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Rcpilot 06-08-2011 04:54 PM

Sig Koverall and Minwax Polycrylic
1 Attachment(s)
I am scratch building a Yard Bee thats been blown up about 50% in size. Wingspan is 42" and I'll be flying it with an E-Flite Power 10 and 2200mah 3-cell li-po.

I'm going to try and cover with Sig Koverall.

I just purchased a pint can of Minwax Polycrylic and a 1" cheapo brush.

As I understand it, the process goes something like this:

Paint all exposed wood surfaces, where the covering will attach, with a light coat of the Minwax.

Let it dry overnight.

Look for fuzz in the balsa. Sand lightly.

Reapply thin coat of Minwax.

Let it dry overnight.

Cut Koverall to size and lay it over the frame work.

Paint it down with Minwax and a brush.

Let it dry overnight.

Hit it with the iron to seal it down good and tight around the edges.

Heat gun to shrink.

Is that correct?

Thanks very much.

Aiden88 06-08-2011 06:05 PM

RE: Sig Koverall and Minwax Polycrylic
I didn't do a whole model with that method but I did test with Minwax. This was a couple years ago but your process sounds about right. Watch the heat or else koverall will harden and look like poo.
Minwax was a lot easier on the brain cells versus dope or Stickit. Once the koverall is applied, apply more coats of minwax to fill the weave. Sand lightly between coats. You can spray hair spray on the edges of the koverall where you want to trim. This reduces fraying.

Rcpilot 06-08-2011 06:16 PM

RE: Sig Koverall and Minwax Polycrylic

Keep em coming guys. I've done a bunch of searches in this forum but not finding an explanation of the exact technique.

GrayBeard you out there? :)

Aiden88 06-08-2011 06:48 PM

RE: Sig Koverall and Minwax Polycrylic
There is a wealth of information in this thread concerning a lot of different areas. A few mention Minwax poly as well.

Covering & Paint:


gene6029 06-09-2011 02:05 AM

RE: Sig Koverall and Minwax Polycrylic
RCPILOT, i use Sig Koverall alot & prefer to use the stix-it method. For me, it seems to go faster. I just iron down the Koverall and its finished. I do apply the polycrylic after everything is ironed down & shrunk. Then i prime with rattle can primer & paint. When useing Dope, i apply stix-it, then iron down the Koverall, then apply my nitrate dope, and then paint. I just like the stix-it because once you touch the iron to the Koverall its adheared there & you can keep moveing on. Other than the smell i like stix-it.....Gene

Just want to mention that the koverall & too much heat will twist that yard bee frame like a pretzle....;)

lazyace 06-09-2011 02:06 AM

RE: Sig Koverall and Minwax Polycrylic
first you need to put on 2 coats of sanding sealer to stop any wood from warping then the poly

gene6029 06-09-2011 02:10 AM

RE: Sig Koverall and Minwax Polycrylic
Lazy ace is correct on the sealer....Gene

Rcpilot 06-09-2011 08:46 AM

RE: Sig Koverall and Minwax Polycrylic
I should clarify a few things...

I'm trying to do this CHEAP. The wood was all scrap that I've built up over the years from kit building. We all have a balsa stash lying around if we're building kits. Some sticks, a couple slabs of ply, a bunch of sheets... usual inventory. Even the Koverall was purchased 4 or 5 yrs ago. I got rattle cans of paint and primer from past projects. I got glue and sand paper. I got the ESC and the motor. I got batteries and props.

The part I didn't have, was the dope, stix-it, balsarite, minwax..... I found a pint can of Minwax Polycrylic at Lowes for $9. Thats within budget.

I needed a way to stick the Koverall down to the frame and it had to be cheap. I did a bunch of searches in this forum and read pages and pages of posts about using Minwax and Koverall. From reading, I thought I could just brush some Minwax Polycrylic onto the frame and let it dry. Then sand it with some 600 to knock the fuzz off. Then put on another layer of polycrylic and begin applying the Koverall.

I've already put one layer of polycrylic on the wing.

Do I need to stop and sand that all off now? Wood looks pretty sealed to me.

My plan for today was to sand lightly and then brush on another coat of poly. Then start applying the Koverall with a brush and more polycrylic while the first layer of poly was still wet. I got the impression you could brush the Koverall down onto wet polycrylic. After it's dry, go around with a heat iron and gently seal all the edges down. Then fill edges with polycrylic to prevent peeling. Then use a heat gun and shrink out any sags. Then fill the weave with thinned polycrylic with several light coats, sanding in between the final 2 or 3 coats. Prime and paint.

Now I'm all screwed up. Don't have money for dope or stix-it. Confused. Do I need to sand off that first coat of polycrylic and start over? I thought you could do the entire job with polycrylic and didn't even need stix-it or balsarite or dope.

