Hi,

I want to cover my Wings+stabilizer+rudder (F3A model), with paint. (airbrush).
The fuselage ofcurse is the "easy" way but its almost ready.
I know 2 ways for cover the balsa :
1. Fiberglass (slight) + epoxy 24 hr + Microballons.
2. Rice papaer + sanding sealer clear.

I'll be glad to hear about those two ways, and what is the best way in your opinion to get best quality ( after the airbrush ) and ofcurse the lightweight way ( if everything made right ).

Thanks

Mongol, I have to say if you're after information on preparing an aircraft for paint, Mike Hester and Hanglider have created (in my mind) the difinitive work on the subject in the Black Magic threads.

Have a read. It tells all!

Well, we didn't exactly "write the book", we just do it a lot, and have pretty much narrowed down some very good, repeatable techniques.

I would say that epoxy/glass is the most easily repeatable way to do it, but there are a couple of critical things that make a lot of difference.

The cloth must have a pretty tight weave. CST has a .7 oz cloth that is the best I have used so far. I used to use .58 until I found this particular .7 cloth.

Seal the wood with balsarite and sand with 600 grit before glassing, this doesn't allow as much resin to soak in.

Use West system or similar 105/205 resin. Not only does it cure to be very sandable, but it also holds up well when thinned with acetone as far as heat deflection.

THIN THE EPOXY 50/50 with acetone. Do NOT skip this step.

Use a dense foam roller after brushing out the resin to spread it evenly and remove any excess resin. This helps to minimize bubbles from forming where the glass lifts.

After the resin cures for a couple of hours, when it is still tacky, rub a generous amount of micro balloons into the weave.

Prime sand, rinse and repeat. Sand it ALL THE WAY DOWN to the weave until the last spray coat, and even then it needs to be barely opaque.

There is a condesned version with a few pics on my site forums [link=http://www.customairframes.com/caaforum/showthread.php?t=93]here[/link] that's pretty detailed up to the paint, which I will be detailing within the next month or so when I get some new pics. you may have to register in that forum to see the pics and if so, please use a name that I might be able to recognize as NOT a spammer (hint: at least set the time zone?) because I get about 30 random generated spammer registrations a day. If I let just one in, the next morning my forum is covered in viagra and porn ads. LOL So.....if the name is some random looking thing with the time zone not set, instant deletion.

-Mike

"The cloth must have a pretty tight weave. CST has a .7 oz cloth that is the best I have used so far. I used to use .58 until I found this particular .7 cloth. "

Mike- Is that their "Plain weave" fiberglass cloth? http://www.cstsales.com/e_glass_cloth.html

-Ron

It's the G0106xx series on that page. That's the sweet stuff!

-Mike

All I'll add to that is made sure you buy a quality roller. Don't think you can get away with one of the dodgy 50c ones, as they have a tendency to throw the roll off and then you're left rolling in epoxy with a sharp plastic stick.


Don't ask me how I know.


Incidentally, Mike have you tried using carbon veil yet? I've noticed a lot of the control line guys using it like tissue. Seems to work well, and I think would reduce the criss cross print through.


Just a thought anyway.

The open areas of veil are just WAY too open for my taste. Will it work? Sure. Is it as easy to get down smooth and light? Not for me.

But, many have tried it and like it. And will probably tell you it's easier/better/whatever. Like anything else, it's all in the way the person uses it. If you need to do a compound curve of any type, forget it. You can make it go, but after you do, tell me whether it's worth the hassle or not. To me.....not.

I do use veil in a few places here and there, just not for that. For finishing, I use a combination of glass and kevlar in key areas. (Fuse underside and LEs). Try to dent THAT [8D]

-M

Kevlar? Really?

I've shied away from aramids as they just don't seem to like epoxy. I've laid up certain parts with carbon kelvar twill before and in the event of a crash or mishap it seems the kevlar just spits the epoxy off, leaving a crusty eggshell left. how are you finding it?

