2M Airfoil ??

[Double Pappa]

If you were building a 2m poly to be flown from a HS what airfoil would you use for the wing and horizontal stab? Oh this will be a pod and boom with a bagged wing.

[Bryan Quick]

AG-16 - AG19 series for the wing.

They have stab foils here too.

http://www.charlesriverrc.org/articles/drela-airfoilshop/markdrela-ag-ht-airfoils.htm

[Double Pappa]

Thanks Bryan, I am familiar with those. I am actually using them on my DLG's. I didn't think there was anything better but I thought I would ask.

[Batmanwpg]

HN 1033 (with a turbulator if it's a very light 2M.)

[Lance Prior]

E387

[atjurhs]

Sa7036

[rdeis]

What makes the AG 16-19 series better than the 41-43 for this purpose?

[Double Pappa]

I have no idea, I'm just good at building them I don't understand them at all. This is why I started this thread to try and get some kind of an understanding...... :confused: :rolleyes: :confused: :rolleyes:

I do understand some of the basics like, thin=speed, low wing load means no penetration (hey maybe that's my problem....naw not a chance), High aspect thermals well but doesn't turn well....

[Bryan Quick]

From the CRRC site:
Foil - Designed/Intended Use - Plane(s)
AG16-19 - Composite HLGs, emphasis on float; Composite light 2M poly gliders - Photon, Watson-Sidewinder, Composite Allegro

AG40-434 - Composite 3M aileron gliders - Supra

When you look at the airfoil shape, the AG40-43 are designed to be used with ailerons/flaps. There is obviously a lot more points in the top of the airfoil in the top airfoil area where the break is.

[rdeis]

I did read that, but didn't quite understand it.

Is it fair to say that the 40s trade away some lift to the 16s in favor of better speed, with the expectation of getting the lift back when needed through the added camber of flap deflection?

So the thing that makes the 16-19 better for this purpose is the lack of flaps (he specified poly in the original post), not the smaller size (2m vs 3m)?

[Soar_dude]

SD7084 has great speed range and good lift qualities soft stall IMHO

Soar Dude

[lincoln]

Actually, if you keep the tips light hi aspect ratio can turn just fine. You may need lower aspect ratio on a 2M to loft the winch line, but you're not using that. If I was doing this I'd probably just use what Mark uses on the Allegro Lite. THat's assuming I thought my building was structurally sound enough for a thin airfoil.

[Bryan Quick]

rdeis-
Your question is the heart of aircraft design.

Here ya go:

http://www.desktopaero.com/appliedaero/preface/preface.html

Here's something else to look at:

http://xflr5.sourceforge.net/xflr5.htm

When you think you have a wing, check this out:

http://web.mit.edu/drela/Public/web/avl/

Have fun-

Bryan

[AMBeck]

If you want to try something different, I've designed a series of sections just for this sort of ship. They follow the Selig SA7035-SA7038 series, but are designed to a flight Reynolds Number of 100K instead of 125K. They are all ~8.5% thick. I've flow three of the four and they work well. Not as easy to build as Mark Drela's sections since the bottom surfaces are not flat. Stalls are soft. Unless you go to excessive taper ratios you shouldn't have tip stall problems.

Drop me a line if you're interested, T_CBECK(at)Charleston.net

[histarter]

I have no idea, I'm just good at building them I don't understand them at all. This is why I started this thread to try and get some kind of an understanding...... :confused: :rolleyes: :confused: :rolleyes:

I do understand some of the basics like, thin=speed, low wing load means no penetration (hey maybe that's my problem....naw not a chance), High aspect thermals well but doesn't turn well....
Good simple phylosophy. Hi AR requires games with washout. Rather than twist the heck out a wing to tune it, I choose to turbulate the outer panels with a 40 mil turbulator, and just trim it back. Works great!

Thin low lift profiles work great for those that believe in flying extra smooth (behind the aircraft); whereas agressive thermallers that stunt fly lift (ahead of the aircraft) prefer a bit of inertia for follow through, and thus would like a bit more camber and weight - to maintain control of center airspeed. ;)