film cover

When we eliminate bubbles in film covering by pricking holes to let the trapped air escape, do the holes subsequently let fuel/exhaust residue through to soak into the model? I.e. is it still fuel proof?

>When we eliminate bubbles in film covering by pricking holes
>to let the trapped air escape, do the holes subsequently let
>fuel/exhaust residue through to soak into the model? I.e. is
>it still fuel proof?

Ian,

Not in my experience, although I preclude this possibility as much as possible before film goes on the model, rarely have to puncture a bubble.

It seems as if ironing with some pressure "kinda" seals the hole. Or maybe there is enough heat used to sorta heat and then squish the glue into sealing hole.

I'm about to do my very first plastic film covering job on a gas model plane. I'm not only concerned about "pin pricks", but those little places where the film covering doesn't quite overlap in and around the engine compartment.

For laughs, I'm doing a Goldberg/Comet Sailplane using something called Ultracote. The instructions caution that you can't spray nitrate or butyrate over the film to seal all those little places where oil can migrate.

My only other option is to use silk, at about $50- for the silk and a like amount for dope for it.

With my usual luck, the plane won't last long enough for oil to seep into the innards!

>I'm about to do my very first plastic film covering job on a
>gas model plane. I'm not only concerned about "pin pricks",
>but those little places where the film covering doesn't
>quite overlap in and around the engine compartment.
>
>For laughs, I'm doing a Goldberg/Comet Sailplane using
>something called Ultracote. The instructions caution that
>you can't spray nitrate or butyrate over the film to seal
>all those little places where oil can migrate.

You ARE brushing thinned epoxy inside the engine/tank areas, aren't you? Why not spray Rustoleum in these areas rather than try to film them? Just a thought . . .

LAST EDITED ON Nov-23-04 AT 00:05 AM (CST)
 
"I'm not only concerned about "pin pricks", but those little places where the film covering doesn't quite overlap in and around the engine compartment."

Floyd,
All my recent planes have been covered with either monocote or ultracote. I use "MINWAX Wipe-On Poly Clear Gloss" polyurethane bought at Home Depot to paint the engine/tank areas of my fuel powered planes. It does a great job of adhering to and sealing both the edges of the film and any bare wood. Regarding longevity, I have a 4 year old SIG Banshee finished this way with 432 flights (47.4 hours flight time) that doesn't show any sign of fuel soaking.
I used to have a problem with film edges and trim/striping coming loose and flapping in the breeze. But I cured this problem by using this same Minwax poly to seal the film seams and any trim/striping. The only negative I've found is that the poly will yellow slightly over time and be noticeable on white covering if applied too thick. I use a Q-Tip to apply a very thin film over trim/seam edges and a brush for a thicker film on bare wood. Must confess I saw this tip in an RC Modeler magazine.
Good luck on your first film covering venture.
DennisV

I'm thinking about using iron on covering on the Banchee I,m doing. It would be nice to also do the fuse, but I have the lack of knowlege in this area. I know there are videos out there but it's nice to get help in person from time to time. I like to use Brodak paint, but this weather is not going to be good for that for some time. Has anyone used hair spray on the wood first before ironing the covering. I used it once on some Nelson fabric. I would think it would work on Monokote. Are their any good photos on a stepping process of applying iron on covering somewhere on this forum?

>I'm about to do my very first plastic film covering job on a
>gas model plane. I'm not only concerned about "pin pricks",
>but those little places where the film covering doesn't
>quite overlap in and around the engine compartment.
>
>For laughs, I'm doing a Goldberg/Comet Sailplane using
>something called Ultracote. The instructions caution that
>you can't spray nitrate or butyrate over the film to seal
>all those little places where oil can migrate.
>
>My only other option is to use silk, at about $50- for the
>silk and a like amount for dope for it.
>
>With my usual luck, the plane won't last long enough for oil
>to seep into the innards!
>
>Floyd

It actually sound like you won't have an engine compartment - sailplane? Maybe that means you're using a power pod? Whatever it is, here's some opinions:

* Pin pricks should not be an issue. The ironing should always be performed to iron the bubbles out as you go. Some are impossible, so a strategic pin prick can help, but it's not something you want to do all over the plane on a regular basis.

