> I just saw an ad for the Graupner Tipsy, it is very cute, like the TwinJet
> and the Terry... and they all seem to have the same cosmetic problem:
> Whether styrene or EPP, they have all these mold marks ans "hickies" on
the > surfaces. Some are small and look like over-scale rivets or fuel
hatches,
> except they cover the whole wing or other surface at even intervals... I
> guess they are from ejector pins. The worse ones are the size of silver
> dollars, and usually you find these un the underside of the wings, but
once
> in a while they are on the fuselage, then I want to hurl cause they look
> ug-ly there....
>
> So, can these be successfully sanded out of EPP or filled with something
that
> is not too heavy or inflexible? Is there any success covering these with a
> low-temp film?
The small marks are from the vents in the mold that allow the super heated
steam used to expand the beads to escape. The larger marks are, as you
guessed, from ejection pins, but some are from the valve(s) that allow(s)
the beads to enter the mold.
Polystyrene (EPS)
They can be sanded off with light strokes of a sharp sandpaper, about 120 or
180 grit, preferably a silicon carbide or aluminum oxide grit (sharper and
stays sharper longer). Depressions can be filled with any good model
product, Model Magic comes to mind, but be prepared for a very different
texture where you have filled - and of course a different color.
The color can be fixed by using one of the water based urethane paints used
on model race cars - expensive, but the dark colors cover VERY well and the
metallics are gorgeous.
All of this is more weight and probably more effort the most foamies are
worth - this from a guy who sanded, filled and painted a Multiplex Twin
Star. Ask Randy McCleave about it.
Polypropylene (EPP)
Sand as above, blow off or vacuum surface, spray a light coat of 3M 77, let
dry and cover with Ultracoat. LOTS easier.
Jim Porter
Bettendorf, Iowa USA
"The airplane stays up because it doesn't have the time to fall."
Orville Wright
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