I'm building a Top Flite Cessna 182, 81" wingspan, from the kit. This is
only my second plane so I'm still quite new to building. The wing is done
and the fuse is nearly done, so I need to decide between painting or
covering it soon. For those not familiar with this plane, it is completely
sheeted with 1/16" balsa on the wing and tail and 3/32" on the fuse. My
covering experience is limited to covering one 40 size trainer with
monocote, which turned out pretty good.
I've been following the thread started earlier today about prepping balsa
for paint and it seems that it is more than just sealing the balsa and then
applying the paint. Question: Is the step of applying tissue or a
lightweight cloth necessary? If so, what is the purpose, strength?, smooth
finish? or ????
My next question: If I decide to cover it with monocote, how should I prep
the balsa surface? Do I just need to clean it well, or does it need to be
sealed?, How and with what?
Last question: Can anyone tell me just what the difference is between
Ultracote, Monocote, Econocote, xyz-cote. I've asked guys at the club and
everyone seems to have a different answer.
Thanks for bearing with me here, I've got a lot of time into this plane and
I don' want to screw it up now.
Nearly all kits are designed with the covering adding significant strength
to the airframe. Even fully sheeted surfaces are not nearly as strong
uncovered. Paint over bare balsa WILL crack eventually without some
supporting cloth or tissue underneath. It will also be very difficult to
fill in the grain without adding a lot of unnecessary weight.
The Cessna (full scale) is an aluminum skinned plane. The models can be
covered in chrome or aluminum Ultracote and trimmed with color and look
great. I don't use Monokote for this because it looks too shiny and is more
prone to producing bubbles when overlapping colors.
I don't paint, so I can't give you any advice about painting. But I can
say a thing or two about polyester film.
Monokote: My favorite covering. I have tried the rest and always came
back to Monokote. I have a large assortment of colors on hand, and
that's what I use. The advantages are that the colors (except different
shades of red other than missile red) are opaque, you can write on the
balsa with ball point pen and it doesn't bleed into the monokote, you
stick it down once and it stays there, it is very strong and tear proof,
and it has a definite temperature range for sticking and shrinking.
Disadvantages: it looks like shiny plastic instead of a real plane, but
all the films do. If you use metallics sometimes they don't stick as
well, and the pigment bleeds out of the edges. But who can afford
metallics? The fluorescent colors fade in a matter of days, but they
are as ugly as a mud fence to start with, so why use them?
Ultracote/Oracover: Good stuff that pulls around compound curves like
nobody's business and is strong like Monokote. It has a lower
temperature adhesive that will allow it to go straight on bare foam.
Disadvantages: The adhesive isn't permanent, which means that you stick
it down around the edges and then apply heat for shrinking and the edges
will come undone and the whole panel will pull together in the middle.
I hate that. The colors are not opaque, meaning that you can see wood
grain through them, and if you have any ink on the wood it will bleed
into the pigment. This isn't usually a problem, but it happened to me
once or twice and I found it irritating. Some say that having adhesive
that will release with heat is an advantage, but I say put it where you
want it, stick it down, and it had better stay there. This is
particularly bad if you use dark colors and put the plane in the sun on
a hot day. I hate it when I take a pretty plane out to the field and
the covering sags right off of it. Also, they used to sell a product
called Ultracote Plus. I don't know if it is still available. I hated
that stuff. It was sticky on one side, which meant that it stuck to
itself and everything else before I could get it on the airplane. It
was a really bad idea.
Other brands of cheap-o-kote: Balsa USA, Hobby Lobby, etc, have sold
various brands of cheaper covering that are a real bargain for the low
budget model airplane builder. However, most of these products will
tear if you get a nick in the edge and won't stop tearing until you
reach the opposite side. Also, if you are unfortunate enough to peel
the plastic off the sticky side and have the covering fold over and
touch itself, you might as well just throw the piece away because you
will never get it to come apart without ripping it to shreds. And there
usually isn't much of a color assortment. But these products generally
pull around curves better than any of the more expensive brands. And
when you stick everything down the seams disappear because the film is
thinner than the more expensive brands. Also, these films usually have
lower temperature adhesive that will stick on foam. I know of at least
one brand, Econokote, that is NOT fuel proof. I am pretty sure that
Towerkote isn't either.
If you were building combat planes with a short lifespan, I would
wholeheartedly recommend the cheap stuff. But if you want to have a
plane that comes out to the field every summer for 15 years you probably
ought to put Monokote on it.
Not very many modern 182's with a polished bare aluminum finish
around. In fact none are that way from the factory. I think that
model has fiberglass wingtips which would be difficult to cover. If
using the kit color which is probably white and would match white
Monokote. If so I would cover with white Monokote, then trim to match
a factory trim scheme. If the wing tips need to be painted then I
would use Ultracote and either Ultracote paint or a differant color
paint for the wingtip. You can prep it with Balsarite if you like, but
not really necessary. If you decide to paint the polyurethanes do not
tend to crack, that is why they work so well on fabric. The main
reason to use silkspan or tissue is to reduce the amount of primer
which adds a lot of weight, it does not add significant strength. If
the instructions do not say that it must have either plastic or fabric
covering, or be fiberglassed before painting, then the wing is strong
enough to be flown with just the bare wood, though it would soak up a
lot of oil that way.
I usually use Balsarite on the bare balsa before covering with monocote.
Balsarite will seal the wood without adding much weight. Then I sand the
balsa, with fine paper, just enough to smooth it down. Balsarite, when it
dries (right away), will harden any "hairy" wood, making it easy to sand.
Then I apply the covering. Here in Kansas, where you can be flying in 100
degree, 99% humidity in the morning, and 45 degrees, 18% humidity that same
afternoon, covering develops wrinkles. Balsarite keeps the covering where
it's supposed to be, no matter what.
I trim the covering with real, old fashioned safety razor blades, mounted in
my own home-made holder. The hobby blades and paint scraper blades as sold
in hardware stores/hobby shops, are just too dull to do a good job.
If you are adding trim over the film, wet the surface, lay down the trim,
squeegee out the air and water with, say, a credit card or cotton cloth, and
then heat it. This eliminates air bubbles if done carefully. Practice this
technique a little. You can also use a small diameter sewing needle to
puncture a few holes in the covering film, to help insure no air bubbles.
opinions will vary, JK