* A true engine compartment should always be sealed. Thinned epoxy, or epoxy paint is best for a monokote job. I would still be concerned with polyurethane - it can turn into a mess.

* For a nose, glassing is the best choice for me. A coat of Balsarite will let the film stick afterwards.

* The most critical area is around a nose ring, where the air stream will most likely lift the edge. It will help to make sure all of your joints overlap, with the pieces on top closest to the nose. It's the same philosophy as shingles on a roof - the overlap should be under and away from the direction of the airstream. If you need additional pieces to do this, then add them.

* Don't hesitate to use high heat and pressure on plywood (but not balsa). For the nose doublers on a profile, you can almost melt the film into the wood for good protection.

Finally, accept the fact that film finishes require maintenance. Using a heat gun on the wing will cut down on future wrinkles. However, you will always need to pull out the iron and re-seal edges, before and after a few rounds of flying.

Thanks everybody. One question springs to mind - I note we shouldn't get bubbles if we do it properly. Sometimes bubbles appear spontaneously, i.e. I have the film stuck down o.k. and then a pass of the iron creates a bubble. Is the iron too hot?

>Thanks everybody. One question springs to mind - I note we
>shouldn't get bubbles if we do it properly. Sometimes
>bubbles appear spontaneously, i.e. I have the film stuck
>down o.k. and then a pass of the iron creates a bubble. Is
>the iron too hot?

Having the film stuck down "okay" is part of the problem; I like it nailed down. Use of heat in this area creates a bubble simply because the expanded air can't get away, is trapped. That's why we puncture the wood with all manner of little holes; it gives the air someplace to go.

>>I'm about to do my very first plastic film covering job on a
>>gas model plane. I'm not only concerned about "pin pricks",
>>but those little places where the film covering doesn't
>>quite overlap in and around the engine compartment.
>>
>>For laughs, I'm doing a Goldberg/Comet Sailplane using
>>something called Ultracote. The instructions caution that
>>you can't spray nitrate or butyrate over the film to seal
>>all those little places where oil can migrate.
>>
>>My only other option is to use silk, at about $50- for the
>>silk and a like amount for dope for it.
>>
>>With my usual luck, the plane won't last long enough for oil
>>to seep into the innards!
>>
>>Floyd
>
>It actually sound like you won't have an engine compartment
>- sailplane? Maybe that means you're using a power pod?
>Whatever it is, here's some opinions:
>
>* Pin pricks should not be an issue. The ironing should
>always be performed to iron the bubbles out as you go. Some
>are impossible, so a strategic pin prick can help, but it's
>not something you want to do all over the plane on a regular
>basis.
>
>* A true engine compartment should always be sealed.
>Thinned epoxy, or epoxy paint is best for a monokote job. I
>would still be concerned with polyurethane - it can turn
>into a mess.
>
>* For a nose, glassing is the best choice for me. A coat of
>Balsarite will let the film stick afterwards.
>
>* The most critical area is around a nose ring, where the
>air stream will most likely lift the edge. It will help to
>make sure all of your joints overlap, with the pieces
>on top closest to the nose. It's the same philosophy as
>shingles on a roof - the overlap should be under and away
>from the direction of the airstream. If you need additional
>pieces to do this, then add them.
>
>* Don't hesitate to use high heat and pressure on plywood
>(but not balsa). For the nose doublers on a profile, you
>can almost melt the film into the wood for good protection.
>
>Finally, accept the fact that film finishes require
>maintenance. Using a heat gun on the wing will cut down on
>future wrinkles. However, you will always need to pull out
>the iron and re-seal edges, before and after a few rounds of
>flying.

Ron B.
F4Fguy

Tom:

The Goldberg "Sailplane" is a classic pylon gas freeflight model.

Floyd:

Spend the $50, there's nothing prettier than a silk covered "Sailplane". Plastic is contraindicated.