Author: "rvatorprr" <prichar@...> Time: Sun Feb 15, 2004 3:36 am PST Link
I've just started the empennage, so I have a question concerning
acceptable surface irregularities on aluminum structural parts.
The aft HS spar reinforcement bars, HS-609PP, are to have a satin
finish in order to ensure no stress risers. However, after initial
grinding with the scrotchbrite surface prep wheels, many pits and
tool marks are still visible.
How much material should be removed to ensure all tool marks and pits
are gone? These pits and scratches are small, but cover a wide area.
What is the preferred procedure to get rid of them? More die grinder
action covering the whole part to ensure even material thickness, or
localized grinding?
Author: "Phil" <pjanderton@...> Time: Sun Feb 15, 2004 5:45 am PST Link
--- In RV7and7A@yahoogroups.com, "rvatorprr" <prichar@m...> wrote:
> I've just started the empennage, so I have a question concerning
> acceptable surface irregularities on aluminum structural parts.
>
> The aft HS spar reinforcement bars, HS-609PP, are to have a satin
> finish in order to ensure no stress risers. However, after initial
> grinding with the scrotchbrite surface prep wheels, many pits and
> tool marks are still visible.
The HS-609PP reinforcement bars do not have the mirror finish of the
Alclad components (e.g. the VS doubler (VS 808PP?) Mine also had a
few pits, scratches and burr marks, and othe builders have reported
the same.
I would not be too keen on grinding away a significant thickness
just to get a few pits out. I used a Scotchbrite pad and a little
elbow grease to smooth the surface where I could. The edges, of
course you smooth with the Scotchbrite wheels.
I think it's OK as long as the component is structurally sound (no
obvious cracks or really deep sharp pits).
It is much more important to make sure you treat these components
against corrosion, as they are not Alclad.
Phil Anderton
Sydney, Aus
Emp, HS finished
http://members.optusnet.com.au/rv7/