction than the 10 mil) and roll it up inside of a peice of carpet
roll tube.Then I bake it at about 160 in the oven for 30 minutes.Then
cut it into strips and use scotch 665 double sided tape to adhear it to
the wings and 3M 850 mylar tape for the safety strip.I can do top and
bottom of my flaps ailerons and tail a couple times over for about 50
bucks.I replace it every 3 to 5 years and I have never had a
problem.This does seem a little less entertaning than your buddys
method, but it works fine.
K Urban

wrote:
Unless you've ot a *really* long oven, that leaves you with
a lot of small pieces, no ?

Dave, you are correct, the pieces are just over two feet long.I use a
peice of the 850 mylar tape at every joint.The main motivation for
doing this is to get a thinner seal.I use 7 mil sheets (I have heard
some guys go a little thinner), and all of the commecial seals that I
have found are 10 mil or bigger.I bought my ship from a guy who was
good freinds with Wil Shumman (SP?), and this is where the idea
originated.Wil Shumman did alot of work on airflow and wing profiles
and such, and he felt thinner would be better.Now I am not an
aerodymamical engineer, so maybe I am just perpetuating folklore, but
these seals work pretty good for me and they seem to provide a little
less control friction.

Its a lot nicer (and easier to apply
with proper technique) to have longer strips, no ?

No argument on the easier part . Actually, I use a homeade jig to cut
the strips (Then carefully shave the edges smooth) and a template to
install each strip and it comes out looking pretty clean.Usually guys
have to look very close to see that there are a bunch of peices of
mylar, and not one continual strip.A little practice doesnt hurt.I fly
an ASW20 in some pretty good desert conditions, so I am at high speeds
quite often, and I have never had a problem.

Best Regards, Dave

Best Regards, K Urban

wrote:
Unless you've ot a *really* long oven, that leaves you with
a lot of small pieces, no ? Its a lot nicer (and easier to apply
with proper technique) to have longer strips, no ?
Best Regards, Dave

Hi Dave,
In fact it is much easier to apply shorter pieces.
Do you mean that proper technique can not be used, when applying
shorter pieces?
I am able to make six foot long pieces. (I do not use an oven)
I find five feet optimum for me as there would be one break in the
aileron section.
and two in the flap area. I use a .002" self adhesive clear Mylar tape
over the break.
The reason for covering the tight butting joint is, when wiping the
wing for cleaning,
the rag does not catch the corners.
There's is an advantage to making custom seals, one can get a curve and
thickness
for the Mylar that is right for your ship. This may not apply for most
modern gliders
as the factory installs them and it can provide after market seals.
There are many older
gliders were some after market seal may not be ideal.
Udo

After 12 years the adhesive tape used to hold the seal in place has
deteriorated to the point that your original seal installation may be
unsafe. I've seen approx. 10 years seal installations where the adhesive is
about to release the seal. A small tug on the seal itself and the seal may
slip away from the adhesive. A lost seal inflight is something we all must
avoid at all cost. Control surfaces can stop working after a total or
partial separation.

I think 7-8 years is max any seal installation should be trusted because of
the potential loss of adhesion.
Also,the seal itself has deteriated from UV ( why it has lost the heat
induced curvature) and although is safe with regard to its physical
intregrity, new ones would look a whole lot nicer and a new seal with new
adhesive, a lot safer.

I think seal installations on gliders can be potentially the weakest link in
our sport. A failed seal can kill you and we should all be aware of time
limiations.

This winter I am reprofiling my wings and quess what, my seals will be
replaced after 5 years.


bob fidler
"Eric Greenwell" wrote in message
news:JfBYg.3919$5v5.3761@trndny08...
My top surface mylar seems to have lost some of it's curvature, because it
doesn't quite touch the aileron and flaps when they are in positive
positions. Does anyone know a way to put the curve back into the mylar
without removing it? It's so well adhered and smoothly installed, I'd like
to leave it on if at all possible, but I think it may be degrading my
climb while thermalling. The mylar is almost 12 years old.

--
Eric Greenwell - Washington State, USA
Change "netto" to "net" to email me directly

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org