Re: Quickie Q1 Canard and wing foam cut
David J. Gall
toggle quoted message Show quoted text
Ha-ha! Touche! Yes, of course you are right. Not owning a -18°C freezer, I was thinking of room temperature cure low-vacuum consolidation to achieve ~50% resin content, not prepreg…. I can’t wait to see your finished bird!
From: main@Q-List.groups.io <main@Q-List.groups.io> On Behalf Of Robert Cringely
Sent: Thursday, September 16, 2021 2:48 PM
Subject: Re: [Q-List] Quickie Q1 Canard and wing foam cut
That may all be true, but the nature of composite aircraft is that they are vastly overbuilt simply because building to the strength requirements alone yields a structure that is too fragile -- too susceptible to hangar rash. A ply is a ply and while it would be ideal to use 0.8 plies or 1.2 plies, in the end we use two or three. So your fiber may be superior to my fiber, but they are both good enough. Here I have locally-sourced pre-preg that has good (not great) characteristics plus the very real advantage of 45 percent resin content. Build it from your stuff and it won't be any stronger or lighter by the time it gets in service.
Thirty years ago I worked with Martin Hollmann who did the structural designs of all the Lancairs up through the L-IVP. A guy wanted to fly his Lancair 320 around the world so he asked Martin to take as much weight out of the kit as possible. This meant moving to S-glass and changing both ply schedules and core materials. We took more than 200 lbs out of that L-320. The service limits were lowered a little but it was still plenty strong. But the builder decided against it when we explained typical hangar rash could compromise his fuel tanks. REAL WORLD composite design comes down to such things and in that real world high-crystalline cellulose or flax don't make a difference.
On Thu, Sep 16, 2021 at 2:18 PM David J. Gall <David@...> wrote: