GL foil suggestions

[xtc]

well, the title says it ,,my gl wing is in need of repair so im thinking that over the winter i should scratch build another so im thinking of the same simple contstand cord design but may be with the more traditional spruce spar arragment but what im looking for is suggestions for the airfoil

i like drela foils but im not sure [if any ] will carry the covering well without LE sheeting ?

my goal is a modern day gl with similiar character in nature ,,in short i just dont see any point in building another stock gl wing when i can experiment!


thanks in advance p.s. rib templetes anywhere?

xtc

[fraggin]

The GL Wing was designed with simplicity of assembly in mind as well as a wing light enough to be a floater, yet strong enough to take a beating. My first GL wing had numerous repairs. There were several incidents where portions of the leading edge had to be cut out and replaced, and once I hit a small sappling on the left outer panel wing and completely dismembered it. Even with all the added weight of repairs and epoxy and covering patches, the GL still floated like it did when it was a new build. That leads me to beleive that the amount of repairs the wing would undergo if in the hands of a learner had to be accounted for in the design as well.
IMO, the GL Wing is what makes it a gentle lady.
If you are looking for a modern GL, maybe think about using modern light weight equipment and battery to lighten her up a bit. Perhaps use solite covering on the wings and mod the rudder to be a one piece rudder with no vertical stabilizer.
That large poly wing and flat bottom airfoil is the Gentle in the GL.

[John Gallagher]

To improve penetration, you can try adding a little Phillips entry to bottom of the leading edge, but then you have changed the angle of attack of the wing. You would have to raise the trailing edge or lower the leading edge of the wing.
There's a small writeup on the charlesriver site about doing this to the Paragon airfoil - very similar to the GL airfoil.
http://www.charlesriverrc.org/articles/kitmods/dickwilliamson_paragonairfoil.htm

[Mike K]

well, the title says it ,,my gl wing is in need of repair so im thinking that over the winter i should scratch build another so im thinking of the same simple contstand cord design but may be with the more traditional spruce spar arragment but what im looking for is suggestions for the airfoil

xtc

I did something similar earlier this year, but with the DrifterII. I did sheet the leading edge back to the spar and the funny thing was that after all was done, the wing was lighter by a gram than the original one.

I used the S3021, tapering to S3014 at the wing tips. Get a copy of Profili, enter in what you are looking for and start building. If you change the spar system to an I-beam with carbon caps, don't bother with spruce spars. Just use appropriate sized carbon and wrap with Kevlar tow. This would be what I would change if I rebuilt it again. Oh, and use sub-ribs in front of the spar if you use 1/32" sheeting on the tips as this will help prevent any sagging between the ribs. Subribs could be done in light 1/16" rather than 3/32".

Great flying little glider now.

Regards.
Mike Kirda

[erikdahlchriste]

Hi xtc,

I have made a better wing for the Blue Phoenix, which is a plane similar to the GL. The new wing uses a thinned Clark Y (9% relative thickness) with 1/16 D-box and capstrips.
The top spar is 3/8 x 1/8 at the center panel and 3/16 x 1/8 at the tip panel.
The bottom spar is 3/8 x 5/64 at the center panel and 3/16 x 6/64 at the tip panel.
The wing joiner is 5mm and not 4mm as written on the plan.
A new fuse and tailgroup makes it a new glider called Simplex 2M.
Istead af the thinned Clark y, you could as well use the original Clark Y and still get a better glider than with the standard flat bottom airfoil.
The coordinates for Clark Y you can find here:
http://www.terrabreak.org/groundloop/clarky.dat

Or you can use the airfoils used and made by Mark Drela on his Alegro Lite:
http://www.charlesriverrc.org/articles/allegrolite2m/Allegro_Lite.pdf

cheers

Erik Dahl Christensen
Denmark
www.gliders.dk

[sailhigh]

XTC,
The GL was designed as a light air floater/trainer and it excells in that regard. I've been building these guys for at least 15 years and love them. The handling and light air capablility is legendary. What makes the GL a GL is the wing geomerty and THAT airfoil. Changing either will make the airplane fly differently, maybe better, but differently. If you want higher performance, it may best to spend the resources on a new plane. The Spirit seems like a very good plane.

