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Polycrylic vs epoxy for glass cloth finishing

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Polycrylic vs epoxy for glass cloth finishing

Old 02-16-2007, 05:25 AM
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Capt Jim
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Default Polycrylic vs epoxy for glass cloth finishing

I would like to hear from users of both epoxy, and polycrylic in applying .75 oz glass cloth over wood...fuse, wings, etc etc. I am hearing that the bonding is better with epoxy...although the cost is much greater, and the application a bit more troublesome. I have used the polycrylic and found it to be extremely easy to work with, and although I have had no problems with it, I wonder if I am gaining the desired structural integrity with it. The polycrylic, being a water based product goes on much more easily, because it's consistency is thinner than epoxy, and of course it wets out the glass cloth thoroughly and quite quickly. Clean up is no problem...just rinse out the brush in water. Polycrylic is useable right out of the can...no mixing..no pot-life to be concerned with. I actually like it a lot, but would appreciate hearing from others with their pros and cons.
Old 02-16-2007, 05:40 AM
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Ejiro
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Default RE: Polycrylic vs epoxy for glass cloth finishing

Interesting subject, which unfortunately I cannot add value to because, just like you, I have only used Poly-C in the past. I would like to hear what others have to say, but I have a hunch that, as with several other issues in this hobby of ours, people have thier own opinions and they would do anything to demonstrate that their's is the right and only way.
Old 02-16-2007, 09:01 AM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

I use PolyC for sealing and filling Sig Koverall,
I know some guys are using it for filling glass on giant scale warbirds with alot of sucess. I am guessing it all depends on the design of the aircraft whether or not it is a strong enough finish. In most cases I would say PolyC is more than strong enough for the application.
Anthony
Old 02-16-2007, 10:04 AM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

I used it on my TF Cessna 182. According to forum member 'Campy', the poly will do the same job as epoxy, with a 40% less weight gain, and it tends to dent easier than an epoxy surface. I've never used epoxy on a complete fiberglass job, so I can't compare. I can tell you that from bare balsa to painted and finished added less than a pound on my 182.

As far as strength goes, it comes from the fiberglass, not the epoxy. If you can get fiberglass to stick with snot, it should still be plenty strong.
Old 02-16-2007, 10:43 AM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

Have you tried using Delft Brush on Lacquer. Even lighter than Poly, smellier and needs ventilation when applying. But most of it evaporates, thus it is lighter. Another factor is that you can use as many coats as you want as Lacquer will bond on Lacquer while an overlay of Poly will not unless the earlier coat is still tacky. You can apply the Lacquer, sand it, and add another coat. Lacquer also dries pretty fast compared to epoxy or poly. A quart of Delft Brush on is about $9.00 but it will last forever.

I have found that if one wants a very strong bond, use epoxy. I use fiberglass/epoxy to bond the two wing halves on ARFs all the time. I no longer experience "folded wings." Of course, that also may mean I am a better pilot nowdays.

Cheers,

Chip
Old 02-16-2007, 10:51 AM
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Capt Jim
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Default RE: Polycrylic vs epoxy for glass cloth finishing

Where does one buy the Delft brush on laquer? And, since I am doing some re-glassing repairs over a Poly-c finish....I guess I should use the Delft in order to get a good bond to the old painted poly-C surface?
Would that be the recommended way to go?

Old 02-16-2007, 12:15 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

I use Minwax sanding sealer,
It is a laquer sanding sealer and it works just fine. I get it at Home Depot.
Anthony
Old 02-16-2007, 12:36 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

I too get it at Home Depot. I use it as A sealer for the Tex type of coverings so the two stroke engine snot doesn't get into the weave.
Old 02-26-2007, 01:02 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

I picked up a can of Minwax "brushing lacquer" at Home Depot. It brushes on just as nicely as the water based Polycrylic, but the smell is horrible. I applied this in a very open well cross ventilated garage, and after a short time, my nostrils were badly irritated from the fumes
On a test piece of balsa, I brused this lacquer over a piece of .75 ounce fiberglass cloth. The application was easy enough, except for the smell, but after drying..I found it offered no better peel-off resistance that the Polycrylic did. I have read these cautions in the forums about Polycrylic not bonding to a previously dried layer of Poly'...but having used multiple coats of Polycrylic on a previous giant scale warbird...I did not notice any failure to bond with each successive coat. I only applied additional coats in an attempt to fill the weave of the cloth...which it will do after many coats...perhaps (4) at a minimum. It seems that a high build primer will fill the weave faster with fewer coats. My take on all of this is that the smell and the resultant nasal irritation is not worth me using it for these applications. Unless someone can show me a significant and meaningful benefit...I will scrap the lacquer and go back to using the Polycrylic. Being water based, everything is easier with it....no smell, water clean up, bonds the glass cloth to the wood just fine....whats not to like about it.
Thanks for all of your comments.
Old 02-26-2007, 02:37 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

