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Building Tips and technical articles. => Building techniques => Topic started by: Michael Massey on October 30, 2009, 09:57:35 PM
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Looking for some hints on covering with silk.
I have covered my 2nd airplane with silk. I thought I got it on fairly tight initially but I am now up to 6 coats of dope and the wrinkles are now looking like they may tighten up and go away. I put the silk on wet, pulled it tight and went from there. When I wet the silk, I sprayed it with cold water, waited a minute and applied it too the wing.
I seems that if I could get the silk to "stretch" a little more on initial application, it may shrink more after it dries thus redusing the number of coats of dope. I have thought about letting the silk spend a few more minutes wet before applying and maybe soaking a few minutes in hot water before applying.
Any thoughts? Thanks for any input.
Mike
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I assume you're talking about real silk fabric. Are you using high shrink dope?
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Hi,
I am using "Tautening Butyrate" dope from Randolph.
Tx.
Mike
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Sorry, I left out that it is silk fabric. 5mm
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It does need to be stretched about as tight as you can get it, and after about 4 or 5 coats of dope, let it set for a couple of days. On open framework stabilizers and elevators, I have found pre covering with tissue or silkspan, will stiffen them up, and makes a good base for the silk. It only takes about 3 coats of dope on the tissue or silkspan before covering with silk, and still comes out very light.
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Did your silk readily wet? Or did the water tend to lay in beads and take it's time soaking in? Some silks I've used are treated with sizing, and it keeps the water from softening the fibers. When I run into that, I wash the silk out in fresh water before I apply it. YOu can do this before hand or as you cover. I use a pan to wet my silk, so in this case I would simply put the silk in the watter and agitate it by hand, then blot it on a towel spread flat and cover. Sized silk is pre-shrunk and since the water can't penetrate the fiber, they don't expand, rinsing it out as discribed allows the fibers to soften and expand and it will shrink well afterward.
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I wet the silk with a spray bottle just before I put it on. Thus no real time to soak. Did not notice any beading, it seemed to soak in but certainly I will do as you suggested and "soak and swish" for a bit before putting it on. As a side note, I got my silk from Thai Silks and I just looked and the invoice and it said that it is 8mm although I recall ordering 5mm. But I could be mistaken, ...imagine that.
Tx.
Mike
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I just get it wet with a spray bottle and pull out the wrinkles. Not streched, not "pulled tight", just wrinkle-free it comes in just right with 5-6 coats of clear.
The key element is doping and sanding the wood so there are no shape points to snag the silk.
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Thanks all for the input. One last question. When you apply dope, what kind of dope to thinner ratios do you use at what part in the process. I started with thicker dope to seal the fabric quicker then changed to thinner dope. Maybe reverse would be better? Let me know what you think.
Tx.
Mike
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I do it like Ty. Another trick for applying the first coat of dope is to drag a piece of toilet paper across the wing, dabbing unthinned dope at the edge of the TP.
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As Rusty Brown taugh me, don't go back over the surface you have just made a brush stroke on. It's when you come back over the surface that you push the dope thru. Another way is to spray with water and then dope with brush. The milky color will disappear with additional coats.
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Thanks for all the great input. See ya on the field.
Mike
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Flying Models, October 1993! Five pages of text and photos. And oddly enough, Model Aviation, October 1993
Try it, You'll like it!
Ward
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I've always put the silk on wings dry and I use Elmers white glue. If the silk is not quite tight enough at places just make the glue wet in that area or add a little more glue and it can be pulled tight in that area. After the glue has set I spray it lightly with water from a spray bottle. I've found this to be an easy way to get a tight job. I've really never had a wing that turned out that the silk wasn't tight enough on. I've tried it wetting the silk before covering the wing and it seems to be a lot harder to get a nice job.