Re: Plastic Covering for A-6 Rule Change Proposal

From: <wdgowen_at_gmail.com>
Date: 04 Sep 2014 07:51:55 -0700

I was asked what the weight difference would be for an A6 model with film vs. CP. Of course there are many variables but here are some representative numbers:
 
 For a "typical" A6 with 50si of covered area (a guess):

Ultrafilm (1.35mg/si) vs. best CP (3.6mg/si) - 113mg
 Ultrafilm (1.35mg/si) vs. good CP (5.2mg/si) - 193mg
 OS film vs. best CP (3.6mg/si) - 150mg
 OS film vs. good CP (5.2mg/si) - 230mg
 
 An extreme example would be for someone building my model with normal CP vs. OS film:
 Normal CP (6.1mg/si) - OS film (.6mg/si) x 63si = 347mg

Besides the better chances for a beginning indoor flyer to make the minimum weight, I think film covering also increases the possibility that established competitors would try the class. A few here and in private conversations have expressed their reluctance to build a model that has to be covered in paper.

My methods of stabilizing CP have worked fairly well but I still have situations where I take a model out of the box and find a huge spanwise bump in the covering which effectively destroys the airfoil. My only successful fix has been to add more ribs to straighten out the covering. This adds more weight to models that are already overweight. I would love to not have this problem. I would also love to not have to make spars and posts out of sub 4# wood that breaks and warps.
Received on Thu Sep 04 2014 - 07:51:56 CEST