Duncan,
That's excellent info - many thanks. I've copied the list as I think it will
most definitely be of interest to some.
Kind regards,
Jeremy
Jeremy Davey
Europa Monowheel 537M G-EZZA
-----Original Message-----
From: Ami McFadyean [mailto:ami@mcfadyean.freeserve.co.uk]
Subject: Re: Europa-List: filler
Jeremy,
My standard mix was 17ml of epoxy (which was 19g or 1 pump of the Michael
Engineering resin pump) + 15ml of fume silica (Aerosil) + 17ml of Q-cell +
120ml of Expancel.
The Expancel was measured in a cup of known capacity with the 'powder'
lightly packed in to the cup; this light compaction was merely to remove
large air voids between the clumps of raw Expancel.
This mixes up like 'breadcrumbs' and looks too dry to go on. But if the
mixing process is energetically extended there comes a point where the whole
lot seems to suddenly plasticise into a doughy consistency.
The problem with all this is that there is no specific lexicon to describe
what is happening; hence adjectives borrowed from the baking industry!.
The mix has a density of 0.316g/cc, which is lighter than Superfill's 0.44
g/cc. But still ten times heavier than blue foam! In case you are tempted to
let your final primer-filler do the filling, the latter weighs 2.1g/cc.
I would not go with such a light mix again. Try leaving out the Q-cell as a
start. There were times when I thought I could push this mix leaner, only to
come unstuck on one occasion resulting in stripping the filler off and
starting again. Also, with the ultra lean mixes, the homogenisation of the
mix (despite appearances and mixing for ages) is not always perfect,
resulting in some dry spots that wouldn't harden properly.
Another thing is that the lightweight filler scratches quite easily when
sanded. Those scratches are then by default filled with primer-filler, which
is much heavier than even epoxy. So might as well add some extra epoxy into
the filler to start with!
So I reckon the above recipe is as lean as you can go.
One other thing you may find useful, when sanding hte above mix, the
underlying substrate becomes just visible when the filler is 1/4 mm thick.
Hope this helps.
Duncan.
PS publish this if you think it may help others.
----- Original Message -----
From: "Jeremy Davey" <jeremycrdavey@btinternet.com>
Subject: FW: Europa-List: filler
> Duncan,
>
> I am indeed most interested in your ratios!
>
> Cheers,
> Jeremy
>
> Jeremy Davey
>
> Europa Monowheel 537M G-EZZA
>
>
> -----Original Message-----
> From: owner-europa-list-server@matronics.com
> [mailto:owner-europa-list-server@matronics.com] On Behalf Of Ami McFadyean
> Sent: 06 November 2003 20:03
> To: europa-list@matronics.com
> Subject: Re: Europa-List: filler
>
> <ami@mcfadyean.freeserve.co.uk>
>
> ---- Original Message -----
> From: "Jeremy Davey" <jeremycrdavey@btinternet.com>
>
> > Has anyone who's used Expancel correctly done any experiments to work
out
> > the ideal ratio of filler to resin by weight?
> >
>
> Depends how much of a struggle you want to accept in putting on a
> lightweight filler, or struggle in sanding-off a heavy weight filler.
>
> The other problem with lightweight filler (ie the stuff made with
Expancel)
> is that it marks very easily (and permanently) in service. I wouldn't do
> mine so light again.
>
> A tip for mixing hte lightweight option is to pound it vigorously for
> several minutes. There comes a point when the mix goes from appearing too
> dry to a plastic putty-like consistency, which is much easier to spread.
The
> addition of fume silica helps this greatly. Let me know if you're
interested
> in the ratios I used (which might answer your original question!).
>
>
> Duncan McF.
>
>
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