Please clarify the procedure. Thanks

Lone Star Charles 06-09-2011 10:13 AM

RE: Sig Koverall and Minwax Polycrylic

Over the years, I have used nearly every type of covering - from silkspan to silk to monokote and for the last few years, Koverall. I have never used Polycrylic, Krylonor Latex for models, so Ican't comment on its use other than I have seen some remarkable projects that used these processes. I am currently using Stits-Lite for the first time. It is very similar to Koverall and has the advantage of being delivered in larger sizes that the standard Koverall package.

My only comment on the procedure that you are using is in the use of a heat gun. In my experience, a heat gun cannot be as precise as an iron in delivering the proper temperature. It's just too easy to get a section too hot or not hot enough for the proper tension on the fabric. Although I do own a heat gun, I do not use it on woven fabrics for that reason. When tightening Koverall or Stits-Lite, I use my Top-Flite monokote iron at a setting of about 1-1/2 to 1-3/4 to make the initial shrink and then make a second final shrink at a setting of about 2-1/4. I have always had pretty good luck with this.</p>

Rcpilot 06-09-2011 10:23 AM

RE: Sig Koverall and Minwax Polycrylic
Thank you. Will stick to the iron.

I've never applied a fabric covering, so did not think about the way a heat gun puts out broad heat instead of controlled heat only where you want it.

huck1199 06-09-2011 10:57 AM

RE: Sig Koverall and Minwax Polycrylic

I have covered with polyester fabric (Koverall) over doped frame.  I just sealed the fabric to the dope with an iron, then shrunk with a gun and iron, then filled weave with several coats of wb poly.  Worked OK.  What you did sounds like it will be OK.

Rcpilot 06-09-2011 01:23 PM

RE: Sig Koverall and Minwax Polycrylic
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The fabric comes folded up in a plastic bag. I unfolded it and sprayed hairspray on the line that I wanted to cut. No big deal.

Now I'm trying to lay the fabric on the bottom of the wing and paint it down with a 1" brush and minwax polycrylic. It's going well, except for the crease lines in the fabric. At the spots where the fabric was folded, there are creases on my wing now and I can't get them out.

I realize the creases over open structure will shrink out with the iron later.

But what can I do about the spots where there's a crease over my sheeting or on the big rounded wing tips of the Yard Bee? [:o]

huck1199 06-09-2011 01:40 PM

RE: Sig Koverall and Minwax Polycrylic
The creases should shrink under your iron. Just be carefull not to iron in a fold.  On curved edges the iron will shrink it up like Monokote if you just touch it for a few seconds repeatedly.  Don't linger too long or you will get bubbling of your adhesive (dope, stix-it, wp poly) - don't ask how I know.

Rcpilot 06-09-2011 02:31 PM

RE: Sig Koverall and Minwax Polycrylic
I was hoping somebody would say that. [sm=thumbs_up.gif]

Thanks very much.

Rcpilot 06-09-2011 04:46 PM

RE: Sig Koverall and Minwax Polycrylic
1 Attachment(s)
Gettin' there. :D

I made the mistake of not completing the corners and rolling the covering around the edges. I just laid the covering out and brushed it down flat without rolling around the leading edge or rolling up and around the corners of the wings to the top side. Hope that makes sense.

That hosed me when I tried to go ahead and roll the covering up and around the wing tips onto the top of the wing. The poly had dried so it wouldn't soak through the fabric anymore. I had to brush the wood again and roll the fabric up onto the wood. Then I took a covering iron and heated the wet fabric to make it stick to the wood.

Next time I'll be sure and cut my fabric closer to size and once I start, I won't stop until all corners are rolled and sealed down.

These are some pics before I shrunk it with the iron to tighten it up.

Rcpilot 06-09-2011 06:10 PM

RE: Sig Koverall and Minwax Polycrylic
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No more wrinkles. Working on the top now.

crash bandicoute 06-09-2011 06:30 PM

RE: Sig Koverall and Minwax Polycrylic

<span style="font-family: Comic Sans MS">SHOW OFF... http://www.rcuniverse.com/forum/js/f...sn/biggrin.gif some people make things just look sooo easy. after you put the fabric over the structure with the stix-it stuff and that dries, how do you get the rest of the fabric to shrink down? does it work with a heat gun just like monokote or those type covering materials? i'm scared to try it, as people at the club buy BARF's or use the plastic film covering, and know nothing about the fabric and paintfinishes.</span></p>

Lowvoltage 06-09-2011 06:48 PM

RE: Sig Koverall and Minwax Polycrylic
After gluing the koverall down, set your heating iron to 250 degrees and completely go over the surface. Do not use pressure. After it is tightened at 250, crank it up to 300 and do it again. After two coats of policrylic start sanding between coats until the weave is filled. I wet sand with 400 grit. If you want to see the weave, use fewer coats. I use a sponge brush. When it starts to leave pieces of sponge on the surface I throw it away and get another one out. If you brush in one direction only it will be as smooth as if you spray painted it. I have even used a heat gun on low heat on the wet policrylic like you would do with epoxy. As a result of using policrylic and koverall Ithink your project is going to be heavier than you had hoped for, but that's the trade-off. You will end up with a very strong covering.


