


Link
Crosscountry/GPS triangle sailplane design using XFLR5
If you were following the "XFLR5 Wing Design Help Needed" thread a while back (https://www.rcgroups.com/forums/show....php?t=1356201), the hijinks have resumed  with some interesting results  here:
http://www.rcaerotowing.com/forum/sh...?120EtaBiter This plane is being designed with flatout straightline performance as its primary design goal. Mike 






What are you allowed to have for a max gross weight in scaled contests ?
That's a big factor in the design of AMA or FAI XC ships. Mike 





Quote:
The regulations for the planes are spelledout in Section 2 of this document: http://www.eurocup.gpstriangle.net/...V3.41%20EN.pdf These ships are aerotowed or selflaunched (electric motor) so you don't have the winch launching, weight limiting issues that the FAI/F3H ships are constrained by. Mike 






Quote:
Lastly it states that under no circumstances will the weight of the glider exceed the number that is derived from a rather strange formula. There's no units in the formula so I assume the units for wing area are dm2 and the end result will be in kg. I don't know the numbers for your ship but it would be handy for you to know your max weight allowed so you can design in the strength that you want and know that you won't have your dream ship disqualified due to weight. Mike 






Quote:







I took a shot at the gross weight of your glider at 1/3.5 scale.
Per the rules cited above Gross weight = 11.5*Original Wing Area/((((Square Value of scale factor/9)1)/1.2)+1)/9 Assuming the wing area is supposed to be in Meters squared and an asw22 BL at 26.5 meter span having 16.3 meters squared wing area Assuming the scale factor of 3.5 Assuming the finish weight is in kg I get 16kg or 35 lbs for a max weight. At 14.28 ft sguared that's a 39oz/ft sq wing loading at max weight. If my assumptions above are right, that ship ought to scream when fully ballasted up, if you can climb. Mike 











Quote:
I'm building the stretched ASW22 DB (28 meter) version so I get a bit more area. All of the XFLR polars are calculated at 10 and 15 kg AUW. Mike 






Quote:
I saw that but one quick attempt using Ms Google to find the wing area didn't reveal what the area might be for the stretched version. Given your 25 foot span and 30+ oz wingloading I can imagine the excitement a ship like yours would be. I wanted to see a ball park for how much weight that you have to work with. My guess is that given the spars and nose weight that you're going to need for this size of a ship that you are likely going to be in the 25 to 30 pound empty weight to begin with even before ballast. Hopefully Santa has plenty of carbon fiber headed your way this year. Mike 



Thread Tools  
Similar Threads  
Category  Thread  Thread Starter  Forum  Replies  Last Post 
Discussion  Greg N's new 160" RE Cross Country scratch built original design  Noel Eberhardt  South Bay Soaring Society  0  Aug 14, 2009 11:48 PM 
Sold  Merlyn Cross Country Vintage Sailplane RTF  Jim OHaver  Aircraft  Sailplanes (FS/W)  10  Mar 24, 2006 09:42 PM 
Wanted  cross country sailplane  Ryan Archer  Aircraft  Sailplanes (FS/W)  7  Jul 14, 2005 05:19 PM 
Cross country glider using Drela airfoils.  Tony D.  Thermal  10  Dec 14, 2004 02:06 PM 