Hi
I am making Squirrel rubber powered airplane. Since balsa is not available I am using other material for spars in tissue version. The problem is that the stick (some plant stem used in kulfi ice cream here) doesnt come in 30cm or more length...max 25cm that I have found till now. That causes problems in joining the spiltted round stick and causes warps and weak joints. For ease of construction and easy availability, I am trying foam plates now which has trade offs according to thickness.
If I use 1mm foam plate then that requires spars at wing LE and TE...another thin stick that I use for spar is dense and is adding weight, though not much I guess. See pic. If I dont want to use spars at all, then I have to use thicker and stiffer 2mm foam plate.
How much weight difference is there between 1mm and 2mm fom plate? What is the material these foam plates are mde of....XPS, Depron, EPP, EPS, Polystyrene, Styrofom..there are many materials that I saw online but which is used in foam plate and what is its density? Wikipedia entry for polystyrene gives a density of 0.96-1.04 g/cm3...if that is the material and figures are correct, then I am adding a lot of weight by switching to 2mm foam....just the 1mm wing of 30*5*0.1cm3 might weigh more than 15g with spars, shim, wing hold-down stick and glue...this would be heavier than the entire tissue airplane (John OZPAF's plan said that tissue version weighs around 9.5-10g).
If the material is depron and the figures by RCfoam can be used as a rough reference for the foam plate material here, then for 1mm depron density is 0.088g/cm3 which is substantially less than the polystyrene density in wikipedia. So switching to 2mm too wont be a big addition.
http://www.rcfoam.com/depron-and-epp-foam-density-a-depron_epp_density.html
