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Old Nov 12, 2009, 09:32 PM
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EDF Jet Jam 2015, May 28-31st
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United States, MO, St Charles
Joined Nov 2002
1,825 Posts
I hear ya Kevin. Guess that means I can't do full hydraulics for the landing gear huh.

One place I will save weight is the formers. On the F-15 I ended up with 1/16 ply formers. On another thread someone suggested substituting 1/16 contest grade balsa covered with cabon veil on both sides for the plywood. They didn't have any numbers on exactly how much weight that saves so I bought some carbon tissue and tried a little experiment. I made a 6" x 6" square of contest grade balsa covered by the tissue and another square the same size out of the plywood. The plywood weighed .9 oz, the composite square weighed .3 oz.

So going with the composite will only weight 1/3 as much if I use the regular ply. Of course, there's other things to consider like toughness. It's no fun to be constantly glueing formers back together while you're building because they break if you look at them the wrong way. I cut a couple of test formers and other than at the stringer notch weak points they held up pretty good. Not as good as regular ply but close enough. Once they are glued into the stringers they should be fine.

The other concern I had was the carbon dust. Cutting regular ply in my CNC mill churns up a fine dust. I didn't want to do the same thing with the carbon. Since the balsa is sealed by the epoxy bonding the tissue to it I found I could just wipe it down with a wet cloth before cutting and that took care of the dust issue.

I was hoping to start construction tonight but the Z axis on my mill shot craps again. Probably be this weekend before I can get anything else cut.

Dan Eaton
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