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Building Tips and technical articles. => Paint and finishing => Topic started by: Brian Massey on April 21, 2009, 06:04:35 PM
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I've read here that silk must be put on and stretched to fit. I purchased some silk and would love to use it on my upcoming TT. Once on and pulled tight, does dope still make it tighten up? Is it best to put on dry? Or wet? Quick, someone hand me a copy of "Silk for Dummies"!
Brian
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I have found silk to be best applied wet. The silk acts like a sticky wet rag when wet and some patience is required to get it flattened out after wetting. I use a shallow pan of water so there aren't too many folds to get straightened out.
Pre-dope the frame a couple of coats of nitrate dope, then use thinner or thinned dope to get the silk to stick. Also, pull as tight as you can when sticking it down. The dope will further tighten the silk when dry, though it may appear to slacken when first wet with the dope.
Don't expect perfect results the first time there is a learning curve, but the time spent is worth it.
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It depends to a considerable extent on what brand of silk you bought! If you got K&S or the superb ESAKI silks (which are not pre-shrunk), then you don't need to stretch it. If you bought your silk from Thai Silks or Dharma Trading (or RSM, which buys from Thai Silks), it is pre-shrunk, and you will want to stretch it over the framework.
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You want the wood underneath well doped, else the open bays will be nice and shiny but the wood will still show the silk weave because the dope soaked through. I'm only familiar with to old Esaki-type silk. I put it on soaking wet and get it lined up with the weave straight, etc. It is easy but you must be patient and demand perfection. First coats of dope very thin, 70% thinner. As the silk seals go to thicker dope. Silk goes around curves very well.
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During the application, keep the silk very wet. Water spray bottle works good. Use clean, pure water. Don't use windex or anything like that. I use Sig products. As mentioned above, use the nitrate dope for application and you may also have to use a little CA to hold silk in place as you stretch it. It should be very "drum" tight while wet. Once dry, a few covering coats of nitrate to fill the weave. Let the nitrate fully dry (I wait a week, but that's me), then a few coats of Sig Super Coat to get further tighten. It is a more taunting dope than Brodak. Once fully dried, I then go to colors and finish clear with Sig Lite Coat. I really like working with silk and the "classic" looking finish you can develop. This is a picture of my niece with my Smoothie. Silk and all dope.
Jim
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i used a silk babushka back in the 60s and it worked fine. but sometimes it got so tight it would start to crush the wing.. %^@ but it goes on just like silk s.
roger
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Dharma trading co. has a great deal of information and tutorials regarding silk. Really good information on using, dying, and, well just look and see.
Keep in mind much of this has little to do with techniques involving the covering of model planes but good info nonetheless. You might use this to help you with handling the silk.
Who knows? Maybe someone here could write a tutorial on covering with silk that Dharma Trading could put on their website with the rest of their tutorials!
http://www.dharmatrading.com/html/eng/208809-AA.shtml?lnav=techniques.html
I hope this will be of some use, Robert
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Thanks all for the responses; yes, I purchased my silk from Thai Silks. I'm wondering why everyone suggested Nitrate dope . . . I've always used the "B" kind. I currently have Reynolds dope on hand and plan on using that. Seems I should put it on wet, and pull it tight.
Thanks for the insights, we'll see what happens.
Brian
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Brian:
Nitrate dope has a little more substance to it, therefore fills the wood better and is more "sticky" than the 'B' dope. It really sticks the silk down and then a few coats fills the silk weave. But this is Very important!!!...Only use the nitrate as the bottom coats. It is OK to put 'B' dope over nitrate, but absolutely not the other way (no nitrate over 'B'), or you will have a gooey mess.
Remember the paint rules:
E = Enamel over all
B= Butyrate over Acetate or Nitrate
A = Acetate over Nitrate
N = Nitrate over nothing. It stays as first coats on the bottom
also:
Nitrate = 30 days (or so) to gas off
Butyrate = 90 days (or so) to gas off
Plasticizing: Castor oil in Nitrate only. For Butyrate use TCP
Jim
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Also make sure you keep the weave (grain!) of the silk running spanwise! and as straight as you can.
Cheers Neville
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I used to use nitrate for sticking the silk down, and sometimes a coat or two before going to butyrate. I have since gone to using Sig Super Coat for both applying the silk and for the first few coat to shrink the silk. If you use nitrate with a translucent finish, it will have a mottled look that is not pretty. The Sig Super Coat butyrate works fine and is almost as sticky as nitrate. This is on both silkspan and Dharma Trading Co. 5mm silk.
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I recently covered a plane with 5mm Thai Silks silk dyed with Dharma's dye. I used brand "B" dope. It didn't shrink tight. I put on some Sig Supercoat, which tightened it. So do as these guys say and use nitrate or Sig Supercoat or some other taughtening dope for the first few coats.
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I will mention that my can of Sig Nitrate says not to use it over the empty bays on silk--it does not taughten enough. They recommend Sig Clear Supercoat (taughtening butyrate).
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Flying Models, October 1993. "Silking... a modeling art form" Pages 42 - 46
Ward-O ::)
What goes around, comes around!
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Ty, the reason you got mottling is that your first coats of dope were too thick. Put on with a brush, the first coats are going to bleed through. If they are really thin, 70% thinner at least, it won't show. I've been told of methods using a foam brush or toilet paper which are said to work well to stop bleed through. Also there is the technique of putting on a coat of gelatin to seal the silk before doping. I've not tried any of these.
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As Rusty used to tell me when questioned about the fabulous finishes on his colored silk planes, "Make a pass with the brush and dope once, don't go back over it until dry". He was so correct even tho the plane looked kinda weird with streaks of dope until it was all filled in. As he said when you go back over the fresh dope you are pushing it thru the fabric. It doesn't matter if it's silk, nylon, poly-ester or even silk span. DOC Holliday