Karl and Kenny,
The Carbon Dragon wings were thicker than most gliders to reduce spar weight, improve bending stiffness and improve torsional strength and stiffness using a very light skin material (1/32 birch plywood). The thick wing also gives a higher maximum lift coefficient and lower stall speed. The flaps would reflex upward about -6 or -7 degrees (don't remember exact amount). At higher speeds, the glide ratio improved quite a bit compared to neutral flaps. Using carbon rods for the spar caps can reduce the need for thickness and a stiffer skin material like carbon can reduce the need for torsional section.
Using a thinner wing can reduce profile drag at nearly all speeds except near stall speed. The CD was optimized for climbing with some concessions for high speed performance. The Arc looks like it has a faster airfoil. I like the Arc planform, with a constant chord center section and double taper outboard. The Arc videos make it look like the coefficient of lift is high enough.
I am a design engineer with some background in aero and structures, but certainly not an expert. I just find this stuff very interesting.
Dan
From: KarlS <This email address is being protected from spambots. You need JavaScript enabled to view it.>
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Sent: Thu, March 22, 2012 4:35:20 PM
Subject: [Carbondragonbuildersandpilots] Re: CDII -fuselage
I know I am not an aerodynamist so I can't answer. There are times you need speed to escape downdraft.
Karl
--- In This email address is being protected from spambots. You need JavaScript enabled to view it., Kenny Andersen wrote:
>
> the thickness adds strength, and without knowing the air-foil at every BL there is no way to know what they are designing into the Arc wing and therefore impossible to copy (IMO)Â
> Is the CD wing need changing for some reason other than thickness? I thought that the thicker wings were stronger, and a low speed (where the CD flies) the drag wasn't so bad (and maybe more drag at a higher speed not a terribly bad thing either in this case).