What kind of kevlar did you use? I'm talking about a .75-.8 weave used like glass. If you manage to damage it, yeah, it does bad things. But it's very resistant to hangar rash. This stuff likes corners and curves better than carbon, but still not as well as glass.

Another hint: Use LOW viscosity resin if you have problems like you describe. Carbon and kevlar don't like to wet out very well with anything over about 300 CPs. If you try to really wet it out with anything much thicker than that, well, it's unhappy. BTW west thinned 50/50 is less than 100 CPs. Way less.....wets out like thin CA.

One more trick to kevlar is sanding. If you sand it too much, it get hmm...."furry". You have to know how much is enough. And how of it primer will take care of too.

Kevlar has it's uses but it's not fiberglass for sure. It's not stiffer, but it's tougher. It takes a LOT to break a strand of kevlar, and usually you will totally trash the area around it before you hurt the kevlar too much. Which brings me to another point: it's a ***** to repair if needed.

So, I'd only suggest using the kevlar trick if you are not generally one to break airplanes. But if the occasional bump into a door frame (or whatever) is dorking up your LEs or tips, try it out. And try also to remember, it's aramid, not adamantium. The stronger something is, the more it takes to break it...and the more catastrophic the end result.

Generally speaking, of course.

Thanks a lot ,

I must say MHester that you've done a great job with the fiberglass ( all that combination ) awesome.
** im not sure but is the blasarite that you mentiond is the Micro Filler ? ***


I tried to figure out about the cloth (7 oz ) im not sure about what i've got -
yesterday i bought a 3 meter of fiberglass , as i ask for , its the most thin cloth which they have.
so i attached a picture .

let me know if its can be good ( if you can understand which cloth it is from the picture ) -



-

Err....no, .7 as in 3/4 oz. That stuff is heavier than I use on cowls and parts!

This stuff will look and feel similar to silk.

I hope you can exchange it or something?

-M

I think that its possible to exchange, i'll check that...
Maybe you have any picture of the cloth or something like that ? im just cant understand about the cloth ... .

Thanks anyway.

Hi,
The weights referred to are oz per square yard.
0.7 oz/ 1 sq yard = 23.3g/sq metre.You can use as light as 15g cloth but not heavier than 25g.
Simply weigh and measure what you have, the pic,, cant tell.

Brian

Great,

I checked and the result is that : 73g for square meter.
Its really heavier..

I think that i'll order a 4-3 square meter of this cloth ( from the website Cst ) ..

water based (Minwax) polycrylic is less durable but a lot lighter. goes on fume free and dries in 20 minutes or less. no mixing, no waste and very simple.

Hi David,
you just answered my question before I could ask it. I had heard it was pretty much odor free (a definite plus for those like myself with a basement workshop). I assume by durable you mean that it is easier to sand through the glass than epoxy resin. Can you add filler to it (like micro ballons) to fill the weave? Or would it be better to stay with epoxy based products for filling/priming? I haven't painted in a few years and I plan on using Klasscote products which seem (relatively) less toxic (and less expensive) than the automotive paint I had been using; plus I had great success with K&B and Hobbypoxy paint prior to 1984 when I was persuaded to try the 'high tech' automotive stuff.
Thanks,
Will

i think the wbpu is less durable in the area of hanger rash. you have to be blind to sand through the cloth. i paint a coat of sanding sealer, then a heavy coat of watered down hobbylite balsa filler and sand smooth. then i apply 1/2 or 3/4 oz cloth with minwax wbpu. i apply 2-3 coats and sand smooth. i then switch to another can of minwax which is heavily diluted with talcum powder and paint 2-3 more coats. this stuff dries in 20 minutes or less. i sand again and switch to the straight wbpu, recoat and sand until satisfied. there won't be much for filler primer to do. always blow and wipe with a tack cloth before continuing after sanding. after the filler primer i switch to bondo spot putty or evercoat lightweight filler for the inevitable low spots, then more primer. by this stage you are usually ready for paint or at least getting close.

