The best way to measure the relative weights of covering material is by surface density. I use grams per square meter while the chart in the files section of this group uses milligrams per 100 square inches. The last few rolls of PPP film that I obtained from Roy White (for the Science Olympiad students) in 2007 and 2009 had a surface density of over 2 grams per square meter. This is over twice the surface density of the PPP film listed in the files section of this newsgroup (just over 0.9 g/sq.m). As a point of comparison, this increase in surface density adds about 100mg to the weight of a limited penny plane.
Ray Harlan sells super UltraFilm with a surface density of just over 1 gram per square meter. This film is fairly tough and works great LPP's. One can also use the more fragile OS film for a weight savings of a bit over 25mg on a typical LPP.
BTW, it is advisable to always weigh a section of whatever film you use when you buy a roll. There are always variances in the surface densities between rolls of the same film. These variance can make for significant weight difference in planes built for the lighter classes (such as F1D, F1L, EZB, and F1R/35cm).
Leo, Bloomington IN
--- In Indoor_Construction_at_yahoogroups.com, "Mark F1diddler" <f1diddler@...> wrote:
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> --- In Indoor_Construction_at_yahoogroups.com, Tapio Linkosalo <tapio.linkosalo@> wrote:
> >
> > On 16.9.2011 11:39, Segundo Zarate wrote:
> > > The density is the same. But .7 is heavier than .5 by 40 per cent.
> > >
> > >
> >
> > WHAT is the density?
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> Well, if you're good friends with either Alan Cohen or TG, you might ask one to weigh and measure one of their big rolls of OS. Consider the cylinder to be solid mass, use Pi to calculate volume, and subtract the center spool volume. After that, they may ask what I also wonder--why?
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Received on Sun Sep 18 2011 - 15:21:26 CEST
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:46 CET