REFLECTOR: Plumbing the Spar

[Tom Falls]

Phil,

The strakes will prevent twisting of the spar once installed. So the
procedure is to level and plumb the plane in all directions, then set the
wing using the wing incidence jig. Once the plane and wing are set, then
install the lower strake, which will "nail" the spar in place and prevent
it from twisting. Make sure to level and true both plane and wing again
when installing the upper strake.

Fiberglass parts will take a "set" if left deformed from their natural
shape for a long period of time. Leaving the wings on for 3 months without
the strakes installed put a torsional force on the spar which now, to some
degree, has a permanent twist in it. What this means for you now is that it
make take some force to set the wing (using the incidence jig) without
disturbing the level/plumb of the plane. The lesson we all learn, usually
the hard way, is to make sure your parts are stored in a relaxed position,
without other parts piled on top of them. For instance, I store my doors on
edge, leading edge down. That way gravity is not trying to open or close
their gentle "C" shape.

Tom


On Mon, Feb 3, 2014 at 5:23 PM, Phil Hooper <phil at hdmnet.com> wrote:

> Slow building Hooper here.  When we installed the spar everything was
> level, on the money.  The vertical line on the spar bushings was also on
> the money.  The fire wall was and remains dead nuts perfect.  The wings
> have been on for three months and we're about to mount the lower strake on
> the pilot side.  I rechecked the levels, and all is exact.  Nothing has
> moved.  *However*, in placing a level against the spare (front,
> outboard), and plumbing a line down between the spar and the wing to the
> center or the earth, it appears that the outboard part of the spar is
> twisted a bit, not in plumb, rotating aft.  My bubble level error may be
> from unevenness in the spar surface.  I am also assuming that twist will
> be induced by the weight of the wings.
>
> *Any thoughts from fellow builders wiser than I*. Thanks very much.
>
> --
>
> --
>
> *Phil Hooper*President
>  *Harvest Development & Media Inc.*
> 19851 Yorba Linda Blvd., Suite 204
> Yorba Linda, CA 92886
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> *email:* phil at hdmnet.com
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