Subject: [harryproa] Building methods / materials
From: "Tim Barker" <>
Date: 4/9/2008, 3:40 AM

Hi Rob/ all
Visited Col Clifford today , as much to see his radial engine as have a
yack about build methods, very interesting guy and very cluey.

What are your thoughts about the alloy internal frame system , as a
person who has done quite a bit of metal fabrication it makes sense to
me and offers some build speed advantages as far as i can see . Coupled
with the idea of glassed ply skins it should be very cost effective
tough and simple to build.

For those on the site who arent familiar the method involves standard
ally extrusions and cast ally fittings which allow the frame to be
fabricated from ally without welding, it is then skinned in ply or
composite however the skin basically only has to act as a waterproof
membrane not as a structural member and also to hold the structure in
tension, light strong simple .

What are the various opinions out there.I myself am very suspiscious of
ply or timber however i know that this is a fairly basless predjudice
given modern methods and materials hence the ongoing investigation of
different methods and materials.

Coupled with the relative costs of some of the composite cores on the
market and the slowly dawning realization that using these composites
may result in a craft not much lighter (if at all) but substantially
more expensive than a craft using ply skins has certainly eroded my

Cheers Tim

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