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Building Tips and technical articles. => Paint and finishing => Topic started by: RC Storick on March 09, 2014, 11:10:33 PM
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how much clear dope does it take to make a ounce on a plane. A pint, a quart, a half gallon. This is before thinner?
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Do you mean how much clear does it take, after it dries and gasses off, to add an ounce? I don't know the answer, but even though the thinner evaps out I imagine the clear/thinner ratio comes into play somewhere...
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Easy if I painted a whole quart (before thinner) on how much does it weigh,
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Not that I'm a painter by trade,(I have dealt with similar coating fun-stuff in the past), but that's a bit of a hard question to answer.
You could lay a super thick coat of dope and get a lot of weight and very little coverage, or thin one and go a mile.
Also are you asking about just the paint, or in a finishing situation, where it's sanded?
For reference, the density of nitrocellulose is 1.58–1.65 g/cm3 (98.63-103lb/ft3). If you figured out your coverage area, and a thickness of dope (this would be a real crapshoot) you could figure out your weight gain. But inconistent application, and sanding between coats will make everything you've calculated wrong.
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This does not have to be a hard question. 1 pint of UN thinned dope mixed 50-50 for spray weighs how much dry? Not a math quiz please. I have heard people say they spray a quart or two and it only weighs a ounce (which I am not buying).
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I don't either. Not unless they're sanding the living s**t out of it between coats, so most of that quart ends up on the floor.
A quart is a 946cc, but it still has a solvent in it which will gas off, and having a look at some MSDS sheets most nitrocelluloses are running at around 11-12% volume. (until I can find better info this is all a bit of a WAG).
so by that math, a quart when dry should weigh about 156g, or around 5.5 ounces when absolutely dry.
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I'm gonna say it's less than a pint of 50/50 clear to add an ounce of weight. The best way to find out is to weigh the model before and after putting on a measured amount.
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But when spraying you have over spray that does not end up on the plane, but on the floor or just in the air. HB~>
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dope is a very low solids material,,
i cannot answer specifically, but a ball park,, most dope is reported as being 13 or 14% solids,, which means in theory after all solvents evacuate, you would have 13 or 14% of the weight remaining,, of course taking into account the amount that blows randomly around your shop,,
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On a 700 sq inch plane, it takes about a quart of dope (mixed 60/40 thinner to clear) to gain an ounce. This is from experience shooting clear. I generally weight after each coat of clear (if using dope) and experience says it takes the entire quart, mixed with thinner, to gain an ounce.
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Between the imbedded vehicle in the product and the added thinner the amount that "gases off" appears to be substantial. The 14% solid mentioned by Mark seems to bear this out.
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On a 700 sq inch plane, it takes about a quart of dope (mixed 60/40 thinner to clear) to gain an ounce. This is from experience shooting clear. I generally weight after each coat of clear (if using dope) and experience says it takes the entire quart, mixed with thinner, to gain an ounce.
So, just to make sure I'm getting this: You put a bit over a pint of clear into a 1 quart paint pot, then you put a bit less than a pint of thinner and stir. Then you shoot the whole quart onto a plane (and half your shop), and when you're done and the plane has dried for a bit, it's one ounce heavier?
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I think there are numerous variables here including brand of dope (Certified has lots more solids in it for example) but my own experience is that on a 700 sq. airplane an airbrushed coat cut 70% will be around 1/2 ounce. If thinned only to flow well and brushed then 1 1/2 ounces per coat. I would then suppose that a coat sprayed with a regular gun would be in the one ounce range.
Dave
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Dave makes a good point. Looking at clears that are in the 13-14% range for solids, this is the case. I've used some clears with a higher (and lower) solids ratio and so, it takes a bit more or less to get to an ounce.
And Yes Tim, I mix up about a half gallon of clear (with 60% being thinner and 40% being butyrate lacquer) and shoot it all. Normally it takes 3 or 4 coats to go through the whole half gallon. Windy used to shoot a gallon this way.
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On a 700 sq inch plane, it takes about a quart of dope (mixed 60/40 thinner to clear) to gain an ounce. This is from experience shooting clear. I generally weight after each coat of clear (if using dope) and experience says it takes the entire quart, mixed with thinner, to gain an ounce.
Very interesting, thanks for the info Randy. y1