Cubnut, i am a little confused. Is this what you are using?
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Old 02-26-2007, 03:08 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

I doubt that your photo is what Cubnut was referring to. That is Polycrylic and it is water based...thats the stuff I particularly like...no smell, easy clean up, etc etc. The Lacquer product would not be a water based product....it requires a lacquer thinner for clean up....and that too smells just awfull.
Jim
Old 02-26-2007, 04:45 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

I use .56 oz cloth covered with a high quality finishing epoxy resin and the results were very good for the first glass job I did. The finishing resin takes a bit longer to dry and is not as think, because of this, I believe you get a thinner, lighter coat on the plane.
Old 02-26-2007, 05:55 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing


ORIGINAL: OldScaleGuy

Cubnut, i am a little confused. Is this what you are using?
Yes that is what I am using. I am getting a good bond with the PolyC. You can pull the fabric up if you try but it does take effort. My next subject will be a Ziroli P-40 fiberglassed using PolyC for the application.
Here is a link to a very good website for glassing with PloyC. The author won best of show at Toledo in 2004 with his SBD and he does awesome work. The web page shows him glassing a FW190 that he is currently finishing up. If you have time browse his entire build and you will be impressed.
[link=http://www.tompierce.net/190/html/paint/glassing.htm]Tom Pierce Glassing FW190[/link]
Later!
Anthony
Old 02-26-2007, 06:09 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing


ORIGINAL: OldScaleGuy

Cubnut, i am a little confused. Is this what you are using?
That is PolyC, Minwax does make a laquer Sanding Sealer. I use it before applying the cloth to seal the wood, if you do not seal the wood prior to using PolyC the wood will absorb the water in the PolyC and swell up[&o] Once you have the wood sealed with a couple coats of sanding sealer ther is not an issue.
Later!!
Anthony
Old 02-26-2007, 06:55 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

Hey, thanks very much for that Tom Pierce link. That's a great "how-to" web site and it is much appreciated.
Jim.
Old 02-26-2007, 06:58 PM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

No Problem,
It is great of Tom to put all that info on the Web for everyone to learn fom, I met him at Toldeo in 2004 and he is a very nice guy.
Anthony
Old 02-27-2007, 06:34 AM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

Gotcha. That clears up the confusion. Sanding sealer first THEN the PolyC. Thanks for that.
Old 02-27-2007, 10:27 AM
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Default RE: Polycrylic vs epoxy for glass cloth finishing

It is not realy valid to compare the two materials for the same purpose and say one is better than the other. They are both suitable for different applications. If using epoxy resin get a copy of the specification sheets for the resin. The sheet will clearly list the physical properties for all to see. I have not seen any spec sheets for water based polyurethane. But then why would there be any when the prime purpose of the material is to finish furniture and other bare woodwork.

I have used epoxy/glass materials extensively. I have experimented with water based poly.

The epoxy/glass system is superior in the following. It has a far greater tensile strength. It has a far greater compressive strength. It has a far greater shear strength. It is stiffer, (Try making a carbon prop with water based polyurethane). As a base for painting it will give a much harder, dent resistant surface. It is more expensive and requires a little more attention to detail when applying. It is a heavier material than water based poly.

Water based Polyurethane does not compare to epoxy with the aforementioned properties. But then maybe they are not needed. Water based poly is readily available, inexpensive (Relatively) and easy to apply. It's use with cloth will add some strength to the airframe. As a base for painting it will provide a slightly softer surface more susceptible to dents than epoxy. There is not much to choose when it comes to filling the weave and sanding, both will give good results. However the epoxy finish being harder will require a little more sanding effort.

It is simply a question of deciding which properties one requires and using the material that best meets those needs.

Ed S


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