On Mon, 15 Aug 2005 18:03:46 -0400, Michael Horowitz
wrote:

Just thinking into the future at the moment.

I know nothing about sandblasting except you can apparently use
different abrasive material i.e. glass beads, sand, nut shells (?)

An aircraft I'm looking at has some rust at the tail cone. If I
purchase it, I'd like to remove the rust and prime it.

Assume my A&P says the tubing is structurally intact, but pits are
evident.

Can someone point me to a reference that talks about what I need to
sandblast the area, what abrasive to use, or if the area is small,
some other method of rust removal? Other considerations?

Sorry, but I know only enough to ask a general question at this point
- Mike

Mike I have beadblasted the rust from my Auster J1B fuselage
successfully.

of the rust removal techniques beadblasting is by far and away the
fastest. it is acceptable for aircraft use because it hammers the
surface minutely and puts it into compression which is good for
fatigue resistance.

I used a cheap modified taiwanese beadblasting handle from an
automotive discount house. as you use the handle it will wear from the
passage of beads and all the worn off particles get blasted onto your
aeroplane. this is not so critical if it is a steel tube fuselage but
is vitally important if you are treating aluminium. my mod was to
replace the nozzle with either one made from teflon rod or stainless
steel rod which was machined on my lathe.(basically bought in the
diameter required and drilled 5/16")

ballotini (glass beads) are inert and have rounded surfaces which make
them perfect for aviation use. the rounded hammering is perfect for
fatigue resistance. I have used one 25lb bag of beads for the last 4
years. I just keep on sweeping them up, pass them through a trash
sieve made from flywire and stick them back in the bucket.

the handle will use, I estimate, 60 cubic feet per minute of air. on
my 13cufm compressor I spend probably 2/3rds of the time waiting for a
pump up. hiring a commercial trailer mounted diesel compressor in
australia works out to be $aus120 a day. it is worth it since you get
continuous pressure air and can get the job done in a day.

most people go overboard on the beadblasting cabinet. a drape of the
flimsiest plastic painting drop sheet is entirely adequate as a bead
stopping backdrop. I've used one sheet, which would be shopping bag
thickness, for so many years that uv deterioration is now making it
tear. a 6ft x 6ft plastic tube frame hung from the ceiling with paint
drop sheets taped on to it and a plastic tarp on the floor is what I
use. you just position the job, then walk around twisting up the seams
to seal them and then clip them. a few 5.00x5 tyres to weight down the
bottom edges and you are away.

protective gear is needed. my face mask is an arc welding head mask
with the glass replaced by a piece of perspex which has some
transparent plastic sheet over it. the sheet will go cloudy from the
bounceback of the beads and it is easy to replace it every few hours.
overalls, and a head cover made from teeshirt material. I wear safety
glasses and breathing protection under the mask. (the beadblasted off
crud becomes a very fine airborne powder)
and some vinyl gauntlet gloves. all very agricultural but it works for
me.

dry compressed air is essential to prevent rust being set off again.
there are filters available which do a good trapping job. a friend
uses two filters with a hoselength between them and gets better
results than I do with one filter.
when you have the surface beaded off degrease it with a solvent then
prime it straight away.(within an hour)

pressures used vary from 60psi for a *very* mild action to 150psi
which will clean off the heaviest rust in a millionth of a second and
will erode surfaces if you arent careful. 100-120psi is a good
starting pressure range.
soft stuff like a stray smear of silicone can be beaded for hours
without a shred of effect. I found that a pocket knife with a
reasonably blunt blade was of great assistance in scraping this sort
of crud off.

I think that that is a reasonable synopsis. I have probably left out
mountains but it isnt hard. just remember that you are working with
aircraft and sharp grit is a no no because of fatigue considerations.
I have used dry water washed rounded quartz sand that was cleaned by
rainfall quite effectively as well.

have a shot at it on a piece of spring first.
Stealth Pilot