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No,
you don't have spots before your eyes, the title is Gudy 870
Adhesive! It is the name of a product which has been
around for some time, and which is not generally known
about. I have been trying it for the past 6 months and I
think you PSS modellers might well find it interesting.
The
product is a high strength acrylic-ester adhesive film, made
by the German firm of Neschen UK. It's main use is in
the industrial photographic industry, for the permanent
mounting of photos onto card backing. The film itself is
pure adhesive, rolled onto a silicon paper backing. For
this reason it is extremely lightweight, somewhere in the
region of 5gm/sq metre, due to the fact that it is only 40
microns thick. OK - so what use is it to you?
Well,
it is really excellent for sticking veneer to foam -
permanently! I have tested it on scraps of white
polystyrene foam block. After 48 hours curing time, any attempt
to break the 2 blocks apart inevitably results in the foam
breaking, and not the glue joint. In addition, I have
built a 50" span wing for a 3.5cc trainer, using the
Clark Y section. This was placed on the work surface so
that half of one panel overhung the edge. The tip was
then loaded with 7kg of scrap metal, which is a fair amount of
weight. There was no obvious bending after 15
minutes. The wing was made of white foam and veneer,
stuck in place with Gudy 870.
Now,
we all know that one of the things that adds a lot of weight
when building with foam is the adhesive used to glue the
veneer. Reducing this makes the smaller models better
flyers. While it is probably an inappropriate example,
think of this - If Simon Cocker had built the wing of his
monster B-52 using Gudy 870 he would have added just 25 grams
in adhesive! How much did he use in fact? With a
model in the 50" span range, the weight of adhesive would
be almost non-existent, and that is only taking the wing into
account.
In
use, Gudy 870 is simplicity itself. Sand the veneer and
the foam to a fine finish. Brush or vacuum both - any
dust will prevent a good joint. Place the veneer on the
film, press down firmly and then cut round the outline with a
good modelling knife. Turn it over, and press the whole
surface firmly with the fingertips. If you have a heat
gun, a quick blast will help. Now pull off the silicon
backing paper, turn it over, place on the foam and press all
over. And that's it!! Because of its chemical
formulation, it will take about 48 hours to achieve 80% of its
final adhesive strength, but in fact it is so strong that it
can be used straight away. And, unlike some glues, it
ages extremely well.
However,
that is not the whole story, Gudy 870 has another property
which many of you will probably find interesting. We all
know what happens when you are building a fuselage or nose
block made up by gluing blocks of foam together. When it
comes to the hot wire cutter bit, the glue joint is a pig to
cut, especially epoxy. Well, the cutter goes through the
Gudy 870 joint as if it wasn't there! In addition, if
you sand the joint, there is no noticeable difference in the
joint and the pure foam either side of it. In fact, I
have made several cowls for power planes using this method,
and now I wouldn't use anything else.
A
further example, if necessary, would be the .60 engined power
plane I have recently built, using Gudy 870 to stick all the
ply doublers to the fuselage sides. The plane has
already had a dozen flights, and there is no sign of any
weakness. If the stuff will take the vibration, it must
be good on a soarer!
One last thing - PRICE. A roll of Gudy 870 32.5ft x 2ft
(10m x 60cm) will set you back the very reasonable sum of £25
(at the time of writing). Compare this to the surface
area you could cover with your usual adhesive. It may be
a little more expensive, but that is not the point - you are
not doing it for the money saving. If you want to get
hold of some Gudy 870, the address is :
|
Neschen
UK
Emerald
Way
Stone
Business Park
Stone
STAFFS
England
ST15
0SR
Tel
: 01785 610110
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