To profile or not to profile

My Speed Astir's wings show a considerable amount of waviness at the
spar caps and every rib. There also appears to have been some repair
work on a leading edge, and the profile is noticeably NOT the same as
the other wing.
I have Compufoil Pro, which will outpout CNC mill files for the
templates, and a friend with a CNC mill, willing to produce the
templates. I will almost certainly take care of the leading edge
issues, but I'm waffling about undertaking a full wing re-profile. On
one hand, you want your glider to be as good as it can be. On the
other hand, I don't fly contests, and I'm pretty sure the pilot is
causing more loss of performance than the extra drag from the waves in
the profile.
Opinions??

BTW, the single biggest improvement I've made to date is the addition
of a flight recorder and a iPAQ with XCSoar. That combo made it
immediately clear that I was being too conservative (chicken!)

Jim

I'd just do the leading edge, Jim. The first 4' are
critical, Schueman proved that when he modified the
Hutter airfoil on his H-301 Libelle by changing the
first 4', or so and left the rest alone.
JJ

At 20:18 08 August 2007, wrote:
My Speed Astir's wings show a considerable amount of
waviness at the
spar caps and every rib. There also appears to have
been some repair
work on a leading edge, and the profile is noticeably
NOT the same as
the other wing.
I have Compufoil Pro, which will outpout CNC mill
files for the
templates, and a friend with a CNC mill, willing to
produce the
templates. I will almost certainly take care of the
leading edge
issues, but I'm waffling about undertaking a full wing
re-profile. On
one hand, you want your glider to be as good as it
can be. On the
other hand, I don't fly contests, and I'm pretty sure
the pilot is
causing more loss of performance than the extra drag
from the waves in
the profile.
Opinions??

BTW, the single biggest improvement I've made to date
is the addition
of a flight recorder and a iPAQ with XCSoar. That combo
made it
immediately clear that I was being too conservative
(chicken!)

Jim

Add the pilot losses and the wing losses, and... It's a large job.
Something you just have to be the judge of... Do you have several
months to do this? I easily spent 500 hours profiling the wings of an
HP-14, and had to sell it due to promotions and moves, (i.e. loss of
shop space, etc.) If you've got time, go for it...

Jack Womack

Hmmmmm,
When I typed the sympol for for inches (') , the system
changed it to feet (') ..............anyway, the first
4 INCHES are important, not the first 4 FEET!
JJ

At 20:18 08 August 2007, wrote:
My Speed Astir's wings show a considerable amount of
waviness at the
spar caps and every rib. There also appears to have
been some repair
work on a leading edge, and the profile is noticeably
NOT the same as
the other wing.
I have Compufoil Pro, which will outpout CNC mill
files for the
templates, and a friend with a CNC mill, willing to
produce the
templates. I will almost certainly take care of the
leading edge
issues, but I'm waffling about undertaking a full wing
re-profile. On
one hand, you want your glider to be as good as it
can be. On the
other hand, I don't fly contests, and I'm pretty sure
the pilot is
causing more loss of performance than the extra drag
from the waves in
the profile.
Opinions??

BTW, the single biggest improvement I've made to date
is the addition
of a flight recorder and a iPAQ with XCSoar. That combo
made it
immediately clear that I was being too conservative
(chicken!)

Jim

On Aug 8, 1:39 pm, John Sinclair
wrote:
Hmmmmm,
When I typed the sympol for for inches (') , the system
changed it to feet (') ..............anyway, the first
4 INCHES are important, not the first 4 FEET!
JJ

At 20:18 08 August 2007, wrote:



My Speed Astir's wings show a considerable amount of
waviness at the
spar caps and every rib. There also appears to have
been some repair
work on a leading edge, and the profile is noticeably
NOT the same as
the other wing.
I have Compufoil Pro, which will outpout CNC mill
files for the
templates, and a friend with a CNC mill, willing to
produce the
templates. I will almost certainly take care of the
leading edge
issues, but I'm waffling about undertaking a full wing
re-profile. On
one hand, you want your glider to be as good as it
can be. On the
other hand, I don't fly contests, and I'm pretty sure
the pilot is
causing more loss of performance than the extra drag
from the waves in
the profile.
Opinions??

BTW, the single biggest improvement I've made to date
is the addition
of a flight recorder and a iPAQ with XCSoar. That combo
made it
immediately clear that I was being too conservative
(chicken!)

Jim- Hide quoted text -

- Show quoted text -

Inches, feet, whatever it takes.

John Sinclair wrote:
Hmmmmm,
When I typed the sympol for for inches (') , the system
changed it to feet (') ..............anyway, the first
4 INCHES are important, not the first 4 FEET!
JJ

Intresting!! I'm going to try both and see what shows up.
Inches is the quote mark """"""" looks good here ,
Foot the apostrophe ''''''' looks OK on "up link" :-)
Now to see what shows up on the news group.
...lew...

Well JJ is the man ...so 4' sounds a lot easier then
the whole thing.

jimphoenix.com has a tremendous amount of imaging and
narrative on the work he did on a Nimbus 3...well worth
a peak

On Aug 8, 7:12 pm, Stewart Kissel
wrote:
Well JJ is the man ...so 4' sounds a lot easier then
the whole thing.

jimphoenix.com has a tremendous amount of imaging and
narrative on the work he did on a Nimbus 3...well worth
a peak

Worth more than a peak. I've spent many hours on his site. Anyone
even vaguely interested in gelcoat work, 1-26 restorations, or wooden
boat restorations would benefit greatly from Jim's work.

If you are just doing the first 4 inches or so with precise templates
(and I agree that from a results per effort view this could be the
right way to go), I would seriously consider eliminating the chordwise
waves on the rest of the wing surface. For laminar airflow you want
no more than a .004 inch bump or dip in 2 inches. You can easily
measure this with a dial indicator set up as Richard Johnson shows.
Using filler and sanding splines (always sand at 45 degrees to the
chordwise direction) it is not that hard to achieve this level of low
waviness. This lack of waviness is likely more important than
fidelity to the specified airfoil contour once you are farther than
about 4 inches from the LE.

Be prepared for a lot of work. But the results can be spectacular.

Regards,

Doug

On Aug 8, 4:12 pm, wrote:
My Speed Astir's wings show a considerable amount of waviness at the
spar caps and every rib. There also appears to have been some repair
work on a leading edge, and the profile is noticeably NOT the same as
the other wing.
I have Compufoil Pro, which will outpout CNC mill files for the
templates, and a friend with a CNC mill, willing to produce the
templates. I will almost certainly take care of the leading edge
issues, but I'm waffling about undertaking a full wing re-profile. On
one hand, you want your glider to be as good as it can be. On the
other hand, I don't fly contests, and I'm pretty sure the pilot is
causing more loss of performance than the extra drag from the waves in
the profile.
Opinions??

BTW, the single biggest improvement I've made to date is the addition
of a flight recorder and a iPAQ with XCSoar. That combo made it
immediately clear that I was being too conservative (chicken!)

Jim

The Speed Astir is one of the few gliders that can be improved
substantially. The 662 airfoil suffers from an upper surface pressure
recovery problem that has been know for along time and Richard Eppler
him self recommended a turbulator on the "top surface" at 65% chord.
Naturally if the wing has a dip over the spar this turbulator will be
of no use, as the laminar flow is already kaput before it gets there.
If I were you I would follow the advise of Doug Hoffman. The other
improvement that would pay big dive would be a winglet, due to its
relative small aspect ratio und big tip chord it would benefit
proportionally more then other gliders of its vintage.

One other note Richard Eppler designed a replacement airfoil call
E673 for the E662, which can be easily arrived at by sanding the
existing one.

Allow 400 hour for the complete job. I would work on it in 2 stages
sanding and painting. Even in an unfinished sanded only state you
would see good results. Most of the filling can be done with a high
build primer. Full chord templates would be helpful but if you only
redoing the first 4 inches and fill in the spar dip then a few small
templates are needed. The spar dip can be done with a flexible steel
ruler and double check with a gage.
Have fun
Udo