Re: Re: Building Light (was: PPP-film)

From: Bruce Mccrory <brucemccrory_at_ymail.com>
Date: Mon, 3 Oct 2011 12:19:31 -0700 (PDT)

Rick P. wrote: "And, how do you guys build that light?  I am impressed."
 
Rick,
Didn't you process some of Tim Goldstein's Tru-Weight balsa that he cut, 6, 7 years ago? The rage was to find balsa that would bend and snap back to original shape, and hold hammers without bending. Once you have this outrageously strong wood with an MOE to match, you can start building really light. (Yes, some indoorists will disagree with this pre-requisite.)
 
I built an under 260mg A-ROG, using reject cuts from under 500mg EZB building efforts. Building light required a mind set, on my part, to do the task. The target weight was 300mg. Plus same for motor. It was not to be braced.
 
My weighing scale was limited to 0.01g, so I weighed mulitple copies of each part and averaged. Never new the total weight until it was finished. Even then, there was a substantial +/-, due to humidity and scale accuracy. I tested parts for about a dozen models, to get the stiffest and strongest (and lighest) parts. Once covered with y2k2, I could not breathe directly onto those parts; and many of the bones, prior to covering.
 
There were two "go-by" models I used for material sizing guides. Both were braced models: Jim Richmond's difficult to trim model, and Louka's, which I copeid. However, I sized parts based on final support of 600mg. I stabbed built wing frames into the weighing scale to make sure each half resisted 0.3g with reasonable deflection. One of the last things I did was crack the wing spars for a 3rd set of polyhedral. It strengthened the spars and reduced fatigue bending during flight. The motor tube collapsed at more than .1in-oz during the first competitive attempt, so that was a limit. The highest time was 20+ minutes at Kibbie.
 
It survived about a dozen launches, until stress fractures crippled flights.


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From: "themaxout_at_aol.com" <themaxout_at_aol.com>

MARKETPLACE
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Received on Mon Oct 03 2011 - 12:19:33 CEST