When you cover with Polyspan, don't forget to have the
shiny side out. The other side is fuzzy and the dope tends to raise the fuzz.
Here is another pretty good bit on Polyspan:
I have been doping 2 small pieces of each roll - one on top/outside of the roll, the other on the inside
- just to make sure I get the smooth side out! You will NEVER get the fuzzy side smooth - might be a
good argument though to try that on the top of a wing. Cleanup won't be much fun, but the fuzz may make a good turbulator!
Also - on overlaps, try to avoid sanding until you have 5-6 coats of dope.
If you sand to early or too vigorously, you will expose fuzzy fibers that also
are hard to deal with. I've had more luck just using a Monocoat iron to
make overlaps lay down better. Oh yes - on a square corner, use the iron to
crease the Polyspan over the corner before using thinner or dope to adhere it -
makes much nicer corners. You can also use the iron just before the thinner/dope dries.
BTW: Larry Davidson was selling really wide rolls of Polyspan at Las Vegas - you might contact him about
Have any of you folks use water based poly to seal the Polyspan? I have used it with great
success on polyester fabric (Polyfiber) and assume ??? it will work on Polyspan
- correct? Can not use the stinky stuff any more due to my respiratory problems.
The following is an excerpt from an article I
wrote a few years ago entitled A Weight Comparison of some
Lightweight Coverings. I compared the weights of the bare frameworks and of the finished covering
the wings of 16 of my aircraft. However only two of my aircraft in the report were covered with Polyspan.
(The yellow and black Lanzo Bomber that Dave Harding now flies was one of them. The other coverings in my
report were Micafilm, Litespan, and Ultracote Lite). I found the average weights of the finished Polyspan
coverings (complete with dope, etc.)to be 3.67 grams/100 sq.in. However this figure varies quite a
bit depending on the cement used for covering, and the number of coats of dope. I usually found I needed 4 or
5 coats of Nitrate to fill the grain before adding colour.
Try Polyspan--You'll love it--I want to add a couple things here that
havn't been covered--If you're looking for that translucent finish that you
got with silkspan, put the first three of four coats of dope on quite thin--I
use 60% dope, 40% thinner--Use a foam brush to dope it--I use a 2 inch
version--The foam brush will swell up from the thinner in the dope so only dip the
brush about 3/4 inch into your dope to charge the brush--Brush in one direction
only always picking up the brush in the previous stroke that you laid down--To
make a neat job of going around the trailing edge of your wing, use your
sealing iron to fold the polyspan around the edge--It will snuggle it right in
place before you attatch it--You can go around some amazing compound curves with
it also--Lift the polyspan above the surface and apply your sealing iron in
the middle of the surface--As you pull from the edge, you will feel it stretch
as it's heated and at that point pull it down over the compound curve--A little
trial and error and you'll get the hang of it--I cover the tops of my wings
in one piece right over the wingtips with the stuff completely wrinkle
free--Using a heat gun or sealing iron, you can shrink out some terrible wrinkles if
need be--I also recommend doing your shrinking before you do any doping--I dope
my frame first with three coats of pretty thick dope and sand with 320
paper--I brush a mix of 75%thinner and 25% dope through the Polyspan to attach
it--One more thing, Polyspan has a grain of sorts--It runs along the long side
Hank on the Bay
No one has yet mentioned using UHU purple glue stick. I have
been using it for about 10 years, ever since my late buddy Gerry Lafreniere used it and
wrote an article about its use back in the February/95 issue of SAM 86
He used it for 1/2A models, for gluing wind screens, as well as for large
and small rubber models. It's easy to use, has no smell, and although it
sticks well, it's easy to remove with a little moisture or spit. It is
water soluble, but after doping, I have never had a problem with high
humidity or even a little rain. With this caution, I would never use it for
an outdoor model with un-doped tissue.
Any other users out there?
As for the shiny side, Ed, that's a good test. I've always used one of my
work bench lamps to look at the polyspan at an angle.
I have found that edges of Polyspan can be easily turned
over using an ultra fast drying cellulose type glue . I use UHU Hart available from Hobby Lobby.
It is expensive but very useful for silk, silkspan and Polyspan work.
Pressing down the UHU through the Polyspan with a wet finger works also. I use spit.
From: Edwin D. Lamb
Very good point Jim! And it is really hard to see which
side is more shiny. One way to be certain is to take a piece of velcro (the hook side) and scrub it on
a scrap piece of the Polyspan. Do that on both sides of the scrap and the hooks of the
velcro will lift some of the fuzz on one side, not the other. That side goes down, the
other(shiny) side goes up.