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Building Tips and technical articles. => Paint and finishing => Topic started by: wwwarbird on May 05, 2010, 06:41:13 PM
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I've never glassed a model before, or even messed with it. I've been thinking about it lately though. I've known of Z Poxy forever it seems but have always chickened out because I've always assumed that it would be very hard to sand after curing, like epoxy. Is this the case, or does it sand easily? By easily I mean can you sand it smooth quickly with like 220 grit or thereabouts? D>K
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finishing epoxy ( I assume the Zpoxy you are talking about is finishing epoxy?) sands decent, not quite like primer but it sands pretty well. do yourself a favor and cover a scrap piece of balsa just like you plan to finish your plane. It does take some getting used to when applying. It is EASY to build up weight with epoxy so heed that. There are several threads I think that deal with epoxy, one trick is to blot the surface when you have it all adhered to remove the excess resin.
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Yes Zpoxy finishing resin sands out very easy. Can be sanded to a real nice finish like glass if that is what you wont.
Jimmy
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Ive had great luck with Z Poxy. It does take a little work with the sanding. I use the credit card method to minimize the weight. Lay the cloth down, dribble on the Z Poxy and spread it with a credit card. Remove all excess epoxy.
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Yeah, I'm sure you really have to watch the weight with it. I would surely be using a credit card or something to squeegee. How long is it workable and how long to fully cure?
Maybe this is a dumb question, but what happens if you just put it right on the wood with no cloth? What I mean by that is simply using it as a sealer instead of the dope and silkspan process. That's more what I was thinking of. Maybe that's a no-no?
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If thats what you want, then I would spray the wood with a coat of laquer, or hair spray maybe, to help keep it from soaking in to much. If you are looking to just create a "hard shell" to work from, I guess it would work, though the cloth adds a great deal of workability and strength . If you do this without cloth, maybe squeegy it out then blot the excess off with paper towels?
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Thanks for the info guys. My biggest curiousity about it is the sandability. I was just kind of wondering about the stuff a little and kicking around some ideas. It would make much more sense to use the cloth with it. y1
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If you warm with a heat gun and blot with paper towels, you will not need to sand. You will need to fill the cloth weave.
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Sanding Z-poxy is not an issue. It sands fine with 220, smooth, workable. Apply fiberglass with first coat. Using a heat gun spreads it out and helps it cure faster - your choice to use or not. Apply second coat, sand and the finish will be first-row smooth. Dope sticks to it or you can silkspan over it (not really necessary). A thin coat can be applied to untreated wood to seal pores. Minimal weight buildup with sanding. I don't use it this way but it does work. Also good for binding balsa skins to foam cores. Close to a miracle product. Highly recommended. 8)
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Do a search on this site for Rabe Mustunt series. Al uses z-poxy on the finishing of the Mustunt IV. He thins it down and uses it to seal the wood. He actually uses a power sander on the flat surface on the wing. Sands very nicely
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The best way to avoid excess weight gain and still have the strength of the wood / glass/ z-poxy sandwich is to use lightweight glass cloth, pre-cut to size. I sometimes mist a very light coat of contact cement ( spray can type) on the cloth and lay it in place- the tack keeps it from moving around when you spresd the expoxy.
Have old credit cards / squeegees, paper towels and a couplke rolls of toilet paper handy. Place a section of cloth on a part and smooth it out.
Warm the Z-poxy bottles in warm / hot water, mix some up resin and pour some on the cloth. Spread / scrape the resin toward the edge of the part, and scrape the excess back into the cup.
When you have the whole part wetted out and scraped down, take a roll of toilet paper and roll it across the part to soak up more resin- press down & make sure to roll it so it stays on the roll. Peel the loaded paper off after each pass so you continue to soak up the excess resin.
This gets the glass cloth fully bonded to the sub-strate with minimal epoxy to keep weight dowm, and will cure to sanding hardness pretty quick. Hit it with some 220 to knock down the high spots, but don't sand so much the cloth statrs to fuzz up. Wipe down good with alcohol and shoot a good coat of primer to finish filling the weave. Then it is just like any other base- and we know you have that under control from your Helldiver post!