Rcpilot 06-09-2011 06:57 PM

RE: Sig Koverall and Minwax Polycrylic
I'm not showing off ................ hardly. [:o] Looks great at 5 feet. Don't get any closer - ya might get scared. :)

I'll go through the process here step by step - now that I actually know how to do it. There's a lot of steps, but it ain't HARD.

Sand your structure and tack it off. I used a damp sponge to pull off the sawdust and then let it dry overnight. The water in the sponge makes all the little hairs in the wood stand up. Sand again lightly with 400 grit. Now use an air hose or tack cloth to get rid of the dust.

I am using Minwax Polycrylic as my adhesive. I bought a cheapo 1" wide brush and painted the structure with it. Not the sides of the ribs, just the spots where covering will attach. I wasn't stingy or overly careful with the brush. I just slopped it on right as it comes out of the can and brushed it in. Clean up the runs with your brush. Let it dry overnight.

I used hairspray out of an aerosol can for pre-treating the cut lines. This fabric is a pain to try and cut, even with a brand new set of scissors. The hairspray is sprayed on where you plan to cut. I didn't soak it, but it was visibly wet. Let it dry 10-15minutes. Now you can cut without getting fuzzies all over the place. It's really a cinch to cut it after the hairspray trick.

Lay the fabric on your structure. Grab the paint brush and your can of polycrylic. I started in the center, since it's sheeted. Figured that would be a good spot to get part of it laid down and then make sure it's squared up on the wing. Then I just pulled the rest of the fabric down onto the wood surface and brushed it with more polycrylic. The corners need to be completely rolled around and up onto the other side of the wing while it's all still wet. Grab a covering iron and turn it to just under 1/2 power. Maybe 1/3 power. Use the iron to roll around the edges - just like any plastic covering.

Once you have it all attached, grab a new exacto blade and slice off the excess.

I gave it 20-30 minutes for all the polycrylic to dry. I live in Colorado and it's usually pretty dry out here. Doesn't take long for a water-based adhesive to fully dry.

Then I went back over all the open structure with my iron turned to about 1/2 power. Wrinkles and creases came right out. It's pretty tight, but I was afraid of warping this fragile little wing, so I stopped as soon as it felt tight. I imagine a guy could keep heating the fabric and crush this wing.

Tops almost done. Pics up within the hour. [8D]

Rcpilot 06-09-2011 07:21 PM

RE: Sig Koverall and Minwax Polycrylic
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Tops done.

DON'T drag your covering iron across the fabric when sealing the seams down around the edges. It makes fuzzies. I only did it once and it's on the bottom - screw it. :)

Roll the iron over the curves.

It makes a mess of the iron when the polycrylic is wet. Bottom of my iron looks like a kid spit a wad of gum on it and it melted and stuck all over the iron. I'm sure some toluene or other solvent will clean it up when the iron is cool.

I managed to shrink the top right side of the wing a little too much and warped it. Had to get my wife to come down and place a hand in the middle of the wing while I warped it back and shrunk the bottom tighter. It's straight now.

I'll put one coat of polycrylic on the weave tonight to begin the fill process. No more pics tonight.

Rcpilot 06-09-2011 07:35 PM

RE: Sig Koverall and Minwax Polycrylic

ORIGINAL: crash bandicoute

<span style=''font-family: Comic Sans MS''>SHOW OFF... [img][/img] some people make things just look sooo easy. after you put the fabric over the structure with the stix-it stuff and that dries, how do you get the rest of the fabric to shrink down?
Yup. After it's all stuck down and the polycrylic is dry - just use a regular covering iron on low-medium heat and shrink the fabric. Works just like monkeykote.

does it work with a heat gun just like monokote or those type covering materials?
Lone Star Charles told me to use an iron because a heat gun blows hot air everywhere - where a covering iron is concentrated heat and ONLY where you want it. I used an iron for the entire process, from sealing to shrinking. Worked perfect.

i'm scared to try it, as people at the club buy BARF's or use the plastic film covering, and know nothing about the fabric and paint finishes.</span></p>
I was scared too. Don't be. It's more work than plastic covering. More steps and more time. But it's not really hard. It only looks difficult. It's not. Just more steps and more time involved between the steps.

