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Display Mesage #90599


Tupperware Tabectomy
Written by bdpickett on 2/10/2010 at 04:08 pm

How would I attach a new tab to the broken fairing?

Once the tab and fairing are shaped to fit together as seamlessly as possible,
they can be connected together in a couple of ways:
1. thermal welding
2. solvent welding

The first method requires a bit of practice at melting and molding plastic, and
an electric plastic welder (I made my plastic welder by brazing a flat, oval
piece of copper onto the tip of a soldering iron). I've done this before,
building up complete tabs, but its no longer my preferred method, because its
too easy to melt too much, and if you're not careful, you can introduce air
pockets or inclusions into the welded area, thus weakening the joint.

The second method uses a simple chemical solvent as the agent for fusing the
plastic pieces together. Most of the PC's plastic body panels are ABS plastic
(except for the for flexible bumper covers which are polyethylene, or PE).
Acetone, a solvent, quickly causes ABS to soften (but not PE) and form a thin
layer of liquid ABS at the surface. By coating the edges of two pieces of ABS
with acetone and letting them soften for a couple seconds, you can then press
them together and the two pieces will meld into each other; the acetone quickly
evaporates and the ABS rehardens. Once set, the two ABS pieces are now as one;
there is no dissimilar material like glue holding separate pieces together. The
fused joint is as strong as an unbroken piece of ABS because its now all the
same piece. If there are any residual gaps, these can be filled by mixing a
slurry of finely chopped ABS and acetone and then spreading the resulting melted
ABS paste into any holes or depressions, then allowing it all to set up. (Note -
its a good idea to keep some old broken ABS panels around to use as filler stock
for future repairs)

If you have a crack in ABS, but the piece isn't broken all the way through, you
can paint acetone over the cracked area, then flex that area so that acetone
flows throughout the crack by capillary action. Once the acetone flows deep into
the crack, you may see traces of melted ABS appearing on the surface as you flex
it, indicating melting of the ABS down inside. At this point, let the crack
close up, pressing it together if necessary, and then let it set up. In a matter
of minutes, the crack is welded tightly shut, often invisibly.

If you need to reinforce a repair, you can embed stainless steel mesh into a
layer of JB weld on the backside of the repair, but in most cases of solvent
welding of a simple break, this is not necessary because the welded area is as
strong as the original, unbroken piece.

In Blue Pacific's wreck last fall, a good number of ABS body panels were broken.
In those cases where I had all the plastic pieces, I rejoined them using the
solvent welding technique described above; they are as strong as original, and
in many cases, the repairs are almost invisible because the surrounding areas
were unaffected - something that couldn't be done with thermal welding! But in
the case of the fairing cowl, a great deal of plastic was lost, so this is why I
am searching for a replacement tab that I can transplant onto Blue's old
fairing. If I can't get a donor tab, then I still have the options of building
up a new tab or replacing the panel entirely.

Be seeing you,
Bruce Pickett
Federal Way, WA
'90 PC800 "Blue Pacific"
'93 ST1100 "STimulus"
'05 GL1800A "Blue's Brother"
http://bluepc.home.comcast.net


--- In ipcrc@yahoogroups.com, "pc800dork" <dokiedo@...> wrote:
>
> Not here to argue - curious how it would be easier to attach a tab? What
method would you use?
>
>

Message Thread for message #90599