Airfoil for a HLG FF glider

[Ricardo RW]

I'm working in a school project for a HLG FF glider that must have ribs, around 30 to 40 inches of span.

What airfoil do you recommend for this kind of project?

I have checked the FF plans in other threads an have some ideas, but all the plans I've seen are with sanded balsa wings, no open structures.

Hope you can give me a hand.

Regards.

Ricardo.

[Alfredo Rubio]

Ricardo, depende que desempeño quieras, un avion lento y estable lo puedes hacer con fondo plano, como las costillas de los trainers, un avion de mayor penetracion puedes usar perfil semisimetrico o simetrico, pero sera mas rapido, 30 o 40" es un avion grande, por eso los HLG que has visto tienen alas solidas, son aviones pequeños que no necesitan gran peralte en su diseño alar, espero que esto te ayude.

Saludos desde Mexico.

A flat bottom wing means low speeds, maybe with semisimetrical orsimetrical you will got better penetration but higer speeds, HLG are small models just forthis reason you found solid wings, a 40" is a big HLG.

[7homuz]

Ricardo-
I would highly recommend a highly undercambered wing. Won't go as high if you are throwing it but it will glide forever. If you are towing it up then it will be no problem, same height as flat bottom. If you are towing it up, you might want to put more decalage on it to give it a better climb and glide. Don't give much decalage for HLG or CLG.
Thomas

[TLyttle]

I was thinking the same thing re size: are you going to use a gorilla to launch it? I've built hl up to 20", and that was more than plenty...

Built-up wings in larger sizes isn't that unusual; I remember seeing some designs, and built one in the 70s when I still had an arm. They work fine; keep it thin, use the le and te for strength instead of a spar, cover with light film. With separate ribs, airfoil recommendations won't change much, as the covering sags between ribs to completely change the airfoil anyway. Best to concentrate on light weight...

[7homuz]

TLyttle,
I find that lightness isn't really a must for HLGs and CLGs, once they are light like a rubber job they will be affected by the wind so very much. Heavier means higher altitude in launch too usually. A heavier glider typically wins over a lighter one. or so I've heard and tried.
Cheers and happy thermal hunting
Thomas Lee

[dephela]

I built a 38" span HLG last year.
It had an airfoil typical of a smaller HLG.
A solid LE of balsa, 3/8" thick at the root where it was 1 1/2" wide down to 1/4" at the tip where it was about 3/4" wide.
Ribs were stuck between this and the TE and sanded down to shape, basically a straight line.
I worked well, strong, light enough to toss, good thermalling, it would pick them up close to the ground.

This was a project to look at a specific wing construction method and give me a tool for teaching kids how to find thermals. I lost the plane while demonstrating which brought home another important point to the kids. The most important part of any plane is the name tag that the owner attaches after the plane is finished. I got the plane back!

[TLyttle]

Ain't that the truth! Everywhere I lived, the landscape was littered with models that "shouldn't" fly away, hence no name & phone. Those that I did mark showed up in some remarkable places.

Much truth in what you say, Thomas, which is why most HLG guys show up with racks of models of different weights and trims for current conditions. Great thing about HLG is that the models are CHEAP; if you don't believe me, price out some golf balls (they don't fly near as well!).

[robert harik]

Check out the free flight resources in the sticky tread at the top of the page .
Look at the model research labs link.
Most hand launch airfoils are 5-6% thick and peak 25 -35% of the chord.
Most are flat bottom but I have built a couple of undercamber designs and they flew well.
I just built a 24 and 30 inch HLG called the "Sting" both had built up wings. They were designed by Len Surtees and I bought the plans through Sting areo ( also listed in the FF resource ).
They both fly great , and I have flown them as both FF and R/C .

[Ricardo RW]

OK, that's what I'm doing:

Span 20" (50 cms)
Airfoil: AG03 thickened to 8%
EDA: 12°
Balsa Pod and a arrow shaft as a boom
Covered with tissue

The built up wing and tissue covered are rules that the teacher stated for this project.

I'll let you know the progress

[Ricardo RW]

... gran peralte en su diseño alar, espero que esto te ayude.
.

Gracias Alfredo, consideré tus sugerencias. Una duda, ¿peralte = diedro?

I'm thanking this pal, and saying I did take account of his suggestions.

Saludos desde el sur del mundo.

[Alfredo Rubio]

Ricardo, el peralte es el espesor de la ala, la distancia que hay es sus extremos superios e inferior, extrados e intrados alar, los HLG tiene el peralte de la madera u hoja de balsa que se use, generalmente es de 1/8 de pulgada, un ala con un peralte muy delgado, de otra forma puedes hacer una ala estructurada con un peralte de 8 a 10% de la cuerda alar, que es la distancia del borde de ataque (parte delantera del ala) al borde de salida ( parte trasera del ala)