Feb 21, 2013, 11:36 PM Registered User Joined May 2008 58 Posts Need Help Designing an EPP Wing I want to design a two meter wing for a scratch built RC airplane. I want to make it out of expanded polypropylene. So I calculated the weight of a 200 cm wingspan, 20 cm wing chord NACA 2412 airfoil made of solid EPP wing (not including any internal structure) with no wing taper and calculated a weight of 8.6 kg (18.9 lbs). I never realized EPP was this heavy. Has anyone else designed and built wings out of EPP? Is there any way to get the weight down? Thanks for the help.
 Feb 22, 2013, 01:19 AM “Do it Right The First Time!” United States, MN, Hermantown Joined Dec 2008 3,436 Posts I think you maybe looking at the wrong foam for a wing. I weighed a piece of Extruded Polystyrene (owens corning pink foam) 2.25" x2.0' x 21.5" = 97.88 cuin@ 1.385oz Figuring 1" thick airfoil, your 632cu/sq in, should weigh 6.55oz. BTW, lots of people have/do use this for there wings. You are correct on the weight, darn heavy! wiki.answers.com The density of polypropylene depends on whether it is crystalline or amorphous. I'll give both numbers: Amorphous: 0.85 g/cm3 Crystalline: 0.95 g/cm3 1 cm3 = 3.53147 x 10-5 cubic feet or 1 foot3 = 28316.847 cm3 So 1 ft3 of polypropylene weighs 24,069.32 g and 26,901.00 g for amorphous and crystalline respectively. That's also equal to 24.069 kg or 26.901 kg 1 kg = 2.204622 pounds So 1 ft3 of amorphous polypropylene weighs: 53.064 lbs and 1 ft3 of crystalline polypropylene weighs: 59.307 lbs From this site: http://www.builderswebsource.com/_discBT/00000d75.htm Insulation ... ...Extruded Polystyrene 1.8 pcf ...Expanded Polystyrene (EPS) 1.0 - 4.0 pcf, depending on density (0.9 to 2.19 pcf typ range) ...Polyurethane 1.5 pcf Weight per Unit pcf = pounds per cubic foot pcy = pounds per cubic yard plf = pounds per lineal foot psf = pounds per square foot Last edited by CoolerByTheLake; Feb 22, 2013 at 01:36 AM.
 Feb 22, 2013, 10:57 AM An itch?. Scratch build. South Wales U.K. Joined Mar 2003 11,667 Posts Just had a quick look in the Foamies(Scratchbuilt) forum for any big EPP models, found a C-130, (long narrow 1968mm span wing) in EPP. C-130 Hercules EPP Never tried EPP, my preference is for balsa or Depron foam.