Ive used the minwax and .5 cloth on my Focus and other planes to, good stuff

Mike,

I was hoping we'd get that Kfactor article on this. I know we could all learn from it!!!! I don't follow the BM threads so I didn't know it existed. Interesting, and thanks for doing it. I'll have to do some reading up on it!!! Hope you're feeling better!

Chris

Thanks all for your help to understand those levels to prepare the balsa to cover with paint ..
As i understand there is no need to sand the fiberglass after all the process if its made good , i think that my second question will be how to paint at the right way so its won't weight too much or to be more specific :

In your opinion, what is the right ratio between paint - thinner. ( I can use with Do-Pont's paint ) to make it lighter as much?

Thanks again.

Has anyone tried the water-based Poly U with silkspan? I'm wondering how it would work since you need to attach wet (i.e. soaked with water) silkspan to the framework. I've used Nitrate dope with silkspan and it works great but it smells REALLY bad! If the poly would work that would be cool.

John Pavlick
Team Black Magic, Tech-Aero Designs

It really depends on the paint, but the general rule of thumb for polyurethanes is mix the paint by the manufacturer's specs....and double the reducer.

Your paint equipment matters here BIG TIME. Generally speaking, the better the gun atomizes the paint, the thinner and smoother you can lay it down. Yep you can use a harbor frieght gun, but realize you're shooting paint with a LARGE nozzle, closer to a water hose than a paint gun. It definitely works, but generally speaking you will lay down a lot more paint, and waste more too.

A large quality airbrush is best for trim colors. Look into the Iwata revolution or Eclipse line. You want a needle/nozzle combination between .35 and .5 in size, and a good QUALITY airbrush. The Iwata revolutions are perfect for this, and don't cost much more than a Badger (and it blows Badger away). Check out the bottom feeds or maybe a good side feed with a large cup. The absolute coolest airbrushes for general painting of trim are the Iwata TR2 and the Kustom CS. Note that these are a little more expensive, but oh MAN they make paint lay down like silk. And you can do a sweet, smooth LARGE trim section with less than 1/2 oz of mixed paint. Of which, only about 1/2 of that stays with the plane.

Chris this is the part I am working on to finish up the article(s). The one on my site is only the beginning, and it was posted over a year ago. I want to go into painting, masking, clearing, buffing etc. Then we'll hit about a 3 part article. Gimme about 2 months....

-Mike

Thanks a lot Mike for sharing your knowledge (huge) with me/us , its really help.
Im not sure but you said about the paint :
"the general rule of thumb for polyurethanes is mix the paint by the manufacturer's specs....and double the reducer. "

What do you mean at this line about "double the reducer " ? is that for the thinner ?

Mongol,

I think what he means: If the manufaturer says to use 4 parts paint and 1 part hardener then you use 5 parts reducer (thinner). This formula is based on using PPG Concept paint. Other manufacturers have the same kind of 2k urathane paint but may not be as thick as the PPG Concept paint and may not require the same amount of reducer (thinner) to get the same consistency for spraying. I hope this has been helpful.

Larry

Yes, double the reducer or thinner. If it calls for one part, use 2. This works with most urethanes, but you have to have either a good gun or good airbrush to atomize it properly.

Just use common sense here, if it's too thin (color) it won't cover before it runs. But if it's too thick, it will be heavy. So, my rule of thumb is 2x the amount of reducer the manufacturer calls for, and so far, so good.

This is one area where it is CRUCIAL to spray some on a test piece first.

Clear is a different animal. Always use a very thin mix of clear, because it is naturally very thick and heavy. You just want it to wet out and lay down and shine, nothing more. Spray super fine foggy mist coats, then as soon as you get it to look wet, RUN in the other direction and don't touch it.

If you add more coats of clear, you will get a better, stronger, wetter looking, and somewhat more durable paint job. But it will also add weight FAST. There is a point where you find that balance, but you have to do it once or twice and find it for yourself. Painting is just like flying pattern: there is no substitute for practice, it's a motion art.

Dean has gotten this pretty much down to a science. He's been over there painting everything he can find while I've been buried in balsa dust. LOL!

-Mike

PS You're welcome, by sharing experience, we all grow....