Tuesday, January 19, 2010

Estimated Wing Core Weight vs. Actual

Based on an estimated foam density of 2.2 pounds / cubic foot, Solidworks estimated the foam cores would weigh 3.81 pounds. (this is the raw cores before cutting the lightening holes, prop cutout or area for electronics.)

After cutting the cores, I weighted them with a precision scale: 97.1g = .21 pounds

This is way off from the estimated weight! Assuming the real parts have the same volume as the Solidworks model, using this value to back-calculate the density of the foam, the actual foam density is 1.48 pounds / cubic foot. So, for anyone using the Blucore foam (sourced at my local Lowe's)- you may want to use value. I'd also recommend checking for yourself what your foam density is to account for mfg. variability.

I adjusted the inputs to Solidworks, and the new total all-up flying wing weight is 1.3 pounds. Besides making the aircraft lighter, it also has the welcome effect of moving the CG forward- it is now in the desired CG zone. (based on the Ritewing Demon CG location)

I also ordered Model Aircraft Aerodynamics. I'm going to do some more thourough calculations to locate the center of lift, thrust angle, etc.

In the mean time, I'm planning on doing a "quick and dirty" build up with the initial wing cores to do a rough feasibility flight test to make sure I'm on the right track.

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