I did a bunch of reading here and on another forum. Figured I had the basics down, but was still a little worried so I started this thread. Thanks to a few guys here and a lot of reading - I think it turned out pretty darn good for my first time ever using any kind of fabric covering.

It's cheap as all get out. A 5 foot x 10 foot piece of Koverall costs a couple bucks more than a single 6 foot roll of monkeykote. 3 times the fabric for the same money. The polycrylic in a pint can was $9 and the brush was $2.50. Most of us have spray paint lying around. I've been flying and building for only 12yrs. I got tons of rattle cans from past projects. I don't want to add it up, but I'll venture a guess it's 1/2 the price of plastic covering when you're done and ready to go flying.

smithcreek 06-10-2011 03:55 AM

RE: Sig Koverall and Minwax Polycrylic

I'll venture a guess it's 1/2 the price of plastic covering when you're done and ready to go flying.
Besides cost, it looks so much better and ages well. Never sags even after sitting in the sun all day, never have to worry about an edge peeling up, it just doesn't happen. It's a bit more work while you're building but pays for itself several times over the life of the plane.

pacoflyer 06-10-2011 03:56 AM

RE: Sig Koverall and Minwax Polycrylic
Lone Star,
What are you using to stick down the Stits Lite ?


sscherin 06-10-2011 04:28 AM

RE: Sig Koverall and Minwax Polycrylic
Looks like you are learning the tricks :)

I went through how I do polyester cloth and polyC a few years ago in my Citabria build thread
One thing I forgot to address is fold lines in the fabric.. I just set my covering iron to a low temp (say a 1/4 turn) and iron out the wrinkles and creases before laying it on the aircraft.
You want it just hot enough to take out any wrinkles but not shrink the fabric.
I never did worry about fraying edges on the rough cut fabric..
I just used good sharp scisors and overcut by ohh alot..
The fabric is dirt cheep so a few extra inches won't kill you.

The most important tips are

when brushing onto the airframe wet out edges that need trimming an inch or sp past the edge and let it dry.. coated fabric cuts cleanly without freying

let the poly completly dry before using an iron or heat gun.. It boils and traps air bubles under the fabric.

do your preimiters, trim, iron edges, shrink then fill in the center.. this lets the fabric move around a little when shrinking.

On the first few full coats the fabric will sag a little.. no worries.. shrink it up again and move on.

BTW I am very happy with the Nelson line of paint.. Great stuff and hard as a rock with the cross linker.

What I'll do is put down 1 coat of polycryllic on areas that I know I won't just be able to brush the fabric down on.
Tight curves and edges..

I'll try to get the LE and TE of all flight surfaces and any edges or corners.

I'll let that dry..

When it's dry I'll lay out the fabric and brush it on with polyc around the edges if it's an open frame work.
I'll let that dry and come back with a heat gun to shrink it..
When it's shrunk tight I'll go back with the poly and coat any open area I left uncoated

For solid surfaces like a sheeted wing or stab I'll just start in the middle and work both ways until it's has a full coat.

Either method I'll be sure to wet out an inch past where I plan to trim off. Coated fabric cuts cleanly. uncoated frays.

After the first full coat dries it's time for the iron work.. Just treat it like any iron on fabric. The polyc melts with heat and the fabric will stick.

This is where I'll work around the wing tips and edges. The coated fabric will stick to the pre-coated wood like it was treated with balsa-rite.

You can get coated fabric to stlick to uncoated wood or vise versa but it's not a strong hold.. it's much better when both are preped.

What you don't want to do is take a heat gun or iron to it while the poly is still wet. The heat will cause the surface to set then boil the water out of the wet poly underneath causing bubbles to form that lift the fabric. These are a royal pain to get out. I've also seen the wet polyc boil on the surface and instantly dry into a bubbly foamy mess.

It's best to let it dry for a few hours then come back to shrink and iron down the edges.

A few more coats of polyc should blend in all the seams.

If you do happen to burn a hole with the gun just cut out a patch from clean fabric and brush it on over the hole. After a few coats you won't see the edges.

Last thing.. keep some new sharp blades handy.. The Fabric dulls them quickly..

WacoNut 06-10-2011 04:36 AM

RE: Sig Koverall and Minwax Polycrylic
1 Attachment(s)
I have used Sig Koverall and PolyCrylic on several planes. The results are well worth the effort. I found 4-5 coats of the polyc gives me the results I am looking for. My 33% Waco is covered in this manner and is painted with latex paint.
It is nice not having to worry about the covering starting to wrinkle over time of the edges lifting.

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