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How much DOPE???

Old 10-20-2015, 12:31 PM
  #1  
J.Paul Saure
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Question How much DOPE???

Hi!!!

I will be using DOPE for the first time, I've always used iron on covering in my 20+ years building and flying.
Dope is not readily available here, so I need to know in adance "how much" will I need.

I want to re-cover an old Greatplanes .20 J-3 Cub of mine (to get the hand on it) and a SIG 1/5 J-3 currently in "kit form".
Already have SIG koverall covering.

QUESTION:
How much DOPE will I need for both models???
It's offered in 4oz bottles, 12oz flasks and 1liter bottle (33.3oz for you non-metric guys)

PS:
I think I'll try Vallejo acrylics over it, the ones for plastic scale models work very well with my Badger airbrush.
http://www.acrylicosvallejo.com/en_U...olor/family/20



Thanks a lot for the advice!!!
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Old 10-20-2015, 01:25 PM
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Six to eight coats on the little J3 will pretty much use up a liter. Consider buying a gallon from Aviation Spruce or Wag-Aero.
I recommend Randolph Non-Tautin Clear Nitrate dope.
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Old 10-20-2015, 02:05 PM
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J.Paul Saure
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Thanks!

SIG Koverall manual talks about "three coats" of dope before painting. If so, I would need between 1 and 2 liters for both planes????
I cannot get DOPE from overseas, no shipment on small orders... ...a friend will get it from Argentina to Chile by car on our next fly-in.
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Old 10-20-2015, 02:35 PM
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My figures relate to Polyspan, so Sig is claiming Koverall requires half that.
One thing for sure, if you don't get enough you'll really be in an unhappy state.
If you can afford it, get twice what you need. Store the remaining in smaller, tightly closed cans.Then you'll have it for the next model.
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Old 10-20-2015, 05:52 PM
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Thanks for the advice!!!
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Old 11-05-2015, 06:24 AM
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I disagree about the non tightening dope, buy the shrinking kind, also buy cellulose thinners, normally from an auto repair shop supplier.Once you've done a couple or three coats of thinned shrinking dope use a small amount of castor oil eg 1/4 liter dope unthinned maybe 5 drops of castor and mix it well. Use it unthinned and this castor plasticises the dope and prevents it cracking, it also prevents it shrinking.
FWIW SIG are taking the piss saying 2 or 3 coats will fill the weave on Koverall, some of my mates have put 7 or 8 coats on and I've stopped using it as the weave can shift and cause problems, I use nylon doped on wet with unthinned shrinking dope then a couple coats of dope plus castor plus mix in a few teaspoons of talcum powder this really fills the weave.
If you are using a glo engine, shy away from acrylic paint as it needs fuel proof paint on top to prevent it dissolving. It's a good idea to leave the doped plane a couple of weeks to "gas off" as the solvent will remain in the fabric for a while. Oh and sand down the fabric with really fine wet and dry paper betwen coats.
To get an idea it's sound pratice to build a frame , cover it with your material of choice and use the dope to get experience of the techniques.
Don't underestimate the power of shrinking dope sometimes it's a good idea to pin down wing panels to prevent warps.
I, too, have a sig 1/5 th scale cub building but I'm going to use solartex as it's much more user friendly. Remember the dope vapours are narcotic and also women hate the smell of it!!!!
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Old 11-05-2015, 06:53 AM
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Thanks for the advice!!!
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Old 11-30-2015, 12:21 PM
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Originally Posted by J.Paul Saure View Post
Thanks for the advice!!!
Either approach will work. Tautening versus non-tautening: no- taut shrinks much less but it shrinks some. Tautening dope on the other hand requires some treatment to make shrink less. A few drops of plasticizer in the dope is a good idea to keep dope from becoming brittle over the years and cracking, as one poster mentioned

To me it is easier to control the amount of shrink using non-taut rather than tautening, particularly when using a heat shrinkable covering such as Polyspan as Grotto mentioned, over open bays and stick built fuselages.

Tautening dope produces so much stress on the covering over the years that the structure may twist if not built really strong and resistant to twisting to begin with. Cub structures are not particularly stiff and strong that way
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Old 11-30-2015, 02:55 PM
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If you are going to power it with a small gasoline motor instead of GLOW fuel....

I am going to offer a different approach just to throw it out there. I like my planes to look more weathered than super shiny and show room perfect. I am using a thick adhesive dope like Sig Stixit to adhere my covering which is ..ceconite.. its an unrated lite weight full scale covering.

You may be able to do the same with your covering..It might be worth testing it with scraps on another piece of a wing. You can learn and SAVE a lot from testing new techniques. I read of people on RCU doing this years ago and after trying it really learned to favor it over other routes.

After I have it attached to the model I do not fill the cloth with dope , I paint with Acrylic hobby paints and a foam brush. I then do a couple light dust coats of Rustoleum clear. This way you use way less toxic chemicals and it is MUCH cheaper... I have had no problems shrinking the covering with it painted this way. I try to cover it as well as I can, and not need to really put the heat to it afterwards. Obviously you can shrink some before painting as well.

I have been very happy with the results. I hope it helps you enjoy the hobby even more as well

the key is to test it on something first..
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