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Author Topic: Cold Dope  (Read 1935 times)

Offline Motorman

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Cold Dope
« on: December 04, 2016, 08:45:48 PM »
Temp control is sketchy in the place where I paint. What happens when you brush on Sig dope and it's too cold in the room?

Thanks,
MM
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Offline Mark Scarborough

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Re: Cold Dope
« Reply #1 on: December 04, 2016, 09:03:57 PM »
maybe nothing...........


likely bad things
my expectation would be that it would skin over, and when it warmed up it would shrink out really bad including possibly surface integrity failurs,, craking and the like
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Offline Dennis Toth

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Re: Cold Dope
« Reply #2 on: December 05, 2016, 08:43:41 AM »
MM,
If you are going to apply it outdoors then after a few minutes bring it inside it should be fine. Windy use to spray in the middle of NJ winter then bring it inside for final drying, his worked fine. Dope is more sensitive to humidity then temperature (within reason, if you can take the temperature then it may not), best to be less than 60% humidity. Use a little slower reducer if you can (auto body shop can help guide you on what to use). If you only have access to hobby reducers use something like SIG thinner rather than Brodak (Randolph) which gases off quicker.

Best,   DennisT
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Offline Fredvon4

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Re: Cold Dope
« Reply #3 on: December 05, 2016, 09:11:45 AM »
Before any definitive answer--- I guess it would be great to know the range of temps for brushing on Dope "in the room" as well as what dope and reducers on hand

Cold is pretty subjective "in a room"

30s~40s~low 50s will need care to the proper reducer and allowed time to gas out or "set", any desired shrinkage will be much slower to happen if it even does

But if the room is just a chilly (to us humans) mid 50s to mid 60s most typical Dopes and reducers will or should work as expected

The Dharma silk, I use, does shrink as it drys but open bays still need tautening dope to get nice and tight... for this, I temp control by winter building area to (sort of comfortable) 65F (( This also keeps the cheap ballasts in my fluorescent lighting happy and mostly humm free))

I Doped a Fuselage a few winters back with Sig Non Tautening where shop was 38F over night and 50ish during the day (me in it)...seemed to take a long (3 days) time to dry enough to sand for another few coats

I bought 2 Wally World relatively cheap thermostat controlled floor heaters ( set to 65F) keep the 16'x28' shop at a fairly constant  57F~62F. Since the winter humidity here is much lower, my dope projects do as I expect--  or even a little better than my, other time of year, projects

As I write this my shop is 61F and 41% RH....OAT is 58F heading for 28F soon....Hey Canada! Keep that chit up north please

During summer the temps can get to 85F and RH up in the mid 70%... Dope flashes off fast and lots of blushing... I get more done in the winter .... but still BRRRRRRR cuz MY bod prefers a nice 77F and >45% RH
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Offline john e. holliday

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Re: Cold Dope
« Reply #4 on: December 05, 2016, 09:24:41 AM »
My Thirteen I finished for VSC a few tears ago I went out my basement to put another coat of clear dope on.   Wasn't worried about blushing as it was already blushed in some areas and the poly-ester cloth was loose.  Temps were in the 40's and I had my overcoat on.   Once done I cleaned everything and hung the plane in the basement.  Next morning I checked the plane and no blushing and covering was drum tight.  This was brushed, not sprayed.
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Offline Motorman

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Re: Cold Dope
« Reply #5 on: December 05, 2016, 10:19:17 AM »
Thanks for the guide lines, I think it'll be good.

MM
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Offline Doug Kretschmar

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Re: Cold Dope
« Reply #6 on: March 27, 2017, 03:04:52 PM »
I've sprayed dope outside down to 20 below without any problem. I've sprayed clear, filler, sealer, and color. Always use Sig dope and thinner.I get everything ready to go and go outside to spray. I bring the sprayed item in the heated shop to dry immediately. I leave the gun outside and don't bring it in the shop between pieces being sprayed. The gun gets REALLY cold but seems to spray fine. Side benefit is no bugs or airborne dust. I live by the Canadian border and it's cold all the time so I was kinda forced to spray in the cold. Now I prefer to spray cold because I think I get a better finish. As an experiment I brushed dope outside when it was really cold and it worked. Too cold to stand outside and brush my toy airplanes but wanted to see if it would work. Cheers,Doug
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Offline Randy Powell

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Re: Cold Dope
« Reply #7 on: March 27, 2017, 04:59:40 PM »
I'd make sure the dope itself is warm, but for the rest, should be a problem as long as it's not too cold. Down to freezing anyway.
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