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Polycrylic vs Deft polyeurothane vs cheap epoxy resin

Old 02-28-2004, 10:31 PM
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Default Polycrylic vs Deft polyeurothane vs cheap epoxy resin

Hey guys....

I have been on a search for the most affordable/easy way to get a HARD, lightweight, protective substance to cover my fiberglass over wings, etc...

I have some Mini Wax polycrylic, Deft gloss clear wood finish, and some of that generic laminating epoxy we all know and love. I figure if I can't get a good finish with one of these I will just save up and go with the MGS epoxy.

I am also looking for an inexpensive way to make nice light weight fuse.

So, when I have time, hopefully sometime during this week, I am going to test all three of these substances on some .75 or .5 oz cloth and possibly kevlar. Lastly I want to see if I can 'sandwich a layer of color between the glass and the final coat of sealer. As always an advice is welcomed...

Jay
Old 02-29-2004, 01:04 AM
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Default RE: Polycrylic vs Deft polyeurothane vs cheap epoxy resin

Hi Jay,

I think you know this, but...

If you use a commercial, proven product like West Systems, and buy it by the gallon, it's not too expensive, and produces great results. Look at the cost-per-ounce of any brand of hobby-type epoxy, versus a gallon of quality laminating resin, and you'll find that the quality product is actually a lot cheaper. Several other known brands would work as well.

Also, when you pull your "finished" part from a mold, it will continue to harden for quite a while. Make a part, and come back two weeks later, and you will find a much harder, stiffer part. Some time ago, I started giving all these chemicals more time than what the instructions say. When you give your molds a day or two longer to cure before removing the plug, give your parts a day or two longer before pulling them from the mold, etc., you get better results. (less flexing and/or "stickiness" )

Like Bob Fiorenze used to say... "Make haste slowly."

About color...
I've tried various pigmenting methods, and had poor results with all of them. Although quality, inert pigments (which are not expensive) are available, they are best used for thick (opaque) parts, like molds. When used on a thin part, such as a fuselage, the separation that occurs during curing can create a "muddy" or "runny" look. I think you'll have better results using a sprayed paint or primer in your molds, (after the wax and PVA).

That's my experience, anyway. If you discover something different and/or better, then by all means, let us see it and hear about it here.

Good luck.
Old 02-29-2004, 10:05 AM
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Default RE: Polycrylic vs Deft polyeurothane vs cheap epoxy resin

Mike,

No doubt that you are right about the epoxysystems (I heard MGS was ideal) But what a convience it would be to be able to get a nice HARD coat for an inexpensive foamy, without having to do an actual mold. Financially I am a year out from making molds and pulling parts (next building season). But I have a foam cutter, some fiberglass, and for $30 I have 3 different ways of coating the glass. (The $30 was spent over the last 6 monhts). I also need a vacuum bagger. All of that means $$$. So If I can do somthing like the following.

1. Cut the foam
2. Mist the foam with spray adhesive.
3. Lay the cloth...
(the order of the rest is yet to be determined)
4. coat the cloath with the laminating substance.
5. Paint w/ inexpensive spray paint.
6. coat with laminating substance until the weave is filled.

What I am hoping for is a STRONG, HARD covering that will strengthen and protect the structure, while being easy decorate.

As for my testing, I will take an old wing and make tests with each laminating substance. After I finish building my Nike 2, I will start the test, as I have some planes I want to build using this technique before summer.

j
Old 02-29-2004, 12:28 PM
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Default RE: Polycrylic vs Deft polyeurothane vs cheap epoxy resin

Jay,
I guess it depends on what you call "hard," but a lot of people are using water-based polyurethane for glassing balsa and foam planes. I have not actually tried it myself, but it should work well. Advantages would be easy cleanup with soapy water, no solvent fumes, fast drying time, etc. Once the wing (for example) is glassed with the polyurethane, it can be sanded smooth and painted with virtually anything.

The Deft product will most likely dissolve the foam. I'm not sure what epoxy you have but, if it's the 1:1 type which comes from the LHS and it's not specifically "finishing resin," then I wouldn't use it... you won't get good flow or a hard surface. WEST or MGS (etc.) would be great, but require more precautions and cure time.

Good luck,
David
Old 02-29-2004, 05:15 PM
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Default RE: Polycrylic vs Deft polyeurothane vs cheap epoxy resin

1. Cut the foam
2. Mist the foam with spray adhesive.
3. Lay the cloth...
(the order of the rest is yet to be determined)
4. coat the cloath with the laminating substance
You will have a problem here. Foam covered with just cloth and resin is very susceptible to dents. Picking up the wing with just finger pressure is very likely to put a dent in it. You can of course slop more glass and resin on it, but just watch the weight go up. To keep the weight down and prevent dents there is no substitute for a balsa skin.

Ed S
Old 04-20-2004, 04:57 PM
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Default RE: Polycrylic vs Deft polyeurothane vs cheap epoxy resin

I tested the Deft out on some foam and it did melt the foam. I did like the way it dried so I will probably use this on the wing for filling and make a hard surface. Then prime and paint.

I am thinking the $3 walmart primer and gloss krylon should do it....

Jay

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