Having said all that, I've done a bunch of mods on the GL and the latest ones involves flattening the wing and incorporating ailerons. Eliminating the Polyhedral break and getting rid of the washout decreases the overall drag of the wing tremendously. There is a very noticable improvement in speed. To me it seems like the true potential of the this airfoil is revealed by eliminating these training cructhes. If you've been at this game for a few years now, you won't need those cruthes anyway. The legnedary tight circling capability (using coordinated aileron/rudder) and lift indicating ability are still intact. You may want to consider this as one of your options.

[histarter]

The GL Wing was designed with simplicity of assembly in mind as well as a wing light enough to be a floater, yet strong enough to take a beating. My first GL wing had numerous repairs. There were several incidents where portions of the leading edge had to be cut out and replaced, and once I hit a small sappling on the left outer panel wing and completely dismembered it. Even with all the added weight of repairs and epoxy and covering patches, the GL still floated like it did when it was a new build. That leads me to beleive that the amount of repairs the wing would undergo if in the hands of a learner had to be accounted for in the design as well.
IMO, the GL Wing is what makes it a gentle lady.
If you are looking for a modern GL, maybe think about using modern light weight equipment and battery to lighten her up a bit. Perhaps use solite covering on the wings and mod the rudder to be a one piece rudder with no vertical stabilizer.
That large poly wing and flat bottom airfoil is the Gentle in the GL.

A simple performance booster for the GL is to use 4 inch wide upper surface sheeting - trimming the ribs for it all the way to the wing tips! Also fill in the space between upper sheeting and main spar for the center section - and the wing become sport winchable. Also, reducing the sweep reduces the stress on the wing tip coupler. The no sag between ribs improves lift quantum more than the weight added - with drag slightly reduced. The GL will fly about the same; however, with ballast there will be no high speed wing oscillations, allowing comfortable scooting! :D

Lightening the machine is the wrong way to go since it is already too light - even for handlaunch, with modern radio equipment. To compensate for an even lighter GL (?) the profile would have to be thinned to about 8% with Phillups entry, or 6.5% without it. Just an opinion after flying and experimenting with them for 25 years. :D

[xtc]

well guys i decided on just a simple spruce spar ,s3021 with s3014 outbourd panels to simply replace my gl wing ,,really im more interested in making use of the fuze buy building this wing

im going to go real simple with the stock bends etc ,,truth is ,,after some twenty three yrs ,i have grown sick of the gentle lady [not that its not great!!]

i may go with a built up balsa [I-beam spar] capped with cf and a whole bunch of shear webs but im not sure yet

xtc

[TLyttle]

I am a huge supporer of D-tube on GLs and other "floaters"; it makes them a little faster, eliminates flutter, and toughens them up nicely. I had the idea of sanding the wing to more closely mimic the old E193, even though I didn't completely sheet it. It did change the flying characteristics, for the better. I just love an airplane that is totally consistent; it allows me to concentrate on the air, and I don't have to remember what the model will do, it just does it.

I have never used (or needed) cf, as nothing I have done with a GL that made me doubt the D-tube/capstrip construction, and more than once I have seen air between the wing and fuse on a severe (!) pullout...

[histarter]

I am a huge supporer of D-tube on GLs and other "floaters"; it makes them a little faster, eliminates flutter, and toughens them up nicely. I had the idea of sanding the wing to more closely mimic the old E193, even though I didn't completely sheet it. It did change the flying characteristics, for the better. I just love an airplane that is totally consistent; it allows me to concentrate on the air, and I don't have to remember what the model will do, it just does it.

I have never used (or needed) cf, as nothing I have done with a GL that made me doubt the D-tube/capstrip construction, and more than once I have seen air between the wing and fuse on a severe (!) pullout...
Yes, there is tremendous overkill for strength in a modern machine that is supposed to dance with lift. Some of this modern technology makes me reminisce of Cinderella going to the ball in a suit of armor, then to reduce the clang clang here and there, she went hi tech with Kevlar!! :D

[TLyttle]

Hahaaa! Now, there's an image, Cinderella in armour... or Kevlar, for that matter... The mind boggles!