Re: Quickie Q1 Canard and wing foam cut

David J. Gall

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: <> 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:

Flax is inferior to highly-crystalline cellulose fiber for exactly the reasons mentioned below. Highly-crystalline cellulose fiber is nearly equivalent to E-glass in all respects except weight -- glass is much heavier -- and in sanding -- glass is itchier. Highly-crystalline cellulose fiber is mechanically derived from what would otherwise be wastes generated in lumber processing industries and is marketed worldwide under the trade name BioMid by Gordon Shank consulting. The roving is used as twine (you know it must be inexpensive!) in the hydroponics industry so availability will persist for a long time for numerous reasons. BioMid is available woven into cloth in the US from Absecon Mills and in Europe from FRP Services & Co (France).

-----Original Message-----
From: <> On Behalf Of Rob de Bie
Sent: Thursday, September 16, 2021 11:04 AM
Subject: Re: [Q-List] Quickie Q1 Canard and wing foam cut

Bob, when you mentioned flax fibers I peaked my ears! I've worked a bit with flax composites some 15 years ago. Is the material mature enough to use in an aircraft? I remember problems like no suitable sizings being available to optimize fiber-resin adhesion, moisture content during curing leading to degraded resin adhesion & quality, and moisture absorption during use leading to lower properties.
Sounded to me like it would a lot more development before it would be safe to fly. But it was 15 years ago.

I also remember reading in an eighties issue of 'Homebuilt aircraft' magazine that hot-wet test specimens could be good indicator of the longer-term quality of the fiber-resin adhesion. Sounded reasonable to me.


On 16 Sep 2021 17:39, Robert Cringely wrote:
> Thanks! I’m using a no-name 680cc aluminum air-cooled V2 diesel to
> which I am adding a tiny turbocharger and intercooler. What’s changed
> since you looked is probably direct injection. Engine weight is around
> 50kg. I’m adding a belt drive from Ace Redrives in India. It’s 1:1
> because I don’t need a slower prop but I do need to raise the thrust
> line and to isolate the prop loads from the mystery metal Chinese
> crankshaft. I’m probably a year from flying, by which time I will have
> replaced most of the airframe with vacuum-bagged pre-preg. It’s not carbon or glass — it’s flax fiber, which fits right between e-glass and s-glass in performance, with a little Coremat added for stiffness.
> Bob
> On Thu, Sep 16, 2021 at 8:16 AM Hot Wings via
> <> < <>> wrote:
>     What diesel engine are you considering?  I looked at the V-twin Chinese diesels more than a
>     decade ago and discarded the idea as not practical.
>     There are some interesting marine 2 stroke diesel development projects nearing market
>     introduction that may provide some of us with a 100LL option.
>     Look up Alan Thayer (sp) in the archives.  He had an LS-1 canard designed using Graphlite
>     rods.Attached is a *.ZIP file of some of his work.  Graphlite is no longer a practical source of
>     carbon rods for us as they are quite unwilling to sell rolled lengths of material.  The Chinese
>     suppliers are willing and at a considerable savings in cost.  Preliminary tests have indicated
>     the quality/strength is as good as the US sourced material.

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