To profile or not to profile

On Aug 9, 9:05 am, Udo wrote:
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- Hide quoted text -

- Show quoted text -

Thanks Udo,
I will look into the E673. Winglets appeal to me, but I lack the
background to do the design work. I've read the Masak article
numerous times, but several aspects of the design work are just over
my head.
At the very least I will have full templates produced, fill the spar
dip, and profile the forward section of the wing.

Jim

On Aug 9, 5:05 pm, Udo wrote:
The Speed Astir is one of the few gliders that can be improved
substantially.

Do all single-seat Astirs use the same wing?


Dan

On Aug 10, 5:49 am, Dan G wrote:
On Aug 9, 5:05 pm, Udo wrote:

The Speed Astir is one of the few gliders that can be improved
substantially.

Do all single-seat Astirs use the same wing?

Dan

No,

The Grob 102 and 103 use the E603 airfoil.

Todd Smith
3S

On Aug 10, 3:41 am, toad wrote:
On Aug 10, 5:49 am, Dan G wrote:

On Aug 9, 5:05 pm, Udo wrote:

The Speed Astir is one of the few gliders that can be improved
substantially.

Do all single-seat Astirs use the same wing?

Dan

No,

The Grob 102 and 103 use the E603 airfoil.

Todd Smith
3S

The Speed Astir wing is also flapped, and 123.4 sq. feet, as opposed
to the 133.5 sq. feet of the unflapped "other" Grob single seaters.

Jim,

I'm about to purchase a Grob 104 that will need a refinish in the next few years. I found this thread while doing research and was wondering if you ever had the leading edge templates made. I would be willing to rent them from you at some point whenever I finally have to bite the bullet and start the refinish.

Can you tell me how your project went and if you ever added winglets as well? Any hints or suggestions would be greatly appreciated. I plan to add the turbulators as soon as I get the glider as they were removed for a quicky spray job and never re-installed.

Thanks,

Greg Delp
203-565-5117


On Wednesday, August 8, 2007 4:12:23 PM UTC-4, 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