Cheers,
On the subject of sanding and 'substrate' I think we have to
consider hwat type of surface we're discussing. I've been scuffing old
epoxy-glass layers, fuselage new outer surfaces, long-open peelply and
alumin(i)um flats at various times. I started with sixty, but soon
discovered I was ripping and tearing. then I read somewhere that Boeing says
"if water will stay on it, it's ready for sticking" - or words to that
effect.
Since then I've treated several different tests surfaces (as
above) with a number of different grades of abraders and frankly I found the
BiD that sticks the best is to ANY of the surfaces that have been treated
within the hour to a palm-sander from 120 to 320 grit, smeared very lightly
with epoxy compound and applied with pressure, but not a lot (weights). The
latter were the hardest to pull apart after 6 hours, two days and two weeks.
Much as I dismiss Boeing - the engineers who build aircraft for
profit - I'm going with the water theory.
My CAN$0.02
Ferg
----- Original Message -----
From: <jeremycrdavey@btinternet.com>
Subject: Re: Surface area increase with sanding 41.4%
> I'd be most interested to know what other builders have used. I've used 60
> grit for the scuff sanding inside my XS wings, but have noticed that the
> sanding marks adjacent to where the rib-to-spar joints have been made
during
> manufacture appear courser - 40 grit?
>
> I find myself constantly torn between the risk of not sanding enough (and
> getting a poor bond) and overdoing it (and damaging the substrate).
>
> Regards,
> Jeremy
>
|